The VideoLAN Forums

Hi there,

When I play a video with VLC 1.1.0 pre2, and DXVA is enabled, which decoder is used? Is it the excellent decoder from ffmpeg VLC has, or some no-name decoder from ATI/NVIDIA nobody has tested in terms of quality?

Thanks,
kurkosdr

Decoder source code is from FFMPEG, but it uses DXVA API to do the decoding steps.

Decoder source code is from FFMPEG, but it uses DXVA API to do the decoding steps.

So, the decoding is done by ffmpeg code, but it uses the GPU instead of the CPU?

I was under the impression that DXVA was a decoder embedded to the video card, and the player's decoder wasn't used at all.

Decoder source code is from FFMPEG, but it uses DXVA API to do the decoding steps.

So, the decoding is done by ffmpeg code, but it uses the GPU instead of the CPU?

I was under the impression that DXVA was a decoder embedded to the video card, and the player's decoder wasn't used at all.

No, decoding is done by GPU manucturer, not ffmpeg.

Just to be sure ... we are taking about DXVA2, not DXVA, right?
DXVA is not supported, only DXVA2, correct?

Decoder source code is from FFMPEG, but it uses DXVA API to do the decoding steps.

So, the decoding is done by ffmpeg code, but it uses the GPU instead of the CPU?

I was under the impression that DXVA was a decoder embedded to the video card, and the player's decoder wasn't used at all.

No, decoding is done by GPU manucturer, not ffmpeg.

This is exactly why I'm more excited about the possibility of multicore decoding than GPU decoding in VLC. I think it is more in VLC's tradition that the CPU (therefore the tried and true ffmpeg backend) does the work. I also think there are less variables to worry about in CPU-land.

Just to be sure ... we are taking about DXVA2, not DXVA, right?
DXVA is not supported, only DXVA2, correct?

Yes.

Here comes the million dollar question:

How can I be sure that the manufacturer's GPU decoder will be as good as the ffmpeg's decoder?

There are at least 3 different GPU decoder implementations out there (Intel, ATI, NVIDIA) and there is no guarantee all of them will be as good as ffmpeg, since ffmpeg doesn't have any control over the decoding process (when using DXVA, ffmpeg just submits the video for decoding and then receives the decoded video, right?).

How can I be sure that the manufacturer's GPU decoder will be as good as the ffmpeg's decoder?

You cannot. You can just hope.

How can I be sure that the manufacturer's GPU decoder will be as good as the ffmpeg's decoder?

You cannot. You can just hope.

So I guess I should wait for 1.2 which will have multicore support. This will be the best, IMO, because the trusted ffmpeg decoder is used, while even a CoreDuo T2400 should be able to handle the load of 1080p h264.

(I never liked DVXA2 much. As the YUV -> RGB debacle in ATI/NVIDIA drivers showed us, code from GPU manufacturers is not to be trusted)

BTW, can I have DXVA2 on while having the YUV->RGB conversions off?

Yes, you can.