I & P Frames? What the...? at DVinfo.net

Owen Bickford · May 24th, 2005, 10:31 AM

So I'm wondering, since I have no formal DVD burning training, what all these I, P, M, N, GOP and other terms mean to the final DVD picture. I've noticed that most of my video when transcoded at 6KBPS at full quality in Premiere Pro looks somewhat degraded and sometimes the picture is jittery. I don't apply the "Posterize Time" effect to simulate 24fps, and I'm keeping 29.97 fps when I export. In a perfect world, we wouldn't have to worry about all these undefined letters, and we could choose from a scale of 1-10 on whether the picture should be "Bad" to "Good."

All i want is a link to definitions for all these M and N frames and I, B, P, and whatever else I'm missing. It doesn't have to be in layman's terms.

Thanks.

Christopher Lefchik · May 24th, 2005, 02:26 PM

See http://www.videohelp.com/glossary and http://bmrc.berkeley.edu/frame/resea..._overview.html.

In practice, however, it's better for most of us to let our encoding program worry about most of the technicalities of P frames and I frames, etc. I doubt fiddling with them would solve the jitter problem, though I could always be wrong. Have you tried 2 pass VBR encoding? How about the 7 Mbs CBR preset?

Dan Euritt · May 24th, 2005, 02:37 PM

"6KBPS at full quality" isn't really full quality... full quality only comes with the highest bitrates, aka 8kbps for instance.

like chris suggested, you can get there by using two-pass encoding, with the vbr max settings at something like 8kbps, and the average settings at 6kbps, depending on how long your program is, and if you are using .ac3 audio encoding(small size).

i would start out with a factory preset on the encoder, then put the quality slider all the way over to the best quality, plus all of the above settings.

i wonder if the jitter could also be from using a progressive encoding setting on the mpeg2 encoder? also make darn sure that the field settings of the encoder match your source footage, for example, lower field first is the typical ntsc dv setting.

May 24th, 2005, 10:31 AM	#1
Owen Bickford Regular Crew Join Date: May 2005 Location: Sulphur Springs, TX Posts: 35	I & P Frames? What the...? So I'm wondering, since I have no formal DVD burning training, what all these I, P, M, N, GOP and other terms mean to the final DVD picture. I've noticed that most of my video when transcoded at 6KBPS at full quality in Premiere Pro looks somewhat degraded and sometimes the picture is jittery. I don't apply the "Posterize Time" effect to simulate 24fps, and I'm keeping 29.97 fps when I export. In a perfect world, we wouldn't have to worry about all these undefined letters, and we could choose from a scale of 1-10 on whether the picture should be "Bad" to "Good." All i want is a link to definitions for all these M and N frames and I, B, P, and whatever else I'm missing. It doesn't have to be in layman's terms. Thanks. __________________ www.thetimelinepost.org

May 24th, 2005, 02:26 PM	#2
Christopher Lefchik Trustee Join Date: Jul 2003 Location: US Posts: 1,152	See http://www.videohelp.com/glossary and http://bmrc.berkeley.edu/frame/resea..._overview.html. In practice, however, it's better for most of us to let our encoding program worry about most of the technicalities of P frames and I frames, etc. I doubt fiddling with them would solve the jitter problem, though I could always be wrong. Have you tried 2 pass VBR encoding? How about the 7 Mbs CBR preset?

May 24th, 2005, 02:37 PM	#3
Dan Euritt Trustee Join Date: Mar 2004 Location: Carlsbad CA Posts: 1,132	"6KBPS at full quality" isn't really full quality... full quality only comes with the highest bitrates, aka 8kbps for instance. like chris suggested, you can get there by using two-pass encoding, with the vbr max settings at something like 8kbps, and the average settings at 6kbps, depending on how long your program is, and if you are using .ac3 audio encoding(small size). i would start out with a factory preset on the encoder, then put the quality slider all the way over to the best quality, plus all of the above settings. i wonder if the jitter could also be from using a progressive encoding setting on the mpeg2 encoder? also make darn sure that the field settings of the encoder match your source footage, for example, lower field first is the typical ntsc dv setting.