[Libav-user] Getting SPS and PPS-information from x264 encoding

[Christian Brümmer]

Am 30.05.2012 04:07, schrieb Kalileo:
> On May 29, 2012, at 20:26 , Christian Brümmer wrote:
>
>> "Cant be that hard - or?"
>>
>> Okay now im pretty sure it is:
>>
>> I read AVCodecContex.extradata contains the informations i need. For decoding i used that code ->  http://cgit.lscube.org/cgit.cgi/feng/tree/src/media/parser/h264.c#n218 - in a slightly modified way (replaced glib functions with e.g. libavs base64.h). Finally the decoding stuff is running - BUT...
>>
>> my AVCodecContext.extradata_size == 0<- what the heck?!? So no data for decoding and really no idea left how to get those informations.... WHAA!
>>
>> I make desperate efforts but i cant get into that...
>>
>> At least i need another hint. Im not asking for complete solution - its enough to know roughly the right way!
> > From what I think I understood extradata contains what you expect when your source is a video format with a global header.
>
> What's the source format you use for your tests?
>
>
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I create dummy images (should be replaced later on) and encoding them to 
x264 frames. Further i stream those images via rtsp which is working on 
VLC but not on android and i thinks its a stream configuration problem.

When should extradata be filled? In my text a dont encode a frame before 
i try to get the sps pps infos out of extradata. I may have to call a 
special function or encode a frame or header before?

So my source format is:

     codec = avcodec_find_encoder(c->codec_id);
     if(!codec)
     {
         std::cout << "Codec not found." << std::endl;
         std::cin.get();std::cin.get();exit(1);
     }

*if(avcodec_get_context_defaults3 (c, codec) < 0) // cause i dont know a 
working x264 configuration without deprecated flags *
     {
         std::cout << "Cannot get default codec context! \n" << std::endl;
         std::cin.get();
         exit(1);
     }

and

     codec = stream->codec;
     codec->codec_id = codecID;
     codec->codec_type = AVMEDIA_TYPE_VIDEO;
     codec->bit_rate = mParameters.mBitRate;
     codec->width = mParameters.mWidth;
     codec->height = mParameters.mHeight;
     codec->time_base.den = mParameters.mFrameRate;
     codec->time_base.num = 1;
     codec->gop_size = mParameters.mFrameRate;
     codec->pix_fmt = PIXEL_FORMAT;
     codec->b_frame_strategy = 0;
     codec->level = 12;
     if(codec->codec_id == CODEC_ID_MPEG2VIDEO)
         codec->max_b_frames = 2; // for testing, B frames

     if(codec->codec_id == CODEC_ID_MPEG1VIDEO)
         codec->mb_decision = 2;

     if(context->oformat->flags & AVFMT_GLOBALHEADER)
         codec->flags |= CODEC_FLAG_GLOBAL_HEADER;

where mParamters are:

   imLiveStreamParameters param;
   param.mBitRate = 4000;
   param.mCodec = "x264";
   param.mFrameRate = 24;
   param.mHeight = 240;
   param.mWidth = 320;

Thank you for your reply!

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