[Ffmpeg-devel] Problem with returned AVCodecContext

[Martin Boehme]

Ahmad Zaidee bin Abu wrote:
> I'm quite beginner with ffmpeg. I have some problems with AVCodecContext.
> 
> I'm using C++ .Net with libavcodec/libavformat CVS 09/29/05.
> 
> In main() i do
[snip]
> AVCodecContext *CodecContext; //=NULL;
> 
> AVFrame *Picture;
> 
> CreateH263Decoder(CodecContext, Picture);
> 
> ...
> 
> I used 3 functions as below:
> 
> int CreateH263Decoder(AVCodecContext *c, AVFrame *picture)
> {
> AVCodec *codec; 
> /* find the h263 video decoder */
> codec = avcodec_find_decoder(CODEC_ID_H263); 
> if (!codec) {
> // Codec NOT Found
> return H263_NOT_FOUND; //my own error / success detection macro
> }
> 
> c = avcodec_alloc_context();
[snip]
> return H263_OK; // return ok if successful.
> }
[snip]
> When I call CreateH263Decoder, AVCodecContext reurn NULL (0). When i trace inside the function,
> the value of "c" before return H263_OK;  are as expected, but value of "CodecContext" in main are not as I expected.
> What could be the problem? Did I miss anything.

This is a C problem. You need to use double pointers, i.e.

int CreateH263Decoder(AVCodecContext **c, AVFrame **picture);

otherwise, the values that you assign to "c" and "picture" inside the 
function won't get returned up.

HTH

Martin

-- 
Martin B?hme
Inst. f. Neuro- and Bioinformatics
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boehme at inb.uni-luebeck.de