what is GOP? , how to convert to this kind of MPEG2

[squadjot]

Hey guys, i really need help.

I'm converting a uncompressed avi to a MPEG2 file with sound. all 720x576 @ 25 FPS.

Specs:

(Pal DVD) 24 bit, 4:3
field order B
Video Bit rate: 6 – 8 Mbit constant

GOP Specs :
Gop Amount : 1
Gop Size : 12
I-Frame distance/freq : 12
Reference distance/freq : 3

Gop sequence : I BB P BB P BB P BB I . . . . .

Could anyone tell me how to obtain this result?, i have access to sony vegas and premiere.. and a bunch of freeware tools..

I definetly need help on this one.

[Richard_G]

GOP stands for Group of Pictures and relates to the relationship between the I, B and P frames. The GOP you are specifying is the standard for DVD compliant PAL, mpeg2 files. Use whatever software you want to encode your uncompressed avi file to DVD compliant mpeg2 and the GOP will be correct.

See What is DVD at the top left of the page to see what file specs are DVD compliant.

[squadjot]

Thank you for fast reply, oke i will make a test in sony vegas with the mainConcept encoder

Is possible to test if i made it right? i'm need to know cause i had a deadline today on a videofile that had to be converted, to then run on our city subway screens.

I need to send the videofile before sunday midnight..and i need to be sure thats its ready to go..

i uploaded a test.. it is possible to test if its done right? ..

download : http://jotbot.dk/test.zip

screens of my render/export settings:

[bottle-necked]

Your clip is 20 seconds long. VirtualDubMOD reports (File Information) that the 20 second file (501 frames) contains 42-I frames, 126-P frames, and 333-B frames.

If the desired GOP is 1:3:2 then the GOP structure would be IBBPBBPBBPBB or 1-I, 3-P, 8-B (12 total)

If every GOP = 12 and the video contains 42 I-frames then 12 x 42 = 504. (Close enough)

If every GOP contains 3-P frames then 3 X 42 = 126 (right on)

If every GOP contains 8 B-frames then 8 x 42 = 336 (close enough)

It looks like 1:3:2 to me. lol

[manono]

It's IBBPBBPBBPBBPBB, 15 frame GOP, or 1/4/2 in TMPGEnc lingo. It's not what you asked for, but perfectly compliant to PAL specs. ReStream gives that info.

You used CBR encoding at a very high bitrate (at 7500, it's too high for the source, in my opinion). Your DCT Precision is 9, where it should be 10. Non-linear, Alternate Scanning, Interlaced Encoding, all common for PAL. Bottom Field First. Bitrate Viewer gives that info.

[bottle-necked]

I don't like to disagree but G-Spot reports the same as VirtualDubMOD: 501 frames: IBBPBBPBBPBB (12) or 1:3:2

lol

[squadjot]

thanks for your time and effort in helping me..

sorry for beeing so noob.. but.. did i succeed or not?.. can i do it better somehow?..

manono> Your saying its not quite right?.. i really really want to deliver what the client requests, so i can be sure it will run on their systems. I'm not sure how they put it on the screens, but i dont think they burn DVD from it, they use it it somekind of commercial-rotation system.

what should i do?...try something else?.. can i get it better by changing the settings in the export panels you see on the pics?

again, thaks for all your help


ps. you all notice 501 frames.. is it better to get it to be at 500 straight?

[manono]

I don't like to disagree but G-Spot reports the same as VirtualDubMOD

Aw, go ahead and disagree. It made me think about it, as whenever I've tested before, ReStream has been correct, and agreed with what I set up in CCE. It got me to thinking that maybe it had been cut in the middle of a GOP, or perhaps something else I didn't understand was going on. So I cut it myself a couple of times and got IBBPBBPBBPBB, just as you said. I apologize for the bad information.

So squadjot, it looks like you accomplished what you set out to do.

[squadjot]

awww.. so nice , thanks people, you have been of great help, my humble thanks to you all

Cheers!

[bottle-necked]

Believe me manono when I say I don't like to disagree with you --- because usually if I do I'm wrong.

lol

[bottle-necked]

It got me to thinking that maybe it had been cut in the middle of a GOP

I found that out doing the math in my first post. @ 25fps x 20 seconds = 500, but both my applications reported 501 frames.

501 / 42 (i-frames) = 11.928571428571428571428571428571 ( not exactly 12). Evidence of a cut.

501 / 126 (p-frames) = 3.9761904761904761904761904761905 . I figure this is where that 1:4:2 came from.

501 / 333 (b-frames) = 1.5045045045045045045045045045045.

Doing the math this way is confusing indeed but leads to evidence of a GOP cut. lol

Calculating full GOP of 12 the numbers would be: 12, 24, 36, --- , 480 , 492 ,504

@ 493 frames ( a new GOP) should be I BB P BB P BB

I (493), BB (494,495) P (496) BB (497,498) P (499) BB (500,501)

[squadjot]

so.. i better make it exactly 500 frames?.. not that it matters much.. but that would even up the numbers..right?

[bottle-necked]

so.. i better make it exactly 500 frames?.. not that it matters much.. but that would even up the numbers..right?

Very funny...

[squadjot]

one last thing to be sure i'm delivering the right material.. is my file 24 or 32 bit?

..guess its newbie question so i posted a new question here..

https://forum.videohelp.com/viewtopic.php?t=319611

[Scorpion King]

Your test.zip (mpg) file is 24bit according to Ulead VideoStudio v10 File Properties.