[FFmpeg-trac] #2484(avfilter:new): atempo - low accuracy

[FFmpeg]

#2484: atempo - low accuracy
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             Reporter:  bars        |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avfilter
              Version:  git-master  |               Resolution:
             Keywords:  atempo      |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Comment (by bars):

 Replying to [comment:1 cehoyos]:
 > I tested the following - could you confirm if this is the problem you
 are seeing?
 > Encoding 24000 seconds (6:40:00) of audio with 48kHz:
 > Slowing audio down as proposed by you (6:57:05), the output size is ~1.5
 seconds off for seven hours, indicating noticeable A/V desync for a two-
 hour movie (iiuc)
 > {{{
 > $ ffmpeg -i out24000.wav -af "atempo=24000/25025" out25025.wav
 > ffmpeg version N-52268-g42bcc40 Copyright (c) 2000-2013 the FFmpeg
 developers
 ...
 > size= 2346232kB time=06:57:06.47 bitrate= 768.0kbits/s
 > }}}
 Yes, the problem in this. For 6:40:00.00 correctly 06:57:05.00 (PAL->NTSC)
 A/V desync ~1470ms if duration=06:40:00
 A/V desync ~440ms for a two-hour movie (440ms this much!)

 P.S.
 24000/25025 = (24000/1001)/25 = 0.959040959041

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2484#comment:2>
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