[FFmpeg-soc] expand filter (alternative to pad syntax)

[vmrsss]

On 11 May 2008, at 21:06, Michael Niedermayer wrote:
>>> There should be no copy.
>>> The source filter should directly draw into the larger buffer of the
>>> destination filter.
>>
>> How should it be done then? Something like:
>>
>> static void end_frame(AVFilterLink *link)
>> {
>>     AVFilterLink* output = link->dst->outputs[0];
>>
>>     avfilter_resize_video_buffer(link->currpic, pad->w, pad->h); //  
>> not
>> yet existent function!
>>
>>     draw_borders(link->currpic);
>>
>>     for (i=0; i<4; i++)
>>     link->currpic->data[i] += the quantity needed to pad top/left
>>
>>     avfilter_draw_slice(output, 0, pad->h);
>>     avfilter_end_frame(output);
>> }
>>
>> and avfilter_resize_video_buffer() implemented using av_realloc()?
>
> not possible, the buffer could be from an API like directdraw, xv, sdl
> or even a buffer on your video card. These almost certainly do not
> provide a function to resize. Also av_realloc() can be very slow.
>
> Anyway, mplayer can do it, so it can be done and actually i belived  
> that
> avfilter already was able to do such things but i do not know  
> precissely
> how ATM. So maybe that has not been completely implemented.

Looking at what mplayer does would be easy enough. It looks to me they  
use (versions of) memcpy.