HD Video Decoding on GPUs with VLC 1.1.0
by Ganesh T S on June 25, 2010 4:35 AM EST- Posted in
- Home Theater
- HTPC
VLC has taken the important first step towards enabling GPU acceleration for various codecs commonly used in high definition videos. However, they have been crippled by their application structure, resulting in the fact that they are unable to provide the same amount of acceleration as other methods like DXVA using MPC-HC / Windows Media Player. While the untested Arrandale provided around 5% CPU usage improvement for VC-1 decode, PureVideo VP2 had speed-ups of around 60% for H264 and 20% for VC1. PureVideo VP4 turned out to be the best of the lot when GPU acceleration is enabled. CPU usage was lesser by a factor more than 65% for H264 and 36% for VC1.
Are these numbers good enough for the occasional HD video watcher? I would say, yes, as soon as the GPU vendors fix their drivers for the remaining minor issues. But, for the HD enthusiast with terabytes of Blu-Ray backups, I would still advise sticking with MPC-HC / Windows Media Player / favourite software Blu-Ray player.
GPU vendors should get their act together and work with the VLC developers to ensure smooth interaction between their drivers and VLC. This has already been done between the MPC-HC / mplayer - VDPAU developers and Nvidia / Intel. VLC, being much more popular, should not have much trouble in this respect (as indicated by how long it took CatalystMaker to tweet regarding Catalyst support for VLC). The vendors and developers should also look into ways to further the performance gains that have been realized with this first release. It will probably not be long before all GPU vendors support this type of acceleration at the basic level. That would be time for the VLC developers to enable GPU acceleration by default, and take away the experimental tag associated with it.
On other HD media aspects related to VLC, it is heartening to note support for WMAPro audio in the past few releases. Would it be wishful thinking to see audio passthrough / HD audio bitstreaming implemented internally in VLC? Hopefully not! Anandtech takes this opportunity to thank the VLC developers for creating and supporting one of the best open source softwares of all time.
Note: Don't forget to check out the update section on the next page, where I have tried to address some comments from readers (both here, and also in private communication)
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MGSsancho - Friday, June 25, 2010 - link
What software did you use to test DXVA compatibility? Also if possible where can we get a hold of it? :)Per Hansson - Friday, June 25, 2010 - link
It is "DXVA Checker"You can doiwnload it here;
http://bluesky23.hp.infoseek.co.jp/en/index.html
barniebg - Friday, June 25, 2010 - link
Come on, the most important benefit of using a GPU to decode video is the fact that you can apply hardware deinterlacing. VLC deinterlacing is nowhere near even remotely comparable to any GPU.MGSsancho - Friday, June 25, 2010 - link
I am disappointed as well but applaud VLC for being another competitor in this very important arena.CSMR - Friday, June 25, 2010 - link
Deinterlacing is a legacy concept relating to content produced with CRTs in mind. It is not important in the modern world. If you have content that is interlaced, your encoding software should deal with it, or else download a better version.probedb - Friday, June 25, 2010 - link
What about those of us that don't want to reencode video? Or that play DVDs back from the drive.De-interlacing is still very much required.
mckirkus - Friday, June 25, 2010 - link
DVD content is stored as progressive (480p) On an old CRT/Tube TV, the DVD player interlaces the content (480i) so it is compatible with the TV.I can't think of any digital content that is stored in interlaced format these days.
mckirkus - Friday, June 25, 2010 - link
(ok, no edit button, non HD tv is interlaced, as is 1080i broadcast ATSC). I should have said DVDs and Blu-Ray are not interlaced.flanger216 - Sunday, June 27, 2010 - link
Swing and a miss, #2. Try again, please.TONS of DVDs are interlaced, both from PAL and NTSC regions. Plenty of content --- HDV and tape sources, for starters --- has never been anything other than interlaced, right from camera acquisition, and is directly encoded from the interlaced source to an interlaced DVD... for obvious reasons.
Many film-based DVDs released prior to 2000 or so are also interlaced, because they were encoded from old cable, laserdisc and VHS masters. Also, heaps of low-budget and foreign (especially Asian) DVDs are made from interlaced masters, due to old or subpar equipment, or simply because interlaced workflows are often cheaper.
And NO, your "encoding software" should NOT "deal with it." Deinterlacing prior to encoding gives you the following options: you can deinterlace to half-resolution and encode w/ a good bitrate but with poor quality, or you can deinterlace to full-resolution, but that'll require a doubled frame-rate and, obviously, doubled file-sizes. Interlaced sources should always be encoded to interlaced targets and deinterlaced during playback, preferably by a high-quality temporal/spatial filter @ a doubled frame-rate. Realistically speaking, you're only going to get that from a GPU (or a smokingly fast CPU running one of the newer software deinterlacers).
WHY do people write things that are flatly untrue?
electroju - Monday, June 28, 2010 - link
I agree, but all DVD movies that I have are interlace. Yes, even the latest movie from 2007 is interlace. I am sure that Blu-ray and HD-DVD are interlaced as well. Like you said, these interlace content have to be set at double the frame rate and be de-interlaced to view correctly on a progressive screen. Though a 3:2 pull-up also have to be used to keep within 24 frame rate of the movie, but this adds distortion.Not all codecs are compatible with interlace content, so the video have to be deinterlace. This means double frame rate and adding 3:2 pull-up if it needs it.
There are dozens of deinterlace algorithms. Not one will suit every content. The only programs that I know that include most of the deinterlacing algorithms is dscaler and tvtime.
None of the GPU that I know of actually increases the frame rate, so you are back where you started. In order to do it right, it is do the post-processing task with the CPU. Though there is a compromise between loading the CPU to 100% and not using the GPU or using the GPU and have fraction of the CPU being utilized.