HDTV optimiation

*nix specific usage questions
chris_hubball
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HDTV optimiation

Postby chris_hubball » 21 Dec 2005 12:57

I'm trying to playback a video file which is the resolution of an LCD panel 1368x768. I find that the playback is very choppy mainly due to the CPU usage being at 100% all of the time.

Can anybody offer any advice on how I could improve the situation. I was thinking that these might be possible places to start...

- Which codec uses the lowest CPU power? My videos are currenty DIVX5 - maybe if I use another codec I can get it faster.

- Is the problem due to the CPU overhead required to copy data to the graphics card?

- I'm currently using the compiled i386 packages for Debian. Is it worth recompiling any libraries for processor - perhaps ffpmeg? I tried compiling VLC itself from source but that didn't make a difference.

nm

Postby nm » 21 Dec 2005 17:17

If your videos are really HD MPEG-4 ASP (XviD, DivX5), you'll need a fast CPU (at least 2GHz / 2000+) and a fast graphics card (GeForce 4 MX440 or later should be enough). If the video files are only standard definition (<720x576), but the screen is 1368x768, you probably have problems with the XVideo (Xv) acceleration.

What processor, graphics card and X drivers are you using?

chris_hubball
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Postby chris_hubball » 21 Dec 2005 19:02

The video really is 1368x768 - I made it myself! Interestingly, I also tried running the same video with the display set to 800x600 and it has the same problems, so I guess the graphics card is ok.

I can play the video OK on a similar spec PC using Windows Media Player so I'm guessing the problem is due to a lack of hardware acceleration - I believe WMP uses MPEG acceleration but VLC does it all in software?

nm

Postby nm » 21 Dec 2005 22:26

The graphics card may still be the problem even when the screen size is smaller if XVideo is not in use. See Settings->Preferences->Video->Output modules and check "Advanced options". Do you have XVideo as Video output module? With a fast nVidia/ATI card and their closed-source drivers. you could also try OpenGL.

Some very new cards support MPEG-4 acceleration on Windows, and that might speed up the decoding there. On Linux only MPEG-2 acceleration (XvMC) is available with nVidia drivers for GF4 and up, but I'm not sure if VLC supports it at all. It won't help with MPEG-4 anyway.

If you just need to play the file and don't care about the player, try MPlayer or Xine (or Kaffeine). They usually perform a bit better than VLC.


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