[mythtv-users] Cropping NTSC to 16:9

Christopher Meredith chmeredith at gmail.com
Fri Feb 13 19:01:56 UTC 2009


I use an SA3250HD cable box. I get my analog channels via s-video and
my HD channels via firewire. My premium HD channels are 5c encrypted
so I can't grab them over firewire. They all have standard definition
equivalents on my channel lineup, but as I have a 16:9 TV, I'd like to
keep the 16:9 aspect ratio even if I can't keep the HD resolution.
When tuned to the HD channels, the cable box "letterboxes" the feed
before outputting to s-video. I would like to see if I can create a
video source or at least set custom "per channel" options that will
crop out the top/bottom black bars and display the video in 16:9
resolution. There are a couple things I've tried:

MANUAL ZOOM
Obviously, if I am watching such a channel and I set the manual zoom
to "full," it displays exactly as I have in mind. The problem is this
is not an automatic solution and I can't figure out a way to set the
default zoom method on a per-channel basis. Is this possible?

CROPPING
The other method I tried is using a video filter to crop the black
bars out. The problem appears to be that the "crop" filter in MythTV
doesn't work the same way as the crop filter in, say, mplayer. It
appears that when using an NTSC capture card, the recorded video will
always be 720x480 and the crop settings are meant to be used with
equal values all around. If I set the record filter to "crop=4:0:4:0",
it does crop out the unwanted bars, but the recorded video is still
720x480 and the "dead space" is filled with distorted patterns. The
same is true if I use the same string in the playback filter field.

Can anyone recommend a method to "un-letterbox" an NTSC feed and
automatically display a 16:9 resolution?

Thanks!

Christopher


More information about the mythtv-users mailing list