[mythtv-users] Video quality?

Brian Wood beww at beww.org
Sun Sep 30 01:22:29 UTC 2007

Piers Kittel wrote:
> On 29 Sep 2007, at 15:52, Brian Wood wrote:
>> Dan Harper wrote:
>>> On 29/09/2007, at 10:05 PM, Piers Kittel wrote:
>>>> What I would see is very very slight
>>>> jerking in between frames - it's not totally smooth, I can see very
>>>> slight jumps when it transitions in between frames.
>>> I get this also, so I'd love to know how to fix it.
>> The first question would be what sort of hardware are you using? Both
>> CPU and Video?
> Like I said before, a relatively large range of hardware which is  
> very diverse.  Here's what I can remember from memory:
> Computers no longer used as frontends:
> Computer 1: Abit NF7 motherboard with Athlon XP 1700+ with some  
> flavour of GeForce (4000? Can't remember) with 512MB dual DDR  
> memory.  Ran Debian Sarge then.
> Computer 2: HP Omnibook 500 laptop, Pentium III M processor, (note:  
> not Pentium M) 512MB memory, onboard ATI video (no longer used due to  
> cracked screen) - Ran Debian Sarge then.
> Computer 3: VIA EPIA MII 12000 motherboard with 1.2GHz VIA C3  
> processor, 512MB memory, some flavour of GeForce (video card moved to  
> Computer 4) this computer is now my backend only machine.  Ran Debian  
> Sarge then.  This set up always was my backend, but temporarily moved  
> the backend to Computer 1 for a few months before moving it back.  No  
> difference was noted in the transfer.  This has 2 Hauppaugue Nova-T  
> tuners with the Conexant chipset.
> Currently used frontends:
> Computer 4: Some sort of motherboard (replaced 3 times) with a Duron 
> (?) 900Mhz (? Maybe 800MHz?) with some flavour of GeForce with 512MB  
> memory (the spec for this one changed a lot including 3 very  
> different motherboards and processors, P3, VIA, and now a Duron)  
> running Debian Etch connected to a 21" TV I got off Freecycle..
> Computer 5: Apple PowerMac Quicksilver 2002 - dual 1GHz G4 PowerPC  
> processors, 1GB memory and Geforce 4MX running OS X 10.4.10 connected  
> to a 19" LCD monitor.
> Computer 6: Apple Mac Mini - 1.25GHz G4 PowerPC processor with 512MB  
> memory and onboard ATI Radeon 9200 running OS X 10.3.9 connected to  
> my 28" main living room TV.
> And a couple more I can't recall - I use frankenputers a lot.
> As for software, I always compiled MythTV myself from 0.16 to 0.20,  
> for 0.20-fixes and 0.20.2 I've used the precompiled packages from  
> debian-multimedia.org.  For the OS X frontends, I use precompiled  
> binaries from www.thesniderpad.com (for the early binaries before The  
> Snider Pad, I used ones off the wiki page)

Except for the Macs none of those machines are very similar to the PCs
I've used.

The first machine I used (years ago) was a 2.4 Ghz. P4.

Two years ago I built an Athlon64 3700+ machine, and I'm now using an
AMD FX60 (dual core 2.6 Ghz.). none of these machines exhibit the
behavior you described.

I'm not saying the PCs you used aren't capable of good playback (should
be indistinguishable from live to an uneducated viewer), but they might
well have to be "optimized", at least to the point of eliminating
unnecessary processes (which a lot of distros start by default),
possibly going for a lightweight desktop (or none) and making sure you
are using nVidia's binary drivers (ATI drivers I don't know anything about).

A "slight jump as it transitions between frames" would mean 30 jumps per
second. I suspect you mean scene changes?

Also make sure your resolution and bitrate are set for decent quality,
the defaults are not anywhere near DVD quality (that is, if you are
encoding, if you're receiving a digital stream you have no control over

And, make sure your storage system is optimized (using DMA etc.).

A 5200 series is pretty much the baseline for Myth systems today. Peple
have made earlier cards work but it seems to be some effort.

Have you tried XvMC?


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