Monday, July 14, 2003

ATI All-In-Wonder MPEG2

Well, somehow I seem to have hit on a setting in ATI TV that actually produces a standard MPEG2 capture file... VGA Capture captures at 6Mbps 640x480 (3:2 pull down is off, de-interlacing is on). Which is fine for what I want (mainly because MPEG2 is better then MPEG1 for me). At 6Mbps (45Mb/min) that gives me 15 min on a CD-R or 99 min on a DVD-R. Or I can scale down to 4Mbps (30Mb/min) and get 23 min on a CD-R or almost 2.5 hours on a DVD-R.

Not bad, not bad... looks like I'll finally be digitizing all of my old VCR tapes. Regular shows look fine at 4Mbps MPEG2 (might even try 3Mbps if I can find a setting), but cartoons require 6Mbps. I've also tried MPEG2 at 10Mbps, but lost 50% of the frames (I've heard of people using MPEG2 at 10-12Mbps as a good quality capture source).

OTOH, VirtualDub refuses to open the MPEG2 files... so I'm not quite there yet. (Update: From doing some searching on the error message "pack synchronization error" that VirtualDub coughs up, I don't think VirtualDub supports MPEG2...)

Other tidbits, folks are saying with MPEG4 you can get reasonable quality at 6Mb/min (0.8 Mbps?) which is around 2 hours on a CD-R. I'm just not sure if MPEG4 is going to be standard enough long-term... heck, I'd be happy with 60 min a CD-R or about 6 hours on a DVD-R (that's about 1.65Mbps).

(hmmm, time for another table, assuming fixed bit-rates... using variable bit rates will actually give you the possibilyt of more time per disk, check out doom9 for FAQs on that stuff). Anyway, here are my common target bitrates. To calculate megabytes per minute of video, just divide the Mbps by 8 and multiply by 60 - but I've put the numbers in parens. First minutes is for a 700Mb CD-R, second time is for a 4450Mb DVD-R.

6.0Mbps (45.0 Mb/min) = 15 min / 99 min
4.0Mbps (30.0 Mb/min) = 23 min / 2.5 hr
3.0Mbps (22.5 Mb/min) = 31 min / 3.3 hr
1.6Mbps (12.0 Mb/min) = 58 min / 6.2 hr
1.0Mbps (7.5 Mb/min) = 93 min / 9.9 hr
0.8Mbps (6.0 Mb/min) = 117 min / 12.4 hr
0.6 Mbps (4.5 Mb/min) = 155 min / 16.5 hr

I prefer not to encode below 0.6 Mbps because even with MPEG4, DivX, etc. the video quality just isn't up to standard (audio starts eating up a significant portion of your bitrate budget). 1.6Mbps is a nice rate for MPEG4 because it lets you fit a full season (usually 13 episodes) of 1/2 hr shows (usually 24 min after commercials are stripped) on a single DVD-R.

posted by Wuphon's at 1:46 PM