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• dnxhddec : Decode and use interlace mb flag

  26 septembre 2015, par Christophe Gisquet

  dnxhddec : Decode and use interlace mb flag
  This bit is 1 in some samples, and seems to coincide with interlaced
  
  mbs and CID1260. 2008 specs do not know about it, and maintain qscale
  
  is 11 bits. This looks oversized, but may help larger bitdepths.
  Currently, it leads to an obviously incorrect qscale value, meaning
  
  its syntax is shifted by 1. However, reading 11 bits also leads to
  
  obviously incorrect decoding : qscale seems to be 10 bits.
  However, as most profiles still have 11bits qscale, the feature is
  
  restricted to the CID1260 profile (this flag is dependent on
  
  a higher-level flag located in the header).
  The encoder writes 12 bits of syntax, last and first bits always 0,
  
  which is now somewhat inconsistent with the decoder, but ends up with
  
  the same effect (progressive + reserved bit).
  Signed-off-by : Vittorio Giovara <vittorio.giovara@gmail.com>
  

  • [DBH] libavcodec/dnxhddec.c

• Failed to execute : 0x80070057, when decoding video via ffmpeg with dxva2

  18 avril 2016, par CD83

  I have successfully implemented a video player using ffmpeg. I am now trying to use hardware decoding but I’m facing a couple issues.
  I found a post that I followed as a starting point here : http://comments.gmane.org/gmane.comp.video.ffmpeg.libav.user/13523

  I have updated the code that setup the necessary stuff for the decoder. The updated code is available here : https://drive.google.com/file/d/0B5ufHdoDzA4ieVk5UVpxcDNzRHc/view?usp=sharing

  And this is how I’m using it to initialize the decoder :

  // Prepare the decoding context
  
  AVCodec *codec = nullptr;
  
  _codecContext = _avFormatContext->streams[_streamIndex]->codec;
  
  if ((codec = avcodec_find_decoder(_codecContext->codec_id)) == 0)
  
  {
  
      std::cout << "Unsupported video codec!" << std::endl;
  
      return false;
  
  }
  
  
  
  _codecContext->thread_count = 1;  // Multithreading is apparently not compatible with hardware decoding
  
  InputStream *ist = new InputStream();
  
  ist->hwaccel_id = HWACCEL_AUTO;
  
  ist->hwaccel_device = "dxva2";
  
  ist->dec = codec;
  
  ist->dec_ctx = _codecContext;
  
  _codecContext->coded_width = _width;
  
  _codecContext->coded_height = _height;
  
  
  
  _codecContext->opaque = ist;
  
  dxva2_init(_codecContext);
  
  
  
  _codecContext->get_buffer2 = ist->hwaccel_get_buffer;
  
  _codecContext->get_format = GetHwFormat;
  
  _codecContext->thread_safe_callbacks = 1;
  
  
  
  if (avcodec_open2(_codecContext, codec, nullptr) < 0)
  
  {
  
      std::cout << "Video codec open error" << std::endl;
  
      return false;
  
  }

  And here is the definition of GetHwFormat referenced above :

  AVPixelFormat GetHwFormat(AVCodecContext *s, const AVPixelFormat *pix_fmts)
  
  {
  
      InputStream* ist = (InputStream*)s->opaque;
  
      ist->active_hwaccel_id = HWACCEL_DXVA2;
  
      ist->hwaccel_pix_fmt = AV_PIX_FMT_DXVA2_VLD;
  
      return ist->hwaccel_pix_fmt;
  
  }

  When I open an mp4 (encoded in h264) video that is HD resolution or less, everything seems to be working fine. However, as soon as I try higher resolution videos like 3840x2160, I get the following errors repeatedly :

  Failed to execute: 0x80070057
  
  Hardware accelerator failed to decode picture

  I also start getting the following errors after a few seconds :

  co located POCs unavailable

  And the video is not displayed properly : I get a lot of artifacts all over the video and it is lagging. I checked the first error in the ffmpeg source code. It seems that IDirectXVideoDecoder_Execute fails because of an invalid parameter. Since this is happening withing ffmpeg, there must be something that I’m missing but I can’t figure out what. The only relevant post that I found with this error was because of multithreading but I set the thread_count to 1 before opening the codec.

  This issue is happening on my main computer which has the following specs :

  • i7-4790 CPU @ 3.6GHz
  • RAM 16 GB
  • Intel HD Graphics 4600
  • Windows 8.1

  The same issue is not happening on my second computer which has the following specs :

  • i7 4510U @ 2GHz
  • RAM 8 GB
  • NVIDIA GeForce GTX 750Ti
  • Windows 10

  If I use DXVAChecker on my main computer, it says that my graphics card supports DXVA2 for H264_VLD_*, and I can see that the calls to the Microsoft API are being made (DXVA2_DecodeDeviceCreated, DXVA2_DecodeDeviceBeginFrame, DXVA2_DecodeDeviceGetBuffer, DXVA2_DecodeDeviceExecute, DXVA2_DecodeDeviceEndFrame) while my video is playing.

  I also don’t see any increase of GPU usage (on either computer) between the version with hardware decoding and the version without ; however, I do see a decrease in CPU usage (not as much as I was expecting though). This is also very strange.

  Note that I tried both the Windows release available on the FFmpeg website, and a version that I compiled with —enable-dxva2. I have searched a lot already but I was unable to find what I’m doing wrong.

  Hopefully, someone can help me, or maybe point me to a better example ?

• mov : Implement parsing of the "HandlerName" from the MP4 HDLR atom

  3 février 2015, par Hendrik Leppkes

  mov : Implement parsing of the "HandlerName" from the MP4 HDLR atom
  This atom typically is used for a track title. The handler name is stored
  
  as a Pascal string in the QT specs (first byte is the length of the string),
  
  so do not export it.
  A second length check based on the first character is added to avoid
  
  overwriting an already specified handler_name (it happens with YouTube
  
  videos for instance, the handler_name get masked), or specifying an
  
  empty string metadata.
  The Pascal string fix and the second length check are written
  
  by Clément Bœsch <clement.boesch@smartjog.com>.
  Signed-off-by : Vittorio Giovara <vittorio.giovara@gmail.com>
  
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  

  • [DBH] libavformat/mov.c