GstMessage: GStreamer 1.0 Core Reference Manual

## GstMessage GstMessage — Lightweight objects to signal the application of pipeline events |

## Functions

#define | GST_MESSAGE_SRC()
#define | GST_MESSAGE_SRC_NAME()
#define | GST_MESSAGE_TIMESTAMP()
#define | GST_MESSAGE_SEQNUM()
#define | GST_MESSAGE_TYPE()
#define | GST_MESSAGE_TYPE_IS_EXTENDED()
#define | GST_MESSAGE_TYPE_NAME()
GQuark | gst_message_type_to_quark ()
const gchar * | gst_message_type_get_name ()
GstMessage * | gst_message_ref ()
void | gst_message_unref ()
GstMessage * | gst_message_copy ()
const GstStructure * | gst_message_get_structure ()
#define | gst_message_make_writable()
guint32 | gst_message_get_seqnum ()
void | gst_message_set_seqnum ()
gboolean | gst_message_has_name ()
#define | gst_message_is_writable()
gboolean | gst_message_replace ()
GstMessage * | gst_message_new_eos ()
GstMessage * | gst_message_new_error ()
void | gst_message_parse_error ()
GstMessage * | gst_message_new_warning ()
void | gst_message_parse_warning ()
GstMessage * | gst_message_new_info ()
void | gst_message_parse_info ()
GstMessage * | gst_message_new_tag ()
void | gst_message_parse_tag ()
GstMessage * | gst_message_new_buffering ()
void | gst_message_parse_buffering ()
void | gst_message_set_buffering_stats ()
void | gst_message_parse_buffering_stats ()
GstMessage * | gst_message_new_state_changed ()
void | gst_message_parse_state_changed ()
GstMessage * | gst_message_new_state_dirty ()
GstMessage * | gst_message_new_step_done ()
void | gst_message_parse_step_done ()
GstMessage * | gst_message_new_clock_provide ()
void | gst_message_parse_clock_provide ()
GstMessage * | gst_message_new_clock_lost ()
void | gst_message_parse_clock_lost ()
GstMessage * | gst_message_new_new_clock ()
void | gst_message_parse_new_clock ()
GstMessage * | gst_message_new_application ()
GstMessage * | gst_message_new_element ()
GstMessage * | gst_message_new_custom ()
GstMessage * | gst_message_new_segment_start ()
void | gst_message_parse_segment_start ()
GstMessage * | gst_message_new_segment_done ()
void | gst_message_parse_segment_done ()
GstMessage * | gst_message_new_duration_changed ()
GstMessage * | gst_message_new_latency ()
GstMessage * | gst_message_new_async_start ()
GstMessage * | gst_message_new_async_done ()
void | gst_message_parse_async_done ()
GstMessage * | gst_message_new_step_start ()
void | gst_message_parse_step_start ()
GstMessage * | gst_message_new_qos ()
void | gst_message_set_qos_values ()
void | gst_message_set_qos_stats ()
void | gst_message_parse_qos ()
void | gst_message_parse_qos_values ()
void | gst_message_parse_qos_stats ()
GstMessage * | gst_message_new_toc ()
void | gst_message_parse_toc ()
GstMessage * | gst_message_new_reset_time ()
void | gst_message_parse_reset_time ()
GstMessage * | gst_message_new_stream_start ()
void | gst_message_set_group_id ()
gboolean | gst_message_parse_group_id ()
GstMessage * | gst_message_new_structure_change ()
void | gst_message_parse_structure_change ()
GstMessage * | gst_message_new_request_state ()
void | gst_message_parse_request_state ()
GstMessage * | gst_message_new_stream_status ()
void | gst_message_parse_stream_status ()
void | gst_message_set_stream_status_object ()
const GValue * | gst_message_get_stream_status_object ()
GstMessage * | gst_message_new_progress ()
void | gst_message_parse_progress ()
GstMessage * | gst_message_new_need_context ()
gboolean | gst_message_parse_context_type ()
GstMessage * | gst_message_new_have_context ()
void | gst_message_parse_have_context ()
GstMessage * | gst_message_new_device_added ()
GstMessage * | gst_message_new_device_removed ()
void | gst_message_parse_device_added ()
void | gst_message_parse_device_removed ()

## Types and Values

struct | GstMessage
enum | GstMessageType
enum | GstStructureChangeType
enum | GstStreamStatusType
enum | GstProgressType

## Object Hierarchy

        GBoxed
        ╰── GstMessage

## Includes

    #include <gst/gst.h>

## Description

Messages are implemented as a subclass of GstMiniObject with a generic GstStructure as the content. This allows for writing custom messages without requiring an API change while allowing a wide range of different types of messages.

Messages are posted by objects in the pipeline and are passed to the application using the GstBus.

The basic use pattern of posting a message on a GstBus is as follows:

    1
    gst_bus_post (bus, gst_message_new_eos());

A GstElement usually posts messages on the bus provided by the parent container using `gst_element_post_message()`.

## Functions

### GST_MESSAGE_SRC()

    #define GST_MESSAGE_SRC(message)        (GST_MESSAGE_CAST(message)->src)

Get the object that posted `message` .

#### Parameters

message | a GstMessage |

### GST_MESSAGE_SRC_NAME()

    #define             GST_MESSAGE_SRC_NAME(message)

Get the name of the object that posted `message` . Returns "(NULL)" if the message has no source object set.

#### Parameters

message | a GstMessage |

### GST_MESSAGE_TIMESTAMP()

    #define GST_MESSAGE_TIMESTAMP(message)  (GST_MESSAGE_CAST(message)->timestamp)

Get the timestamp of `message` . This is the timestamp when the message was created.

#### Parameters

message | a GstMessage |

### GST_MESSAGE_SEQNUM()

    #define GST_MESSAGE_SEQNUM(message)     (GST_MESSAGE_CAST(message)->seqnum)

Get the sequence number of `message` .

#### Parameters

message | a GstMessage |

### GST_MESSAGE_TYPE()

    #define GST_MESSAGE_TYPE(message)       (GST_MESSAGE_CAST(message)->type)

Get the GstMessageType of `message` .

#### Parameters

message | a GstMessage |

### GST_MESSAGE_TYPE_IS_EXTENDED()

    #define GST_MESSAGE_TYPE_IS_EXTENDED(message)       (!!(GST_MESSAGE_CAST(message)->type & GST_MESSAGE_EXTENDED))

Check if the message is in the extended message group

#### Parameters

message | a GstMessage |

Since: 1.4

### GST_MESSAGE_TYPE_NAME()

    #define GST_MESSAGE_TYPE_NAME(message)  gst_message_type_get_name(GST_MESSAGE_TYPE(message))

Get a constant string representation of the GstMessageType of `message` .

