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quality question.. ways to make it better?

 

 

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craig at 8010

May 19, 2004, 5:01 AM

Post #1 of 14 (5845 views)
Permalink
quality question.. ways to make it better?

hey guys.. have a general question regarding quality..

my current setup is a Athlon 1800XP / 120Gb / 512Mb / AverTV Studio for
the backend

an Athlon 1.4Ghz / 120gb / 512Mb / Radeon 9200 SE for the front end..
the composite out goes through to a composite-scart converter which is
plugged into the TV.

I'm in the UK and have NTL Cable.. so I have a coax arial cable from the
output of the cable box running to the arial cable on the TV card in the
backend..

I've set the recording profile for LiveTV to mpeg4 and set it to pretty
much maximum quality.. but its still quite "bitty" (not a lot.. but you
can see it).. and the colors just seem really dull.. it seems to lose
the vibrant quality from the original..

Is there anything fundamentally wrong with this setup? is there anything
I can do to make it better without shedding out tons of cash?

Also.. am using the latest CVS version..

[root [at] mythtv root]# rpm -qa | grep mythtv-backend
mythtv-backend-0.15-69cvs.rhfc1.at
[root [at] mythtv root]# rpm -qa | grep mythtv-frontend
mythtv-frontend-0.15-69cvs.rhfc1.at

I've tried pressing "G" and adjusting color/hue/brightness etc.. but
that doesn't seem to do very much..

Setup was from Jarods guide and am up to date I think with everything
else.. (apt-get dist-upgrade says I am anyways)

Thanks for any ideas..

Craig


garry at sneakyninja

May 19, 2004, 10:20 AM

Post #2 of 14 (5740 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

Craig Tinson wrote:

> hey guys.. have a general question regarding quality..
>
> my current setup is a Athlon 1800XP / 120Gb / 512Mb / AverTV Studio
> for the backend
>
> an Athlon 1.4Ghz / 120gb / 512Mb / Radeon 9200 SE for the front end..
> the composite out goes through to a composite-scart converter which is
> plugged into the TV.
>
> I'm in the UK and have NTL Cable.. so I have a coax arial cable from
> the output of the cable box running to the arial cable on the TV card
> in the backend..
>
> I've set the recording profile for LiveTV to mpeg4 and set it to
> pretty much maximum quality.. but its still quite "bitty" (not a lot..
> but you can see it).. and the colors just seem really dull.. it seems
> to lose the vibrant quality from the original..
>
> Is there anything fundamentally wrong with this setup? is there
> anything I can do to make it better without shedding out tons of cash?
>
> Also.. am using the latest CVS version..
>
> [root [at] mythtv root]# rpm -qa | grep mythtv-backend
> mythtv-backend-0.15-69cvs.rhfc1.at
> [root [at] mythtv root]# rpm -qa | grep mythtv-frontend
> mythtv-frontend-0.15-69cvs.rhfc1.at
>
> I've tried pressing "G" and adjusting color/hue/brightness etc.. but
> that doesn't seem to do very much..
>
> Setup was from Jarods guide and am up to date I think with everything
> else.. (apt-get dist-upgrade says I am anyways)
>
> Thanks for any ideas..
>
> Craig
>

Glad it't not just me. I too live in the uk, and use an RF feed from the
back of a Sky Digital box, via the arial socket on my PVR-250. TV out is
via the Pundits' onboard SiS/

Weird thing is... watching recordings is fine, not far off watching
normal TV. And, burning to DVD results in a picture that looks as good
as normal TV (audio goes out of sync, but that's another thread :-)
)But, watching liveTV via myth is well, slightly less than perfect. You
can tell it's not 'real' tv. The motion seems to stutter. Maybe stutter
is too strong a word.. it just doesn't seem to flow properly. And the
colours are a bit washed out too.

