[Ffmpeg-devel] Help understanding AVParser

[Michael Niedermayer]

Hi

On Wed, Dec 20, 2006 at 09:55:15AM +0000, Cool_Zer0 wrote:
> On 12/20/06, Cool_Zer0 <c00jz3r0 at gmail.com> wrote:
> >
> >
> >Michael Niedermayer wrote:
> >> Hi
> >>
> >> On Tue, Dec 19, 2006 at 09:59:00AM +0000, Cool_Zer0 wrote:
> >>
> >>> Michael Niedermayer wrote:
> >>>
> >>>> Hi
> >>>>
> >>>> On Mon, Dec 18, 2006 at 06:37:22PM +0000, Cool_Zer0 wrote:
> >>>>
> >>>>
> >>>>> On 12/18/06, Michael Niedermayer <michaelni at gmx.at > wrote:
> >>>>>
> >>>>>
> >>>>>> Hi
> >>>>>>
> >>>>>> On Mon, Dec 18, 2006 at 11:04:47AM +0000, Cool_Zer0 wrote:
> >>>>>>
> >>>>>>
> >>>>>>> Hi there.
> >>>>>>>
> >>>>>>> I'm trying to use AVParser but I'm a bit lost and I can't find any
> >>>>>>> documentation.
> >>>>>>>
> >>>>>>> So... Here's what I'm doing...
> >>>>>>>
> >>>>>>>
> >>>>>>> I'm calling *av_parser_init(CODEC_ID_H263)* and then I think that I
> >have
> >>>>>>>
> >>>>>>>
> >>>>>> to
> >>>>>>
> >>>>>>
> >>>>>>> call *av_parser_parse()* for each H.263 packet that I receive.
> >>>>>>> My main problem is understanding the parameters of the last
> >function:
> >>>>>>>
> >>>>>>> AVCodecParserContext
> >>>>>>> AVCodecContext
> >>>>>>> poutbuf
> >>>>>>> poutbuf_size
> >>>>>>> buf
> >>>>>>> buf_size
> >>>>>>> pts
> >>>>>>> dts
> >>>>>>>
> >>>>>>> The first ones I understand but the last 6 I can't understand what
> >they
> >>>>>>> are...
> >>>>>>> Other question...  If buf_size takes the value 0 it means that I
> >have a
> >>>>>>> complete frame, right? So... Where is that frame and how can I put
> >on a
> >>>>>>> AVFrame/AVPicture in order to convert it to BGR24?
> >>>>>>>
> >>>>>>> If you don't want to answer my question at least give me some link
> >to
> >>>>>>>
> >>>>>>>
> >>>>>> any
> >>>>>>
> >>>>>>
> >>>>>>> documentation about AVParser.
> >>>>>>>
> >>>>>>>
> >>>>>> see av_read_frame_internal() in utils.c and the doxygen comment
> >above
> >>>>>> av_parser_parse in parser.c
> >>>>>>
> >>>>>>
> >>>>> Hi.
> >>>>> When I update my code the comment appear :)
> >>>>> But I'm having the same problems that I had without the AVParser :(
> >>>>>
> >>>>>
> >>>>> AVCodecParserContext *parser_context;
> >>>>> uint8_t *poutbuf = new uint8_t[6000];
> >>>>> int poutsize=0;
> >>>>>
> >>>>> {
> >>>>> ...
> >>>>> parser_context = av_parser_init(CODEC_ID_H263);
> >>>>> ...
> >>>>> }
> >>>>>
> >>>>> void video_decode(unsigned char* payload, int payloadsize)
> >>>>> {
> >>>>>   static int frame_numero = 0;
> >>>>>
> >>>>>   int len = 0;
> >>>>>   while (payloadsize) {
> >>>>>       len = av_parser_parse(parser_context, c, &poutbuf, &poutsize,
> >>>>> payload, payloadsize, frame_numero, frame_numero);
> >>>>>
> >>>>>       payload += len;
> >>>>>       payloadsize -= len;
> >>>>>
> >>>>>       if (len < 0)
> >>>>>           return;
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>> Hi.
> >>>
> >>>
> >>>> if(!poutsize)
> >>>>    continue;
> >>>>
> >>>>
> >>> Less frames are saved but still presents the same problems :(
> >>>
> >>>
> >>>> and if this doesnt help then does it work if you dump the stuff to a
> >file
> >>>> and
> >>>> try to play that with ffmpeg or ffplay?
> >>>>
> >>>>
> >>> That's a good sugestion!!! If ffmpeg could play and decompress the
> >movie
> >>> correctly should mean that the problem is in my code. There is only one
> >>> problem...
> >>> I'm receiving packets through RTP (not using RTSP)... I have saved
> >about
> >>> 160 h.263 packets... In order to pass that packets to ffmpeg what I
> >have
> >>> to do? Merge all the packets into a single file? It will work? The file
> >>> doesn't need to have a special format?
> >>>
> >>
> >> yes ff* should be able to play h.263 if the frames are just concatenated
> >>
> >>
> >
> >Hummmmm...
> >But when I decompress I get a YUV420P frame, right?
> >To make a .avi of YUV420P frames I have to convert them to another
> >format before the concatenation, right? Can you sugest me other format?
> >
> 
> 
> I forgot to say one thing... I've tested the concatenation of the packets
> but it doesn't work...
> Take a look at this code:
> 
> void decompress() {
> 
>    FILE *f; // file pointer to the rtp packet
>    FILE *destino; // file pointer to the destionation file (concatenate)
>    destino = fopen("compressed.avi", "ab");
> 
>    char filename[200];
>    unsigned char buffer[10000];
>    int read;
>    for (int i=0; i<125; i++) { // I have saved 125 packets that I received
> >from RTP (I've already extracted the RTP Headers)
>        sprintf(filename, "0%d_frame.raw", i);
>        f = fopen(filename, "rb");
> 
>        if (f != NULL) {
>            read = fread(buffer, 1, sizeof(buffer), f);
>            fwrite(buffer,1,read,destino); // concatenate
>            fclose(f);
> 
>        }
>    }
> 
>    fclose(destino);
> }
> 
> 
> Then I tried to used ffmpeg:
> $ ffmpeg -i compressed.avi -vcodec mpeg1video tt.mpg

raw h263 normally doesnt have a .avi in the filename


[...]
> I've tried other combinations like
> $ ffmpeg -i -vcodec h263 compressed.avi -vcodec mpeg1video tt.mpg

this is of course meaningless nonsese what you want is
ffmpeg -f h263 -i compressed.avi ...


[...]
> But any have worked...
> :(
> 
> We must be really dumb... I have three more people working in this project

yes, and to help others who have the same problem ... maybe you want to
suggest some improvements to the docs after you figured out where the problem
was ...

also dont mix packets from unrelated streams like sending audio packets to
the video decoder and dont forget to parse and strip any RTP headers or what
else non-h263 is there (iam just guessing, these could cause such errors)

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In a rich man's house there is no place to spit but his face.
-- Diogenes of Sinope