[mythtv-users] Widescreen 720x576 and problems with squashed Watch Recordings preview images?

Michael T. Dean mtdean at thirdcontact.com
Mon Jan 21 17:31:04 UTC 2008

On 01/21/2008 04:48 AM, nospam312 wrote:
>>> I use a 720x576 *widescreen* resolution running with rectangle pixels
>>> but my preview images in the Watch Recordings screen appear to be
>>> squashed and do not look like they have been resized with the correct
>>> aspect ratio.
>> Have you tried running 1024 x 576 *widescreen* with square pixels?
>> That's what a guy I know uses on his widescreen PAL CRT...
> No mainly because what I have maps directly onto the TV resolution so
> I get a generally perfect picture without it generating too much heat
> or using unnecessary electricity resizing the picture to a resolution
> too big for my CRT TV.  Thanks for suggesting something however.

"Pixel for pixel" in an analog world?  I think there's a bit more to the 
sampling/hardware design than you probably realize (i.e. unless you 
design the hardware and software yourself, it's very difficult to know 
how the TV out signal is created).  I highly recommend looking up some 
of Cory Papenfuss's old posts about analog TV out.  He goes to great 
detail in testing and determining some of the best approaches for 
getting "the best possible" TV out.

IME, the NVIDIA TV out hardware tends to create a better image using an 
800x600 or 1024x768 X resolution and sampling that to create the NTSC 
signal than using 720x480 (or any other x480) resolution.

Note that it's possible to store more information in a given digital 
image than can be represented using an output device whose resolution 
equals the image resolution.  And, unless you have a source image that 
provides limited information (i.e you're upscaling an image), the image 
/will/ contain more information than the "pixels" show.  If you generate 
an image at 720x576 for <N/A>:1 sampling for output using PAL, you're 
assuming that X/freetype/... are better able to render to that low 
resolution than the hardware sampler is able to incorporate the 
additional information from a higher-resolution source into the output 
signal.  I'd guess that since the software is designed primarily for 
speed (and for "normal" resolutions--not the extremely low resolutions 
of SDTV), the hardware sampler might actually be the better.

But then again, when talking about subjective things like "image 
quality," whatever looks better to you is better.  Even if the "better" 
is tempered with the placebo effect.  :)

In other words (all the above boils down to), it's worth a try (or 
another try--going by memory discounts the additional information you 
may have learned since you last tested).

If you're still unwilling to try it:


Though, note that for SVN trunk, you need to specify the right aspect 
ratio, and DPI is irrelevant.




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