MP4 resolution choices - ?!?!?!?

Cuddly Squid

===== WARNING: Lengthy post =====
I've been doing some reading: DVDFab docs & this forum, and I can see I'm unsure and others are unsure about MP4 resolution choices. I have many observations & questions. Thanks to all who look at them. - C.S.

The discussion below is keyed to the attachments (left-to-right):
1 raw capture.jpg
2 masked.jpg
3 framed.jpg
4 resolution choices.jpg
5 resolution choices for 1.78 aspect.jpg

1, I captured a frame from the film Enigma. Of course it is 720x480.

2, I cropped off the hard mask. The result is 705x367.

3, I framed the result by increasing the pixel width by the value of PAR (=32/27). The result is 836x367 (square pixels). Note that DAR is approx. 2.28, which means that the 2.35 aspect film was slightly cropped for the DVD, probably to make the telecine settings come out right.

4, These are the choices DVDFab gave me. Of course, what I want is the second choice: 840x368. It's very close to the real size.

Question 1: Why am I even presented with the 1st choice: 720x316? That's a terrible choice.

Question 2: Why is the terrible choice the default choice?

Question 3: How does DVDFab know there's only 368 unmasked lines and that DAR = 2.28? It's doing that heuristically, right?

5, I put a 16:9 DVD into the optical drive and restarted DVDFab. This time the 2nd choice is 856x480.

Question 4: Why 856x480 instead of 853x480 (or 854x480), which is what is correct and what I would expect?

Question 5: Are the extra 3 (or 2) pixels per line masked or is the aspect slightly larger? (I know it doesn't much matter, but I'm curious.)

Question 6: Is what I want always going to be choice #2?

Thank You,
C.S.

Wilson.Wang

DVDFab calculate the height according the width 720, the default resolution is 720*XXX in DVDFab. To keep the video size and video quality, I suppose that the default settings is enough, and DVDFab list the high resolution 856*XXX in Advanced Settings, you could change the bitrate setting if you want the high video quality.

framed the result by increasing the pixel width by the value of PAR (=32/27). The result is 836x367 (square pixels). Note that DAR is approx. 2.28, which means that the 2.35 aspect film was slightly cropped for the DVD, probably to make the telecine settings come out right.

You are right, crop area is according the aspect ratio. But it should also include other computational formula.

5, I put a 16:9 DVD into the optical drive and restarted DVDFab. This time the 2nd choice is 856x480.

Question 4: Why 856x480 instead of 853x480 (or 854x480), which is what is correct and what I would expect?

The opened source should not have the black boarders and does not need to crop.

Wilson

Cuddly Squid

Thank you, Wilson,

The video is 836x367 (attachment 3). Note that DAR is approx. 2.28...

[QUOTE=Wilson.Wang;165353]DVDFab calculate the height according the width 720...[/quote]That doesn't appear to be the case because the storage width is not 720. Its 705. The display size is 836x367. Choice #2 = 840x368 is close. Since PAR = 32/27, DVDFab must be calculating storage width as = 840/PAR = 840/32*27 = 708, not 720, so DVDFab must be cropping vertically & horizontally. I would expect that, but the actual storage width is 705, not 708, so where are the extra 3 pixels of storage width coming from? Are the 3 pixels black mask or is the storage width being 'up-converted' from 705 to 708 prior to DAR = PAR*SAR conversion?

To clarify:
The actual video is:
DAR = PAR*SAR = (32:27)*(705:367) = int(705*32/27):480 = 836:367.
Actual video display size = 836x367.
DVDFab choice #2 is:
840x368.
But (working backwards) it must be working with the following storage size:
SAR = DAR/PAR = (840:368)/(32:27) = int(840/32*27):368 = 708:368.
So DVDFab is assuming video storage size = 708x368. How? And where is it getting the extra 3 pix/line of storage width data?

[QUOTE]To keep the video size and video quality, I suppose that the default settings is enough...[/quote]
Huh? Enough for what?

The default has only 316 lines (see attachment 4). The video has 367 lines. If I took the default, I'd be losing 51 lines (14%), wouldn't I? (The 836x367 video would end up 720x316.)

[QUOTE]...and DVDFab list the high resolution 856*XXX in Advanced Settings...[/quote]
856 pix/line is not one of the choices.

[QUOTE]...you could change the bitrate setting if you want the high video quality.[/quote]
One step at a time, my friend. I've tried several differing bit rates and none of the resulting MP4 videos will play. ...But that's for a future post.

[quote]You are right, crop area is according the aspect ratio. But it should also include other computational formula.[/quote]
What other computational formula?

Regarding the 1.78 aspect video (attachment 5):
[quote]The opened source should not have the black boarders and does not need to crop.[/quote]
That's true, but my questions are:
1, Shouldn't choice #2 be "853x480"? And
2, Why is choice #1 even there?

Regarding question 1, int(720*32/27) = 853. The display size should be 853x480, but it's 856x480.

Regarding question 2, 720 pix/line is number of storage pixels, not display pixels. What does 720 pix/line have to do with anything? I don't understand why choice #1 is even there.

Can you kindly confirm/clarify what I've written?

Thank You.