#### Parameters

message | a GstMessage |

### gst_message_type_to_quark ()

    GQuark
    gst_message_type_to_quark (GstMessageType type);

Get the unique quark for the given message type.

#### Parameters

type | the message type |

#### Returns

the quark associated with the message type

### gst_message_type_get_name ()

    const gchar *
    gst_message_type_get_name (GstMessageType type);

Get a printable name for the given message type. Do not modify or free.

#### Parameters

type | the message type |

#### Returns

a reference to the static name of the message.

### gst_message_ref ()

    GstMessage *
    gst_message_ref (GstMessage *msg);

Convenience macro to increase the reference count of the message.

#### Parameters

msg | the message to ref |

#### Returns

`msg` (for convenience when doing assignments)

### gst_message_unref ()

    void
    gst_message_unref (GstMessage *msg);

Convenience macro to decrease the reference count of the message, possibly freeing it.

#### Parameters

msg | the message to unref |

### gst_message_copy ()

    GstMessage *
    gst_message_copy (const GstMessage *msg);

Creates a copy of the message. Returns a copy of the message.

#### Parameters

msg | the message to copy |

#### Returns

a new copy of `msg` .

MT safe.

[transfer full]

### gst_message_get_structure ()

    const GstStructure *
    gst_message_get_structure (GstMessage *message);

Access the structure of the message.

#### Parameters

message | The GstMessage. |

#### Returns

The structure of the message. The structure is still owned by the message, which means that you should not free it and that the pointer becomes invalid when you free the message.

MT safe.

[transfer none]

### gst_message_make_writable()

    #define         gst_message_make_writable(msg)  GST_MESSAGE_CAST (gst_mini_object_make_writable (GST_MINI_OBJECT_CAST (msg)))

Checks if a message is writable. If not, a writable copy is made and returned.

#### Parameters

msg | the message to make writable. | [transfer full]

#### Returns

a message (possibly a duplicate) that is writable.

MT safe.

[transfer full]

### gst_message_get_seqnum ()

    guint32
    gst_message_get_seqnum (GstMessage *message);

Retrieve the sequence number of a message.

Messages have ever-incrementing sequence numbers, which may also be set explicitly via `gst_message_set_seqnum()`. Sequence numbers are typically used to indicate that a message corresponds to some other set of messages or events, for example a SEGMENT_DONE message corresponding to a SEEK event. It is considered good practice to make this correspondence when possible, though it is not required.

Note that events and messages share the same sequence number incrementor; two events or messages will never have the same sequence number unless that correspondence was made explicitly.

#### Parameters

message | A GstMessage. |

#### Returns

The message's sequence number.

MT safe.

### gst_message_set_seqnum ()

    void
    gst_message_set_seqnum (GstMessage *message,
                            guint32 seqnum);

Set the sequence number of a message.

This function might be called by the creator of a message to indicate that the message relates to other messages or events. See `gst_message_get_seqnum()` for more information.

MT safe.

#### Parameters

message | A GstMessage. |
seqnum | A sequence number. |

### gst_message_has_name ()

    gboolean
    gst_message_has_name (GstMessage *message,
                          const gchar *name);

Checks if `message` has the given `name` . This function is usually used to check the name of a custom message.

#### Parameters

message | The GstMessage. |
name | name to check |

#### Returns

`TRUE` if `name` matches the name of the message structure.

### gst_message_is_writable()

    #define         gst_message_is_writable(msg)     gst_mini_object_is_writable (GST_MINI_OBJECT_CAST (msg))

Tests if you can safely write into a message's structure or validly modify the seqnum and timestamp fields.

#### Parameters

msg | a GstMessage |

### gst_message_replace ()

    gboolean
    gst_message_replace (GstMessage **old_message,
                         GstMessage *new_message);

Modifies a pointer to a GstMessage to point to a different GstMessage. The modification is done atomically (so this is useful for ensuring thread safety in some cases), and the reference counts are updated appropriately (the old message is unreffed, the new one is reffed).

Either `new_message` or the GstMessage pointed to by `old_message` may be `NULL`.

#### Parameters

old_message | pointer to a pointer to a GstMessage to be replaced. | [inout][transfer full][nullable]
new_message | pointer to a GstMessage that will replace the message pointed to by `old_message` . | [allow-none][transfer none]

#### Returns

`TRUE` if `new_message` was different from `old_message`

### gst_message_new_eos ()

    GstMessage *
    gst_message_new_eos (GstObject *src);

Create a new eos message. This message is generated and posted in the sink elements of a GstBin. The bin will only forward the EOS message to the application if all sinks have posted an EOS message.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]

#### Returns

The new eos message.

MT safe.

[transfer full]

### gst_message_new_error ()

    GstMessage *
    gst_message_new_error (GstObject *src,
                           GError *error,
                           const gchar *debug);

Create a new error message. The message will copy `error` and `debug` . This message is posted by element when a fatal event occurred. The pipeline will probably (partially) stop. The application receiving this message should stop the pipeline.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
error | The GError for this message. | [transfer none]
debug | A debugging string. |

#### Returns

the new error message.

MT safe.

[transfer full]

### gst_message_parse_error ()

    void
    gst_message_parse_error (GstMessage *message,
                             GError **gerror,
                             gchar **debug);

Extracts the GError and debug string from the GstMessage. The values returned in the output arguments are copies; the caller must free them when done.

Typical usage of this function might be:

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    ...
    switch (GST_MESSAGE_TYPE (msg)) {
      case GST_MESSAGE_ERROR: {
        GError *err = NULL;
        gchar *dbg_info = NULL;

        gst_message_parse_error (msg, &err, &dbg_info);
        g_printerr ("ERROR from element %s: %s\n",
            GST_OBJECT_NAME (msg->src), err->message);
        g_printerr ("Debugging info: %s\n", (dbg_info) ? dbg_info : "none");
        g_error_free (err);
        g_free (dbg_info);
        break;
      }
      ...
    }
    ...

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_ERROR. |
gerror | location for the GError. | [out][allow-none][transfer full]
debug | location for the debug message, or `NULL`. | [out][allow-none][transfer full]

### gst_message_new_warning ()

    GstMessage *
    gst_message_new_warning (GstObject *src,
                             GError *error,
                             const gchar *debug);

Create a new warning message. The message will make copies of `error` and `debug` .

