[FFmpeg-user] ffprobe -show_frames and coded_picture_number

Pavel Koshevoy pkoshevoy at gmail.com
Thu Aug 15 04:01:09 CEST 2013

On 8/14/13 6:37 PM, thljcl wrote:
> It’s technically impossible to change the playback speed of audio without
> affecting pitch, length, or other issues due to round-off
> errors/quantization.

atempo implements WSOLA algorithm.  It's not resampling -- it's 
cut-shift-align-overlap-blend.  Its effect is to change the duration of 
the track by duplicating or de-duplicating some repeating patterns in 
the audio waveform.  For voice-only audio its artifacts are quiet 
unnoticeable even at relatively large tempo changes.  I've tested it by 
playing music at 80% tempo and found the sound acceptable.  Higher tempo 
artifacts are even harder to notice. Going from 24 to 25 fps is about 
4.17% tempo change, well within the range where atempo was tested.


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