Change playback rate (video + audio only use cases)

[viacheslavokolitiy]

Hello guys. Is it possible to change playback rate of video track e.g play faster or play slow ?

[runningcode]

+1 this would be very useful!

[ojw28]

To clarify, do you mean with audio (sped up but corrected to still be at the correct pitch) or without?

[viacheslavokolitiy]

@ojw28 with audio

[ojw28]

This isn't something that's supported currently. It is something you could potentially do yourself, either by extending MediaCodecAudioTrackRenderer, or by creating your own audio renderer to use instead of the one provided by the library.

Basically, you'd need to do some adjustment in your extension to get the audio playing at the desired rate (and reporting time as progressing at that rate). This may involve pitch correction. The video track will follow the speed of the audio track (provided it can decode fast enough).

[lsjwzh]

+1

[shukob]

+1

[vishwa-vyom]

+1

[emakovsky]

+1

[shukob]

I need this functionality for my current project and used libSonic to change audio speed as in Prestissimo's Track.java.

Changing reported time part requires multiplying result of framesToDurationUs and durationUsToFrame, and conditions regarding MIN_PLAYHEAD_OFFSET_SAMPLE_INTERVAL_US and MIN_TIMESTAMP_SAMPLE_INTERVAL_US by current speed on MediaCodecAudioTrackRenderer.

I think I should multiply other Usec numbers in both renderers to work without flaw.
As I had to comment out dropOutputBuffer section in processOutputBuffer on MediaCodecVideoTrackRenderer to correctly refresh video frame.

Also
" // TODO: Don't bother doing this once [redacted] is fixed.
// Work out how many bytes we can write without the risk of blocking."
part in processOutputBuffer may need some edit when actually written byte length differs from bytesToWrite because of changing pitch?

[evanhalley]

@skonb Can you provide more details. I'm attempting to incorporate variable speed playback in MediaCodecAudioTrackRenderer (subclassed it, overriding the processOutputBuffer function) . I've done some of it (passing the byte buffer into and out of sonic), but even as a speed and pitch of 1.0f, it's really static-ky. Thanks!

[shukob]

@emuneee I have uploaded current implementation here. That is based on Sep 8 version of ExoPlayer so may not work with the latest one.
It contains bug that getCurrentPositionUs returns larger/smaller value than expected if speed is up/down.

[kboyarshinov]

+1

[kboyarshinov]

@skonb Have you tried to update your implementation to latest ExoPlayer version? Thanks!