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• h264: fix decoding multiple fields per packet with slice threads

  12 June 2016, by Anton Khirnov

  h264: fix decoding multiple fields per packet with slice threads
  Since we only know whether a NAL unit corresponds to a new field after
  
  parsing the slice header, this requires reorganizing the calls to slice
  
  parsing, per-slice/field/frame init and actual decoding.
  In the previous code, the function for slice header decoding also
  
  immediately started a new field/frame as necessary, so any slices
  
  already queued for decoding would no longer be decodable.
  After this patch, we first parse the slice header, and if we determine
  
  that a new field needs to be started we decode all the queued slices.
  

  • [DBH] libavcodec/h264_slice.c
  • [DBH] libavcodec/h264dec.c
  • [DBH] libavcodec/h264dec.h

• Could not open encoder using ffmpeg C APi for MOV format

  22 June 2016, by lupod

  Context

  I am writing a program for doing some video processing on an input file. I wrote two classes for handling the "reading/writing frames" part that essentially wrap the functions of ffmpeg. These classes may be instantiated by providing an input and output file name, and in their constructor I initialize everything that is needed (or at least I hope so).

  This are the two routines that are called inside the constructors:

  // InputVideoHandler.cpp
  
  void InputVideoHandler::init(char* name) {
  
    streamIndex = -1;
  
    int numStreams;
  
  
  
    if (avformat_open_input(&formatCtx, name, NULL, NULL) != 0)
  
      throw std::exception("Invalid input file name.");
  
  
  
    if (avformat_find_stream_info(formatCtx, NULL)<0)
  
      throw std::exception("Could not find stream information.");
  
  
  
    numStreams = formatCtx->nb_streams;
  
  
  
    if (numStreams < 0)
  
      throw std::exception("No streams in input video file.");
  
  
  
    for (int i = 0; i < numStreams; i++) {
  
      if (formatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
  
        streamIndex = i;
  
        break;
  
      }
  
    }
  
  
  
    if (streamIndex < 0)
  
      throw std::exception("No video stream in input video file.");
  
  
  
    // find decoder using id
  
    codec = avcodec_find_decoder(formatCtx->streams[streamIndex]->codec->codec_id);
  
    if (codec == nullptr)
  
      throw std::exception("Could not find suitable decoder for input file.");
  
  
  
    // copy context from input stream
  
    codecCtx = avcodec_alloc_context3(codec);
  
    if (avcodec_copy_context(codecCtx, formatCtx->streams[streamIndex]->codec) != 0)
  
      throw std::exception("Could not copy codec context from input stream.");
  
  
  
    if (avcodec_open2(codecCtx, codec, NULL) < 0)
  
      throw std::exception("Could not open decoder.");
  
  
  
    codecCtx->refcounted_frames = 1;
  
  }
  
  
  
  // OutputVideoBuilder.cpp
  
  void OutputVideoBuilder::init(char* name, AVCodecContext* inputCtx) {
  
    if (avformat_alloc_output_context2(&formatCtx, NULL, NULL, name) < 0)
  
      throw std::exception("Could not determine file extension from provided name.");
  
  
  
    codec = avcodec_find_encoder(inputCtx->codec_id);
  
    if (codec == nullptr) {
  
      throw std::exception("Could not find suitable encoder.");
  
    }
  
  
  
    codecCtx = avcodec_alloc_context3(codec);
  
    if (avcodec_copy_context(codecCtx, inputCtx) < 0)
  
      throw std::exception("Could not copy output codec context from input");
  
  
  
    codecCtx->time_base = inputCtx->time_base;
  
  
  
    if (avcodec_open2(codecCtx, codec, NULL) < 0)
  
      throw std::exception("Could not open encoder.");
  
  
  
    stream = avformat_new_stream(formatCtx, codec);
  
    if (stream == nullptr) {
  
      throw std::exception("Could not allocate stream.");
  
    }
  
  
  
    stream->id = formatCtx->nb_streams - 1;
  
    stream->codec = codecCtx;
  
    stream->time_base = codecCtx->time_base;
  
  
  
    av_dump_format(formatCtx, 0, name, 1);
  
    if (!(formatCtx->oformat->flags & AVFMT_NOFILE)) {
  
      if (avio_open(&formatCtx->pb, name, AVIO_FLAG_WRITE) < 0) {
  
        throw std::exception("Could not open output file.");
  
      }
  
    }
  
  
  
    if (avformat_write_header(formatCtx, NULL) < 0) {
  
      throw std::exception("Error occurred when opening output file.");
  
    }
  
  
  
  }

  As you see, for the Init function of the output handler I require that an AVCodecContext must be provided. In my code, I pass to the constructor the AVCodecContext that is stored in the input handler and that was previously created.

  Question:

  The two functions work fine when I test my program with some video formats, like .mpg or .avi. When I try to process .mov/.mp4 files, however, my code throws the exception that I labeled "Could not open encoder." in OutputVideoBuilder::Init(). Why is this happening? I read from the General documentation of ffmpeg that that format should be supported as well by ffmpeg. I am assuming that I am doing something wrong in my code, which I do not completely understand because it was created by trying to adapt the tutorials of the documentation to my specific case. Also for this reason, any comments on things that are useless or things that are missing will be greatly appreciated.

• libopusenc: Add channel mapping family argument

  15 June 2016, by Michael Graczyk

  libopusenc: Add channel mapping family argument
  The default value of -1 indicates that ffmpeg should determine the channel
  
  mapping automatically, which was the behavior before this commit.
  Unless the -mapping_family argument is provided, behavior is unchanged.
  Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] doc/encoders.texi
  • [DH] libavcodec/libopusenc.c