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• avformat/segafilmenc : Don't store packet info in linked list

  17 juillet 2020, par Andreas Rheinhardt

  avformat/segafilmenc : Don't store packet info in linked list
  Up until now, the Sega FILM muxer would store some information about
  
  each packet in a linked list. When writing the trailer, the information
  
  in said linked list would be used to write a table in the file header.
  
  Each entry in said table is 16 bytes long, but each entry of the linked
  
  list is 32 bytes long (assuming 64 bit pointer and no padding).
  
  Therefore it makes sense to remove the linked list and write the array
  
  entries directly into a dynamic buffer while writing the packet (this is
  
  possible because the table entries don't depend on any information not
  
  available when writing the packet (the offset is not relative to the
  
  beginning of the file, but to the end of the table). This also
  
  simplifies writing the array at the end (there is no need to traverse a
  
  linked list).
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/segafilmenc.c

• avformat/mxfenc : Store locally whether DNXHD profile is interlaced

  9 novembre 2021, par Andreas Rheinhardt

  avformat/mxfenc : Store locally whether DNXHD profile is interlaced
  It is just a flag per supported CID. So there is no reason to use
  
  an avpriv function for this purpose.
  Reviewed-by : Tomas Härdin <tjoppen@acc.umu.se>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavformat/mxfenc.c

• libav : Store h264 frames in mp4 container

  25 janvier 2024, par ImJustACowLol

  I'm making a C++ application that retrieves frames from a camera and then encodes each frame with a H264 encoder (not using libav). This encoded H264 frame is then kept in memory as a void *mem as I need to do several things with the encoded frame.

  


  One of the things I need to do, is store the frames (so the void *mem pointers) in a .mp4 container using libavcodec/libavformat. I do NOT want to transcode each frame, I just want to store them directly into the mp4 container.

  


  Preferably for each individual frame that I push through, I get the resulting data as a return type from the function (not sure if this is possible ?). If this is not possible, then writing to a file directly is OK as well.

  


  How does one go about doing this with libav ?

  


  The only part I have got so far, and where I'm getting stuck, is this :

  


  /*
some private fields accessible in MP4Muxer:
int frameWidth_, frameHeight_, frameRate_, srcBitRate_;
*/


void MP4Muxer::muxFrame(void *mem, size_t len, int64_t timestamp, bool keyFrame) {
    const AVOutputFormat* outputFormat = av_guess_format("mp4", NULL, NULL);
    AVFormatContext* outputFormatContext = avformat_alloc_context();
    outputFormatContext->oformat = outputFormat;
    AVStream* videoStream = avformat_new_stream(outputFormatContext, NULL);

    videoStream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
    videoStream->codecpar->codec_id = AV_CODEC_ID_H264;
    videoStream->codecpar->width = frameWidth_;
    videoStream->codecpar->height = frameHeight_;
    videoStream->avg_frame_rate = (AVRational) {frameRate_, 1};
    videoStream->time_base = (AVRational) {1, 90000};

}


  


  How do I continue from here ? Are there any good resources I can follow ? There are some resources I found online, but all of them either write the output directly to a file, read input directly from streams/files etc. so I have a hard time translating them to my needs.