On 11 Feb 2003 23:35:40 -0800 Florin Andrei <[EMAIL PROTECTED]> wrote:
> > Of the 720 width line only 704 pixels have image info. PAL pixel > > aspect ratio is 59:54 so to get square pixels you scale 704x576 > > to 768x576. > > That means you have to cut 8 pixels each from the left and the right > margins before rescaling? Actually, with the Marvel I have to cut 16 pixels from the left, although this varies slightly with the TV channel. With lavrec I can do this at the recording stage. > That's odd, at least for someone who worked only with NTSC DV (i > only do a rescale on the Digital8 streams i'm working with). I only have to do it when capturing from the tuner. Capturing a VHS tape through the composite doesn't seem to require it, though I could be mistaken here as I tend to crop and scale this much more. > What is the reason it is preferred to increase the size of the image > (from 704 to 768)? The information remains the same after all > (notwithstanding the interpolation noise). > Is it because it is preferred to have the final product in a > standard image size? You can either scale before encoding or set the aspect ratio on playback if your player supports it. Not all players do so it's safer to prescale. I use mplayer which does support it so I set the playback AR, my thinking being that with fewer pixels you can use a lower bitrate. If you don't do either the image will look slightly squashed on playback. Martin ------------------------------------------------------- This SF.NET email is sponsored by: SourceForge Enterprise Edition + IBM + LinuxWorld = Something 2 See! http://www.vasoftware.com _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
