[Libav-user] RTP server for audio stream

[Robert Schmidt]

On Wed, Oct 23, 2013 at 8:52 AM, Netcoder1989
<sachinrajput1989 at outlook.com> wrote:
> I'm in the mid of my project where I'm trying to send the audio data over RTP
> using ffmpeg in VC++.
> but I'm unable to do that.:
> setRTPOutputAddr("192.168.100.48");
>         setRTPOutputPort(9985);
>         av_register_all();
>         avformat_network_init();
>         formatCtx= avformat_alloc_context();
>
>         //av_dump_format(formatCtx,0,"rtp",1);
>                 avio_open_dyn_buf(&ioctx);
>                 avio_open(&formatCtx->pb, "rtp", AVIO_FLAG_WRITE);
>                 //av_dump_format(formatCtx,0,"rtp",1);
>                 formatCtx->pb = ioctx;
>
>                 rtpCtx = avformat_alloc_context();
>                 rtpCtx->oformat = av_guess_format("rtp",0,0);
>                 AVStream *fakeVideo = 0;
>                 fakeVideo = avformat_new_stream(rtpCtx,0);
>                 avcodec_get_context_defaults3(fakeVideo->codec, NULL);
>                 fakeVideo->codec->codec_id = AV_CODEC_ID_MPEG2TS;
>                 rtpCtx->audio_codec_id = AV_CODEC_ID_NONE;
>                 rtpCtx->video_codec_id = AV_CODEC_ID_MPEG2TS;
>                 // avformat_write_header(rtpCtx,0);
>
>                 char *url = new char[1024];
>                 sprintf(url,"rtp://%s:%d",rtpOutputAddr,rtpOutputPort);
>                 printf("will output to url:%s\n",url);
>                 avio_open(&rtpCtx->pb,url,AVIO_FLAG_WRITE);
>                 avformat_write_header(rtpCtx, NULL);
>                 delete url;
>
>
>                 if (avio_open(&formatCtx->pb, "rtp", AVIO_FLAG_WRITE) < 0)
>                 {
>                         fprintf(stderr, "Could not open '%s'\n", formatCtx->filename);
>             return -1;
>         }
>                 else
>                 {
>
>                 printf("succeed \n");
>                 }
>
>
>         avformat_write_header(formatCtx, NULL);
> Getting error here
>
>
> Do any one having any idea why my program crashes here.

Without more information on the type of crash, it's hard to say.  I
suspect the issue may be that you don't associate any output format,
streams, etc. with formatCtx, only with rtpCtx.  I'm guessing that
avformat_write_header() is attempting to access some part of the
formatCtx structure and encountering an unexpected NULL pointer.  If
you run the code under a debugger, you should be able to determine
exactly what field is being accessed and the cause of your crash.

Rob