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
error | The GError for this message. | [transfer none]
debug | A debugging string. |

#### Returns

The new warning message.

MT safe.

[transfer full]

### gst_message_parse_warning ()

    void
    gst_message_parse_warning (GstMessage *message,
                               GError **gerror,
                               gchar **debug);

Extracts the GError and debug string from the GstMessage. The values returned in the output arguments are copies; the caller must free them when done.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_WARNING. |
gerror | location for the GError. | [out][allow-none][transfer full]
debug | location for the debug message, or `NULL`. | [out][allow-none][transfer full]

### gst_message_new_info ()

    GstMessage *
    gst_message_new_info (GstObject *src,
                          GError *error,
                          const gchar *debug);

Create a new info message. The message will make copies of `error` and `debug` .

MT safe.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
error | The GError for this message. | [transfer none]
debug | A debugging string. |

#### Returns

the new info message.

[transfer full]

### gst_message_parse_info ()

    void
    gst_message_parse_info (GstMessage *message,
                            GError **gerror,
                            gchar **debug);

Extracts the GError and debug string from the GstMessage. The values returned in the output arguments are copies; the caller must free them when done.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_INFO. |
gerror | location for the GError. | [out][allow-none][transfer full]
debug | location for the debug message, or `NULL`. | [out][allow-none][transfer full]

### gst_message_new_tag ()

    GstMessage *
    gst_message_new_tag (GstObject *src,
                         GstTagList *tag_list);

Create a new tag message. The message will take ownership of the tag list. The message is posted by elements that discovered a new taglist.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
tag_list | the tag list for the message. | [transfer full]

#### Returns

the new tag message.

MT safe.

[transfer full]

### gst_message_parse_tag ()

    void
    gst_message_parse_tag (GstMessage *message,
                           GstTagList **tag_list);

Extracts the tag list from the GstMessage. The tag list returned in the output argument is a copy; the caller must free it when done.

Typical usage of this function might be:

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    ...
    switch (GST_MESSAGE_TYPE (msg)) {
      case GST_MESSAGE_TAG: {
        GstTagList *tags = NULL;

        gst_message_parse_tag (msg, &tags);
        g_print ("Got tags from element %s\n", GST_OBJECT_NAME (msg->src));
        handle_tags (tags);
        gst_tag_list_unref (tags);
        break;
      }
      ...
    }
    ...

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_TAG. |
tag_list | return location for the tag-list. | [out callee-allocates]

### gst_message_new_buffering ()

    GstMessage *
    gst_message_new_buffering (GstObject *src,
                               gint percent);

Create a new buffering message. This message can be posted by an element that needs to buffer data before it can continue processing. `percent` should be a value between 0 and 100. A value of 100 means that the buffering completed.

When `percent` is < 100 the application should PAUSE a PLAYING pipeline. When `percent` is 100, the application can set the pipeline (back) to PLAYING. The application must be prepared to receive BUFFERING messages in the PREROLLING state and may only set the pipeline to PLAYING after receiving a message with `percent` set to 100, which can happen after the pipeline completed prerolling.

MT safe.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
percent | The buffering percent |

#### Returns

The new buffering message.

[transfer full]

### gst_message_parse_buffering ()

    void
    gst_message_parse_buffering (GstMessage *message,
                                 gint *percent);

Extracts the buffering percent from the GstMessage. see also `gst_message_new_buffering()`.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_BUFFERING. |
percent | Return location for the percent. | [out][allow-none]

### gst_message_set_buffering_stats ()

    void
    gst_message_set_buffering_stats (GstMessage *message,
                                     GstBufferingMode mode,
                                     gint avg_in,
                                     gint avg_out,
                                     gint64 buffering_left);

Configures the buffering stats values in `message` .

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_BUFFERING. |
mode | a buffering mode |
avg_in | the average input rate |
avg_out | the average output rate |
buffering_left | amount of buffering time left in milliseconds |

### gst_message_parse_buffering_stats ()

    void
    gst_message_parse_buffering_stats (GstMessage *message,
                                       GstBufferingMode *mode,
                                       gint *avg_in,
                                       gint *avg_out,
                                       gint64 *buffering_left);

Extracts the buffering stats values from `message` .

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_BUFFERING. |
mode | a buffering mode, or `NULL`. | [out][allow-none]
avg_in | the average input rate, or `NULL`. | [out][allow-none]
avg_out | the average output rate, or `NULL`. | [out][allow-none]
buffering_left | amount of buffering time left in milliseconds, or `NULL`. | [out][allow-none]

### gst_message_new_state_changed ()

    GstMessage *
    gst_message_new_state_changed (GstObject *src,
                                   GstState oldstate,
                                   GstState newstate,
                                   GstState pending);

Create a state change message. This message is posted whenever an element changed its state.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
oldstate | the previous state |
newstate | the new (current) state |
pending | the pending (target) state |

#### Returns

the new state change message.

MT safe.

[transfer full]

### gst_message_parse_state_changed ()

    void
    gst_message_parse_state_changed (GstMessage *message,
                                     GstState *oldstate,
                                     GstState *newstate,
                                     GstState *pending);

Extracts the old and new states from the GstMessage.

Typical usage of this function might be:

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    ...
    switch (GST_MESSAGE_TYPE (msg)) {
      case GST_MESSAGE_STATE_CHANGED: {
        GstState old_state, new_state;

        gst_message_parse_state_changed (msg, &old_state, &new_state, NULL);
        g_print ("Element %s changed state from %s to %s.\n",
            GST_OBJECT_NAME (msg->src),
            gst_element_state_get_name (old_state),
            gst_element_state_get_name (new_state));
        break;
      }
      ...
    }
    ...

MT safe.

#### Parameters

message | a valid GstMessage of type GST_MESSAGE_STATE_CHANGED |
oldstate | the previous state, or `NULL`. | [out][allow-none]
newstate | the new (current) state, or `NULL`. | [out][allow-none]
pending | the pending (target) state, or `NULL`. | [out][allow-none]

### gst_message_new_state_dirty ()

    GstMessage *
    gst_message_new_state_dirty (GstObject *src);

Create a state dirty message. This message is posted whenever an element changed its state asynchronously and is used internally to update the states of container objects.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]

#### Returns

the new state dirty message.

MT safe.

