scaletempo

## scaletempo scaletempo — Sync audio tempo with playback rate |

## Synopsis

    struct              GstScaletempo;

## Object Hierarchy

      GObject
       +----GInitiallyUnowned
             +----GstObject
                   +----GstElement
                         +----GstBaseTransform
                               +----GstScaletempo

## Properties

      "overlap"                  gdouble               : Read / Write
      "rate"                     gdouble               : Read
      "search"                   guint                 : Read / Write
      "stride"                   guint                 : Read / Write

## Description

Scale tempo while maintaining pitch (WSOLA-like technique with cross correlation) Inspired by SoundTouch library by Olli Parviainen

Use Sceletempo to apply playback rates without the chipmunk effect.

### Example pipelines

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    filesrc location=media.ext ! decodebin name=d \
        d. ! queue ! audioconvert ! audioresample ! scaletempo ! audioconvert ! audioresample ! autoaudiosink \
        d. ! queue ! videoconvert ! autovideosink

OR

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    playbin uri=... audio_sink="scaletempo ! audioconvert ! audioresample ! autoaudiosink"

When an application sends a seek event with rate != 1.0, Scaletempo applies the rate change by scaling the tempo without scaling the pitch.

Scaletempo works by producing audio in constant sized chunks ("stride") but consuming chunks proportional to the playback rate.

Scaletempo then smooths the output by blending the end of one stride with the next ("overlap").

Scaletempo smooths the overlap further by searching within the input buffer for the best overlap position. Scaletempo uses a statistical cross correlation (roughly a dot-product). Scaletempo consumes most of its CPU cycles here. One can use the "search" propery to tune how far the algoritm looks.

## Synopsis

### Element Information

plugin | audiofx
author | Rov Juvano <rovjuvano@users.sourceforge.net>
class | Filter/Effect/Rate

### Element Pads

name | sink
direction | sink
presence | always
details | audio/x-raw, format=(string)F32LE, rate=(int)[ 1, 2147483647 ], channels=(int)[ 1, 2147483647 ]
| audio/x-raw, format=(string)S16LE, rate=(int)[ 1, 2147483647 ], channels=(int)[ 1, 2147483647 ]

name | src
direction | source
presence | always
details | audio/x-raw, format=(string)F32LE, rate=(int)[ 1, 2147483647 ], channels=(int)[ 1, 2147483647 ]
| audio/x-raw, format=(string)S16LE, rate=(int)[ 1, 2147483647 ], channels=(int)[ 1, 2147483647 ]

## Details

### struct GstScaletempo

    struct GstScaletempo;

## Property Details

### The `"overlap"` property

      "overlap"                  gdouble               : Read / Write

Percentage of stride to overlap.

Allowed values: [0,1]

Default value: 0.2

### The `"rate"` property

      "rate"                     gdouble               : Read

Current playback rate.

Allowed values: [-2.14748e+09,2.14748e+09]

Default value: 1

### The `"search"` property

      "search"                   guint                 : Read / Write

Length in milliseconds to search for best overlap position.

Allowed values: <= 500

Default value: 14

### The `"stride"` property

      "stride"                   guint                 : Read / Write

Length in milliseconds to output each stride.

Allowed values: [1,5000]

Default value: 30