I have the liveTV profile set with the bitrates up to the max, with a
low resolution.. (300 x 500 ish- can't remember the exact numbers)

-Garry

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steve.dobson at uthink

May 19, 2004, 11:09 AM

Post #3 of 14 (5749 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

Craig / Garry

On Wed, May 19, 2004 at 04:53:13PM -0700, Garry wrote:
> Craig Tinson wrote:
> >my current setup is a Athlon 1800XP / 120Gb / 512Mb / AverTV Studio
> >for the backend
> >
> >an Athlon 1.4Ghz / 120gb / 512Mb / Radeon 9200 SE for the front end..
> >the composite out goes through to a composite-scart converter which is
> >plugged into the TV.
> >
> >I'm in the UK and have NTL Cable.. so I have a coax arial cable from
> >the output of the cable box running to the arial cable on the TV card
> >in the backend..
> >
> >I've set the recording profile for LiveTV to mpeg4 and set it to
> >pretty much maximum quality.. but its still quite "bitty" (not a lot..
> >but you can see it).. and the colors just seem really dull.. it seems
> >to lose the vibrant quality from the original..
> >
> >Is there anything fundamentally wrong with this setup? is there
> >anything I can do to make it better without shedding out tons of cash?
> >
> >I've tried pressing "G" and adjusting color/hue/brightness etc.. but
> >that doesn't seem to do very much..
> >
> >Setup was from Jarods guide and am up to date I think with everything
> >else.. (apt-get dist-upgrade says I am anyways)
>
> Glad it't not just me. I too live in the uk, and use an RF feed from the
> back of a Sky Digital box, via the arial socket on my PVR-250. TV out is
> via the Pundits' onboard SiS/
>
> Weird thing is... watching recordings is fine, not far off watching
> normal TV. And, burning to DVD results in a picture that looks as good
> as normal TV (audio goes out of sync, but that's another thread :-)
> )But, watching liveTV via myth is well, slightly less than perfect. You
> can tell it's not 'real' tv. The motion seems to stutter. Maybe stutter
> is too strong a word.. it just doesn't seem to flow properly. And the
> colours are a bit washed out too.
>
> I have the liveTV profile set with the bitrates up to the max, with a
> low resolution.. (300 x 500 ish- can't remember the exact numbers)

I use a PVR-350 - so encoding and decoding are both MPEG-2 and handled
by the same hardware. But I did some bench marks to find out how much
CPU was being used.

A simple raw copy (dd if=/dev/video0 of=/dev/video16 bs=64k) loaded my
VIA 586 533MHz CPU to 3%!!! (from about 2% when not doing the dd).

When "dd"ing via disk
dd if=/dev/video0 of=/tmp/test.mpg bs=64k
dd if=/tmp/test.mpg of=/dev/video16 bs=64k
The loading when up to 6%

When running MythTV the loading was higher, around 30% IIRC, so I think
it is your setup that is a problem here.

Try running top(1) to see what your CPU loading is. The PVR-2550 (&-350)
is a MPEG-2 card not MPEG-4 - so I would guess that the CPU is overloaded.

Steve


bjm at lvcm

May 19, 2004, 5:48 PM

Post #4 of 14 (5725 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

Craig Tinson wrote:
...
> I've set the recording profile for LiveTV to mpeg4 and set it to pretty
> much maximum quality.. but its still quite "bitty" (not a lot.. but you

The "bitty"ness has to do with bitrate and the compression
factors. Ironically, if you use a higher resolution at the same
fixed bitrate, the "bitty"ness gets worse. What you need is
a moderate resolution and a higher relative bitrate.

For example, for my Default profile, I use 480x480 (480x576
for PAL) and a scaled bitrate of 4000. For low bitrates like the
default 2200, it is best to set the "Maximum quality" at 2 so
that it doesn't waste precious bits on frames that are almost
perfect anyway. However, at 4000 and above, setting the Max
limit at 1 will reduce the blockiness in the background.

> can see it).. and the colors just seem really dull.. it seems to lose
> the vibrant quality from the original..

Yeah, there are some silly problems with the luma and chroma
values for bttv cards that make bright colors washed out and
pale even when the saturation is set high enough to make the
dark colors bleed. Because of the 'out of the box' picture, most
people assume PVR cards are superior even though they use the
same chip for video capture. With the correct adjustments, a
bttv card can look even better than a hardware encoder card.

