scaletempo: GStreamer Good Plugins 1.0 Plugins Reference Manual

## scaletempo scaletempo |

## Properties

gdouble | overlap | Read / Write
gdouble | rate | Read
guint | search | Read / Write
guint | stride | Read / Write

## Types and Values

struct | GstScaletempo

## Object Hierarchy

        GObject
        ╰── GInitiallyUnowned
            ╰── GstObject
                ╰── GstElement
                    ╰── GstBaseTransform
                        ╰── GstScaletempo

## 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/Audio

### 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)F64LE, 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)F64LE, rate=(int)[ 1, 2147483647 ], channels=(int)[ 1, 2147483647 ]
| audio/x-raw, format=(string)S16LE, rate=(int)[ 1, 2147483647 ], channels=(int)[ 1, 2147483647 ]

## Functions

## Types and Values

### struct GstScaletempo

    struct GstScaletempo;

## Property Details

### The `“overlap”` property

      “overlap”                  gdouble

Percentage of stride to overlap.

Flags: Read / Write

Allowed values: [0,1]

Default value: 0.2

### The `“rate”` property

      “rate”                     gdouble

Current playback rate.

Flags: Read

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

Default value: 1

### The `“search”` property

      “search”                   guint

Length in milliseconds to search for best overlap position.

Flags: Read / Write

Allowed values: <= 500

Default value: 14

### The `“stride”` property

      “stride”                   guint

Length in milliseconds to output each stride.

Flags: Read / Write

Allowed values: [1,5000]

Default value: 30