2 B-Frames before first GOP with closed GOPs

ECB wrote on 5/20/2005, 3:26 AM
I am using Vegas MC Mpeg 2 Encoder to encode an NTSC DVD mpeg 2 elemental stream using the default settings with the closed GOP option checked. When the encode is complete and I look at the beginning of the m2v elemental stream they are 2 B-Frames before the first I-frame(first GOP). If I uncheck closed GOP the 2 B frames are not created. I have not seen this problem with Procoder 2 or MainConcept's stand-alone mpeg encoder. The leading B-Frames have not caused me any problems. I notified Sony Tech support.

Ed

Comments

B_JM wrote on 5/20/2005, 4:28 AM
been mentioned before - should not be an issue
ECB wrote on 6/6/2005, 4:42 PM
Sony Tech Support reported the leading B frames before the first GOP in a closed GOP mpeg stream are intentional and not a problem.

Ed B
B_JM wrote on 6/6/2005, 6:25 PM
well they are in some programs and applications and also make it imposable to put a chapter on the first frame ...

but generally not a major issue ....
ECB wrote on 6/6/2005, 9:40 PM
BJ_M

Could you share what some of these programs and applications that would have a problem with the B-frames ahead for the first GOP?

"make it imposable to put a chapter on the first frame ..." I agree but let me explain an experiment I ran and maybe you can shed some light as to what is going on. I have an avi file with a number in each frame starting at 1 and running up to 72 in sequential order so I can easly identifiy which frame is be viewed. I MC mpeg encoded with closed GOPs the numbered avi file and authored a simple menu with DVDA3. I played the DVD in a Sony DVP-S360 stand-alone DVD player. I clicked on the play button for numbered frame movie and immediately hit pause on the remote. The movie consistantly paused on frame 1. I would expect the movie to start on frame 3 the location of the I frame.

Does the beginning of movie have to start on an I frame the same as chapters?

Ed B
B_JM wrote on 6/7/2005, 6:43 AM
only the pioneer 7400/7300 dvd players have true frame accuracy - so what other players do , i.e. fudge it .... i have no comment ..

but in many entertainment systems used in museums and theme parks and science centers, DVDs (for one reason or another) need to be often sync'd with each other - and at times there may be many many such units playing all in sync and also need to search to specific frames - park and start in sync from those points .. You also have to devolope sometimes playlists and other things .

much as the way laser disks were used for years and still cant really be beat for this on terms of the machines (LDV8000's) .

well - using DVDA , you can not do this -- but for the average DVD, DVDA is just fine.

..

QT with the mpeg2 plug in doesnt play some mpeg files from vegas, nor does the datatron system. DVD Studio (apple) also chokes on some mpeg files from vegas .
ECB wrote on 6/7/2005, 7:32 AM
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