There is a new filter added after the 0.14 release in CVS that
fixes an outright mistake for bttv luma. It also has parameters
that allow you to make further adjustments that you can't do for
the hardware cards. I've played with this over the past few months.
By comparing direct cable on one input and myth on another, I've
got the color reproduction almost identical. Even though the
myth input is a little fuzzier, the picture is otherwise as
vivid. To set these parameters, run your mysql client and
enter these two lines.

update channel set contrast=21500,brightness=37500,colour=32768,hue=32768;
update channel set videofilters='adjust=34:253:1.0:23:232:1.0';

If your worried that you might have to undo this, these will
reset the defaults:

update channel set contrast=32768,brightness=32768,colour=32768,hue=32768;
update channel set videofilters='';

Also, especially if you have an AverTV card, they tend to over-
saturate quite a by default. Hauppague tend to under-saturate.
If you have v4l2 support in your kernel, v4lctl can normalize
the chroma levels with Automatic Gain Control (AGC).

: bjm [at] mokto ; v4lctl -c /dev/video0 setattr 'chroma agc' on
: bjm [at] mokto ; v4lctl -c /dev/video0 list
attribute | type | current | default | comment
-----------+--------+---------+---------+-------------------------------------
norm | choice | NTSC | PAL | PAL NTSC SECAM PAL-Nc PAL-M PAL-N NTSC-JP PAL-60
input | choice | Televis | Televis | Television Composite1 S-Video
audio mode | choice | lang1 | mono | mono stereo lang1 lang2
bright | int | 37500 | 32768 | range is 0 => 65535
contrast | int | 21500 | 32768 | range is 0 => 65535
color | int | 32768 | 32768 | range is 0 => 65535
hue | int | 32768 | 32768 | range is 0 => 65535
mute | bool | off | off |
chroma agc | bool | on | off |
combfilter | bool | off | off |
automute | bool | on | off |
luma decim | bool | off | off |
agc crush | bool | on | off |
vcr hack | bool | off | off |
whitecrush | int | 207 | 207 | range is 0 => 255
whitecrush | int | 127 | 127 | range is 0 => 255

If your output is missing "chroma agc" and some of the others
then you do not have v4l2 support.

> Is there anything fundamentally wrong with this setup? is there anything
> I can do to make it better without shedding out tons of cash?

Yes and yes.

-- bjm


johnny at fishcounts

May 20, 2004, 12:45 AM

Post #5 of 14 (5721 views)
Permalink
RE: quality question.. ways to make it better? [In reply to]

Bruce, So what kind of card do you currently use? I've played only with my
color/brightness/contrast settings and I seem to like everything default
other than changing the contrast to 25000. I currently run a Winfast Deluxe
BT878A card w/ dbx stereo. So what does the filter do exactly? I am going to
run it now to see if I can see a difference or not...


Johnny Lee

-----Original Message-----
From: mythtv-users-bounces [at] mythtv
[mailto:mythtv-users-bounces [at] mythtv] On Behalf Of Bruce Markey
Sent: Wednesday, May 19, 2004 5:49 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] quality question.. ways to make it better?

Craig Tinson wrote:
...
> I've set the recording profile for LiveTV to mpeg4 and set it to pretty
> much maximum quality.. but its still quite "bitty" (not a lot.. but you

The "bitty"ness has to do with bitrate and the compression
factors. Ironically, if you use a higher resolution at the same
fixed bitrate, the "bitty"ness gets worse. What you need is
a moderate resolution and a higher relative bitrate.

For example, for my Default profile, I use 480x480 (480x576
for PAL) and a scaled bitrate of 4000. For low bitrates like the
default 2200, it is best to set the "Maximum quality" at 2 so
that it doesn't waste precious bits on frames that are almost
perfect anyway. However, at 4000 and above, setting the Max
limit at 1 will reduce the blockiness in the background.

> can see it).. and the colors just seem really dull.. it seems to lose
> the vibrant quality from the original..

Yeah, there are some silly problems with the luma and chroma
values for bttv cards that make bright colors washed out and
pale even when the saturation is set high enough to make the
dark colors bleed. Because of the 'out of the box' picture, most
people assume PVR cards are superior even though they use the
same chip for video capture. With the correct adjustments, a
bttv card can look even better than a hardware encoder card.

