[mythtv] Cropping

Tim McClarren tim at 7thheaven.org
Fri Sep 16 19:44:40 UTC 2005

I had posted a while back about a problem I was having with video capture.

Basically, I get about 10 black pixels on the left edge of captured 
stream, and about 20 pixels at the bottom, which are mostly black, but 
with some grey blocks in it.  I'm pretty sure it's entirely an issue 
with my very cheap SAA7130 based capture card.  I looked into the 
hardware specs for the chip, and it turns out this chip can do hardware 
cropping and scaling.  Based on looking at the source for the Linux 
driver for this chip, it looks like it supports at least some of the 
cropping functionality.

I futzed around and added some code into NuppelVideoRecorder.cpp to ask 
the driver to crop (inside DoV4L2()), and viola, it seems to work 
perfectly now, and I don't have to use the crop filter on playback 
(which was no good anyways, because I want the captured stream to be 
right, not to correct it in the viewer on playback, which means I have 
to configure each front end seperately, and I have to set up the 
transcoder to crop out those annoying bits if I want to watch my stuff 
in some other format).

Am I the only one who has this issue?  Do other cards capture pretty 
much perfectly, right out of the box?

Would it be worth having the UI in the "Capture Card" settings dialogs 
to be able to specify a crop rectangle?

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