[FFmpeg-devel] Handling of mono data in WMA lossless

Jakub Stachowski qbast at go2.pl
Wed May 2 18:48:40 CEST 2012

W dniu 2012-05-02 10:28, Mashiat Sarker Shakkhar pisze:
> On 5/2/2012 2:11 PM, Jakub Stachowski wrote:
>> W dniu 2012-05-02 09:55, Mashiat Sarker Shakkhar pisze:
>>> On 5/2/2012 4:53 AM, Jakub Stachowski wrote:
>>> [...]
>>>> This is exactly what I have been missing. I guess it really pays to
>>>> actually have some idea how audio coding works. All my weird
>>>> attempts to
>>>> copy data were unnecessary, for some reason reverse decorrelation was
>>>> restricted to case when both channels are coded. Removing that check
>>>> fixes my synthetic test files, real world test case and does not
>>>> break 3
>>>> other random WMA files I tested. Patch is attached.
>>> [...]
>>> It's unfortunate that we are duplicating work. At libav-devel, we
>>> already have a patch for this -
>>> http://patches.libav.org/patch/21031/
>> I do check libav for anything new in WMA, but it was unfortunate timing
>> - Kostya's patch was applied the same day I was working on mine.
> [...]
> I'd recommend cherry-picking that part of Kostya's patch. (Which of
> course will be done anyway, when Michael merges changes.)

I tested libav with Kostya's patch, but that change in mclms_predict 
actually makes things worse in some files. In one of them small 
difference (0xFEFE in one place that should be 0xFFFF) changes into 
several frames being completely different.

> - Shakkhar
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