scan type detection ?

[kheops]

hi :)

i'm using DVD Rebuilder 0.72 and cce 2.70.01.05

the scan type of my material is ZigZag (i use bitrate viewer to know that)

once created, my REBUILDER.ECL says (for each item) :
alternate_scan=1
which give once encoded an alternate scan type

i had to change the value to 0 to get a ZigZag scan type (not a big pain)

i've seen in the settings that cce accepts an "auto" choice for the scan type, maybe it's a new choice that DVD Rebuilder doesn't care about

apologies if i've missed something

[jdobbs]

If the source is progressive, DVD-RB sets alternate_scan=0, if the source is interlaced, it sets it to alternate_scan=1. It makes the determination based upon the MPEG-2 stream itself.

[kheops]

the dvd i'm working with is PAL

the source is interlaced BUT scan type should be set to ZigZag so alternate_scan should be 0
i'm wrong ?

(i attach a jpeg)

[jdobbs]

Interlaced sources should not use zigzag scanning. Do a search of Doom9, there are a lot of discussions on this. It's also spelled out in the CCE Users Manual.

[kheops]

so in your opinion is it a good idea to force zigzag scanning (my source really is) or letting DVD Rebuilder doing his job ?

[wmansir]

It won't break anything, but it could make encoding less efficient. CCE encodes progressive material more efficiently with Zig-Zag, and interlaced with Alternate. It shouldn't matter what the original encoder used since the video is completely decoded and then the raw images re-encoded by CCE.

[kheops]

thanks a lot for your answer and knowledge wmansir :)
from now i'll take care of this encoding efficiency

+

[jdobbs]

I don't think the nature of interlaced sources lends itself to zigzag. But to each his own.

[Added] Quote from the CCE manual: "If Zigzag scanning order is not selected, DCT coefficients are sequenced by alternate scan. Generally, for interlace pictures, alternate scan often achieves high image quality compared with zigzag scan."