Scan Type: Alternate??

[hoops10]

When viewing a vob file from a DVD source, Bitrate Viewer shows the Scan Type: Alternate. Since there is no setting like this in CCE, how do you treat this in CCE? Do you just NOT check zigzag or can you ignore this scan type?

[ronnylov]

Uncheck zigzag and you get alternate scan.
Alternate scan is better when encoding interlaced video.

[mikeathome]

Originally posted by ronnylov
Uncheck zigzag and you get alternate scan.
Alternate scan is better when encoding interlaced video.

Hi,

this is only half of the truth. It will work ONLY if you use a quantization matrix which takes the alternative scanorder into account e.g. the 'mb1 DV Interlaced' matrix has been developed by mb1 for this purpose. It's also useful to work with it when re-encoding interlaced DVD material (like live concerts, YES Symphonic, or clear interlaced titles like ID4). It'll give NOTICEABLE BETTER results on those titles than the ZigZag scanorder.

attached the matrix for easy input:
REGEDIT4

[HKEY_CURRENT_USER\Software\Custom Technology\Cinema Craft Encoder SP Trial\qmat]
"'mb1 interlaced DV'"=hex:08,0d,0d,11,11,15,15,1c,0d,0d,11,11,13,15,17,1e,0d,\
11,13,13,15,17,1c,22,0d,11,13,13,15,17,1c,30,11,13,13,13,17,1c,22,30,13,13,\
17,19,1c,20,22,30,13,15,17,19,1c,20,22,30,15,15,19,19,1c,20,22,30,08,0b,0b,\
0f,0f,11,11,18,0b,0b,0f,0f,11,11,15,18,0d,0f,0f,11,15,15,1a,22,0d,11,0f,11,\
15,15,1a,30,11,15,15,17,15,1e,22,30,11,15,15,17,1c,1e,22,30,13,13,19,1a,1c,\
1e,30,30,13,13,19,1a,1c,1e,30,30


mike

[hoops10]

@mikeathome

Woah, dude. Can you explain that to me a little clearer? What exactly is the mb1 DV interlaced thing?

[colebert]

99% of the time when bitrate viewer gives me scan type alternate and interlaced its because its only picking up the first few frames of the movie which is often interlaced, while the rest of the movie is pure-bred progressive.

-Cole

[mikeathome]

Originally posted by colebert
99% of the time when bitrate viewer gives me scan type alternate and interlaced its because its only picking up the first few frames of the movie which is often interlaced, while the rest of the movie is pure-bred progressive.
-Cole

Yes, the WB logo e.g., I refer to true Interlaced titles, like ID4 or live rock gigs. You need to be careful here, although the Alternate Scanorder + Alternate Matrix does less harm to the quality of a progressive movie as a ZigZag Scan would do to a Interlaced movie.

@hoops:
Many words have been written about this, I give you few links:

http://bmrc.berkeley.edu/research/mpeg/faq/mpeg2-v38/faq_v38.html#tag15 (go down to the alternate)
http://www.physics.utu.fi/ett/kurssi/sfys3066/teemu_tiivis.pdf
http://www.ece.cmu.edu/~ee899/lecture7.pdf

I don't know whether it is clearer, but at least correct ;-).

In simple words, the scan order determines the way of the encoder thru the quantization matrix, the order how the encoder picks the quantization coeffizients from the matrix. So, that's why it is essential that both, the matrix and the scan order correspond. Hopefully I don't need to explani how the quantization works, that would take a little longer...

mike