[Libav-user] Failed to execute when using hardware decoding on some computers

[Cyril Drouet]

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 tested on a Surface Pro 3 with an i5 4300U @ 1.9GHz (4 CPUs), 8 GB
of RAM, Intel HD Graphics 4400, Windows 10, and the video looks good. There
are no error messages.CPU usage is 40% less than without hardware decoding
like the second computer mentioned above.GPU is only 1% or maybe 2% more
(same as for the other 2 computers mentioned above) while testing the same
video at 3840x2160

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?


Thanks!
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