[mythtv-users] Capture sharpness
jaymallar at gmail.com
Mon Nov 26 19:39:46 UTC 2007
Rod Smith wrote:
> On Sunday 25 November 2007 14:35:16 Jay Mallar wrote:
>> Rod Smith wrote:
>>> What inputs are you using? S-video is better, composite is middle, and
>>> coaxial (RF) is worst. If you're using S-video for your TiVo and RF for
>>> MythTV, that could explain it.
>> I'm using coax from the STB to the PVR-250 and the same for the PTV-300.
> Coax is certainly the poorest input form. If you're using it for both the
> PVR-250 and the TiVo, then this is a constant and so isn't the root cause,
> with one important caveat: It's conceivable that the PVR-250 (or perhaps your
> specific tuner) does a poorer job with coax than with other inputs, above and
> beyond the degradation that coax will necessarily introduce. Thus, I suggest
> you try using composite or S-video instead of coax, at least for a test. (A
> Web search suggests that your SAT-B3 DirecTV receiver has both composite and
> S-video outputs.) If you notice a dramatic improvement on the MythTV box or
> if you want it to be a fair test, you should make the same change on both the
> MythTV box and TiVo.
Okay - it's not my coax connect; I hooked the coax output from my STB to
my TV and the signal is perfect. When I run it through my MythTV
system, I see the sharpness degrade (as well as a bit of color
saturation, but I think I can correct that with some twiddling).
>>> - What type of DirecTV receiver(s) do you have? I've seen claims that
>>> they vary in video output quality, so it's conceivable that you've got
>>> one with better quality feeding your TiVo and one with worse quality
>>> feeding your MythTV box.
>> My PVR-250 and my PTV-300 are both connected in the same way, to Sony
>> SAT-B3 via coax. The signal is split off from my dish via a multi-switch.
> FWIW, the multiswitch shouldn't make any difference. With digital satellite
> TV, if the signal to one box were being degraded, you'd see no signal or
> blocky digital artifacts, not blurriness.
> That said, there's a possibility that one of your receivers is outputting a
> bad signal, even though they're the same model. You could try swapping their
> outputs to see if one is bad, and/or viewing them both directly on a TV. This
> possibility is a bit of a long shot, though.
Based on the above, I don't think the problem is my switch either (I was
mostly issuing disclosure. :) )
> An entirely new possibility has occurred to me, too: It could be that the
> blurriness is being introduced in the video PLAYBACK rather than in the
> recording. You could check this with known clean recordings -- say, something
> of decent resolution and bitrate downloaded from the Internet.
> (Unfortunately, I don't have any specific pointers to suggest.) FWIW, my own
> system runs at 800x600 resolution output via S-video to an NTSC TV, and this
> works pretty well for me. Are you using the same output method from both the
> TiVo and your MythTV box? What video card are you using in the MythTV box?
> Different cards can yield noticeable differences in output quality, so it's
> conceivable you've got bad output.
I'm using an nVidia GeForce 6200 LE, which I would expect to be of
decent quality. In fact, AVIs and such that I've downloaded from the
net and imported via MythVideo seem to display perfectly. I also see no
such sharp-less-ness from the MythTV UI itself, only from the captures.
Also, DVDs play beautifully with no loss of sharpness.
Update: I think I found my problem. I decided to delete and re-add my
capture card to see what would happen and realized when doing so that it
was set as a V4L card rather than an MPEG-2 card. Don't know how that
happened, but re-adding it with the correct type seems to have corrected
my fuzziness problem.
I *think* it might have changed when I migrated to v0.21-trunk... but -
in any case, thanks a million for all the suggestions.
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