[FFmpeg-devel] [PATCH] Export large crop values via AVCodecContext

[David Conrad]

On Jun 3, 2009, at 11:34 AM, Michael Niedermayer wrote:

> On Thu, May 28, 2009 at 09:10:45PM -0400, David Conrad wrote:
>> Hi,
>>
>> As far as I can tell, it's impractical to crop large values  
>> internally,
>> since buffers returned from decode_frame must have the same  
>> dimensions as
>> AVCodecContext, which also must be the coded dimensions (or up to  
>> 15 less)
>> in order for get_buffer to allocate buffers of the needed size.
>>
>> Thus, the only solution I see is to export these values and leave  
>> it to
>> individual applications that care about such offsets to deal with it
>> themselves.
>
> I think these values can be exported through AVCodecContext.pan_scan

 From my understanding of mpeg-2 (the only place AVPanScan is  
currently used), the area(s) in a AVPanScan are the more important  
areas in a frame that shouldn't be cropped e.g. when changing aspect  
ratio, while these cropping offsets aren't intended to be displayed  
ever.

Also, H.264 has separate pan-scan fields than what are exported here,  
relative to this cropping (D.2.3 Pan-scan rectangle SEI message  
semantics)