New Quantization Matrices - Full Anamorphic

[Cunhambebe]

Hi there! I was reading this topic http://forum.doom9.org/showthread.php?t=83125&highlight=xvid+matrixes
on New Quantization Matrices and found out that they mention "full anamorphic dvd resolution (720x432):
1) High Bitrate: This is a HIGH BITRATE matrix designed to work at full anamorphic DVD res (720x432) with bitrates over 1600kbits...
2)Ultra-High Bitrate: This is an ULTRA-HIGH BITRATE matrix designed to work at full anamorphic DVD res (720x432) at very very high bitrates...
3)Low Bitrate: This is a LOW BITRATE matrix designed to work at full anamorphic DVD res (720x432) with bitrates lower than 1500kbits...
Question: Why full anamorphic at 720x432 if NTSC runs at 720x480? Furhtermore, some people here have told me to encode at full PAR/DAR (720x480) but sometimes I notice artifacts whem the action is too fast on the screen, something that can't be notice if you encode at a PAR of 1:1 (640x480; 640x360; 640x272...) Anyone, please?
Thanks in advance

[Irakli]

Hi, Cunhambebe!

I think 720x432 refers to PAL anamorphic DVDs. In this case, resolution is 720x576 and there are black bars on top and bottom of the frame. So after cropping these black bars 720x576 -> 720x432. NTSC is similar (anamorphic resolution after cropping may be different, though).

Regarding full anamorphic encodes, what people are saying about rataining full resolution (=cropping only, no resizing) is true. However, the problem is that you need enough bitrate in order to encode such material. Lack of bitrate may result in blockiness and other artifacts. So, if you notice artifacts, I would suggest to either increase bitrate, use some denoising, or resize to encode at 1:1 PAR if you can't increase bitrate for some reason (ok, resolution is lower in this case but some artifacts will be gone).

Best wishes,
Irakli

[Cunhambebe]

Thank you very much for taking time to respond. In fact my doubt now is about the correct resolution. I've got a chart here for encoding at 4:3 and 16:9. Let's take a look at it:
When encoding to a 4:3 Aspect MPEG
SourceAspect NTSC/PAL DVD
1.33 - 720x480 / 720x576
1.78 - 720x360 / 720x432
1.85 - 720x348 / 720x416
2.20 - 720x292 / 720x344
2.35 - 720x272 / 720x324

Now, this is the chart for 16:9:

When encoding to a 16:9 Aspect MPEG
Source Aspect NTSC/PAL DVD
1.33 - 1.33 Not Applicable: See above table for 1.33 resolutions
1.78 - 720x480 / 720x576
1.85 - 720x460 / 720x552
2.20 - 720x388 / 720x464
2.35 - 720x360 / 720x432

I thought using 4:3 resoltions (regulat tv screen) would be OK for both 4:3 and 16:9, but now there are other figures for 16:9 screens (plasma/lcd). The question is: what should I do (or choose) to make it all compatible bwith both sizes (4:3 and 16:9)? I'm a bit confused. Thanks in advance.
Cheers,
Mark :confused:

[Brother John]

some people here have told me to encode at full PAR/DAR (720x480) but sometimes I notice artifacts whem the action is too fast on the screen, something that can't be notice if you encode at a PAR of 1:1 (640x480; 640x360; 640x272...)
Usually “PAR 1:1” not only means a change of the pixel shape but also a significant downsizing of the video. All your 1:1 resolutions are way smaller than the full (cropped) original res. That means you need more bitrate to encode the full res.

I've got a chart here for encoding at 4:3 and 16:9. Let's take a look at it
Those tables show the resolutions you might get after cropping and before resizing/AR correction. They’re nothing to rely on blindly, though. The only “correct” resolution after cropping is the one you reach when all black bars are completely gone.
Btw: You’ll hardly encounter lines 2 to 5 of your 4:3 table. Fortunately 4:3 DVDs containing widescreen video are extremely rare. (They waste vertical resolution.)

what should I do (or choose) to make it all compatible bwith both sizes (4:3 and 16:9)?
You can’t. A movie with around AR 4:3 on playback willl always be 4:3. The only way to make it 16:9 is to cut away parts of the picture on top/bottom. Don’t confuse the AR of the resolution stored on disc with the proper AR on playback. They might be different and eventually the playback AR is the one that counts since it’s the one you see when watching the movie.
“4:3 DVD” and “16:9 DVD” refer to the playback AR of the whole picture including all black bars. As soon as you crop those numbers become meaningless.

This thread (http://forum.doom9.org/showthread.php?p=1058927#post1058927) might also be interesting for you.

And since you mentioned matrices. It’s better to think of a matrix in terms of “level of detail retention” because that’s the matrix’s major impact on the picture. The bitrate/resolution numbers are rough estimates for common scenarios to give the general public a better idea of what the matrix might be useful for. (Because only few know the implications of a given detail level.) If you want to use Sharktooth’s matrices with non-anamorphic resolutions that’s perfectly ok. Just use the high/low/something bitrate numbers as a general guideline.

[Cunhambebe]

Thanks for taking time to respond brother :)
You can’t. A movie with around AR 4:3 on playback willl always be 4:3. The only way to make it 16:9 is to cut away parts of the picture on top/bottom.
I guess I was a little misunderstood, sorry. I could have put it better. I wanted to make it compatible with both pc and hadware players (DviX - XviD DVD players) - which might be difficult. Anyway, thanks a lot for the detailed explanations. I have posted a topic at VideoHelp and we found a 1:1 solution like yours...
Using 1:1 PAR; we've got
[4:3 that is 1.33] 720/1.33= near 540 ; 720/540=1.33;
[16:9 that is 1.78] 720/1.78=404 ; 720/404=1.78
[1.85] 720/1.85=389 ; 720/389=1.85
[2.20] 720/2.20=326 (nearest even number) ; 720/326=2.20
[21:9 that is 2.35] 720/2.35=306 ; 720/306=2.35

Anyway, no matter what aspect ratio the movie is, with a 16:9 DVD, resizing the 720x480 frame to 720x404 and cutting away the black borders will give the correct square pixel aspect ratio (important: leaving the height a multiple of 16).