trim curiosity

[magic144]

just by chance glanced at the first .avs file after the prepare phase
in a 1.06Pro movie-only rebuilder run

is there any particular reason why the Trim command's first parameter would be greater than 0 (30 in this case)?

[Jeffster]

Why don't you load the avs in question into VirtualDub and comment out the Trim command (#), then see what the first 30 frames contain... it might answer your question for you (or not)?

I guess the first cell of that VTS doesn't actually belong to the main movie though.

[magic144]

cheers Jeffster
why didn't I think of that?!! - doh

well at least from that experiment I can see that WITH the Trim(30,n) command in place, nothing happens until about frame 28-29, whereas WITHOUT the trim command, nothing happens until about frame 58-59 (i.e. 30 frames later), so I guess there are 30 frames of nothing embedded in there somehow

I just wonder how DVD-RB knows there are 30 frames of nothing to skip over??!! - anybody know? I had always just assumed these things always started on frame 0!?!

Is this something that DVD-RB discovers for itself, or through some calls in DGDecode.dll...

This leads me to another quick question - where does the d2v file come from - I thought DGIndex had to be used to create that (or does DVD-RB use some API in DGDecode.dll to create that somehow?)

And within the D2V file I find these lines:-

DGIndexProjectFile11
(is '11' correct for DGDecode.dll v1.4.5? - I'm sure it must be, or there'd be an error)

iDCT_Algorithm=2
(even though I've selected idct=6 in DVD-RB, which indeed is in the avs file - is this right?)

No urgency or great importance here, I'm just curious to learn more about the process... shorter answers are greatly appreciated :-)

[NaN]

@magic144: DGIndexProjectFile11 should be correct since DGIndexProjectFile06 is the 1.1.x format. idct=2 in the d2v is overriden by the idct parameter in the mpeg2source(...,idct=...) line in the avs-script.

Cheers, NaN

[jdobbs]

There's lots of situations that might cause the first segment to start at frame 30. (Example: you are doing a movie-only encode and the first cell of the main PGC didn't start until frame 30)

[magic144]

thanks guys - as always, THE place for quick answers to my insatiable curiosity (and home of the best backup utility)

so if the first cell in the PGC doesn't start until frame 30
a) where (would) I see evidence of that in IfoEdit/VobEdit
b) what is "in" frames 0-29? are they real frames that are still encoded on the disc (apparently black/blank from my VirtualDub test) that have been signalled to be skipped?? I know sometimes the first audio packet is delayed or in advance of the first video packet for sync purposes, but this is a new one

just curious, like I said

[Trahald]

the situation that jdobbs discribed would likely have your ifo look something like this

<pgc 1>
v/c 1/1 00:00:01;00 00:00:01;00
<pgc 2>
v/c 1/2 00:01:00;01 00:01:00;01
v/c 1/3 00:05:34;22 00:06;34;23
*...snip*
v/c 1/20 00:00:00;15 01:54:23;12

or lots of other possibilities...

...the pgcs could be reversed... etc etc

with this scenario, a .d2v is created for all of vobid 1.. cell 1 is trimmed off since it isnt part of the movie pgc. there is a good chance that 1/1 is just a dummy cell that is used for chapter skipping. or the movie studio did it for no reason..

[magic144]

ok thanks trahald
I'll check out the pgcs when I get home - odd, but that's the magic of DVDs I guess

thanks again for the info