There is a new filter added after the 0.14 release in CVS that
fixes an outright mistake for bttv luma. It also has parameters
that allow you to make further adjustments that you can't do for
the hardware cards. I've played with this over the past few months.
By comparing direct cable on one input and myth on another, I've
got the color reproduction almost identical. Even though the
myth input is a little fuzzier, the picture is otherwise as
vivid. To set these parameters, run your mysql client and
enter these two lines.

update channel set contrast=21500,brightness=37500,colour=32768,hue=32768;
update channel set videofilters='adjust=34:253:1.0:23:232:1.0';

If your worried that you might have to undo this, these will
reset the defaults:

update channel set contrast=32768,brightness=32768,colour=32768,hue=32768;
update channel set videofilters='';

Also, especially if you have an AverTV card, they tend to over-
saturate quite a by default. Hauppague tend to under-saturate.
If you have v4l2 support in your kernel, v4lctl can normalize
the chroma levels with Automatic Gain Control (AGC).

: bjm [at] mokto ; v4lctl -c /dev/video0 setattr 'chroma agc' on
: bjm [at] mokto ; v4lctl -c /dev/video0 list
attribute | type | current | default | comment
-----------+--------+---------+---------+-----------------------------------
--
norm | choice | NTSC | PAL | PAL NTSC SECAM PAL-Nc PAL-M PAL-N
NTSC-JP PAL-60
input | choice | Televis | Televis | Television Composite1 S-Video
audio mode | choice | lang1 | mono | mono stereo lang1 lang2
bright | int | 37500 | 32768 | range is 0 => 65535
contrast | int | 21500 | 32768 | range is 0 => 65535
color | int | 32768 | 32768 | range is 0 => 65535
hue | int | 32768 | 32768 | range is 0 => 65535
mute | bool | off | off |
chroma agc | bool | on | off |
combfilter | bool | off | off |
automute | bool | on | off |
luma decim | bool | off | off |
agc crush | bool | on | off |
vcr hack | bool | off | off |
whitecrush | int | 207 | 207 | range is 0 => 255
whitecrush | int | 127 | 127 | range is 0 => 255

If your output is missing "chroma agc" and some of the others
then you do not have v4l2 support.

> Is there anything fundamentally wrong with this setup? is there anything
> I can do to make it better without shedding out tons of cash?

Yes and yes.

-- bjm


johnny at fishcounts

May 20, 2004, 12:58 AM

Post #6 of 14 (5726 views)
Permalink
RE: quality question.. ways to make it better? [In reply to]

I was playing with my colors,brightness,contrast after adding these filter
settings you gave and this is what I got that looked almost identical to
what my TV was showing...

update channel set contrast=30000,brightness=37500,colour=32768,hue=32768;

The same video filter settings since I have no clue what they do

update channel set videofilters='adjust=34:253:1.0:23:232:1.0';

Seems to work great for me! Thanks a lot Bruce.


Johnny Lee

-----Original Message-----
From: mythtv-users-bounces [at] mythtv
[mailto:mythtv-users-bounces [at] mythtv] On Behalf Of Johnny Lee
Sent: Thursday, May 20, 2004 12:46 AM
To: 'Discussion about mythtv'
Subject: RE: [mythtv-users] quality question.. ways to make it better?

Bruce, So what kind of card do you currently use? I've played only with my
color/brightness/contrast settings and I seem to like everything default
other than changing the contrast to 25000. I currently run a Winfast Deluxe
BT878A card w/ dbx stereo. So what does the filter do exactly? I am going to
run it now to see if I can see a difference or not...


Johnny Lee

-----Original Message-----
From: mythtv-users-bounces [at] mythtv
[mailto:mythtv-users-bounces [at] mythtv] On Behalf Of Bruce Markey
Sent: Wednesday, May 19, 2004 5:49 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] quality question.. ways to make it better?

Craig Tinson wrote:
...
> I've set the recording profile for LiveTV to mpeg4 and set it to pretty
> much maximum quality.. but its still quite "bitty" (not a lot.. but you

The "bitty"ness has to do with bitrate and the compression
factors. Ironically, if you use a higher resolution at the same
fixed bitrate, the "bitty"ness gets worse. What you need is
a moderate resolution and a higher relative bitrate.