[transfer full]

### gst_message_new_step_done ()

    GstMessage *
    gst_message_new_step_done (GstObject *src,
                               GstFormat format,
                               guint64 amount,
                               gdouble rate,
                               gboolean flush,
                               gboolean intermediate,
                               guint64 duration,
                               gboolean eos);

This message is posted by elements when they complete a part, when `intermediate` set to `TRUE`, or a complete step operation.

`duration` will contain the amount of time (in GST_FORMAT_TIME) of the stepped `amount` of media in format `format` .

#### Parameters

src | The object originating the message. |
format | the format of `amount` |
amount | the amount of stepped data |
rate | the rate of the stepped amount |
flush | is this an flushing step |
intermediate | is this an intermediate step |
duration | the duration of the data |
eos | the step caused EOS |

#### Returns

the new step_done message.

MT safe.

[transfer full]

### gst_message_parse_step_done ()

    void
    gst_message_parse_step_done (GstMessage *message,
                                 GstFormat *format,
                                 guint64 *amount,
                                 gdouble *rate,
                                 gboolean *flush,
                                 gboolean *intermediate,
                                 guint64 *duration,
                                 gboolean *eos);

Extract the values the step_done message.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_STEP_DONE. |
format | result location for the format. | [out][allow-none]
amount | result location for the amount. | [out][allow-none]
rate | result location for the rate. | [out][allow-none]
flush | result location for the flush flag. | [out][allow-none]
intermediate | result location for the intermediate flag. | [out][allow-none]
duration | result location for the duration. | [out][allow-none]
eos | result location for the EOS flag. | [out][allow-none]

### gst_message_new_clock_provide ()

    GstMessage *
    gst_message_new_clock_provide (GstObject *src,
                                   GstClock *clock,
                                   gboolean ready);

Create a clock provide message. This message is posted whenever an element is ready to provide a clock or lost its ability to provide a clock (maybe because it paused or became EOS).

This message is mainly used internally to manage the clock selection.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
clock | the clock it provides. | [transfer none]
ready | `TRUE` if the sender can provide a clock |

#### Returns

the new provide clock message.

MT safe.

[transfer full]

### gst_message_parse_clock_provide ()

    void
    gst_message_parse_clock_provide (GstMessage *message,
                                     GstClock **clock,
                                     gboolean *ready);

Extracts the clock and ready flag from the GstMessage. The clock object returned remains valid until the message is freed.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_CLOCK_PROVIDE. |
clock | a pointer to hold a clock object, or `NULL`. | [out][allow-none][transfer none]
ready | a pointer to hold the ready flag, or `NULL`. | [out][allow-none]

### gst_message_new_clock_lost ()

    GstMessage *
    gst_message_new_clock_lost (GstObject *src,
                                GstClock *clock);

Create a clock lost message. This message is posted whenever the clock is not valid anymore.

If this message is posted by the pipeline, the pipeline will select a new clock again when it goes to PLAYING. It might therefore be needed to set the pipeline to PAUSED and PLAYING again.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
clock | the clock that was lost. | [transfer none]

#### Returns

The new clock lost message.

MT safe.

[transfer full]

### gst_message_parse_clock_lost ()

    void
    gst_message_parse_clock_lost (GstMessage *message,
                                  GstClock **clock);

Extracts the lost clock from the GstMessage. The clock object returned remains valid until the message is freed.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_CLOCK_LOST. |
clock | a pointer to hold the lost clock. | [out][allow-none][transfer none]

### gst_message_new_new_clock ()

    GstMessage *
    gst_message_new_new_clock (GstObject *src,
                               GstClock *clock);

Create a new clock message. This message is posted whenever the pipeline selects a new clock for the pipeline.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
clock | the new selected clock. | [transfer none]

#### Returns

The new new clock message.

MT safe.

[transfer full]

### gst_message_parse_new_clock ()

    void
    gst_message_parse_new_clock (GstMessage *message,
                                 GstClock **clock);

Extracts the new clock from the GstMessage. The clock object returned remains valid until the message is freed.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_NEW_CLOCK. |
clock | a pointer to hold the selected new clock. | [out][allow-none][transfer none]

### gst_message_new_application ()

    GstMessage *
    gst_message_new_application (GstObject *src,
                                 GstStructure *structure);

Create a new application-typed message. GStreamer will never create these messages; they are a gift from us to you. Enjoy.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
structure | the structure for the message. The message will take ownership of the structure. | [transfer full]

#### Returns

The new application message.

MT safe.

[transfer full]

### gst_message_new_element ()

    GstMessage *
    gst_message_new_element (GstObject *src,
                             GstStructure *structure);

Create a new element-specific message. This is meant as a generic way of allowing one-way communication from an element to an application, for example "the firewire cable was unplugged". The format of the message should be documented in the element's documentation. The structure field can be `NULL`.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
structure | The structure for the message. The message will take ownership of the structure. | [transfer full]

#### Returns

The new element message.

MT safe.

[transfer full]

### gst_message_new_custom ()

    GstMessage *
    gst_message_new_custom (GstMessageType type,
                            GstObject *src,
                            GstStructure *structure);

Create a new custom-typed message. This can be used for anything not handled by other message-specific functions to pass a message to the app. The structure field can be `NULL`.

#### Parameters

type | The GstMessageType to distinguish messages |
src | The object originating the message. | [transfer none][allow-none]
structure | the structure for the message. The message will take ownership of the structure. | [transfer full][allow-none]

#### Returns

The new message.

MT safe.

[transfer full]

### gst_message_new_segment_start ()

    GstMessage *
    gst_message_new_segment_start (GstObject *src,
                                   GstFormat format,
                                   gint64 position);

Create a new segment message. This message is posted by elements that start playback of a segment as a result of a segment seek. This message is not received by the application but is used for maintenance reasons in container elements.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
format | The format of the position being played |
position | The position of the segment being played |

#### Returns

the new segment start message.

MT safe.

[transfer full]

### gst_message_parse_segment_start ()

    void
    gst_message_parse_segment_start (GstMessage *message,
                                     GstFormat *format,
                                     gint64 *position);

Extracts the position and format from the segment start message.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_SEGMENT_START. |
format | Result location for the format, or `NULL`. | [out][allow-none]
position | Result location for the position, or `NULL`. | [out][allow-none]

### gst_message_new_segment_done ()

    GstMessage *
    gst_message_new_segment_done (GstObject *src,
                                  GstFormat format,
                                  gint64 position);

Create a new segment done message. This message is posted by elements that finish playback of a segment as a result of a segment seek. This message is received by the application after all elements that posted a segment_start have posted the segment_done.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
format | The format of the position being done |
position | The position of the segment being done |

#### Returns

the new segment done message.

