[FFmpeg-devel] armeb fix for mpegaudio

Siarhei Siamashka siarhei.siamashka
Fri Aug 1 01:39:55 CEST 2008

On Friday 01 August 2008, matthieu castet wrote:
> Hi,
> this patch fix mp2 regression test on arm big endian.

Does FFmpeg officially support big endian byte order on ARM?

Just if you look at 'armv4l' abbreviation, it can be decoded
as ARMv4 or higher cores with little endian byte order.

> PS : as Mans said dct is broken as you can see with the video regression
> failure.

Most assembly optimizations for ARM (including IDCT) assume little endian byte
order, some assembly optimized code even mentions it in comments as a

Brokenness of 'jrevdct_arm.S' has nothing to do with byte order, it does not
work correctly on little endian systems either.

BTW, if I'm not mistaken, regression test from FFmpeg uses just C
implementation of (i)DCT at least on ARM unless you have specifically 
modified something.

> PS2 : test were done with qemu-armeb

Do you know of any real systems (HW + OS) that could be used as ARM big endian
target for FFmpeg? Failed regression tests do not automatically mean problems
in FFmpeg, it could be also some bugs in qemu.

With all that said, I'm not opposing big endian ARM support but just don't see
much practical use in it.

Best regards,
Siarhei Siamashka

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