#11576: amrwb constant bitrate wrong time estimation
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Reporter: LanMarc77 | Owner: (none)
Type: defect | Status: new
Priority: important | Component: avcodec
Version: unspecified | Resolution:
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by LanMarc77):
Using this file https://github.com/anars/blank-audio/blob/master/30
-minutes-of-silence.mp3 and the static builds from here:
https://johnvansickle.com/ffmpeg/ I could verify that ffmpeg 4.4.1 and
7.0.2 encode the 30minutes silence using -acodec amr_wb -ar 16000 -ac 1
-ab 23850 into the exact same file. sha256sums match.
But ffprobe from 4.4.1 shows the correct 00:30:00.30 while version 7.0.2
shows 00:31:01.33.
Judging by these numbers it seems always 3.3% too long.
This pretty much aligns with the frame overhead. One frame for the above
amr-wb bitsize is 61bytes containing 2bytes frame overhead and 59bytes
data. 61/59 also boils down to 3.3%.
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Ticket URL: <https://trac.ffmpeg.org/ticket/11576#comment:1>
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