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