Anamorphic questions

[raziel666]

I thought I had understood everything concerning the encoding of anamorphic DVDs, but after I saw something I'm a little confused. I noticed in some (very respectable) group's encoding (x264, mkv) the following
(from MPC->Properties->Details):

Video size: 704x384 (AR 117:64)
Video: MPEG4 Video (H264) 704x384 (64:35) 23.98fps
If I open it in MKVmerge, the display width/height is 704x385. How are these numbers explained? The standard I've seen on most DVD encodes is a video size of 720/704x480 with AR of 853x480, so this was somewhat strange.

Let's say now that there's a R1 NTSC DVD for encoding. When I create the AVScript in MeGUI choosing Clever Anamorphic encoding, it says Input DAR ITU 16:9 1,823. Before cropping the AVScript is as follows:

# Set DAR in encoder to 37 : 20. The following line is for automatic signalling
global MeGUI_darx = 37
global MeGUI_dary = 20
DGDecode_mpeg2source("")
Lanczos4Resize(720,480) # Lanczo4 (Sharp)

If I crop it to remove black bars, the script becomes as follows:

# Set DAR in encoder to 37 : 20. The following line is for automatic signalling
global MeGUI_darx = 37
global MeGUI_dary = 20
DGDecode_mpeg2source("")
crop( 2, 6, -2, -14)
Lanczos4Resize(720,464) # Lanczo4 (Sharp)

My question is, after cropping, should I change the 37:20 DA ratio, and if yes, how should I change it? Is there some "general" rule? Is there a need to change the setting in MKVmerge?

[check]

The first issue is simply that this 'group' (read rule #6 and further clarify please) can't be that clever if they set the DAR dimensions with an odd number, because that isn't supported in YUV formats.
The video was cropped to 704 because the additional pixels are essentially not part of the real video and should be removed. You can read any of scharfis_brain's posts on this subject if you want to learn more / argue about it :). In short, crop 8 pixels from both sides of any DVD source.

The second issue is that the DAR (which is the Display Aspect Ratio, ie the ratio of the final image as it appears during playback) is not the same as the ratio of width/height. It seems your DVD has a pixel ratio of 720/480=1.5, which will be deformed on playback to show at 37/20=1.85. The catch is that there are black bars in the encoded frame, so it probably means the video is 2.35:1.

If this is correct, you need to do the following:
o crop off 8 px from both sides
o crop out any reminaing black bars
o set the playback DAR to 2.35:1. If this looks incorrect (squished), use 1.85:1

[raziel666]

I tried taking a screenshot of the DVD and cropped it myself and the result is a picture of 849x460. MeGUI displays an input DAR of 1,83 approximately and 849x460 is somewhat close to it. Of course I guess I have to do mod16 resizing in MeGUI - I think 720x464 will have to do. Am I right?
The value 849x460 corresponds (almost) to 853x464 if I'm right. So is this the DAR I should put in the MeGUI script? Should I change this in the mkv file?