AssumeSampleRate

AviSynth+
Up-to-date documentation: https://avisynthplus.readthedocs.io

AssumeSampleRate(clip clip, int samplerate)

Changes the sample rate of the current clip without changing the number of samples.

This changes the sample rate, pitch, playback speed and running time of the audio.

It will also affect synchronization with the video.

Examples

• Fix an audio sync problem:

AviSource("video_audio.avi")
# Let's say that this clip loses audio sync:
# by the end, the audio is behind by 200 milliseconds.

Ar  = AudioRate # original audio sample rate
dur = AudioDuration  # total duration in seconds
adj = -0.200    # correction needed (decrease audio duration by 200 msec)

# Adjust audio duration:
AssumeSampleRate(Round(dur / (dur+adj) * Ar))

# Video and audio are now in sync.

# (optional) restore original sample rate.
#ResampleAudio(Ar) 

• Play video and audio at half speed:

AviSource("video_audio.avi")

# Play video at half speed: audio will be out of sync 
AssumeFPS(FrameRate/2)

# Play audio at half speed: (pitch will be lowered by an octave)
AssumeSampleRate(AudioRate/2)  

# Video and audio are now in sync.
# Equivalent to calling AssumeFPS(..., sync_audio=true) (see below)

See Also

• AssumeFPS: sync_audio

If true, the audio sample rate is changed by the same amount; the pitch of the resulting audio is shifted.

If false (the default), the audio is unchanged; this means the audio will lose synchronization over time.