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• how to decode wmp3 video using libavcodec ? (ffmpeg)

  13 mars 2012, par Renan Elias

  I'm developing an application that reads a live tv stream from the internet and I need to play it on my ipad application.

  I've compiled the ffmpeg into my ipad application to use the libavcodec lib, but I've not been able to use it in this lib...

  I know how to get the stream packets, read if it is an audio or video packet, but I don't know how to use the lib to convert the original packet codecs to h264 and mp3 codec...

  I need to convert an stream packet wmv3 to h264 and save it on a file.

  My code is below...

  AVFormatContext* pFormatCtx = avformat_alloc_context();
  
  int             i, videoStream, audioStream;
  
  AVCodecContext  *pCodecCtx;
  
  AVCodecContext *aCodecCtx;
  
  AVCodec         *pCodec;
  
  AVCodec         *aCodec;
  
  AVFrame         *pFrame; 
  
  AVFrame         *pFrameRGB;
  
  AVPacket        packet;
  
  int             frameFinished;
  
  int             numBytes;
  
  uint8_t         *buffer;
  
  
  
  static struct SwsContext *img_convert_ctx;
  
  
  
  
  
  // Register all formats and codecs
  
  av_register_all();
  
  avcodec_register_all();
  
  avformat_network_init();
  
  
  
  // Open video file
  
  if(avformat_open_input(&pFormatCtx, [objURL cStringUsingEncoding:NSASCIIStringEncoding] ,NULL,NULL) != 0){
  
      return -1;
  
  }
  
  
  
  // Retrieve stream information
  
  if(avformat_find_stream_info(pFormatCtx, NULL)<0)
  
      return -1; // Couldn't find stream information
  
  
  
  // Dump information about file onto standard error
  
  av_dump_format(pFormatCtx, 0, [objURL cStringUsingEncoding:NSASCIIStringEncoding], 0);
  
  
  
  // Find the first video stream
  
  videoStream=-1;
  
  audioStream=-1;
  
  for(i=0; i < pFormatCtx->nb_streams; i++) {
  
      if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO && videoStream < 0) {
  
          videoStream=i;
  
      }
  
      if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO && audioStream < 0) {
  
          audioStream=i;
  
      }
  
  }
  
  if(videoStream==-1)
  
      return -1; // Didn't find a video stream
  
  if(audioStream==-1)
  
      return -1;
  
  
  
  // Get a pointer to the codec context for the video stream
  
  pCodecCtx=pFormatCtx->streams[videoStream]->codec;
  
  
  
  // Find the decoder for the video stream
  
  pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
  
  if(pCodec==NULL) {
  
      fprintf(stderr, "Unsupported codec!\n");
  
      return -1; // Codec not found
  
  }
  
  
  
  // Open codec
  
  if(avcodec_open2(pCodecCtx, pCodec, NULL)<0)
  
      return -1; // Could not open codec
  
  
  
  // Get a pointer to the codec context for the audio stream
  
  aCodecCtx=pFormatCtx->streams[audioStream]->codec;
  
  
  
  // Find the decoder for the audio stream
  
  aCodec = avcodec_find_decoder(aCodecCtx->codec_id);
  
  if(!aCodec) {
  
      fprintf(stderr, "Unsupported codec!\n");
  
      return -1; // Codec not found
  
  }
  
  
  
  // Open codec
  
  if(avcodec_open2(aCodecCtx, aCodec, NULL)<0)
  
      return -1; // Could not open codec
  
  
  
  // Allocate video frame
  
  pFrame=avcodec_alloc_frame();
  
  
  
  // Allocate an AVFrame structure
  
  pFrameRGB=avcodec_alloc_frame();
  
  if(pFrameRGB==NULL)
  
      return -1;
  
  
  
  // Determine required buffer size and allocate buffer
  
  numBytes=avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width,
  
                              pCodecCtx->height);
  
  buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
  
  
  
  // Assign appropriate parts of buffer to image planes in pFrameRGB
  
  // Note that pFrameRGB is an AVFrame, but AVFrame is a superset
  
  // of AVPicture
  
  avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24,
  
                 pCodecCtx->width, pCodecCtx->height);
  
  
  
  // Read frames and save first five frames to disk
  
  i=0;
  
  while(av_read_frame(pFormatCtx, &packet)>=0) {
  
      // Is this a packet from the video stream?
  
      if(packet.stream_index==audioStream) {
  
          NSLog(@"Audio.. i'll solve the video first...");
  
      } else if(packet.stream_index==videoStream) {
  
  
  
          /// HOW CONVERT THIS VIDEO PACKET TO H264 and save on a file? :(
  
      }
  
  
  
      // Free the packet that was allocated by av_read_frame
  
      av_free_packet(&packet);
  
  }
  
  
  
  // Free the RGB image
  
  av_free(buffer);
  
  av_free(pFrameRGB);
  
  
  
  // Free the YUV frame
  
  av_free(pFrame);
  
  
  
  // Close the codec
  
  avcodec_close(pCodecCtx);
  
  
  
  // Close the video file
  
  avformat_close_input(&pFormatCtx);
  
  
  
  return 0;

• ffmpeg - how does moving overlay / text command work ?

  7 mars 2015, par Stpn

  In Ffmpeg you can create moving text :

  ffmpeg -y -t 10 -s qcif -f rawvideo -pix_fmt rgb24 -s 1280x720 -i /dev/zero -g 1 -r 24 -vf drawtext="fontfile=~/fonts/Trebuchet_MS.ttf:text='thing crawls':fontsize=155:fontcolor=red:y=h-20*t" wow.mpg

  So this will give me a black frame with "thing crawls" slowly going from bottom up..

  If I know the length of the video (20 seconds) and want to, for example create "thing falls" that starts at the top of the screen at time 0 and goes to the bottom of the screen until 00:00:20, how do I do that ?

  Also can I create the situation where the text will start going from top to bottom, but stop at the middle of the screen ?

• Set up a Red5 server with FFmpeg for live streaming to iOS

  13 mars 2013, par Giancarlo Molina

  I'm an app developer and I need to implement FFmpeg to transcode/change an rtmp live stream to an http live stream so that I can play it on any iOS device (iPhone and iPad).

  My problem is that I am fairly new when it comes to server, media stuff and FFmpeg. And I need to change the server so that I can transcode the live stream on the server side (which I have read that is possible). Any tips, suggestions, sample code, or tutorials would be of great help.