For example, for my Default profile, I use 480x480 (480x576
for PAL) and a scaled bitrate of 4000. For low bitrates like the
default 2200, it is best to set the "Maximum quality" at 2 so
that it doesn't waste precious bits on frames that are almost
perfect anyway. However, at 4000 and above, setting the Max
limit at 1 will reduce the blockiness in the background.

> can see it).. and the colors just seem really dull.. it seems to lose
> the vibrant quality from the original..

Yeah, there are some silly problems with the luma and chroma
values for bttv cards that make bright colors washed out and
pale even when the saturation is set high enough to make the
dark colors bleed. Because of the 'out of the box' picture, most
people assume PVR cards are superior even though they use the
same chip for video capture. With the correct adjustments, a
bttv card can look even better than a hardware encoder card.

There is a new filter added after the 0.14 release in CVS that
fixes an outright mistake for bttv luma. It also has parameters
that allow you to make further adjustments that you can't do for
the hardware cards. I've played with this over the past few months.
By comparing direct cable on one input and myth on another, I've
got the color reproduction almost identical. Even though the
myth input is a little fuzzier, the picture is otherwise as
vivid. To set these parameters, run your mysql client and
enter these two lines.

update channel set contrast=21500,brightness=37500,colour=32768,hue=32768;
update channel set videofilters='adjust=34:253:1.0:23:232:1.0';

If your worried that you might have to undo this, these will
reset the defaults:

update channel set contrast=32768,brightness=32768,colour=32768,hue=32768;
update channel set videofilters='';

Also, especially if you have an AverTV card, they tend to over-
saturate quite a by default. Hauppague tend to under-saturate.
If you have v4l2 support in your kernel, v4lctl can normalize
the chroma levels with Automatic Gain Control (AGC).

: bjm [at] mokto ; v4lctl -c /dev/video0 setattr 'chroma agc' on
: bjm [at] mokto ; v4lctl -c /dev/video0 list
attribute | type | current | default | comment
-----------+--------+---------+---------+-----------------------------------
--
norm | choice | NTSC | PAL | PAL NTSC SECAM PAL-Nc PAL-M PAL-N
NTSC-JP PAL-60
input | choice | Televis | Televis | Television Composite1 S-Video
audio mode | choice | lang1 | mono | mono stereo lang1 lang2
bright | int | 37500 | 32768 | range is 0 => 65535
contrast | int | 21500 | 32768 | range is 0 => 65535
color | int | 32768 | 32768 | range is 0 => 65535
hue | int | 32768 | 32768 | range is 0 => 65535
mute | bool | off | off |
chroma agc | bool | on | off |
combfilter | bool | off | off |
automute | bool | on | off |
luma decim | bool | off | off |
agc crush | bool | on | off |
vcr hack | bool | off | off |
whitecrush | int | 207 | 207 | range is 0 => 255
whitecrush | int | 127 | 127 | range is 0 => 255

If your output is missing "chroma agc" and some of the others
then you do not have v4l2 support.

> Is there anything fundamentally wrong with this setup? is there anything
> I can do to make it better without shedding out tons of cash?

Yes and yes.

-- bjm


jdonavan at jdonavan

May 20, 2004, 1:15 AM

Post #7 of 14 (5738 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

Bruce Markey wrote:

> There is a new filter added after the 0.14 release in CVS that
> fixes an outright mistake for bttv luma. It also has parameters
> that allow you to make further adjustments that you can't do for
> the hardware cards.

Can't you do it on the output side on the hardware cards?


bjm at lvcm

May 20, 2004, 12:06 PM

Post #8 of 14 (5730 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

J. Donavan Stanley wrote:
> Bruce Markey wrote:
>
>> There is a new filter added after the 0.14 release in CVS that
>> fixes an outright mistake for bttv luma. It also has parameters
>> that allow you to make further adjustments that you can't do for
>> the hardware cards.
>
>
> Can't you do it on the output side on the hardware cards?

You can apply "adjust" as an output filter and you may be able
to do some worthwhile tweaks. NOTE: the defauts parameters would
be hozed because it is set to compensate for bttv problems.

