[mythtv-users] Choppy hd live tv playback with HD3000

Daniel Kristjansson danielk at cuymedia.net
Mon Dec 19 19:27:20 EST 2005

On Mon, 2005-12-19 at 15:42 -0800, Mark Johannessen wrote:
> I have been able to install mythtv/mythweb sucessfully (after about a
> weekend of work) on the following box:
> Intel Celeron 2.66 gHz
> 768 ram
> Nvidia e-GeForce MX4000 AGP card
> Soundbalster audio card

> The system is hooked up to an HD antenna and the signal is fine,
> channels can be selected, audio from the sound card works, mythweb
> works, etc.  However, when either playing live TV or playing back
> recorded shows, the playback studders.  It plays for a couple of
> seconds, studders, and plays for another couple of seconds, and so
> forth.  The pattern is regular.  I have plenty of HD space, using an
> LVM with jsf format.

There are three major causes of studder:
  Audio problems
  Underpowered systems
  nVidia's XvMC implementation

The audio can often be addressed by turning on "Extra Audio buffering" in
the frontend settings, but sometimes requires the purchase of a new audio card.

A Celeron 2.66Ghz should be able to handle 1080i, if you compile specifically
for it. Download the latest SVN and use:
  '--compile-type=release --enable-proc-opt --enable-dvb'
as your ./configure options.

I recommend against using XvMC with nVidia cards for HDTV unless you can't
get MythTV to work without it. If you do need it, you need to enable it in
./configure, and in the frontend settings under:
  "Setup"->TV Settings"->"Playback"->"Preferred MPEG2 Decoder"
I believe your card has IDCT acceleration, but it only has 8 decoding surfaces,
which is enough for the video player which comes with the pcHDTV card, but not
for MythTV. MythTV has a fancy OSD, and does captions, etc. There is some 
preliminary work to implement less fancy OSD in the code; search for Chromakey
OSD in mythtv-dev if you want to try it out.

-- Daniel

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