[FFmpeg-devel] [PATCH] libavfilter-soc: implement pad filter

[Stefano Sabatini]

On date Wednesday 2009-05-20 20:42:21 +0200, Vitor Sessak encoded:
> Stefano Sabatini wrote:
>> On date Tuesday 2009-05-19 02:09:53 +0200, Stefano Sabatini encoded:
>>> On date Monday 2009-05-18 23:49:50 +0200, Stefano Sabatini encoded:
>>>> On date Sunday 2009-05-17 13:14:22 +0200, Stefano Sabatini encoded:
>>>>> On date Monday 2009-05-11 19:17:51 +0200, Vitor Sessak encoded:
>>>> [...]
>>>>> I'm going to try this approach:
>>>>> int request_frame(AVFilterLink *link, int width, int height, int left, int top);
>>>>> picref *avfilter_get_video_buffer(link, int exp_w, int exp_h, int left, int top, AV_PERM_WRITE);
>>>>>
>>>>> the additional parameters given to avfilter_get_video_buffer() (at
>>>>> least left and top) seem to be necessary to correctly free the buffer.
>>>>>
>>>>> An alternative approach would be to extend avfilter_config_links() to
>>>>> take the additional parameters w, h, left, top and store them in the
>>>>> link, but looks somehow more complicated.
>>>> And implementation attached.
>>>>
>>>> Note how I also extended avfilter_poll_frame(): this seems to be
>>>> required for the way it is used in vf_fps.c.
>>> Please don't still review it, I'm still nailing down some bugs.
>>
>> Should be fixed now, try for example with:
>>
>> ffplay in.avi -vfilters "pad = exp_w=in_w+30 : exp_h=in_h + 30 : color = red,
>>                          pad = exp_w=in_w+30 : exp_h=in_h + 30 : color = blue,
>>                          pad = exp_w=in_w+30 : exp_h=in_h + 30 : color = yellow"
>>
>> This should provide a good base for further development, in particular
>> it shouldn't be too hard to add support for RGB colorspaces.
>
> Nice! Thanks for digging into this!
>
> Some comments:
>
>>  /**
>>   * Polls a frame from the filter chain.
>> @@ -515,7 +521,7 @@
>>   * @return the number of immediately available frames, a negative
>>   * number in case of error
>>   */
>> -int avfilter_poll_frame(AVFilterLink *link);
>> +int avfilter_poll_frame(AVFilterLink *link, int exp_w, int exp_h, int left, int top);
>
> What is the rationale for adding this parameters also to poll_frame()?

Have a look at vf_fps.c, in that filter poll_frame() calls
request_frame() and I wanted a quick way to get it done. If you have
better ideas...

>> Index: libavfilter-soc/ffmpeg/ffmpeg.c
>> ===================================================================
>> --- libavfilter-soc.orig/ffmpeg/ffmpeg.c	2009-05-18 23:25:48.000000000 +0200
>> +++ libavfilter-soc/ffmpeg/ffmpeg.c	2009-05-18 23:26:03.000000000 +0200
>> @@ -355,7 +355,7 @@
>>  {
>>      AVFilterPicRef *pic;
>>  -    if(avfilter_request_frame(ctx->inputs[0]))
>> +    if(avfilter_request_frame(ctx->inputs[0], ctx->inputs[0]->w, ctx->inputs[0]->h, 0, 0))
>
> I suppose you didn't test the changes to ffmpeg.c, unless you forgot to  
> attach the patch for vsrc_buffer.c. I imagine that here handling  
> avfilter_request_frame() without memcpy'ing the whole frame (as is done  
> in ffplay.c) would be non trivial.

Ouch, yes I only tested ffplay.c, movie/buffer sources require quite a
different approach.

I'll try to dig into that.

Regards.
-- 
FFmpeg = Fundamental and Frightening Mind-dumbing Patchable Evangelical Generator