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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;

• iPhone - A problem with decoding H264 using ffmpeg

  25 mars 2012, par HAPPY_TIGER

  I am working with ffmpeg to decode H264 stream from server.

  I referenced DecoderWrapper from http://github.com/dropcam/dropcam_for_iphone.

  I compiled it successfully, but I don't know how use it.

  Here are the function that has problem.

  - (id)initWithCodec:(enum VideoCodecType)codecType 
  
           colorSpace:(enum VideoColorSpace)colorSpace 
  
                width:(int)width 
  
               height:(int)height 
  
          privateData:(NSData*)privateData {
  
      if(self = [super init]) {
  
  
  
          codec = avcodec_find_decoder(CODEC_ID_H264);
  
          codecCtx = avcodec_alloc_context();
  
  
  
          // Note: for H.264 RTSP streams, the width and height are usually not specified (width and height are 0).  
  
          // These fields will become filled in once the first frame is decoded and the SPS is processed.
  
          codecCtx->width = width;
  
          codecCtx->height = height;
  
  
  
          codecCtx->extradata = av_malloc([privateData length]);
  
          codecCtx->extradata_size = [privateData length];
  
          [privateData getBytes:codecCtx->extradata length:codecCtx->extradata_size];
  
          codecCtx->pix_fmt = PIX_FMT_YUV420P;
  
  #ifdef SHOW_DEBUG_MV
  
          codecCtx->debug_mv = 0xFF;
  
  #endif
  
  
  
          srcFrame = avcodec_alloc_frame();
  
          dstFrame = avcodec_alloc_frame();
  
  
  
          int res = avcodec_open(codecCtx, codec);
  
          if (res < 0)
  
          {
  
              NSLog(@"Failed to initialize decoder");
  
          }
  
      }
  
  
  
      return self;    
  
  }

  What is the privateData parameter of this function ? I don't know how to set the parameter...

  Now avcodec_decode_video2 returns -1 ;

  The framedata is coming successfully.

  How solve this problem.

  Thanks a lot.

• Unknown encoder 'libx264'

  10 juillet 2015, par why

  I installed ffmpeg 0.8.9 on ubuntu11 by

  ./configure —enable-gpl —enable-nonfree —enable-pthreads
  —enable-libfaac —enable-libmp3lame —enable-libx264

  When I run it

  ffmpeg -y -i test.mp4 -f mpegts -acodec libmp3lame -ar 48000 -ab 64k -vcodec libx264 -b 250k -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -subq 5 -trellis 1 -refs 1 -coder 0 -me_range 16 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -bt 250k -maxrate 250k -bufsize 250k -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 -aspect 320:240 -g 30 -async 2 a.ts

  It said

  Unknown encoder ’libx264’

  (Note : the same error could occour with avconv)

  How can I fix this ? Thanks !