[vlc-devel] [PATCH] avcodec: only disable frame threading if DXVA2 is likely to be used

[Steve Lhomme]

On Wed, Apr 1, 2015 at 3:01 PM, Steve Lhomme <robux4 at videolabs.io> wrote:
> Never mind, I've had the buffer lock issue with a HEVC sample. So
> avcodec still can't pick the right threading module by itself. Or
> we're not handling the buffers the way it wants...

I think it's worth putting my efforts in solving this. Because
pre-detecting that DXVA2 could be use will never work, as Remi
mentioned. The codec can always change in the middle of the stream.

And because we pretty much always disable frame threading on windows
we have a big performance drop in 2.2.0.

> On Wed, Apr 1, 2015 at 2:11 PM, Steve Lhomme <robux4 at videolabs.io> wrote:
>> On Wed, Apr 1, 2015 at 1:27 PM, Rémi Denis-Courmont <remi at remlab.net> wrote:
>>> Le 2015-03-31 13:16, Steve Lhomme a écrit :
>>>>
>>>> Fixes #14054
>>>
>>>
>>> This will leave threading enabled if the video track starts with an
>>> hardware-unsupported profile, then downgrades to a hardware-supported
>>> profile (e.g. due to new H.264 SPS). If DxVA2 is compatible with threading,
>>> then you should remove the whole ifdef. If DxVA2 is not compatible with
>>> threading, then the patch is wrong.
>>
>> The file of this issue that introduced the change is working for me in
>> frame threading.
>> https://trac.videolan.org/vlc/ticket/11930
>>
>> It didn't originally work on a Surface Pro 1 but it could be worth if
>> it's working without the change, now that the code has been
>> cleaned/optimized a little.
>>
>> poke j-b or Thomas Nigro.
>>
>>>> ---
>>>>  modules/codec/avcodec/video.c | 7 +++----
>>>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/modules/codec/avcodec/video.c b/modules/codec/avcodec/video.c
>>>> index 381fe62..379bc62 100644
>>>> --- a/modules/codec/avcodec/video.c
>>>> +++ b/modules/codec/avcodec/video.c
>>>> @@ -396,19 +396,18 @@ int InitVideoDec( decoder_t *p_dec,
>>>> AVCodecContext *p_context,
>>>>              break;
>>>>      }
>>>>
>>>> +# if defined(_WIN32)
>>>>      /* Workaround: frame multithreading is not compatible with
>>>>       * DXVA2. When a frame is being copied to host memory, the frame
>>>>       * is locked and cannot be used as a reference frame
>>>>       * simultaneously and thus decoding fails for some frames. This
>>>>       * causes major image corruption. */
>>>> -# if defined(_WIN32)
>>>> -    char *avcodec_hw = var_InheritString( p_dec, "avcodec-hw" );
>>>> -    if( avcodec_hw == NULL || strcasecmp( avcodec_hw, "none" ) )
>>>> +    enum PixelFormat test_formats[] = { AV_PIX_FMT_DXVA2_VLD,
>>>> AV_PIX_FMT_NONE };
>>>> +    if( AV_PIX_FMT_DXVA2_VLD == ffmpeg_GetFormat( p_context,
>>>> &test_formats ) )
>>>>      {
>>>>          msg_Warn( p_dec, "threaded frame decoding is not compatible
>>>> with DXVA2, disabled" );
>>>>          p_context->thread_type &= ~FF_THREAD_FRAME;
>>>>      }
>>>> -    free( avcodec_hw );
>>>>  # endif
>>>>
>>>>      if( p_context->thread_type & FF_THREAD_FRAME )
>>>
>>>
>>> --
>>> Rémi Denis-Courmont
>>>
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