[mythtv-users] Movement "blurring" [was (no subject)]

[Lan Barnes]

On Tue, May 15, 2007 5:05 pm, Paul G. Allen wrote:
> (no subject) eh? Interesting. :)
>

Stupid mistake -- mea culpa

> On Tue, 2007-05-15 at 16:34 -0700, Lan Barnes wrote:
>> This is a race to see where I get the answer first ;-)

Yeaa! Kplug wins. I'll cross post the answer to get it in the Myth-users
archives.

>> I have seen several variations on this question and suspect it may be
more
>> than one possible problem.
>> I recently upgraded from MythDora 3.2 to 4.0 with a reinstall. I did
not
>> have this problem in 3.2.
>> While watching a baseball game, mostly all was OK, but while watching a
large thing in motion, like a man running, the white uniform would
"stretch" along the axis of motion blurring out like a cartoon
character
>> leaving streaks behind him. The blur looked pixilated and "caught up"
when
>> the guy stopped.
>
> Without seeing it, it sounds like what I spent two years looking for in
my previous life working with MPEG-2 video compression hardware. I also
see this more than I'd like on nearly every cable and satellite station on
the planet.
>
> The reason this happens in cable and sat. reception is simple, but often
ignored by most folks. It's a result of too much compression at the sat.
uplink (Note: All TV transmissions come via satellite, unless you're using
a TV antenna and licking up local channels). In the quest to make more
money, the providers have compressed the data to the ragged edge, causing
pixelation and macro-blocking (A macro block is a large square the size of
several pixels and often appearing as all one color. They usually appear
in multiples of 4). The compressors I worked on could get about 270:1
compression with almost no discernible pixelation, which translates to
about 2Mb/second of streaming MPEG-2 video data. After this point, the
pixelation becomes worse and worse, but boy does it save bandwidth. By
compressing the video a bunch, the providers can get more channels on the
sat., thereby making more money off of you and me.
>
> In the early days of digital TV, I found the picture excellent. As time
wore on, I began seeing the crap that I tested for in my previous life
(and when we saw it, we repaired the unit causing it). These days I rarely
see a HDTV picture I like.
>
> So, it could be the compression ratio either at the uplink, the
> downlink, or in your Myth setup. If your setup can't handle decoding the
stream, then this will be the result. If something is configured wrong,
this could be the result. If you provider has a screwed up system, this
could be the result.
>
> Since you indicate things were OK before the update, I'd lean toward
something being amiss with the newer version of MythDora (as opposed to a
problem caused by your provider, receiver, or computer).
>
> PGA

Thanks. I even understood that ... quite lucid.

In reviewing the Myth docs and wiki, which seem to span the known
universe, I managed to locate an instruction for using the nVidia HW
Mpeg-2 decoder, XvMC.

http://www.mythtv.org/wiki/index.php/XvMC#Configuration

One thing that changed was I activated this before to control color of
playback, not realizing it might also improve motion. But I hadn't
reactivated it on this install. These are the hazards of doing stuff bu
rote.

Anyway I reinstalled that configuration, so we'll have to wait for another
ball game to see if that was the secret sauce.

BTW, the config has two XvMC settings, one with a VIA Unichrome chipset
and one without. I wouldn't know a Unichrome chip from a bear in the
forest, but my (cheap) MB is chockablock with VIA chips.

[root at xena sysconfig]# grep -i via hwconf
driver: via-ircc
desc: "VIA Technologies, Inc. VT8235 ISA Bridge"
desc: "VIA Technologies, Inc. VT8366/A/7 [Apollo KT266/A/333 AGP]" desc:
"VIA Technologies, Inc. VT8366/A/7 [Apollo KT266/A/333]"
driver: via-rhine
desc: "VIA Technologies, Inc. VT6102 [Rhine-II]"
driver: snd-via82xx
desc: "VIA Technologies, Inc. VT8233/A/8235/8237 AC97 Audio Controller"
desc: "VIA Technologies, Inc. USB 2.0"
desc: "VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller"
desc: "VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller"
desc: "VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller"
desc: "VIA Technologies, Inc. VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus
Master IDE"

Any hints on which XvMC to set it to, VIA or non-VIA?

-- 
Lan Barnes

SCM Analyst              Linux Guy
Tcl/Tk Enthusiast        Biodiesel Brewer