MT safe.

[transfer full]

### gst_message_parse_segment_done ()

    void
    gst_message_parse_segment_done (GstMessage *message,
                                    GstFormat *format,
                                    gint64 *position);

Extracts the position and format from the segment done message.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_SEGMENT_DONE. |
format | Result location for the format, or `NULL`. | [out][allow-none]
position | Result location for the position, or `NULL`. | [out][allow-none]

### gst_message_new_duration_changed ()

    GstMessage *
    gst_message_new_duration_changed (GstObject *src);

Create a new duration changed message. This message is posted by elements that know the duration of a stream when the duration changes. This message is received by bins and is used to calculate the total duration of a pipeline. Elements may post a duration message with a duration of GST_CLOCK_TIME_NONE to indicate that the duration has changed and the cached duration should be discarded. The new duration can then be retrieved via a query.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]

#### Returns

The new duration-changed message.

MT safe.

[transfer full]

### gst_message_new_latency ()

    GstMessage *
    gst_message_new_latency (GstObject *src);

This message can be posted by elements when their latency requirements have changed.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]

#### Returns

The new latency message.

MT safe.

[transfer full]

### gst_message_new_async_start ()

    GstMessage *
    gst_message_new_async_start (GstObject *src);

This message is posted by elements when they start an ASYNC state change.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]

#### Returns

The new async_start message.

MT safe.

[transfer full]

### gst_message_new_async_done ()

    GstMessage *
    gst_message_new_async_done (GstObject *src,
                                GstClockTime running_time);

The message is posted when elements completed an ASYNC state change. `running_time` contains the time of the desired running_time when this elements goes to PLAYING. A value of GST_CLOCK_TIME_NONE for `running_time` means that the element has no clock interaction and thus doesn't care about the running_time of the pipeline.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
running_time | the desired running_time |

#### Returns

The new async_done message.

MT safe.

[transfer full]

### gst_message_parse_async_done ()

    void
    gst_message_parse_async_done (GstMessage *message,
                                  GstClockTime *running_time);

Extract the running_time from the async_done message.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_ASYNC_DONE. |
running_time | Result location for the running_time or `NULL`. | [out][allow-none]

### gst_message_new_step_start ()

    GstMessage *
    gst_message_new_step_start (GstObject *src,
                                gboolean active,
                                GstFormat format,
                                guint64 amount,
                                gdouble rate,
                                gboolean flush,
                                gboolean intermediate);

This message is posted by elements when they accept or activate a new step event for `amount` in `format` .

`active` is set to `FALSE` when the element accepted the new step event and has queued it for execution in the streaming threads.

`active` is set to `TRUE` when the element has activated the step operation and is now ready to start executing the step in the streaming thread. After this message is emitted, the application can queue a new step operation in the element.

#### Parameters

src | The object originating the message. |
active | if the step is active or queued |
format | the format of `amount` |
amount | the amount of stepped data |
rate | the rate of the stepped amount |
flush | is this an flushing step |
intermediate | is this an intermediate step |

#### Returns

The new step_start message.

MT safe.

[transfer full]

### gst_message_parse_step_start ()

    void
    gst_message_parse_step_start (GstMessage *message,
                                  gboolean *active,
                                  GstFormat *format,
                                  guint64 *amount,
                                  gdouble *rate,
                                  gboolean *flush,
                                  gboolean *intermediate);

Extract the values from step_start message.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_STEP_DONE. |
active | result location for the active flag. | [out][allow-none]
format | result location for the format. | [out][allow-none]
amount | result location for the amount. | [out][allow-none]
rate | result location for the rate. | [out][allow-none]
flush | result location for the flush flag. | [out][allow-none]
intermediate | result location for the intermediate flag. | [out][allow-none]

### gst_message_new_qos ()

    GstMessage *
    gst_message_new_qos (GstObject *src,
                         gboolean live,
                         guint64 running_time,
                         guint64 stream_time,
                         guint64 timestamp,
                         guint64 duration);

A QOS message is posted on the bus whenever an element decides to drop a buffer because of QoS reasons or whenever it changes its processing strategy because of QoS reasons (quality adjustments such as processing at lower accuracy).

This message can be posted by an element that performs synchronisation against the clock (live) or it could be dropped by an element that performs QoS because of QOS events received from a downstream element (!live).

`running_time` , `stream_time` , `timestamp` , `duration` should be set to the respective running-time, stream-time, timestamp and duration of the (dropped) buffer that generated the QoS event. Values can be left to GST_CLOCK_TIME_NONE when unknown.

#### Parameters

src | The object originating the message. |
live | if the message was generated by a live element |
running_time | the running time of the buffer that generated the message |
stream_time | the stream time of the buffer that generated the message |
timestamp | the timestamps of the buffer that generated the message |
duration | the duration of the buffer that generated the message |

#### Returns

The new qos message.

MT safe.

[transfer full]

### gst_message_set_qos_values ()

    void
    gst_message_set_qos_values (GstMessage *message,
                                gint64 jitter,
                                gdouble proportion,
                                gint quality);

Set the QoS values that have been calculated/analysed from the QoS data

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_QOS. |
jitter | The difference of the running-time against the deadline. |
proportion | Long term prediction of the ideal rate relative to normal rate to get optimal quality. |
quality | An element dependent integer value that specifies the current quality level of the element. The default maximum quality is 1000000. |

### gst_message_set_qos_stats ()

    void
    gst_message_set_qos_stats (GstMessage *message,
                               GstFormat format,
                               guint64 processed,
                               guint64 dropped);

Set the QoS stats representing the history of the current continuous pipeline playback period.

When `format` is `GST_FORMAT_UNDEFINED` both `dropped` and `processed` are invalid. Values of -1 for either `processed` or `dropped` mean unknown values.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_QOS. |
format | Units of the 'processed' and 'dropped' fields. Video sinks and video filters will use GST_FORMAT_BUFFERS (frames). Audio sinks and audio filters will likely use GST_FORMAT_DEFAULT (samples). |
processed | Total number of units correctly processed since the last state change to READY or a flushing operation. |
dropped | Total number of units dropped since the last state change to READY or a flushing operation. |

### gst_message_parse_qos ()

    void
    gst_message_parse_qos (GstMessage *message,
                           gboolean *live,
                           guint64 *running_time,
                           guint64 *stream_time,
                           guint64 *timestamp,
                           guint64 *duration);

Extract the timestamps and live status from the QoS message.

