On 15/03/2005, at 12:42 PM, Justin Hornsby wrote:
Matthew Phillips wrote:
I think what you're seeing is timecode which is sometimes present on the broadcast video - I'm not sure if it's 'proper' timecode but some channels have it while others don't...Hello all,
I've just finished setting up MythTV on an EPIA M10000N system with a VisionPlus DVB-T card - very happy with the results so far. Kudos to the myth developers.
I've been looking into one outstanding problem: the SD pictures I'm getting on some channels have, either at the top or bottom of the picture, a line of blank pixels which sometimes have some white streaks (see top left of attached example).
An enquiry to the linux-dvb mailing list indicated this is a normal artifact of the WSS (Wide Screen Signaling) standard embedded into analog PAL intended for digital broadcast.
So, it looks like I need to have Myth crop a few lines from the top and bottom of 16:9 content. However, I'm using XvMC and it (a) appears filter chains can't be used with it and (b) I couldn't find any info on cropping filters anyway (given they even exist).
Does anyone have any idea whether there's something I can try?
Cheers,
Matthew.
Anyway you're seeing it because the broadcasters haven't bothered to take it out of the video stream - this is probably because you wouldn't normally see it on a TV because of the 5 to 10% overscan prevalent in most domestic TV sets.
The WSS signal isn't actually present in the PAL signal itself - the aspect ratio flags in the MPEG stream determine whether or not the receiver is to treat it as 16:9 or not.
If you're using TV-out why not take the overscan up a notch to eliminate it?
The problem happens when I'm playing 16:9 on my 4:3 TV where the black bars at the top are a given unless I want to crop the picture. I wouldn't bother with it, but the lines are exactly the right thickness to flicker nastily on an interlaced TV display (they look totally innocuous on a digital display of course).
I'll write a letter to the lazy Australian broadcasters and ask them to get with the program ;)
Cheers,
Matthew.
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