Enable GPU acceleration in VLC for sure? (Or: Video lags behind audio)

[Asterra]

I have 1080p60 AVCHD videos that I need to be able to watch in order to figure out what to include in a home video project. This has turned out to be no simple feat. My PC is a Core i7 920 with a Radeon 4870HD and I'm using XP 32bit.

Playing the video normally in my media player of choice results in smooth playback for about 15 seconds, at which point it increasingly chokes both the audio and video, making it unwatchable. Playing the video in Media Player Classic Home Cinema with GPU acceleration enabled causes the video to seemingly play fine (with about 1 or 2% CPU utilization), but upon closer inspection it is doubling one or two frames per second, while the audio plays without a hitch, and the result is that the video quickly and increasingly lags behind the audio. After about 30 seconds, the video is a full second behind the audio.

In some desperation, I tried using VLC. But regardless of whether "Use GPU acceleration (experimental)" is checked or not, the CPU utilization remains unchanged and hovers at around 30%, which, for whatever reason, is the most VLC or any media player is willing to devote to the playback of this media. Changing the output module from "Default" to "OpenGL" or "DirectX" has no apparent effect. The non-GPU-accelerated playback in VLC exhibits stable audio and stuttering, unwatchable video (actually just still frames about 75% of the time).

Updating to the latest Catalyst and DirectX had no effect on any of the above observations.

[jagabo]

I believe 1080p60 isn't DXVA compliant. Although WMP seems to play it with DXVA and minimal (1 or 2 percent) CPU usage.

[Asterra]

Hmm. Which WMP? Also, my brother's PC plays them with MPC, GPU acceleration works, and there is no video delay. His card (5850) is supposedly faster than mine, which could be a factor, but if it's my video card causing the delay, then why doesn't the player either skip frames to keep in sync, or use a combination of CPU and GPU? Allowing the video to slide drastically out of sync seems like a terrific oversight.

[jagabo]

It was WMP12 in 64 bit Windows 7. That was on an Intel Q6600 CPU and ATI 4850 GTX.

The use of DXVA is an either or situation. If you use DXVA the GPU decodes the video. Otherwise the CPU decodes the video. VLC didn't have a multithreaded h.264 decoder until recently. Make sure you have a recent build.

[Asterra]

I'm having difficulty just getting these programs to actually use the GPU. VLC and MPCHC, on both XP and Win7. Only MPCHC on XP has worked. I think the difficulty may be that some codec or other is taking over the decoding, despite my having set up filters in MPCHC.

I've checked the video files with MediaInfo, which confirms that it's 28.0 Mbps BDAV. The video is 24.1Mbps, 1920x1080, 59.94 fps, AVC (High@L4.2) (CABAC / 4 ref frames). The audio is 384Kbps, 48.0KHz, 16-bit, 6-channel AC-3.

The fact that MPCHC in XP used the GPU to play these videos means it does or is supposed to work. It is my hope that I can get things working in Windows 7 and that the difference in OS will somehow force one of the media players to play nice and either play without issues or at least skip frames in order to avoid the video lagging problem.

I think what I need is some means to determine once and for all which codec(s) is/are stealing the process from the DXVA codecs that I'm trying to force MPCHC to use.

[jagabo]

I can get MPCHC-64 to use DXVA in Win7-64 (and XP-32) but it can't play all the 1080p60 files I have. I only have a few, one from a Sanyo Xacti camcorder, and an x264 reencoded version of that. The x264 encoded version plays smoothly but the native Xacti file doesn't -- about twice a second it inserts a random frame from earlier in the video. Remuxing the Xacti file doesn't help.

If I disable MPCHC's internal h.264 decoders and use CoreAVC it can play the 1080p60 files properly. With CUDA, DXVA (~8 percent CPU usage), or software decoding (~40 percent CPU usage).

VLC is pretty hopeless. It doesn't play 1080p60 smoothly (either file mentioned above) and I can't get it to use DXVA.

By the way, you can right click on the video window while MPCHC is playing and select Filters to see the list of DirectShow filters that are in use. Clicking on the filters lets you see their properties and change settings.

[Asterra]

Okay, here's where I'm at so far. I open the Filters menu as you suggest. It lists:

Default WaveOut Device
Enhanced Video Renderer (custom presenter)
Audio Switcher >
MPC Video Decoder
AC3 Audio Decoder

Choosing "MPC Video Decoder" opens a settings menu wherein I can modify both the FFmpeg and the DXVA settings. I can tell that MPC is trying to use the GPU because the "DXVA Mode" is shown to be (greyed out) "H.264 bitstream decoder, no FGT", whereas if I go to the Internal Filters, turn off DXVA, and turn on FFmpeg, the "DXVA Mode" says it's not being used. But it is pretty obvious that the GPU is not in fact being used because ATI's Catalyst Control Center lets one watch the GPU activity and the nature of this activity does not change; it fluctuates between 5 and 15% no matter what I'm doing. (And also the nature of the CPU utilization is unchanged.) To be certain, I shrink the actual video output down to a tiny box so that almost nothing is taking place on my desktop.

It also doesn't seem to matter where my H264 video comes from. If it's 1080p60, the result chokes. It just chokes in different ways. The video from the camcorder plays the video component too slowly and quickly goes out of sync. My own encode from MeGUI constantly stutters in an apparent attempt to allow the decoder to catch up. With the GPU activity remaining unchanged, it seems obvious that despite the evidence provided by MPC, the GPU is not being utilized. So what remains is to find out how I can truly force GPU utilization, and/or how I can determine what is actually being used despite MPC's report.

[edDV]

What camera/camcorder shot the 1080p60 file? I'd like to collect some samples for experiment.

I'm sure you are aware that 1080p60 is not part of the AVCHD or Blu-Ray standards. 720p60 is supported by Blu-Ray but not always by AVCHD hardware or apps.

Ref: http://en.wikipedia.org/wiki/AVCHD#1080p

[jagabo]

Choosing "MPC Video Decoder" opens a settings menu wherein I can modify both the FFmpeg and the DXVA settings. I can tell that MPC is trying to use the GPU because the "DXVA Mode" is shown to be (greyed out) "H.264 bitstream decoder, no FGT",

If it says that it is using DXVA. It's always greyed out like that.