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View Full Version : How DVD2AVI determines frame type ?

len0x
28th September 2003, 16:14
I wonder how this feature is coded inside DVD2AVI - detection of progressive or interlaced source?

The reason I'm asking is that having used it a lot on PAL sources I can tell than almost half of the time it says that frame type is interlaced, when it's actually not...
hakko504
29th September 2003, 10:09
AFAIK DVD2AVI reads how the picture was encoded (progressive/interlaced) from the MPEG stream. The difference between PAL and NTSC/FIL is that a FILM source that is going to be telecined through flags must have progressive frames or the telecining process won't work. For PAL sources no such restriction exists, and one can choose progressive/interlaced without any real penalties.
Nic
29th September 2003, 11:01
hakko is right AFAIK. DVD2AVI gets the information from the progressive frame flag inside the picture coding extension and just spits out the result of that. So, although misleading, dvd2avi isn't doing anything wrong as such.
Cheers,
-Nic
len0x
29th September 2003, 11:08
I see... So basically there is no accurate way to tell whether source is interlaced or not without looking at the picture?
hakko504
29th September 2003, 11:15
'fraid not. You just have to blame the people who encoded the stuff.
len0x
29th September 2003, 11:25
ok, thanks.

btw, progressive/interlaced info from mpeg stream - is it available somehow from d2v project or may be when that project is opened by mpeg2dec3.dll ?
hakko504
29th September 2003, 11:36
No, it's not available: but is should be possible to add it if necessary. It would break all backward compatibility though.

trf= pf<<2 + tff<<1 + rff

If (pf==1) for interlaced pictures then an interlaced movie would have 4 or 6 in the D2V where progressive movies would keep the 0&2's that we are used to see.
Nic
29th September 2003, 12:35
Well I could always add something to mpeg2dec3 that would retrieve it for you for the current frame, but Im not sure how much use it would be ?

-Nic
Wilbert
29th September 2003, 14:29
I think this would be very useful for AviSynth v3.0. Maybe you can drop a pm to bidoche to ask what he thinks about it.
len0x
29th September 2003, 14:59
Originally posted by Nic
but Im not sure how much use it would be ?


I'm not sure either, since for PAL it will have to be ignored anyway. NTSC may benefit from it though...