The returned values give the running_time, stream_time, timestamp and duration of the dropped buffer. Values of GST_CLOCK_TIME_NONE mean unknown values.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_QOS. |
live | if the message was generated by a live element. | [out][allow-none]
running_time | the running time of the buffer that generated the message. | [out][allow-none]
stream_time | the stream time of the buffer that generated the message. | [out][allow-none]
timestamp | the timestamps of the buffer that generated the message. | [out][allow-none]
duration | the duration of the buffer that generated the message. | [out][allow-none]

### gst_message_parse_qos_values ()

    void
    gst_message_parse_qos_values (GstMessage *message,
                                  gint64 *jitter,
                                  gdouble *proportion,
                                  gint *quality);

Extract the QoS values that have been calculated/analysed from the QoS data

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_QOS. |
jitter | The difference of the running-time against the deadline. | [out][allow-none]
proportion | Long term prediction of the ideal rate relative to normal rate to get optimal quality. | [out][allow-none]
quality | An element dependent integer value that specifies the current quality level of the element. The default maximum quality is 1000000. | [out][allow-none]

### gst_message_parse_qos_stats ()

    void
    gst_message_parse_qos_stats (GstMessage *message,
                                 GstFormat *format,
                                 guint64 *processed,
                                 guint64 *dropped);

Extract the QoS stats representing the history of the current continuous pipeline playback period.

When `format` is `GST_FORMAT_UNDEFINED` both `dropped` and `processed` are invalid. Values of -1 for either `processed` or `dropped` mean unknown values.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_QOS. |
format | Units of the 'processed' and 'dropped' fields. Video sinks and video filters will use GST_FORMAT_BUFFERS (frames). Audio sinks and audio filters will likely use GST_FORMAT_DEFAULT (samples). | [out][allow-none]
processed | Total number of units correctly processed since the last state change to READY or a flushing operation. | [out][allow-none]
dropped | Total number of units dropped since the last state change to READY or a flushing operation. | [out][allow-none]

### gst_message_new_toc ()

    GstMessage *
    gst_message_new_toc (GstObject *src,
                         GstToc *toc,
                         gboolean updated);

Create a new TOC message. The message is posted by elements that discovered or updated a TOC.

#### Parameters

src | the object originating the message. |
toc | GstToc structure for the message. | [transfer none]
updated | whether TOC was updated or not. |

#### Returns

a new TOC message.

MT safe.

[transfer full]

### gst_message_parse_toc ()

    void
    gst_message_parse_toc (GstMessage *message,
                           GstToc **toc,
                           gboolean *updated);

Extract the TOC from the GstMessage. The TOC returned in the output argument is a copy; the caller must free it with `gst_toc_unref()` when done.

MT safe.

#### Parameters

message | a valid GstMessage of type GST_MESSAGE_TOC. |
toc | return location for the TOC. | [out][transfer full]
updated | return location for the updated flag. | [out]

### gst_message_new_reset_time ()

    GstMessage *
    gst_message_new_reset_time (GstObject *src,
                                GstClockTime running_time);

This message is posted when the pipeline running-time should be reset to `running_time` , like after a flushing seek.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
running_time | the requested running-time |

#### Returns

The new reset_time message.

MT safe.

[transfer full]

### gst_message_parse_reset_time ()

    void
    gst_message_parse_reset_time (GstMessage *message,
                                  GstClockTime *running_time);

Extract the running-time from the RESET_TIME message.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_RESET_TIME. |
running_time | Result location for the running_time or `NULL`. | [out][allow-none]

### gst_message_new_stream_start ()

    GstMessage *
    gst_message_new_stream_start (GstObject *src);

Create a new stream_start message. This message is generated and posted in the sink elements of a GstBin. The bin will only forward the STREAM_START message to the application if all sinks have posted an STREAM_START message.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]

#### Returns

The new stream_start message.

MT safe.

[transfer full]

### gst_message_set_group_id ()

    void
    gst_message_set_group_id (GstMessage *message,
                              guint group_id);

Sets the group id on the stream-start message.

All streams that have the same group id are supposed to be played together, i.e. all streams inside a container file should have the same group id but different stream ids. The group id should change each time the stream is started, resulting in different group ids each time a file is played for example.

MT safe.

#### Parameters

message | the message |
group_id | the group id |

Since: 1.2

### gst_message_parse_group_id ()

    gboolean
    gst_message_parse_group_id (GstMessage *message,
                                guint *group_id);

Extract the group from the STREAM_START message.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_STREAM_START. |
group_id | Result location for the group id or `NULL`. | [out][allow-none]

#### Returns

`TRUE` if the message had a group id set, `FALSE` otherwise

MT safe.

Since: 1.2

### gst_message_new_structure_change ()

    GstMessage *
    gst_message_new_structure_change (GstObject *src,
                                      GstStructureChangeType type,
                                      GstElement *owner,
                                      gboolean busy);

Create a new structure change message. This message is posted when the structure of a pipeline is in the process of being changed, for example when pads are linked or unlinked.

`src` should be the sinkpad that unlinked or linked.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
type | The change type. |
owner | The owner element of `src` . | [transfer none]
busy | Whether the structure change is busy. |

#### Returns

the new structure change message.

MT safe.

[transfer full]

### gst_message_parse_structure_change ()

    void
    gst_message_parse_structure_change (GstMessage *message,
                                        GstStructureChangeType *type,
                                        GstElement **owner,
                                        gboolean *busy);

Extracts the change type and completion status from the GstMessage.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_STRUCTURE_CHANGE. |
type | A pointer to hold the change type. | [out]
owner | The owner element of the message source. | [out][allow-none][transfer none]
busy | a pointer to hold whether the change is in progress or has been completed. | [out][allow-none]

### gst_message_new_request_state ()

    GstMessage *
    gst_message_new_request_state (GstObject *src,
                                   GstState state);

This message can be posted by elements when they want to have their state changed. A typical use case would be an audio server that wants to pause the pipeline because a higher priority stream is being played.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
state | The new requested state |

#### Returns

the new request state message.

MT safe.

