Correct Cropping/Aspect Ratio with Ripbot vs Handbrake

[Tony Jenkins]

I have a 1920x1080 Bluray file of a film with an aspect ratio of 2.40:1. When cropping this file and ripping to 720p I am getting two different results with Ripbot vs Handbrake. I would like to know which is doing it correctly (or maybe they both are).

With Handbrake, I am encoding it with automatic cropping and it produces a file that Mediainfo shows as:
Width : 1 280 pixels
Height : 528 pixels
Display aspect ratio : 2.40:1

With Ripbot I also encode with auto cropping, and then under size I choose Custom [2,40:1] and set the width to 1280 (instead of 1920) which produces a Mediainfo indication of:
Width : 1 280 pixels
Height : 534 pixels
Display aspect ratio : 2.35:1

Is there something I am missing here? For Handbrake 1280/528 is 2.42:1 and Ripbot's 1280/534 is 2.397(2.4):1. Why is Mediainfo showing the correct Display aspect ratio as indicated on the box of the Bluray, but Ripbot is not? I see that Handbrake produced a height that is more cropped than Ripbot, but I still don't get why Mediainfo is showing the Display aspect ratios as it is.

I am hoping someone can shed some light on this- thank you.

[Atak_Snajpera]

This must be a bug in mediainfo because math does not lie. According to math rules aspect ratio value should be rounded to 2.4 not to 2.35.
1280/534 is 2.397(2.4):1

Display aspect ratio : 2.35:1 = ~1280/545

BTW. 2.42:1 does not exist.Valid aspect ratios are 2.40:1 ,2.35:1, 1.85:1,1.77:1 ...

[poisondeathray]

528 complies with mod16 , probably why handbrake chose that value even though AR is off

[jagabo]

MPEG family codecs work best with mod 16 frame sizes (integer multiple of 16). Some hardware will have problems with non mod 16 frame sizes. So many programs will round to the nearest mod 16 size.

[Atak_Snajpera]

In H264 world you don't have to worry about that.

[jagabo]

h.264 is an MPEG family codec, MPEG 4, part 10. Try making an AVCHD DVD or a Blu-ray disc with a non mod16 frame size.

[poisondeathray]

well 1080 isn't mod16 either , I think it's encoded or padded to 1088 internally but crop flag is applied

[Atak_Snajpera]

x264 does that automatically. Problem with AVCHD DVD or a Blu-ray is that they require specific resolutions like 1920x1080/1440x1080/1280x720/720x480 so you can't just use 1280/528

[poisondeathray]

Yes, if your intent was to make AVCHD / BD compliant format, then just resize to 1280x720 and keep original letterboxing. Forget about cropping. AR is perfect too, identical to original.

[Tony Jenkins]

Thanks for the reply's! I am glad to hear that it isn't something I over looked and some type of problem with MediaInfo. I made a post on their forums to see what they have to say/make them aware of the problem.

I see why Handbrake lowered the height to 528 due to it set on mod16. I realize now that is not necessary when ripping to mkv? Meaning, I can set the mod to 2 so it produces the same result as Ripbot does (height of 534)- thus creating a more accurate aspect ratio compared to the original? The only reason to maintain a mod16 is if I create a BD formatted file/disk (avchd)?- This doesn't pertain to an mkv file burned to a DVDR or BDR?

[poisondeathray]

mod2 is fine for PC playback, or media boxes (e.g. wdtv, oplay etc...)

Some filters may require mod4 or mod8 restrictions, but if you're not filtering...

You have to examine the original - is 2.40:1 the blu-ray transfer to the BD, or what the original film was, or something written on the box ? Sometimes there is a deviation between them . ie. if you crop the borders on the 1920x1080 frame what do you get ? Most people don't care about <1% AR error

[jagabo]

I'd stick with mod 16. Or at least mod 8. How would you like it if you bought a set-top media player in the future and found half your videos didn't play properly. You'll never notice the small (~1%) aspect ratio error.

Also, since the encoder will internally pad other sizes out to mod 16 with black bars, you can get DCT ringing artifacts at the edge of the image with non mod 8 or mod 16 frame sizes.

[Atak_Snajpera]

The only reason to maintain a mod16 is if I create a BD formatted file/disk (avchd)?

1920x1080 is not mod 16 but it works. AVCHD accepts only specified resolutions. It has nothing to do with mod 16 rule!

How would you like it if you bought a set-top media player in the future and found half your videos didn't play properly.

ALL set-top media players play and will play non 16/8/4 resolutions. PERIOD! Why? Because encoder (x264) always automatically uses mod 16 resolution. Simply added lines are not displayed by decoder.

[Tony Jenkins]

Interesting- so with Ripbot, when cropping and encoding to 1280x534, the x264 encoder automatically adds lines that are not displayed to use mod16 resolution?

So what then is the purpose of being able to select the mod in Handbrake? If mod2 is selected does that override x264 in some way and remove the auto mod16 non-displayed lines or are they still generated? Is there a way to get Handbrake to output 1280x534 and have it still be mod16 compliant?

[Atak_Snajpera]

If you use 1280x534 resolution x264 encoder internally adds black lines. So instead of 1280x534 x264 encodes at 1280x544 (10 empty lines have been added in this case). This happens because internal encoders resolution must be MOD 16 (MPEG specification). Everything is done automatically. Later encoder adds special flag to stream so decoder knows that those 10 lines should not be displayed.

BTW. Handbreake also uses x264 encoder.

[Tony Jenkins]

If you use 1280x534 resolution x264 encoder internally adds black lines. So instead of 1280x534 x264 encodes at 1280x544 (10 empty lines have been added in this case). This happens because internal encoders resolution must be MOD 16 (MPEG specification). Everything is done automatically. Later encoder adds special flag to stream so decoder knows that those 10 lines should not be displayed.

Copy that, thank you for clarifying my understanding of what Ripbot is doing.

BTW. Handbreake also uses x264 encoder.

Correct, that is why I don't understand the reason the mod can be selected with Handbrake. If mod16 is chosen, why isn't is doing something like Ripbot by keeping the exact picture size (1280x534) and then adding "invisible" lines to make it 1280x544? Instead it reduces the actual picture crop to 1280x528. Why wouldn't mod2 or "strict anamorphic" be selected every time then?

[Tony Jenkins]

Just to follow up: Media Info indicated it was a bug and they have already fixed it with a new version. Just wanted to update as I hate threads that never reveal the outcome of an issue.