[mythtv-users] My HDTV woes

Jason Donahue mythtv at timekiller.org
Sun Apr 2 19:37:13 UTC 2006


After a lot of time, and a lot of cursing, I am now fairly close to having
MythTV with HD. I just need a little help to get the rest figured out.

So, here's some info on my setup:

Pentium 4 3.00GHz w/ hyperthreading (64bit chip, but 32bit install)
1GB RAM
Nvidia GeForce FX 5700LE (using DVI out to 42" Plasma TV)

TV input: Comcast DCT-6200 via Firewire

I finally got an X config that works (pasted below). I am able to watch
live TV ok, although I do get some prebuffering pauses. The real problem
starts when I go to an HD channel (side note: I know I can't get encrypted
HD - I am referring to public HD, such as ABC, etc).

When I tune to an HD channel, it display, and the picture is great, but it
stutters BADLY. The mythfrontend log shows:

2006-04-02 15:09:06.109 NVP: prebuffering pause
2006-04-02 15:09:06.133 WriteAudio: buffer underrun
2006-04-02 15:09:06.179 NVP: prebuffering pause
2006-04-02 15:09:06.202 WriteAudio: buffer underrun
2006-04-02 15:09:06.243 NVP: prebuffering pause
2006-04-02 15:09:06.257 WriteAudio: buffer underrun
2006-04-02 15:09:06.310 NVP: prebuffering pause
2006-04-02 15:09:06.326 WriteAudio: buffer underrun
2006-04-02 15:09:06.343 NVP: prebuffering pause
2006-04-02 15:09:06.410 NVP: prebuffering pause
2006-04-02 15:09:06.477 NVP: prebuffering pause
2006-04-02 15:09:06.493 WriteAudio: buffer underrun
2006-04-02 15:09:06.543 NVP: prebuffering pause
2006-04-02 15:09:06.560 WriteAudio: buffer underrun
2006-04-02 15:09:06.610 NVP: prebuffering pause

..and on and on...

For my TV playback I setup XVMC out, with the color OSD hack, and set
aspect override to 16:9 stretch so non-hd channel fill the screen (shoud
not apply to hd channels). Also, when I watch an HD channel, and it start
stuttering, th load on the box goes up (over 1.5...)

The only thingI can figure is that I do not have something set right with
the codec, or the scaling, and the box is spending all it's time fixing
it.

I KNOW 3Ghz w/hyperthreading & XVMC should be able to handle HD.

Any help on this would be awesome.

Here's the juicy parts of my X config (it's adapted from Jarod's config):

Section "Monitor"
        Identifier   "Monitor0"
        VendorName   "Maxent"
        ModelName    "42in HDTV"
        #Option      "IgnoreEDID"
#       DisplaySize             820 310
        #DisplaySize            1085.34125 610.504451
        HorizSync    33.75
        VertRefresh  59.94
        #VertRefresh  60.0
        Option     "dpms"
        # My 960x540p mode
        Mode "960x540p"
                DotClock 37.26
                HTimings 960 976 1008 1104
                VTimings 540 542 548 563
                Flags "+HSync" "+VSync"
        EndMode
        # My 880x480in540p mode
        Mode "in540p"
                DotClock 37.26
                HTimings 880 944 1048 1104
                VTimings 480 506 520 563
                Flags "+HSync" "+VSync"
        EndMode
        # My 1920x1080i mode
        Mode "1920x1080i"
                DotClock 74.52
                HTimings 1920 1952 2016 2208
                VTimings 1080 1084 1096 1126
                Flags "-HSync" "-VSync" "Interlace"
        EndMode
        # My 1760x960in1080i mode
        Mode "in1080i"
                DotClock 74.52
                HTimings 1760 1888 2096 2208
                VTimings 960 1012 1028 1126
                Flags "-HSync" "-VSync" "Interlace"
        EndMode
EndSection

Section "Device"
        Identifier  "Videocard0"
        Driver      "nvidia"
        VendorName  "PNY"
        BoardName   "GeForce 5700"
        Option      "ConnectedMonitor" "DFP"
        Option      "NoLogo" "1"
        Option      "RenderAccel" "1"
        Option "XvmcUsesTextures" "false"
        Option      "NvAGP" "1"
        Option      "NoDDC"
EndSection

Section "Screen"
        Identifier "Screen0"
        Device     "Videocard0"
        Monitor    "Monitor0"
        DefaultDepth     24
        SubSection "Display"
                Viewport   0 0
                Depth     24
                #Modes    "1920x1080i"
                Modes    "in1080i"
        EndSubSection
EndSection



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