12.01.2021, 02:50
Quote:My first attempt to rip and transcode a film made in Cinemascope (2.35:1 aspect ratio) was a major failure.>> Since you didn't share in what way it was a failure, I can't really help.
I wanted to try to make sense of it myself if I could ;-)
>>My wild guess would be that your input is Cinemascope (2.35:1 display aspect ratio), but isn't properly flagged.
Exactly so. This is what I found by experimenting with the (very useful) tools in Hybrid-
The source was a DVD of Flash Gordon (1980). The original film is a Cinemascope 2.35:1 feature, and the DVD describes itself as 16:9 anamorphic. However the mkv rip shows up in Hybrid with an aspect ratio of 16:15 (1.067:1) which is clearly nonsense.
Attempt 1
First pass I just treated this like a normal 16:9 film. I was rewarded with a picture occupying about 50% of the screen horizontally and 40% vertically. A little vertically squeezed sticking plaster of a picture.
Attempt 2
For the next attempt I did the following-
- Crop the picture to 720x440
- Applied 68 pixel letterbox bars top and bottom
- Tansformed the picture to 1.63:1 aspect ratio with square pixels (1.63 is 720/440)
This was better, it occupied more of the screen and the picture wasn't distorted, but it still wasn't using the full screen width on the TV. My guess was i'd failed to take account of the fact that a standard 720x576 image (1.25:1) has to have an "anamorphic" transform to fit a 1.77:1 TV screen, so setting "square pixels" was incorrect.
Attempt 3
For this one I cropped the picture down to just the 720x440 active area, then resized the result to 720x306. This worked, and actually filled the TV screen horizontally, but it struck me that I was maybe wasting CPU resizing the image during transcoding, when presumably the TV or streamer can do this on the fly pretty easily, because they do it every time you play a 720x576 DVD on a 1080p or 2160p display.
Attempt 4
After several experiments trying to make sense of the various pieces of the aspect ratio puzzle I ended up with-
Input PAR: 4x3 (= 64/45 (16:9 PAL PAR) x 15/16 (reported PAR of the rip)
Output PAR: 72x44 (active area of resulting image)
Convert output to PAR: On
No crop, no resize.
it worked! (mostly by luck...) I don't know if this recipe will work for all widescreen material but at least I understand the controls in the Crop/Resize section a bit better now.
One comment- It took me a while to understand that you could set use the Crop/Resize options to override the output PAR settings WITHOUT resizing the picture (because choosing an output PAR automatically enables resizing). Fine once I "got" it, but the fact that the PAR section was still in effect even if Picture Resizing was not enabled was not obvious to me in the user interface.
BTW sorry for the crazy spacing in the previous post, but every time I removed the extra line breaks between paragraphs the eidtor seemed to re-insert them?! Hence the excessive spaces between paragraphs.