[mythtv-users] Aspect ratio wrong

Michael T. Dean mtdean at thirdcontact.com
Wed Apr 5 23:50:20 UTC 2006

On 04/05/2006 02:28 PM, Greg Stark wrote:

>The aspect ratio seems to be wrong when I play tv on the computer screen.
>This is for video grabbed from a PVR-350 from NTSC and played back via X on my
>regular display. I have the playback window set for 800x600.
>It appears the default playback has black bars on the top and bottom and the
>display part is stretched horizontally. That's with the aspect mode set to
>"Off". It appears the same if press W to go to 4:3 mode. And of course much
>worse if I go to any of the 16:9 modes.
>It appears more or less correct in "Fill" and maybe "4:3 Zoom" though it's
>hard to tell.
>I don't remember having this problem previously and I don't think I've changed
>anything since I remember it working.
What do you get from:

xdpyinfo | grep -B 3 'dots per inch'

>Why does mythtv set the weird 480x480 mode on the PVR anyways 
Because you told it to set that resolution in your recording profile.  
If you don't like it change it.

>and then have to
>stretch it back to the right aspect ratio? If I just play raw video from it
>using mplayer it feeds mpeg in the correct aspect ratio automatically.
Remember your monitor typically uses square pixels (resolution aspect 
ratio and physical display's aspect ratio is identical).  Video often 
doesn't (720x480 is 3:2 and is often displayed on a 4:3 TV (even 16:9 
letterboxed is 3:2 on 4:3), unless it's 16:9 or 2.39:1 video in 
anamorphic widescreen--in which case it's displayed in letterboxed 16:9 
or 2.39:1, respectively, on your 4:3 screen.  So, capture ratio and 
output ratio are seldom the same.

Note, however, to get 1:1 ratio between capture resolution and output 
resolution on a 4:3 display, you need to use 640x480.  However, it won't 
really matter...


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