[transfer full]

### gst_message_parse_request_state ()

    void
    gst_message_parse_request_state (GstMessage *message,
                                     GstState *state);

Extract the requested state from the request_state message.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_REQUEST_STATE. |
state | Result location for the requested state or `NULL`. | [out][allow-none]

### gst_message_new_stream_status ()

    GstMessage *
    gst_message_new_stream_status (GstObject *src,
                                   GstStreamStatusType type,
                                   GstElement *owner);

Create a new stream status message. This message is posted when a streaming thread is created/destroyed or when the state changed.

#### Parameters

src | The object originating the message. |
type | The stream status type. |
owner | the owner element of `src` . | [transfer none]

#### Returns

the new stream status message.

MT safe.

[transfer full]

### gst_message_parse_stream_status ()

    void
    gst_message_parse_stream_status (GstMessage *message,
                                     GstStreamStatusType *type,
                                     GstElement **owner);

Extracts the stream status type and owner the GstMessage. The returned owner remains valid for as long as the reference to `message` is valid and should thus not be unreffed.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_STREAM_STATUS. |
type | A pointer to hold the status type. | [out]
owner | The owner element of the message source. | [out][transfer none]

### gst_message_set_stream_status_object ()

    void
    gst_message_set_stream_status_object (GstMessage *message,
                                          const GValue *object);

Configures the object handling the streaming thread. This is usually a GstTask object but other objects might be added in the future.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_STREAM_STATUS. |
object | the object controlling the streaming |

### gst_message_get_stream_status_object ()

    const GValue *
    gst_message_get_stream_status_object (GstMessage *message);

Extracts the object managing the streaming thread from `message` .

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_STREAM_STATUS. |

#### Returns

a GValue containing the object that manages the streaming thread. This object is usually of type GstTask but other types can be added in the future. The object remains valid as long as `message` is valid.

### gst_message_new_progress ()

    GstMessage *
    gst_message_new_progress (GstObject *src,
                              GstProgressType type,
                              const gchar *code,
                              const gchar *text);

Progress messages are posted by elements when they use an asynchronous task to perform actions triggered by a state change.

`code` contains a well defined string describing the action. `test` should contain a user visible string detailing the current action.

#### Parameters

src | The object originating the message. |
type | a GstProgressType |
code | a progress code |
text | free, user visible text describing the progress |

#### Returns

The new qos message.

[transfer full]

### gst_message_parse_progress ()

    void
    gst_message_parse_progress (GstMessage *message,
                                GstProgressType *type,
                                gchar **code,
                                gchar **text);

Parses the progress `type` , `code` and `text` .

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_PROGRESS. |
type | location for the type. | [out][allow-none]
code | location for the code. | [out][allow-none][transfer full]
text | location for the text. | [out][allow-none][transfer full]

### gst_message_new_need_context ()

    GstMessage *
    gst_message_new_need_context (GstObject *src,
                                  const gchar *context_type);

This message is posted when an element needs a specific GstContext.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
context_type | The context type that is needed |

#### Returns

The new need-context message.

MT safe.

[transfer full]

Since: 1.2

### gst_message_parse_context_type ()

    gboolean
    gst_message_parse_context_type (GstMessage *message,
                                    const gchar **context_type);

Parse a context type from an existing GST_MESSAGE_NEED_CONTEXT message.

#### Parameters

message | a GST_MESSAGE_NEED_CONTEXT type message |
context_type | the context type, or `NULL`. | [out][allow-none]

#### Returns

a gboolean indicating if the parsing succeeded.

Since: 1.2

### gst_message_new_have_context ()

    GstMessage *
    gst_message_new_have_context (GstObject *src,
                                  GstContext *context);

This message is posted when an element has a new local GstContext.

#### Parameters

src | The object originating the message. | [transfer none][allow-none]
context | the context. | [transfer full]

#### Returns

The new have-context message.

MT safe.

[transfer full]

Since: 1.2

### gst_message_parse_have_context ()

    void
    gst_message_parse_have_context (GstMessage *message,
                                    GstContext **context);

Extract the context from the HAVE_CONTEXT message.

MT safe.

#### Parameters

message | A valid GstMessage of type GST_MESSAGE_HAVE_CONTEXT. |
context | Result location for the context or `NULL`. | [out][transfer full][allow-none]

Since: 1.2

### gst_message_new_device_added ()

    GstMessage *
    gst_message_new_device_added (GstObject *src,
                                  GstDevice *device);

Creates a new device-added message. The device-added message is produced by GstDeviceProvider or a GstDeviceMonitor. They announce the appearance of monitored devices.

#### Parameters

src | The GstObject that created the message |
device | The new GstDevice. | [transfer none]

#### Returns

a newly allocated GstMessage

Since: 1.4

### gst_message_new_device_removed ()

    GstMessage *
    gst_message_new_device_removed (GstObject *src,
                                    GstDevice *device);

Creates a new device-removed message. The device-removed message is produced by GstDeviceProvider or a GstDeviceMonitor. They announce the disappearance of monitored devices.

#### Parameters

src | The GstObject that created the message |
device | The removed GstDevice. | [transfer none]

#### Returns

a newly allocated GstMessage

Since: 1.4

### gst_message_parse_device_added ()

    void
    gst_message_parse_device_added (GstMessage *message,
                                    GstDevice **device);

Parses a device-added message. The device-added message is produced by GstDeviceProvider or a GstDeviceMonitor. It announces the appearance of monitored devices.

#### Parameters

message | a GstMessage of type `GST_MESSAGE_DEVICE_ADDED` |
device | A location where to store a pointer to the new GstDevice, or `NULL`. | [out][allow-none][transfer none]

Since: 1.4

### gst_message_parse_device_removed ()

    void
    gst_message_parse_device_removed (GstMessage *message,
                                      GstDevice **device);

Parses a device-removed message. The device-removed message is produced by GstDeviceProvider or a GstDeviceMonitor. It announces the disappearance of monitored devices.

#### Parameters

message | a GstMessage of type `GST_MESSAGE_DEVICE_REMOVED` |
device | A location where to store a pointer to the removed GstDevice, or `NULL`. | [out][allow-none][transfer none]

Since: 1.4

## Types and Values

### struct GstMessage

    struct GstMessage {
      GstMiniObject   mini_object;

      GstMessageType  type;
      guint64         timestamp;
      GstObject      *src;
      guint32         seqnum;
    };

A GstMessage.

#### Members

GstMiniObject `mini_object`; | the parent structure |
GstMessageType `type`; | the GstMessageType of the message |
guint64 `timestamp`; | the timestamp of the message |
GstObject *`src`; | the src of the message |
guint32 `seqnum`; | the sequence number of the message |

### enum GstMessageType

The different message types that are available.

