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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ganeshts - Friday, June 25, 2010 - link
Software able to use multiple cores are better off, as you rightly observe.However, we just saw how VLC had to use 100% of the CPU to decode some of the HD videos.
For the non-technology folks, VLC is probably the only media player installed by whoever set up the computer for them. If they try to see HD videos, they are going to hit issues with CPU usage. VLC's GPU acceleration is meant for people like them :)
fabarati - Friday, June 25, 2010 - link
Using ffdshow tryouts that came with CCCP (from 2008 at that), i could decode almost all 720p files at 1.2 GHz (on a 2.4 Ghz T7700). At 2.4 GHz I could take on any 1080p file, including a massive 24 GB rip of The Godfather.Now I have it set up to run DXVA first, then a fairly recent FFdshow tryout, with the h.264 decoder on MT.
fabarati - Friday, June 25, 2010 - link
(no Edit)When I was using coreavc (1.9.0), i could take on nearly any 1080p file at 1.6GHz, and that beastly godfather rip at 2 GHz.
0roo0roo - Friday, June 25, 2010 - link
well no once again, if you install vlc on a n00bs computer, they are simply not likely to run a raw bluray rip. they are neither going to download or know how to get their hands on such a file of massive proportions. any web rip or youtube type ripped 1080p files or apple trailers are FAR easier to playback than bluray. playing back those on even an older dual core is easy as pie.That being said, somethings wrong with the 100% usage thing. even with software players based on anandtechs own 2006 article an e6700 2.6ghz could playback bluray in software. and that was back when chips were both slower, and the software decoders far less efficient. or perhaps vlc is just not that efficient at bluray.
ganeshts - Friday, June 25, 2010 - link
High-Def is becoming more and more popular. A n00b will probably get MKVs from friends on a USB drive and expect to play it back couple of years down the line ( maybe, even right now :) )The 100% usage is because VLC is pretty crappy and uses a single threaded implementation to decode when GPU is not enabled. Also, the streams are pretty taxing (16 reference frames , 60 frames per second and so on).
Also, I would mention that having 'trouble' with CPU decoding might mean dropped frames, stutters, sudden spikes in CPU usage and kicking in of the CPU fan etc. etc.
0roo0roo - Friday, June 25, 2010 - link
yea but those "mkv"' are at a fraction of the original blurays bitrate, and thus easier to play, at most they are 12gb or so, and those are more rare, the more common 1dvd size or 2 dvd rips easily play even on a 2ghz core 2. i know, i've tried this before. and even that is really not common usage for a true n00b who will at best run apple trailers, and those don't use vlc.ganeshts - Friday, June 25, 2010 - link
It is just not the bit rate, right? Actually, more than the bit rate, it is other encoding characteristics such as reference frames which are the issue in a PC. (On a PMP with hardware acceleration, it is the other way round). Most PCs have more than enough bandwidth to handle high bit rate scenes, but the CPU intensive calculations are what causes the spikes in CPU usage and stutters (I am trying to find some information about which part of the decode process consumes most time in CPU based decoding.. Let me know if you find any thing relevant !)VLC's development motto, I feel, is that they should be able to play back anything and everything perfectly. From that viewpoint, it makes sense for them to develop GPU accelerated playback, though their primary target audience might not make use of it :)
0roo0roo - Friday, June 25, 2010 - link
stuff like global hot keys/multimedia kb support have sat in the interface broken for years now while they play iwth other stuff.. Its just kind of annoying.legoman666 - Friday, June 25, 2010 - link
Can you compare the HD decoding performance of VLC, WMP, MPC-HC and other software? I'd do it myself, but I have an ATI card ;)mindbomb - Friday, June 25, 2010 - link
i can tell you what the results would be.WMP 12 would have the lowest cpu usage, followed closely by mpc hc, and vlc would be in last by a large margin.