[mythtv-users] Advice on Building a Quiet MythTV Box?

[Scott Traurig]

> Date: Sat, 29 Nov 2008 11:47:26 +0000
> From: "Nick Morrott" <knowledgejunkie at gmail.com>
> 
> On 29/11/2008, Paul Gardiner <lists at glidos.net> wrote:
> 
>>  So, yes, perhaps these are all hardware problems, but it seems
>>  to me there is no good hardware for MythTV to drive SD TVs,
>>  except perhaps ancient ATI cards. Certainly, no one has been able
>>  to suggest anything that will definitely output PAL timings on
>>  VGA, or any other fool proof way to drive my SD TV that will give
>>  results as good as my DVRs.  If alternatively it really is settings
>>  then what settings might it be? I have all postprocessing turned
>>  off I believe.
> 
> As I'm sure I've written before, the best quality I've seen for PAL
> TV-out (with the equipment I have) was from a PVR-350 outputting
> directly to my Sony WEGA CRT. I originally went this route in 2004/05
> because the driver support for PAL TV out was broken in the ATI fglrx
> driver, and my box was using an integrated chipset. No TV display
> problems at all that I can remember, perfect interlacing and vibrant
> colour. The downside with using the PVR-350 back then as an X display
> device was the lack of any ability to play non-MPEG-2 content.
> 
> For some years now I've used an ATI Radeon 9000 Pro card coupled to a
> homebuilt VGA-> SCART cable with that TV, for both DVB-T and analog
> video capture from a PVR-150 from a cable box. I use kernel
> deinterlace and am more than satisfied with the great image quality
> (although I have no frame of reference to compare it to an OTS
> FreeView PVR in terms of video output).
> 
> Other frontends currently use 720p-ready TFT monitors, but as I'm
> still only playing with DVB-S at the moment and there's such a small
> amount of HD content broadcast, and the TV still gives an amazing
> image, like you we're in no hurry to replace it.
> 
> The PVR-350 was used up until very recently as a capture device when
> we got rid of our second cable box, so has still been a useful
> investment. Due to the inherent disadvantages of using one as a
> general multi-purpose display device though, I very much doubt I'lll
> ever go back to using it as such.

I've been down the same road you've been going down, i.e. the realization
that commercial DVR appliances have much better picture quality than Myth
setups. If you search the archives you'll find me concerned about the same
thing when I was a Myth newbie. It seems there is a large contingent of
Myth-folk who have not previously owned a DVR appliance (not a surprise,
really) and therefore are truly unable to appreciate the differences, which
are substantial as you have discovered.

It seems the focus in your recent discussion has been on the output side.
IMHO the output side is rarely the problem or at least not a significant
problem. For example, on my Myth setup, a mundane, older dual-Athlon/Nvidia
motherboard, DVD and HDHomerun derived source material look absolutely great
on either an old Sony 32" XBR tube or my Phillips 120Hz 1080p LCD. However
the same cannot be said for any material sourced from an analog
tuner/capture card.

It is actually the input side, the tuner/capture cards, that are the source
of your quality issue. The PVR series of capture devices are absolutely
horrible. Sadly that is what most of us are stuck with until drivers for the
ATI products or some other better product are available.

The quality differences between the various flavors of the PVR series are
minimal and insubstantial. I have one tuner accepting S-Video from a Comcast
STB and another taking in straight cable. On the former the resulting stream
still sucks compared to my old, trusty Pioneer DVR appliance. On the latter
the crappy tuner just adds insult to injury.

I would suggest you tune your playback settings using high quality digital
source material (DVD or HD sources). Personally I find any Myth renderer to
do a fine job as long as Bob deinterlacing is used. If you are using an
Nvidia output I've found the nvidia-settings utility to tune the color,
brightness and contrast to be very helpful as well. Make sure it runs on
startup to load the configuration (see
ftp://download.nvidia.com/XFree86/Linux-x86/nvidia-settings-user-guide.txt).

After tuning the output that way you will find all of your problems lie with
your capture cards. After some careful consideration and the realization
that 90% of my recordings are from broadcasts available as unencrypted QAM
on my cable system (i.e. major OTA network channels) I bought an HDhomerun
and have been much happier. More importantly, my customers (the family) have
also been much happier!

Have fun with your system!

Scott (who continues to wait for better analog capture hardware...)