scaletempo

scaletempo — Sync audio tempo with playback rate

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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2
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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 ]

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