Cropping black bars on a 2.35:1 aspect video

[spicediver10191]

When encoding and AVI or MP4, does removing the black bars from a 2.35:1 aspect-ratio movie increase overall quality?

This is an argument I'm having with another editor. He says no, I say (probably) yes. Would be grateful if the resident wiz's here at VH could clear this one up for us.

My source file is a collection of NTSC DVD clips rendered to a lossless AVI file from Premiere, 720 x 480 resolution, 23,976fps, and 2:35:1 aspect ratio.

From that, I'm encoding MP4 and XVID AVI versions at 2000kbps bit rate, and I crop the black bars using the following AVIsynth script:

LanczosResize(720,408)
Crop(0,48,0,-44)

The result looks great, and to my eyes a little better quality than the same source encoded without the resize and cropping. My DVD Divx player and media streaming box both display the 2.35:1 picture correctly on a 16:9 TV, adding their own black bars at top and bottom.

But my friend says that because I've reduced the number of lines of horizontal resolution, the resulting video should look worse (ps. I haven't been able to show him the clips as yet).

What do you think?

[intracube]

EDIT: Ignore this post. Misunderstood the question.

The answer is yes and no. But mostly no.

It partly depends on the size/quality of the screen you're viewing on. As the source is SD, cropping and watching on a HDTV will lead to a fairly obvious reduction in horizontal resolution. Also the height of the picture will be increased, so the image might also look softer vertically. But if you watch on a smaller SD TV, cropping the image may be preferable as it'd fill the screen and have more impact.

Some other options:
- acquire an HD version of the movie. The drop in res. after cropping will be less noticable
- get an already formatted 'full height 16:9' version of the film. TV networks often show these versions and the re-formatting work will be done for you. Depending on how the movie was shot, the 16:9 version may have additional picture at the top and bottom of the frame and very little cropped from the edges of the 2.39:1 version.

The choice of cropping might also depend on the other footage you're cutting in with it. If it's a mixture of 2.39:1, 1.85:1, 16:9, you might decide that the jumps in AR are jarring and normalizing to a common AR would be better.

[jagabo]

When encoding and AVI or MP4, does removing the black bars from a 2.35:1 aspect-ratio movie increase overall quality?

Only by a tiny bit. Unless there is noise in the black bars (like with a VHS recording) the black bars compress down to nearly nothing.

I just did a quick test encode with a 720x480 DVD source. Using x264 and CRF encoding (constant quality) there was less than a 0.2 percent difference in file size between the full frame size (720x480) and the cropped frame (720x368). Rather than resizing to square pixel I use "--sar 32:27" to get the correct display aspect ratio. The resizing (LanczosResize) is where you are losing "quality", not the cropping or lack thereof.

[intracube]

When encoding and AVI or MP4, does removing the black bars from a 2.35:1 aspect-ratio movie increase overall quality?

Only by a tiny bit. Unless there is noise in the black bars (like with a VHS recording) the black bars compress down to nearly nothing.

Hmm, I completely misunderstood what the OP was doing

"I've reduced the number of lines of horizontal resolution" - actually vertical resolution.

[spicediver10191]

Thankyou both!

That settles it.