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• FFmpeg dxva2 H264 decoder reinitialize codec - access violation

  18 janvier 2023, par Spuriga

  I have a small project which decodes h264 I frame (SPS+PPS in extradata).
It uses "dxva2" hw acceleration and works fine until I reinitialize the codec. This can be occured when an rtsp stream change the format. Fe. : h264 to h264H. and the extradata must be changed.

  


  The extradata modifying code is :

  


      ...

    ret = decode_write(decoder_ctx, packet);          //GOOD    
    ret = decode_write(decoder_ctx, NULL);

    if (avcodec_close(decoder_ctx) < 0)
        return -2;

    if (hw_decoder_init(decoder_ctx, type) < 0)
        return -1;

    if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0) {
        fprintf(stderr, "Failed to open codec for stream.\n");
        return -1;
    }

    ret = decode_write(decoder_ctx, packet);         //ACCESS VIOLATION
    ret = decode_write(decoder_ctx, NULL);


  


  The next avcodec_send_packet goes access violation exception.
When I switch off the HW acceleration and fallback to CPU this change is works fine.

  


  So the only problem when I use dxva2 and reinitialize the codec.

  


  The extradata change code is not in this small example, because the error reason is the reinitialize.

  


• libavdevice/v4l2 : fix invalid access to struct v4l2_buffer

  20 septembre 2017, par Jaroslav Beran

  libavdevice/v4l2 : fix invalid access to struct v4l2_buffer
  In case we are short of queued buffers, at first v4l2_buffer was enqueued to kernel so it's not owned by
  
  user-space anymore. After that it's timestamp field was read, but it might be overwritten by driver at
  
  that moment. It resulted in invalid timestamp sometimes.
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavdevice/v4l2.c

• Ffmpeg not able to access file on aws labmda

  1er septembre 2016, par Surendra Agarwal

  I am using ffmpeg to create video thumbnails on AWS Lambda. I downloaded the file in /tmp directory but ffmpeg is not able to access it and giving error

  [Error : meta data contains no duration, aborting screenshot creation]

  when I am checking the media info using ffmpeg then it is giving the output

  { ffmpegversion: 0, title: '', artist: '', album: '', track: '', date: '', durationraw: '', durationsec: 0, synched: false, major_brand: undefined, video: { container: '', bitrate: 0, codec: '', resolution: { w: 0, h: 0 }, resolutionSquare: { w: 0, h: NaN }, rotate: 0, fps: 0, stream: 0, aspect: 0, pixel: 0 }, audio: { codec: '', bitrate: 0, sample_rate: 0, stream: 0 } }

  I used fs module to check file existance on that location and it is giving the output

  { dev: 1793, mode: 33204, nlink: 1, uid: 496, gid: 495, rdev: 0, blksize: 4096, ino: 11, size: 21152, blocks: 48, atime: Thu Sep 01 2016 13:30:46 GMT+0000 (UTC), mtime: Thu Sep 01 2016 13:30:46 GMT+0000 (UTC), ctime: Thu Sep 01 2016 13:30:46 GMT+0000 (UTC), birthtime: Thu Sep 01 2016 13:30:46 GMT+0000 (UTC) }