The problem is that if the settings are distorted during recording,
you can't fix it by compensating on playback. For instance. Say
you recorded with the contrast too high and it caused blooming
(edges of white areas become bloated and fuzzy). Once that distortion
is recorded in the digital values of the still frame, playback
at lower contrast won't make the edges sharp again. Same for bleeding
colors with too much saturation and so on.

Essientially what I'm doing is recording into a limited set of
values then strecthing then with adjust to push the chroma higher
relative to the luma right away before writing out to the output
file. You could do the same by using funky picture setting when
recording then strecth with the playback filter but the recorded
files would look weird unless if the playback filter wasn't used.

The point is that the capture chip is the same and not inferior.
With some tweaking, the software encoded files can looks as good
or better than the output files from hardware encoders.

-- bjm


bjm at lvcm

May 20, 2004, 1:39 PM

Post #9 of 14 (5717 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

Johnny Lee wrote:
> Bruce, So what kind of card do you currently use? I've played only with my

I have two old WinTV model 401 (rev 02), two AverTV, one WinTV GO,
and had a TV Wonder VE that went bad. I also have a PRV-250 that I
only use for testing and have never used in production for a
number of reasons (no CC, post processing of commercial flagging,
driver stability issues, audio issues, and matching picture setting
to the other cards to name a few). I suppose I'm out of step in
saying that I prefer the software encoders over the hardware
encoders but, hey, I do ;-).

The default saturation can be very different from one model of
card to the next. This is why the AGC is important so that it
normalizes the chroma level and I do now get nearly identical
results from each card when using the same settings.

> color/brightness/contrast settings and I seem to like everything default
> other than changing the contrast to 25000. I currently run a Winfast Deluxe
> BT878A card w/ dbx stereo. So what does the filter do exactly? I am going to
> run it now to see if I can see a difference or not...

It remaps the luma and chroma values to always fall within the
normal ranges for the ITU 601 standard (aka CCIR 601). The adjust
filter is needed because there is a known problem with the bt
chipset. Here is a comment from videodev2.h:

/* broken BT878 extents (601, luma range 16-253 instead of 16-235) */

Can you spot the bonehead typo that lead to the hardware design
flaw? ;-)

My thanks to Andrew Mahone for taking on the task of writing the
adjust filter to fix this. By default the adjust filter remaps the
luma range 16-253 down to 16-235. However, the input range can
be set in the first two parameters and it gets remaped to the
normal range. In the settings I sent of 34:253 the distance is
the same as the output (219) so there is no scaling, it just
uses the high range of the card then is moved down. The brightness
seems high because slightly higher than black needs to be about
35. We won't see anything in the 16-34 range.

The main trick in these setting is stretching the chroma range
relative to the luma so that there is more color density at
higher luma (bright). Without this on bttv, dark red bleeds and
bright red looks pale and pinkish. by stretching the range, the
bright red becomes more solid without dark red bleeding.

Taken to an extreme, things look too vivid to be true. It's like
The Ultimate Highlight on Sunday night Sportcenter. Things are
more colorful but not overdriven as if the saturation was simply
turned up. If saturation is the color width, this would be the
color height.

Stretching the chroma is done by narrowing the range for the
values in the forth and fifth parameters thus stretching them
wider on output. Chroma isn't like luma. A higher number doesn't
simply become more color. If you move just the bottom or just
the top, the color would shift to green or to purple. For the
colors to be balanced, the distance from the bottom to 0 has to
be the same as the distance from the top to 255. The best way to
check this is to be sure the two numbers add up to 255. So, 2:253
would work but probably pale. 50:205 would look surreal.

When it is pushed too far or not nearly enough, big changes make
very little difference. When it is close to right, changing by
even 1 or 2 in the values makes an obvious difference.

> I was playing with my colors,brightness,contrast after adding these filter
> settings you gave and this is what I got that looked almost identical to
> what my TV was showing...
>
> update channel set contrast=30000,brightness=37500,colour=32768,hue=32768;

If you're happy with that then that's great. I can't see your set
so I can't know for a fact, however, I would suspect that your
white and near white would be pushed out of the range and you
would lose detail on the high end. Channel surf until you find
an outdoor scene with sunny clouds in the sky. I suspect you would
lose the detail of the folds and see just white blobs like an
overexposed photograph.

