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PostPosted: Fri Jan 28, 2005 8:51 am 
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Joined: Fri Apr 02, 2004 10:08 am
Posts: 1637
Location: Virginia, USA
I wanted to list the current problems I'm having with playback of HD3000 streams, to see if they are surmountable. As a reminder, I'm not using it with MythTV, for a variety of reasons. Theoretically at least, I should get better results with playback outside of MythTV.

Here's the rundown:

* I'm not using xine-hd as I've already got the 1.0 release of xine installed and working fine for upsampling DVD playback. If I could install xine-hd independently of the more-recent xine, I might give it a shot.

* Insted, from reading the PCHDTV forum, I've tried viewing the live stream via vlc and via mplayer. Both exhibit the same symptoms: all's fine for a while, then the sound begins to cut in and out, then sound drops out altogether, then picture gets choppy, then picture freezes.

* Thought it was an issue with the version of ALSA I had (1.0.6). Just upgraded to 1.0.8. No help.

* If I record a transport stream, I can play it back with vlc and it plays back pretty well, as far as I can tell, even with some of the deinterlacing modes and a 1080i recording playing back at 720p. However, the keystrokes to jump ahead or back in playback do not seem to work: every key takes me back to the beginning of the recording. Maybe this is a transport stream issue

* If I playback a transport stream with mplayer, I can jump around the recording just fine, but audio goes out of sync. At least mplayer also has the courtesy of telling me "your system is too slow to play this" after I quit out of it. It recommends some things, some of which I've tried, which help to a degree, but audio is still out of sync after jumping forward through a recording.

* Inkling at PCHDTV forum claims that scaling 1080i recordings to 720p playback is problematic. Once I find a modeline that works with my screen and 540p, I'll give that a shot. However, I see similar problems with recordings from 720p stations in the area.

Xsecrets posted somewhere here about enabling ALSA's OSS emulation for sound. Are there any good pointers for how to do this? I did some Googling for "ALSA OSS emulation" and checked some things on my setup and the appropriate modules seemed to be in the appropriate places.

Could I have better success with not using motherboard video? It's a Shuttle SN41G2 with nForce2 video. I could add a video card but then the system would be noisier (a fanless card heats up the system and makes the Shuttle's fan work harder/noisier).

Anyhow, just hoping for some ideas. Thanks.


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PostPosted: Fri Jan 28, 2005 9:50 am 
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Joined: Mon Oct 06, 2003 10:38 am
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Location: Nashville, TN
Well first thing my guess would be your cpu is indeed underpowered. pretty much any athlonXP is not going to cut it. The alsa oss emulation thing was really only an issue with mythtv, and either seems to work fine for me now that I have upgraded my cpu to a PIV 3G. in mythtv you can tell you are using OSS emulation if you are using /dev/dsp for your sound. If you are using native alsa your sound will be set to use ALSA:something the something being default analog or spdif.

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PostPosted: Fri Jan 28, 2005 11:22 am 
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Joined: Fri May 21, 2004 11:55 pm
Posts: 1206
Location: Silicon Valley, CA
You didn't say what your GHz is, but I agree with Xsecrets. I tried up to Athlon XP 2800 and couldn't play reliably on Myth. Take a look at top while playing and see what idle cpu you have (not much I'll bet). You could investigate with the "forbidden fruit" of XvMC with mplayer. That'll cut your cpu needs but it doesn't work with the myth player. Should be fine with mplayer tho.

The only thing wrong with the built in video is that it's limited to AGP 4X instead of 8X. I dunno why, but all the boards I've seen and used with the nVidia IGP are limited to 4X for the internal video, even tho the AGP slot works at 8X. Even so, AGP 4X should work with XvMC, but probably not too well with Xv.

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PostPosted: Fri Jan 28, 2005 11:58 am 
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Joined: Fri Apr 02, 2004 10:08 am
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Location: Virginia, USA
Yeah, figured. Thanks to both of you for your advice. I did find an mplayer command line that will reportedly allow it to use XvMC, so we'll see how that goes.


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PostPosted: Sat Feb 05, 2005 1:33 pm 
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Joined: Fri Apr 02, 2004 10:08 am
Posts: 1637
Location: Virginia, USA
Sure enough, I finally got around to compiling the latest mplayer with XvMC support, and fed it some big long command line with various options that I found in this thread. And lo and behold, I can play back HD channels live with no audio sync problems or dropped frames!

The only catch: I can't get deinterlacing to work on 1080i channels. I guess this is comparable to the situation in MythTV, where turning on XvMC support keeps you from using kerneldeint. Or I'm not doing something right (always a high probability). Anyhow, the local Fox affiliate is 720p, so I'm good to go for the Super Bowl!

Thanks and hope this helps.


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