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H.264 slow playback but fast recording - huh?

Last response: in Apps General Discussion
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August 18, 2011 5:33:17 AM

If I can record 1024x768 video at 60 frames per second just fine with the H.264 codec, why I can't I play back the video in real time (rather than 80% true speed with skipping audio to go with it (as if playing back at 48 fps))? I also cannot play back video of 1920x1080 at 29.97 fps from my camcorder (the M2TS original file is converted to AVI using H.264 as well), but again, I'm only getting about 60% true speed for playback (this plays back at about 18 frames per second instead of 29.97). Virtual Dub and Windows Media Player seem to behave the same way. I have the core i7-2600K processor which seems to be 60% faster per core than my previous system, but it's apparently not fast enough. Could it be that playback is not multithreaded like recording is? Short of attempting to overclock my CPU by at least 30%, rather considerable (I still need to replace the temporary RAM and get a better CPU fan first), are there any alternatives available?
August 18, 2011 7:55:49 PM

Playback is generally accelerated by your video card. Do you have the latest video driver installed?
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August 19, 2011 1:49:29 AM

I didn't think the video card has anything to do with the decompression of videos, only the displaying of the decompressed results on the screen. My video card is quite dated though - the GeForce 7600 GT. I haven't updated the drivers at all - I'm only using what came on the CD. Upgrading my CPU, however, has resulted in faster playback, though it's not all that much since it seems that only one thread is used instead of several like with compression. Is there a way, in Virtual Dub, to offload decompression of video to the CPU like I was expecting?
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August 22, 2011 7:47:10 PM

ulillillia said:
I didn't think the video card has anything to do with the decompression of videos, only the displaying of the decompressed results on the screen. My video card is quite dated though - the GeForce 7600 GT. I haven't updated the drivers at all - I'm only using what came on the CD. Upgrading my CPU, however, has resulted in faster playback, though it's not all that much since it seems that only one thread is used instead of several like with compression. Is there a way, in Virtual Dub, to offload decompression of video to the CPU like I was expecting?

I am sorry, but you are misinformed. That video card supports an early version of Nvidia's PureVideo which accelerates video decompression. And the latest video drivers can make a HUGE difference in video and gaming performance, so it is recommended to keep them up to date. Most video playback software will take advantage of hardware decoding when it is available.
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August 23, 2011 3:08:21 AM

I've updated the drivers and I notice a very slight improvement in the speed of playback. I went from playing back at 80% speed to 85%, not much of an improvement but at least it's something.

I don't play video games on my computer so I've been neglecting upgrading my video card for several years. I do play video games quite a bit, even on my computer, but it's only console games (on the computer through a TV tuner which has little dependence on the video card).
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August 23, 2011 8:13:25 PM

Newer video chips perform better acceleration for decoding video. That is how you can have a low powered Atom netbook that can decode and display 1080 HD video without maxing out the CPU.
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August 24, 2011 5:58:58 AM

So then, basically, I'll have to upgrade the video card some. Would something like a GeForce 9600 GT work, or, at least, something that's 3 times as powerful as the GeForce 7600 GT?
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August 24, 2011 8:06:32 AM

Hi, ulillillia. So you can paly M2TS on cam smoothly, but after you convert to H.264 avi, you cannot play in on computer? I suspect that (1.) the trans-coding was not done correctly. Check the bit rate of the video while playing. or (2.) You haven't got video acceleration working yet. Can you download GPU-Z and see if the GPU is used during video playback?

Try CCCP MPC. Enable DXVA by going:

View>options>internal filters and select everything with (DXVA) and apply

Then, on playback>output select

for xp: vmr9 (renderless), directx9 and directx9
for vista,7: evr custom pres, directx9 and directx9

for directshow video, realmedia video and quicktime video

Ok and restart MPC and play video.
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August 28, 2011 2:17:44 AM

Can u try to play the file without graphic card? It is usually Video driver or codec pack.

What OS do u have? I had issues like that in XP and when I went to Win7 the problem was solved.

Your core i7-2600K processor is very fast. It should not have this problem.
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September 7, 2011 5:01:12 AM

Sorry I didn't respond in so long - I went on vacation and I have no computer/internet access available. Virtual Dub appears to have 21% GPU usage and CCCP MPC doesn't seem to use the video card. Disable all hardware acceleration in Virtual Dub and no change occurs at all. I need VD for video editing (including stitching video segments together as one single video), video recording (for screen capture). I made no chances to CCCP MPC and I'm hardly seeing any CPU or GPU usage. YouTube videos also have playback problems when I use full screen.
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September 11, 2011 1:24:57 PM

Videos play fine on my i7-2600k, 1920X1080 using 50mbps bit rates, all fine, also my video card is absolutly crap, 8600gt 256mb that has to have fan on 100% all time and has been severly underclocked to stop it messing up. It sounds to me like its a codec issue, or its probably to do with your settings in your media player, i did somet to media player classic and now when i play some videos in it, it plays them slow and lags, just download VLC media player and play it in that.
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September 11, 2011 1:46:39 PM

Your video card is better than mine, a generation better. Does anyone know how to get Virtual Dub to play back faster? A media player won't do me any good - you can't edit video with these.
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September 11, 2011 1:57:23 PM

I dunno sorry, don't use virtual dub or avi for that matter, avi doesn't seem very good to me, is it even able to take advantage of multithreadec cpu's?, also just out of interest what software do you use to convert the M2TS to avi?
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September 11, 2011 2:01:40 PM

nevermind saw it on another thread
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