[mythtv] s-video input / widescreen tv ?

Bruce Markey bjm at lvcm.com
Mon Jan 20 04:08:55 EST 2003


Laurent Farcy wrote:
.
> 3/ Not so many threads talk about widescreen tvs/programmes. Although, 
> some of you guys own one. So, to make short, my question is whether 
> MythTV compatible with widescreen programmes and TVs ? IMHO, 'compatible 
> with widescreen programmes' would mean recordings happen in anamorphic 
> aspect ratio (whenever the source is anamorphic) so that when you read 
> them you can still expand it to 16:9 (whilst it's been recorded in 4:3 
> anamorphic format). And 'compatible with widescreen tv' would mean you 
> can generate a tv-output signal which is 4:3 anamorphic so that your tv 
> can expand it to 16:9. Am I clear/right ?

Yes. The fullscreen mode is set to the dimensions of the
X desktop. If you recorded 4:3 video and displayed on a
16:9 desktop it would be stretched horizontally by default.
In fact, the default record dimensions are 480x480 to save
on resources. These become 4:3 when displayed at 800x600 for
example. It will be easy to letterbox 16:9 on a 4:3 display
or 4:3 on 16:9 as an option but, as you've noticed, there
hasn't been any call for it yet so it is not a high
priority ;-)

> 4/ Last, I'm wondering if there's a difference in terms of quality 
> between tv tuner cards for video grabbing, and particularly in my case 
> for s-video input grabbing. The differences could be, I guess, on 
> maximum resolution, visual quality, widescreen handling, ... So if you 
> could share your experience, I would appreciate your feedback.

I've played the "Video Essentials" DVD from a DVD player
into the S-video input of bttv card and recorded at 720x480.
My conclusion was that the bt chip clocks latch at the right
time and correctly assign digital values for the analog signal
that it is sampling and sends the raw video data down the bus.
There doesn't appear to be much room for improvement in the
quality of capture.

Most quality problems have to do with presentation and the
quality of the input signal. The capture card task of sampling
is really pretty simple. However, there was a card discussed
on this list that apparently has a shielding problem which
adds interference.

For broadcast TV over coaxial cable, 480x480 or ever 352x480
look nearly as good as 640x480. However, with your digital
cable, and especially channels that are true digital, you will
see better quality at higher resolutions.

--  bjm




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