Hi Billy, Thanks for the tips. I'm still not having much luck though. :( I'll take some more stabs at this with ffmpeg, but it's not really producing video that's any better. These 'comb lines' are showing up even with a mostly static picture. I'm starting to wonder if there's something wrong with the PCTV card, or the options I'm passing the driver... Regards, Pat -----Original Message----- From: video4linux-list-admin@xxxxxxxxxx [mailto:video4linux-list-admin@xxxxxxxxxx] On Behalf Of Billy Biggs Sent: Tuesday, February 19, 2002 9:24 AM To: video4linux-list@xxxxxxxxxx Subject: Re: Interlace Noise (field swapping?) on Pinnacle PCTV video@xxxxxxxxxxxxx (video@xxxxxxxxxxxxx): > When I capture, however, I always get what appears to be a comb > effect, or feathering. It's quite pronounced, and is wreaking havok > with the compression algorithm. An interlaced video frame contains two 'fields', each of half height, and each from a different point in time. You have a few options for what to do about it: 1) Compress with a codec that can handle interlaced frames. MPEG2 is an example, and the interlaced coding mode is supported by mpeg2enc in the mjpegtools CVS. But mpeg2enc can't record, so you'll need some mostly-lossless encoder to first get stuff onto your drive. [1] You'll also need a player which can 'deinterlace' when you play back the video on a progressive display. This will give you the best quality. 2) Only compress every second field. You give up vertical resolution and framerate, but it makes things easier. All you do is record at 720x240 or 352x240 and you get 29.97fps instead of the full 59.94fps. Huge loss of quality, but lots of people think this is reasonable. :( 3) Find a recorder/compressor that can deinterlace. Some recorders can do this, however, look out for recorders that deinterlace simply by dropping one of the two fields and interpolating the first one, since you're not better than just recording at 720x240. However, most deinterlacing recorders won't deinterlace to 59.94fps, so you're still losing framerate, but you might save some resolution. An example is 'ffmpeg', which has an 'ok' filter that will take data from both fields, but won't give you full framerate: 720x480x29.97fps only. Good luck! [1] I wrote a lossless video codec for realtime capturing, the code is here: http://www.dumbterm.net/graphics/compression/ This codec is used by my v4l recorder app http://www.sf.net/projects/reetpvr/ but it's not finished yet. I was able to use it to create interlaced MPEG2 streams using mpeg2enc though, but I haven't worked on the app lately since school is keeping me busy. -- Billy Biggs vektor@xxxxxxxxxxxx _______________________________________________ Video4linux-list mailing list Video4linux-list@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/video4linux-list
