[FFmpeg-devel] [PATCH] ALS: Solve Issue 1657

Thilo Borgmann thilo.borgmann
Tue Jan 5 03:59:41 CET 2010


Am 05.01.10 02:43, schrieb Michael Niedermayer:
> On Tue, Jan 05, 2010 at 02:23:09AM +0100, Thilo Borgmann wrote:
>> Am 05.01.10 01:43, schrieb Michael Niedermayer:
>>> On Tue, Jan 05, 2010 at 12:34:53AM +0100, Thilo Borgmann wrote:
>>>> Am 05.01.10 00:30, schrieb Thilo Borgmann:
>>>>> Hi,
>>>>>
>>>>> issue 1657 seems to be caused by negative indices used in [].
>>>>> See: http://roundup.ffmpeg.org/roundup/ffmpeg/issue1657
>>>>>
>>>>> Using *() resolves this issue.
>>>>>
>>>>> Tested with gcc 4.0 on MacOS 10.6. There were other versions/compilers
>>>>> mentioned in roundup, maybe these could be tested by someone (you)?
>>>>>
>>>>> I'm sorry, my svn still seems to be broken and produces unusable patches
>>>>> (%ld...). Nevertheless I can apply them if the workaround is ok.
>>>>>
>>>>
>>>> Some artifacts left in als_data.h. Ignore the old patch, updated patch
>>>> attached.
>>>>
>>>> -Thilo
>>>
>>>>  alsdec.c |    4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>> 987821d84540420efa6f2e67be17094074e638f8  als_issue1657.rev1.patch
>>>> Index: libavcodec/alsdec.c
>>>> ===================================================================
>>>> --- libavcodec/alsdec.c	(Revision 21025)
>>>> +++ libavcodec/alsdec.c	(Arbeitskopie)
>>>> @@ -%ld,%ld +%ld,%ld @@
>>>>              y = 1 << 19;
>>>>  
>>>>              for (sb = 0; sb < smp; sb++)
>>>> -                y += MUL64(lpc_cof[sb],raw_samples[smp - (sb + 1)]);
>>>> +                y += MUL64(lpc_cof[sb], *(raw_samples + smp - (sb + 1)));
>>>
>>> patch ok
>>
>> Applied.
>>
>>>
>>> independant of this, it could be that if lpc_cof was reversed
>>>
>>> for (sb = 0; sb < smp; sb++)
>>>     y += MUL64(lpc_cof[sb], raw_samples[sb]);
>>
>> In the second case the index has to be negative which is not possible
>> with this approach.
> 
> i dont see why
> also it should be 
> raw_samples[sb]
> and
> raw_samples++

Hmm. If you could please elaborate a bit more, I will pick this up
tomorrow and will see if I can make it better.

Thanks,
Thilo



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