[FFmpeg-devel] PATCH - libmad MP3 decoding support

[Lynne]

5 May 2022, 01:47 by David at megapico.co.uk:

>> Andreas Rheinhardt wrote:
>>
>> David Fletcher:
>> > Following today's posts about help with submitting patches I realised I
>> > sent the libmad patch yesterday in the wrong format. Apologies, I was
>> > not familiar with the git format patches.
>> > 
>> > Hopefully the attached version is now in the correct format against the
>> > current master branch.
>> > 
>> > The bug report about why this exists is at the following link, including
>> > a link to sample distorted audio from decoding an mp3 stream on ARMv4
>> > hardware: https://trac.ffmpeg.org/ticket/9764
>> > 
>> > Best regards, David.
>> > 
>>

I disagree with this patch. The native decoder should be fixed instead,
or if it's not able to be fixed, users should use specialized libraries.
We're not adding a yet another decoding library to fix an issue on
very old ARM chips.

I suspect the problem is with the MDCT. We already have a better and
more precise fixed-point MDCT in libavutil/tx. The plan was to replace
the MDCT in mp3 once lavu/tx has more assembly, but if it helps,
should be fine to replace it now.