If so, you may want to try setting this contrast value lower and
either turn up the brightness and contrast of your TV set or use
the "F" key for the XV controls (there is a checkbox in the playback
settings that must be set first). Increasing the XV brightness and
contrast may get you the brighter image you are looking for without
distorting the high end while recording.

-- bjm


gtgj at pacbell

May 20, 2004, 7:44 PM

Post #10 of 14 (5704 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

>>>>> Bruce Markey writes:

b> If you have v4l2 support in your kernel, v4lctl can normalize
b> the chroma levels with Automatic Gain Control (AGC).

The bttv-0.7 driver has a "chroma_agc=1" module option. Do
you know if that works? I haven't really noticed a difference but it
could just be my eyes because I didn't notice a difference either when
I enabled AGC on the bttv-0.9 driver.
--
Gregorio Gervasio, Jr.


bjm at lvcm

May 20, 2004, 8:06 PM

Post #11 of 14 (5713 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

Gregorio Gervasio, Jr. wrote:
>>>>>>Bruce Markey writes:
>
>
> b> If you have v4l2 support in your kernel, v4lctl can normalize
> b> the chroma levels with Automatic Gain Control (AGC).
>
> The bttv-0.7 driver has a "chroma_agc=1" module option. Do

That should do the trick. Probably the better way to go. I first
found out about this through v4lctrl and it is a handy way to see
if it is supported.

> you know if that works? I haven't really noticed a difference but it
> could just be my eyes because I didn't notice a difference either when
> I enabled AGC on the bttv-0.9 driver.

For some cards it makes very little difference. For AverTV it
is very noticible.

-- bjm


craig at 8010

May 21, 2004, 2:29 AM

Post #12 of 14 (5726 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

Thanks for all the answers guys..

I didn't even know about these filter options.. (and the v4ctl app is
*very* useful!)

Have tried all your suggestions but its not really making much of a
difference.. but at least I know where to start looking now.. :)

Will let ya know if I come up with any breakthroughs.. and am going to
try a different input too (its going through my cable at the moment from
a 15 meter coax.. so am going to try a smaller cable from my sky box
never to the myth box.. just to double check the signal)

Thanks again for the excellent suggestions... and keep up the good work
guys! I *love* this thing.. and so does the wife.. and the kids.. and
the in-laws.. and the neighbours.. and the postman... lol

Cheers

Craig


--
Craig Tinson

8010 Media Ltd

\|||/
(o o)
----------------------------------ooO-(_)-Ooo-----------------------------
_ _ /: Thbbft. | Craig Tinson | "The most overlooked
\'o.O; _/ | 8010 Media Ltd | advantage of owning a
=(___)= | Email: craig [at] 8010 | computer is that if
|U| | Tel: 0113 249 7027 | they foul up there's
| Mob: 0788 061 3892 | no law against whacking
| MSN: cgtinson [at] hotmail | them around a bit."
--------------------------------------------------------------------------


jdonavan at jdonavan

May 21, 2004, 11:09 AM

Post #13 of 14 (5700 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

Bruce Markey wrote:

> The problem is that if the settings are distorted during recording,
> you can't fix it by compensating on playback.


Make perfect sense. Can I claim brain cramp?
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bjm at lvcm

May 21, 2004, 11:52 AM

Post #14 of 14 (5710 views)
Permalink
Re: quality question.. ways to make it better? [In reply to]

J. Donavan Stanley wrote:
> Bruce Markey wrote:
>
>> The problem is that if the settings are distorted during recording,
>> you can't fix it by compensating on playback.
>
> Make perfect sense. Can I claim brain cramp?

Maybe for the MENU/INFO thing but this is actually a better
question than it appears to be on the surface. The v4l setting
affect the tuner's analog signal before the chip digitizes. You
actually could modify these setting with the intention of
remapping the digital values on playback. The difference being
that the hardware file would be funky where as the software
file would already be corrected before it was written. Thus
the long answer.

-- bjm

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