#### Members

GST_MESSAGE_UNKNOWN | an undefined message |
GST_MESSAGE_EOS | end-of-stream reached in a pipeline. The application will only receive this message in the PLAYING state and every time it sets a pipeline to PLAYING that is in the EOS state. The application can perform a flushing seek in the pipeline, which will undo the EOS state again. |
GST_MESSAGE_ERROR | an error occurred. When the application receives an error message it should stop playback of the pipeline and not assume that more data will be played. |
GST_MESSAGE_WARNING | a warning occurred. |
GST_MESSAGE_INFO | an info message occurred |
GST_MESSAGE_TAG | a tag was found. |
GST_MESSAGE_BUFFERING | the pipeline is buffering. When the application receives a buffering message in the PLAYING state for a non-live pipeline it must PAUSE the pipeline until the buffering completes, when the percentage field in the message is 100%. For live pipelines, no action must be performed and the buffering percentage can be used to inform the user about the progress. |
GST_MESSAGE_STATE_CHANGED | a state change happened |
GST_MESSAGE_STATE_DIRTY | an element changed state in a streaming thread. This message is deprecated. |
GST_MESSAGE_STEP_DONE | a stepping operation finished. |
GST_MESSAGE_CLOCK_PROVIDE | an element notifies its capability of providing a clock. This message is used internally and never forwarded to the application. |
GST_MESSAGE_CLOCK_LOST | The current clock as selected by the pipeline became unusable. The pipeline will select a new clock on the next PLAYING state change. The application should set the pipeline to PAUSED and back to PLAYING when this message is received. |
GST_MESSAGE_NEW_CLOCK | a new clock was selected in the pipeline. |
GST_MESSAGE_STRUCTURE_CHANGE | the structure of the pipeline changed. This message is used internally and never forwarded to the application. |
GST_MESSAGE_STREAM_STATUS | status about a stream, emitted when it starts, stops, errors, etc.. |
GST_MESSAGE_APPLICATION | message posted by the application, possibly via an application-specific element. |
GST_MESSAGE_ELEMENT | element-specific message, see the specific element's documentation |
GST_MESSAGE_SEGMENT_START | pipeline started playback of a segment. This message is used internally and never forwarded to the application. |
GST_MESSAGE_SEGMENT_DONE | pipeline completed playback of a segment. This message is forwarded to the application after all elements that posted `GST_MESSAGE_SEGMENT_START` posted a GST_MESSAGE_SEGMENT_DONE message. |
GST_MESSAGE_DURATION_CHANGED | The duration of a pipeline changed. The application can get the new duration with a duration query. |
GST_MESSAGE_LATENCY | Posted by elements when their latency changes. The application should recalculate and distribute a new latency. |
GST_MESSAGE_ASYNC_START | Posted by elements when they start an ASYNC GstStateChange. This message is not forwarded to the application but is used internally. |
GST_MESSAGE_ASYNC_DONE | Posted by elements when they complete an ASYNC GstStateChange. The application will only receive this message from the toplevel pipeline. |
GST_MESSAGE_REQUEST_STATE | Posted by elements when they want the pipeline to change state. This message is a suggestion to the application which can decide to perform the state change on (part of) the pipeline. |
GST_MESSAGE_STEP_START | A stepping operation was started. |
GST_MESSAGE_QOS | A buffer was dropped or an element changed its processing strategy for Quality of Service reasons. |
GST_MESSAGE_PROGRESS | A progress message. |
GST_MESSAGE_TOC | A new table of contents (TOC) was found or previously found TOC was updated. |
GST_MESSAGE_RESET_TIME | Message to request resetting the pipeline's running time from the pipeline. This is an internal message which applications will likely never receive. |
GST_MESSAGE_STREAM_START | Message indicating start of a new stream. Useful e.g. when using playbin in gapless playback mode, to get notified when the next title actually starts playing (which will be some time after the URI for the next title has been set). |
GST_MESSAGE_NEED_CONTEXT | Message indicating that an element wants a specific context (Since 1.2) |
GST_MESSAGE_HAVE_CONTEXT | Message indicating that an element created a context (Since 1.2) |
GST_MESSAGE_EXTENDED | Message is an extended message type (see below). These extended message IDs can't be used directly with mask-based API like `gst_bus_poll()` or `gst_bus_timed_pop_filtered()`, but you can still filter for GST_MESSAGE_EXTENDED and then check the result for the specific type. (Since 1.4) |
GST_MESSAGE_DEVICE_ADDED | Message indicating a GstDevice was added to a GstDeviceProvider (Since 1.4) |
GST_MESSAGE_DEVICE_REMOVED | Message indicating a GstDevice was removed from a GstDeviceProvider (Since 1.4) |
GST_MESSAGE_ANY | mask for all of the above messages. |

### enum GstStructureChangeType

The type of a `GST_MESSAGE_STRUCTURE_CHANGE`.

#### Members

GST_STRUCTURE_CHANGE_TYPE_PAD_LINK | Pad linking is starting or done. |
GST_STRUCTURE_CHANGE_TYPE_PAD_UNLINK | Pad unlinking is starting or done. |

### enum GstStreamStatusType

The type of a `GST_MESSAGE_STREAM_STATUS`. The stream status messages inform the application of new streaming threads and their status.

#### Members

GST_STREAM_STATUS_TYPE_CREATE | A new thread need to be created. |
GST_STREAM_STATUS_TYPE_ENTER | a thread entered its loop function |
GST_STREAM_STATUS_TYPE_LEAVE | a thread left its loop function |
GST_STREAM_STATUS_TYPE_DESTROY | a thread is destroyed |
GST_STREAM_STATUS_TYPE_START | a thread is started |
GST_STREAM_STATUS_TYPE_PAUSE | a thread is paused |
GST_STREAM_STATUS_TYPE_STOP | a thread is stopped |

### enum GstProgressType

The type of a `GST_MESSAGE_PROGRESS`. The progress messages inform the application of the status of asynchronous tasks.

#### Members

GST_PROGRESS_TYPE_START | A new task started. |
GST_PROGRESS_TYPE_CONTINUE | A task completed and a new one continues. |
GST_PROGRESS_TYPE_COMPLETE | A task completed. |
GST_PROGRESS_TYPE_CANCELED | A task was canceled. |
GST_PROGRESS_TYPE_ERROR | A task caused an error. An error message is also posted on the bus. |

## See Also

GstBus, GstMiniObject, GstElement