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• Can't open encoder when use libavcodec

  1er novembre 2013, par liuyanghejerry

  I'm using libavcodec, version 9.7, to write a simple demo, almost exactly like example in official example.

  However, I can't open encoder. Also, av_opt_set(context->priv_data, "preset", "slow", 0) always leads to crush.

  This is my code :

  // other code...
  
  int ret = 0;
  
  avcodec_register_all();
  
  AVCodec* codec = NULL;
  
  AVCodecContext* context = NULL;
  
  AVFrame* frame = NULL;
  
  uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  codec = avcodec_find_encoder(AV_CODEC_ID_H264);
  
  if(!codec){
  
      qDebug()<<"cannot find encoder";
  
      return;
  
  }
  
  qDebug()<<"encoder found";
  
  
  
  context = avcodec_alloc_context3(codec);
  
  if(!context){
  
      qDebug()<<"cannot alloc context";
  
      return;
  
  }
  
  qDebug()<<"context allocted";
  
  
  
  context->bit_rate = 400000;
  
  /* resolution must be a multiple of two */
  
  context->width = 352;
  
  context->height = 288;
  
  /* frames per second */
  
  context->time_base= (AVRational){1,25};
  
  context->gop_size = 10; /* emit one intra frame every ten frames */
  
  context->max_b_frames=1;
  
  context->pix_fmt = AV_PIX_FMT_YUV420P;
  
  qDebug()<<"context init";
  
  
  
  // av_opt_set(context->priv_data, "preset", "slow", 0); // this will crush
  
  AVDictionary *d = NULL;
  
  av_dict_set(&d, "preset", "ultrafast",0); // this won't
  
  
  
  ret = avcodec_open2(context, codec, &d);
  
  if ( ret < 0) {
  
      qDebug()<<"cannot open codec"</ other code...

  This outputs :

  encoder found

  context allocted

  context init

  cannot open codec -22

  [libx264 @ 0340B340] [IMGUTILS @ 0028FC34] Picture size 0x10 is invalid

  [libx264 @ 0340B340] ignoring invalid width/height values

  [libx264 @ 0340B340] Specified pix_fmt is not supported

  I don't think the width/height is invalid and format there either. I have no idea what's wrong here.

  Any help. plz ?

• Convert live stream of Rgba32 images and stream over RTP as H264 video stream

  7 juillet 2017, par Michael B

  Please bear with me as I’m relatively new to camera network streaming and ffmpeg.

  I’m currently receiving live IP camera stream as h264 over rtp via ffmpeg.autogen api code.

  We decode the live stream of frames as rgb24bpp and convert to writablebitmaps which we then apply some frame diagnostic markup consisting of text and rectangle filled background, and this is currently network streamed as encode jpegs from our server. Our client uses the Accord.Net framework receive a MJPEGstream to pull out the images and bind them as bitmaps to image source control in WPF front end to mimick a streaming video. This works well, but sending data over network like this is large.

  We’ve decided to look at moving away from mjpeg and instead use a higher compression format of h264.

  My aim is to compress and stream the marked up writable bitmaps over the network as compressed h264 video, as a live stream.

  Having done much research it seems it might be achievable my taking the source data of the writablebitmaps, which is RGBA32 raw data, convert this YUV and encode the yuv frames to h264 video. Below is a link that seems to demonstrate this conversion.

  https://github.com/codefromabove/FFmpegRGBAToYUV/blob/master/FFmpegRGBAToYUV/ConvertRGBA.cpp

  This example I think is what I need, but it is writing out to a video file, what I would like is to change the out of this example, so that it outputs as a video stream over network

  Is this achievable as a live stream ?

  Thanks

• the ffmpeg library cannot open camera on android

  27 septembre 2013, par GilGaMesh

  I have successfully ported ffmpeg 2.0.1 lib to android. The code to open camera is very simple :

  AVFormatContext *fmt_ctx = NULL;
  
  AVInputFormat *input_fmt;
  
  
  
  input_fmt = av_find_input_format("video4linux2"); 
  
  if (input_fmt == NULL)
  
      return -1；
  
  
  
  char f_name[] = "/dev/video0";
  
  if ((ret = avformat_open_input(&fmt_ctx, f_name, input_fmt, NULL)) < 0)        // stuck here
  
  {
  
      LOG_D("can not open camera, ret = %d", ret);
  
      return ret;
  
  }

  the strange thing is the ret value is always negative with the following logcat output by av_log :

  09-26 15:27:48.901: E/Codec-FFMpeg(17716): ioctl(VIDIOC_G_PARM): Invalid argument

  I change the f_name to /dev/video1 and /dev/video2 (these files indeed exist on my tablet, and my tablet has 2 cameras) and the problems remains.
  Do i forget anything before calling avformat_open_input() ? Thank you !