Iposted this to the mjpeg list but it might be worth discussing here as well: ===== This question might take a bit of explaining, so bear with me. Like a lot of the world it seems, I have a linux box that is working as a PVR. It's a celeron-500 with a 30G disk, a bt848 card, lirc receiver, and some software that I've crufted up that basically calls other apps to encode, save, play, etc. according to a simple scheduler and a remote-control menu. Probably what a lot of people here have running. Up to now, I've been using mp1e to record in real time directly to the file I wanted to keep. So I'd run mp1e with a VCD-sized frame, a suitable bit rate, and that would be the file that I would later watch. However, the more I use it, the more I realize that even given a high bitrate mp1e still doesn't look very good, and being a real-time encoder, I don't really blame it. It looks horrible at 500kbps, acceptable at 1Mbps, but doesn't seem to get any better looking even at 5Mbps or more at the same resolution. It sounds like to get the best quality file, I would capture directly in YUV format and then recompress it later with mjpeg to get my video files. Enter mjpeg... The problem with this is that I sometimes need to record 2-3 hours a night, and I don't have nearly enough disk space to record 2-3 hours of YUV data. So... I've been experimenting with this: - Recording with mp1e at 640x480 (v4l size) at a fairly high bitrate of about 5Mbps. The goal is to get as few compression artifacts as possible at this stage but still to be able to record a busy evening's stuff with only 4-5G of scratch space. - After taping, recompressing the video with mjpeg, this seems to work decently well at a reasonable 3-4 fps. cat $1_large.mpg | mpeg2dec -s -o YUVh | nice -n 20 yuvdenoise | mpeg2enc -4 1 -2 1 -s -f 1 -o $1_temp.m1v This produces acceptable results. I lose a few gigs when I tape but overnight scripts recompress the video and I get the space back. I leave about 4G free at all times so I have about 26G to store programs and the system is happy. The quality is fairly watchable and better overall than straight mp1e was even at twice the bitrate. However, there still are some visual funnies that are very likely the effect of double-compressing, and I am looking at ways to improve the final quality. Is there a better method of doing what I am trying to do? Basically what I could use is something that can do real time capture with the highest possible quality in say, 2G per hour of video. (an order of magnitude more than mpeg1 but an order of magnitude less than straight YUV) Then I could postprocess down to VCD in the wee hours with mjpeg. Ideas? Suggestions? -- Trevor Boicey, P. Eng. Ottawa, Canada, tboicey@xxxxxxx ICQ #17432933 http://www.brit.ca/~tboicey/ "Hail to thee, oh wide screen TV..." - Johnny Bravo
