LinHES Forums
http://forums.linhes.org/

HiDef recordings with mpeg2 vs mpeg4?
http://forums.linhes.org/viewtopic.php?f=15&t=17486		 Page 1 of 1
Author:  cahlfors [ Thu Dec 27, 2007 10:30 am ]
Post subject:  HiDef recordings with mpeg2 vs mpeg4?
I am unable to make successful HD recordings. :cry: Although my Shuttle FE is said to have enough horsepower, it doesn't cut it. Neither does my son's gaming AMD64x2 4400+ with an Nvidia 7800GTX, although it got the closest - five secs between pauses. Xvmc and deinterlacing settings did not help enough.
Through the help of a helpful KnoppMyth friend, I got a couple of known good HD recordings and they played fine on everything but my BE, but it managed to get very close.

It appears that my own recordings are quite different from the HD material discussed in this forum.
In Scandinavia, they use mpeg4 for HD transmissions. Could it be that US HD transmissions use mpeg2 and mpeg4 requires still more horsepower? I'm quite puzzled. :?

If this theory is correct, is there a graphics card that can help decoding mpeg4 efficiently, so that a reasonable cpu could be used?

Grateful for any words of wisdom.

Cheers,
/Chris
Author:  marc.aronson [ Thu Dec 27, 2007 11:06 am ]
Post subject: 
Quote:
In Scandinavia, they use mpeg4 for HD transmissions. Could it be that US HD transmissions use mpeg2 and mpeg4 requires still more horsepower? I'm quite puzzled. Confused


US HD over-the-air and cable transmissions are mpeg2 at 20mbits/second. The only source of mpeg4 transmissions is one of the satellite TV providers. mpeg4 does require more horsepower to decode. XVMC does help with mpeg2 playback; I have not experience with it's impact on mpeg4.

Here are some experiments to try:

1. Try playing back your recordings with another video player. Knoppmyth comes with mplayer & xine pre-installed. While playing them back monitor CPU utilization with "top" from another windows, say via "putty".

2. Try playback of those recordings in a media play of your choosing on a windows machine, if you have one. See if you get a different outcome.

Marc
Author:  Xsecrets [ Thu Dec 27, 2007 12:20 pm ]
Post subject: 
xvmc does not help with decoding mpeg4 only mpeg2.

there was a discussion in this forum a long time ago where someone from UK was running into the same issue they were using mpeg4. I don't remember the outcome, but you might try searching for that and see if anything ever came of it. As I remember it at that time the mythtv project was just beginning to get mpeg4 implemented.
Author:  cahlfors [ Sat Dec 29, 2007 8:36 am ]
Post subject: 
Quote:
1. Try playing back your recordings with another video player. Knoppmyth comes with mplayer & xine pre-installed. While playing them back monitor CPU utilization with "top" from another windows, say via "putty".

mplayer tops out the CPU with the mpeg4 stuff and xine gets a blank screen.
Quote:
2. Try playback of those recordings in a media play of your choosing on a windows machine, if you have one. See if you get a different outcome.

I have a 2,8GHz P4 running XP. None of the players I had available could play the mpeg4 material at all. The screen was all black. The players I tried were BSplayer, Windows media player, Nero showtime (older version). Not sure what this tells me?

Quote:
xvmc does not help with decoding mpeg4 only mpeg2.

"top" confirms this. Performance of the US material (mpeg2) is affected by the xvmc settings, but the Swedish (mpeg4) stuff is not. Does this imply that a graphics card will not be able to help and that I will need to do all the processing in the CPU?

Cheers and thanks for your thoughts!
/Chris
Author:  marc.aronson [ Sat Dec 29, 2007 9:53 am ]
Post subject: 
It looks like the problem is that maxing out of your CPU on playback. My experience with the pentirum 4 and pentirum D processors was that HD mpeg2 playback requires 2.8ghz to playback without xvmc. My recollection is that mpeg4 playback requires more CPU speed than mpeg2.

If it is useful, you can obtain an additional data point by trying playback on the 2.8ghz windows machine with the right codecs installed. (I suspect the lack of the correct codec is why you got the black screen.) The easiest way to do this is to install the windows version of mplayer or VLC on the windows laptop and try playing it with one of those 2 media players. If playback is smooth you can then hit alt-ctrl-del and bring up task manager to monitor CPU utilization.

mplayer for windows is available at http://www.mplayerhq.hu/design7/dload.html

vlc for windows is available at http://www.videolan.org/

Marc
Author:  tkoster [ Sun Dec 30, 2007 8:39 am ]
Post subject: 
This is a bit out of my realm of expertise but I do use the feature to transcode to ipod for mobile viewing which utilizes a mp4 format. That offers a couple ideas for workarounds.

1. Can you use the the transcode features to get a viewable format? Straight ipod would probably be too low a quality, but perhaps you could tweak transcode to give you what you want. The downside is that you would probably have to wait overnight to watch your shows.

2. Is there a quicktime viewer for linux? Would that be more efficient in handling .mp4 files?
Author:  Martian [ Wed Jan 02, 2008 2:24 pm ]
Post subject: 
I think some of Nvidia's very latest cards have MPEG4 support but they are still pretty pricey and I doubt the MPEG4 support is present in the Linux drivers yet, but I could be wrong. Might be worth a look.

Martian
Author:  erod20 [ Mon Jan 14, 2008 12:30 pm ]
Post subject: 
The is a project on google code call coreavc for linux which lets you use the decoder for windows in linux with a patch for mythtv.
Page 1 of 1 All times are UTC - 6 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/