VLC GPU Decoding

2010-01-10T17:00:26Z

Caldo de cana: circonstances -> circumstances.

= Introduction to GPU decoding in VLC =

The VLC framework can use your '''''graphic card''''' (aka GPU) to decode H.264 streams (wrongly called HD videos) under certain circumstances.

VLC, in its '''modular''' approach and its transcoding/streaming capabilities, does decoding in GPU at the '''decoding stage only''' and then gets the data back to go to the other stages (streaming, filtering or plug any video output after that).

What that means is that, compared to some other implementation, GPU decoding in VLC can be slower because it needs to get the ''data back from the GPU''. But you can plug '''ANY''' video output (sink) to it and use '''all '''the VLC video filters.

=== Windows ===
VLC 1.1 supports [http://en.wikipedia.org/wiki/DirectX_Video_Acceleration DxVA] in its version '''2.0'''. That means that ''Windows Vista'', ''Windows 2008'' or ''Windows 7'' are '''required'''. If you are using ''Windows XP'', VLC cannot work for you yet.

=== Linux ===

On Linux, there is code for VDPAU and VAAPI. There is also some code for a VAAPI video output, that isn't merged in the current Git.

Read [[VLC_VAAPI]] and [thresh's blog|http://strangestone.livejournal.com/107092.html] for more details.

=== Mac OS X ===
Mac OS X doesn't provide a GPU decoding API. Complain to Apple.

= Requirements for Windows DxVA2 in VLC =

To check your DxVA compatibility, please '''download [http://bluesky23.hp.infoseek.co.jp/en/index.html#DXVAChecker DxVA Checker]'''

== Graphic card ==
VLC developers recommend to use nVidia cards so far to have the best performance.

=== nVidia ===

For nVidia GPU, you are required to use a GPU supporting [http://en.wikipedia.org/wiki/Nvidia_PureVideo PureVideo] in its 2nd generation (VP2 or newer), which means that you need a [http://en.wikipedia.org/wiki/GeForce_8_Series GeForce 8], [http://en.wikipedia.org/wiki/GeForce_9_Series GeForce 9] (advised), [http://en.wikipedia.org/wiki/GeForce_200_Series GeForce 200] or newer.

To be sure, check your GPU against this table on [http://en.wikipedia.org/wiki/Nvidia_PureVideo#Table_of_PureVideo_.28HD.29_GPUs wikipedia] and check if you are VP2 or newer.

=== ATI ===

For ATI GPUs, it is a bit trickier.

First, you are required to use a GPU supporting [http://en.wikipedia.org/wiki/Unified_Video_Decoder Unified Video Decoder].

We believe you need a [http://en.wikipedia.org/wiki/Unified_Video_Decoder#UVD_enabled_GPUs GPU supporting UVD+], but you might require a UVD2 compatible GPU. We don't have the hardware to test so far. We have tested against ''Radeon 4K'' so far.

Then, ATI cards seems to be very slow to get the data back from the GPU. So far, it seems that you need a SSE4.1 compatible CPU to decode, in order to use MOVNTDQA instruction. This may change in the future!

=== Intel ===

We haven't tested any Intel implementation so far.

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VLC GPU Decoding