AssumeSampleRate
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==== Examples ==== | ==== Examples ==== | ||
| − | <div {{BoxWidthIndent| | + | * Fix an audio sync problem: |
| − | + | <div {{BoxWidthIndent|56|1}} > | |
[[AviSource]]("video_audio.avi") | [[AviSource]]("video_audio.avi") | ||
| + | # Let's say that this clip loses audio sync: | ||
| + | # after 55 minutes the audio is behind by 200 milliseconds. | ||
| − | # Play video at half speed: | + | dur = 3300.0 # total duration in seconds (55 minutes x 60) |
| + | adj = -0.200 # correction needed (decrease audio duration by 200 msec) | ||
| + | Ar = [[Clip_properties|AudioRate]] # original audio sample rate | ||
| + | |||
| + | # Adjust audio duration: | ||
| + | '''AssumeSampleRate'''([[Internal_functions#Round|Round]](dur / (dur+adj) * Ar)) | ||
| + | |||
| + | # Restore original sample rate while retaining new duration; | ||
| + | # this step is may be skipped if you don't mind a slightly nonstandard sample rate. | ||
| + | [[ResampleAudio]](Ar) | ||
| + | |||
| + | # Video and audio are now in sync. | ||
| + | </div> | ||
| + | |||
| + | * Play video and audio at half speed: | ||
| + | <div {{BoxWidthIndent|56|1}} > | ||
| + | [[AviSource]]("video_audio.avi") | ||
| + | |||
| + | # Play video at half speed: audio will be out of sync | ||
[[AssumeFPS]]([[Clip_properties|FrameRate]]/2) | [[AssumeFPS]]([[Clip_properties|FrameRate]]/2) | ||
| − | # Play audio at half speed: | + | # Play audio at half speed: (pitch will be lowered by an [[wikipedia:Octave|octave]]) |
| − | AssumeSampleRate([[Clip_properties|AudioRate]]/2) | + | '''AssumeSampleRate'''([[Clip_properties|AudioRate]]/2) |
# Video and audio are now in sync. | # Video and audio are now in sync. | ||
| + | # Equivalent to calling [[AssumeFPS]](..., sync_audio=true) (see below) | ||
</div> | </div> | ||
Revision as of 22:52, 17 May 2016
AssumeSampleRate(clip clip, int samplerate)
Changes the sample rate of the current clip without changing the number of samples.
- This changes the 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: # after 55 minutes the audio is behind by 200 milliseconds. dur = 3300.0 # total duration in seconds (55 minutes x 60) adj = -0.200 # correction needed (decrease audio duration by 200 msec) Ar = AudioRate # original audio sample rate # Adjust audio duration: AssumeSampleRate(Round(dur / (dur+adj) * Ar)) # Restore original sample rate while retaining new duration; # this step is may be skipped if you don't mind a slightly nonstandard sample rate. ResampleAudio(Ar) # Video and audio are now in sync.
- 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.
