#10878: Muxing PCM_S24LE Audio Into MP4 Incorrectly Marked as 16-Bit
-------------------------------------+-------------------------------------
Reporter: | Owner: (none)
HyperStryker |
Type: defect | Status: new
Priority: important | Component:
| undetermined
Version: git-master | Resolution:
Keywords: pcm_s24le | Blocked By:
mp4 wav mov muxing ipcm |
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
Description changed by HyperStryker:
Old description:
> Summary of the bug:
> When muxing an H264-encoded video in a .MOV container with a .WAV file
> containing PCM_S24LE audio to an .MP4 container (discarding original
> video audio), the resulting file purportedly contains PCM_S24LE audio,
> but is incorrectly marked as 16-bit when checking the resulting .MP4 file
> in Mediainfo:
> {{{
> Audio
> ID : 2
> Format : PCM
> Format settings : Little / Signed
> Codec ID : ipcm
> Duration : 56 min 5 s
> Bit rate mode : Constant
> Bit rate : 1 536 kb/s
> Maximum bit rate : 2 304 kb/s
> Channel(s) : 2 channels
> Channel layout : L R
> Sampling rate : 48.0 kHz
> Bit depth : 16 bits
> Stream size : 924 MiB (8%)
> Default : Yes
> Alternate group : 1
> }}}
> FFmpeg in the command line shows the resulting audio still in the
> PCM_S24LE format when muxing (using an PCM_S24LE audio-only .MOV file
> instead of .WAV, made no practical difference):
> {{{
> Stream #0:1(eng): Audio: pcm_s24le (ipcm / 0x6D637069), 48000 Hz, stereo,
> s32 (24 bit), 2304 kb/s (default)
> Metadata:
> creation_time : 2024-02-21T04:54:45.000000Z
> handler_name : Apple Sound Media Handler
> vendor_id :
> timecode : 00:00:00:00
> }}}
> Further, when extracting/stream-copying the audio from the .MP4 file back
> into a .WAV file, FFmpeg notes:
> {{{
> [wav @ 000002532f935a80] requested bits_per_coded_sample (16) and
> actually stored (24) differ
> }}}
> This lined up with me checking the same .MP4 file in Adobe Audition,
> which reported the file as containing 24-bit audio instead of 16-bit.
>
> How to reproduce:
> Muxing .MOV and .WAV to .MP4
> {{{
> ffmpeg -i in1.mov -i in2.wav -map 0:v -map 1:a -c copy out.mp4
> }}}
> Stream copying back to .WAV
> {{{
> ffmpeg -i out.mp4 -map 0:a -c copy out2.wav
> }}}
New description:
Summary of the bug:
When muxing an H264-encoded video in a .MOV container with a .WAV file
containing PCM_S24LE audio to an .MP4 container (discarding original video
audio), the resulting file purportedly contains PCM_S24LE audio, but is
incorrectly marked as 16-bit when checking the resulting .MP4 file in
Mediainfo:
{{{
Audio
ID : 2
Format : PCM
Format settings : Little / Signed
Codec ID : ipcm
Duration : 56 min 5 s
Bit rate mode : Constant
Bit rate : 1 536 kb/s
Maximum bit rate : 2 304 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Bit depth : 16 bits
Stream size : 924 MiB (8%)
Default : Yes
Alternate group : 1
}}}
FFmpeg in the command line shows the resulting audio still in the
PCM_S24LE format when muxing (using an PCM_S24LE audio-only .MOV file
instead of .WAV, made no practical difference):
{{{
Stream #0:1(eng): Audio: pcm_s24le (ipcm / 0x6D637069), 48000 Hz, stereo,
s32 (24 bit), 2304 kb/s (default)
Metadata:
creation_time : 2024-02-21T04:54:45.000000Z
handler_name : Apple Sound Media Handler
vendor_id :
timecode : 00:00:00:00
}}}
Further, to verify it was FFmpeg and not Mediainfo, when extracting
/stream-copying the audio from the .MP4 file back into a .WAV file, FFmpeg
notes:
{{{
[wav @ 000002532f935a80] requested bits_per_coded_sample (16) and actually
stored (24) differ
}}}
This lined up with me checking the same .MP4 file in Adobe Audition, which
reported the file as containing 24-bit audio instead of 16-bit.
How to reproduce:
Muxing .MOV and .WAV to .MP4
{{{
ffmpeg -i in1.mov -i in2.wav -map 0:v -map 1:a -c copy out.mp4
}}}
Stream copying back to .WAV
{{{
ffmpeg -i out.mp4 -map 0:a -c copy out2.wav
}}}
--
--
Ticket URL: <https://trac.ffmpeg.org/ticket/10878#comment:1>
FFmpeg <https://ffmpeg.org>
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