[FFmpeg-devel] [PATCH] Fix 4XM decoding on big-endian and unaligned reads
Vitor Sessak
vitor1001
Thu Nov 11 16:49:22 CET 2010
On 11/11/2010 02:03 PM, Michael Niedermayer wrote:
> On Thu, Nov 11, 2010 at 11:11:26AM +0100, Vitor Sessak wrote:
>> $subj, see issue2195.
>>
>> -Vitor
>
>> 4xm.c | 22 +++++++++++++++-------
>> 1 file changed, 15 insertions(+), 7 deletions(-)
>> 54479967536ec20908d3caa7d62b4e28fb8c2c3e 4xm.diff
>> Index: libavcodec/4xm.c
>> ===================================================================
>> --- libavcodec/4xm.c (revision 25108)
>> +++ libavcodec/4xm.c (working copy)
>> @@ -260,6 +260,14 @@
>> }
>> }
>>
>> +#define LE_CENTRIC_MUL(dst, src, scale, dc) \
>> + { \
>> + unsigned tmpval = ((src)[1]<< 16) + (src)[0]; \
>> + tmpval = tmpval * (scale) + (dc); \
>> + (dst)[0] = tmpval& 0xFFFF; \
>> + (dst)[1] = tmpval>> 16; \
>> + }
>
> some ifdef so this doesnt slow down LE should be added
The "(src[1] << 16) + src[0]" stuff is also needed on LE since we only
have 16-bit alignment for src. OTOH, one can use a 32-bit write, as
attached.
-Vitor
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