[FFmpeg-cvslog] r18599 - trunk/libavcodec/xan.c

[Måns Rullgård]

Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:

> On Fri, Apr 17, 2009 at 10:05:27PM +0200, reimar wrote:
>> Author: reimar
>> Date: Fri Apr 17 22:05:27 2009
>> New Revision: 18599
>> 
>> Log:
>> Use sign_extend function instead of reimplementing it.
>> 
>> Modified:
>>    trunk/libavcodec/xan.c
>> 
>> Modified: trunk/libavcodec/xan.c
>> ==============================================================================
>> --- trunk/libavcodec/xan.c	Fri Apr 17 22:01:45 2009	(r18598)
>> +++ trunk/libavcodec/xan.c	Fri Apr 17 22:05:27 2009	(r18599)
>> @@ -333,16 +333,10 @@ static void xan_wc3_decode_frame(XanCont
>>              }
>>          } else {
>>              /* run-based motion compensation from last frame */
>> -            motion_x = *vector_segment >> 4;
>> -            motion_y = *vector_segment & 0xF;
>> +            motion_x = sign_extend(*vector_segment >> 4,  4);
>> +            motion_y = sign_extend(*vector_segment & 0xF, 4);
>
> Someone forgot to document sign_extend, should I be doing the "& 0xF"
> or can I assume that any future optimized implementation will flush
> the upper bits, too?

What do you mean?  sign_extend() fills the size of an int, whatever
that happens to be, typically 32 bits.

-- 
M?ns Rullg?rd
mans at mansr.com