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• FFMPEG streaming RTP : time base not set

  25 octobre 2020, par Managarm

  I'm trying to create a small demo to get a feeling for streaming programmatically with ffmpeg. I'm using the code from this question as a basis. I can compile my code, but when I try to run it I always get this error :

  



  


  [rtp @ 0xbeb480] time base not set

  


  



  The thing is, I have set the time base parameters. I even tried setting them for the stream (and the codec associated with the stream) as well, even though this should not be necessary as far as I understand it. This is the relevant section in my code :

  



  AVCodec* codec = avcodec_find_encoder(AV_CODEC_ID_H264);
AVCodecContext* c = avcodec_alloc_context3(codec);
c->pix_fmt = AV_PIX_FMT_YUV420P;
c->flags = CODEC_FLAG_GLOBAL_HEADER;
c->width = WIDTH;
c->height = HEIGHT;
c->time_base.den = FPS;
c->time_base.num = 1;
c->gop_size = FPS;
c->bit_rate = BITRATE;

avcodec_open2(c, codec, NULL);
struct AVStream* stream = avformat_new_stream(avctx, codec);

// TODO: causes an error
avformat_write_header(avctx, NULL);


  



  The error occurs when calling "avformat_write_header" near the end. All methods that can fail (like avcodec_open2) are checked, I just removed the checks to make the code more readable.

  



  Digging through google and the ffmpeg source code didn't yield any useful results. I think it's really basic, but I'm stuck. Who can help me ?

  


• FFMPEG streaming RTP : time base not set

  15 novembre 2016, par Managarm

  I’m trying to create a small demo to get a feeling for streaming programmatically with ffmpeg. I’m using the code from this question as a basis. I can compile my code, but when I try to run it I always get this error :

  [rtp @ 0xbeb480] time base not set

  The thing is, I have set the time base parameters. I even tried setting them for the stream (and the codec associated with the stream) as well, even though this should not be necessary as far as I understand it. This is the relevant section in my code :

  AVCodec* codec = avcodec_find_encoder(AV_CODEC_ID_H264);
  
  AVCodecContext* c = avcodec_alloc_context3(codec);
  
  c->pix_fmt = AV_PIX_FMT_YUV420P;
  
  c->flags = CODEC_FLAG_GLOBAL_HEADER;
  
  c->width = WIDTH;
  
  c->height = HEIGHT;
  
  c->time_base.den = FPS;
  
  c->time_base.num = 1;
  
  c->gop_size = FPS;
  
  c->bit_rate = BITRATE;
  
  
  
  avcodec_open2(c, codec, NULL);
  
  struct AVStream* stream = avformat_new_stream(avctx, codec);
  
  
  
  // TODO: causes an error
  
  avformat_write_header(avctx, NULL);

  The error occurs when calling "avformat_write_header" near the end. All methods that can fail (like avcodec_open2) are checked, I just removed the checks to make the code more readable.

  Digging through google and the ffmpeg source code didn’t yield any useful results. I think it’s really basic, but I’m stuck. Who can help me ?

• C++/CLI FFmpeg av_read_frame returns a size but no data ?

  26 novembre 2013, par tommed

  I have written some C code to access ffmpeg and wrapped it in a C++/CLI (.NET managed) class. The program fetches a live video stream and extracts frames and converts them to PNG files.

  Unfortunately the images that are saved to disk are always black (opening them in Notepad++ shows that they are full of nulls).

  I am using the assemblies aformat/codec-55.dll and the development headers and libs for compilation from ffmpeg-20131120-git-e502783-win64-dev. The whole project is compiled using Managed C++ (Cpp/cli) .NET 4.0 for 64-bit.

  After some investigation the problem appears to be that av_read_frame fills the AVPacket->size value correctly, but the AVPAcket->data is always null. When the frame is finished (got==1) then the data for the AVFrame is just a matrix of nulls. :(

  Here is the code :
  Example code (sorry, but it didnt paste well into SO)

  I think the problem is at line 34 when the packet is returned like so :
  

  Please, how can I get this to work ? What have I done wrong ?