Have problem understanding anamorphic, again. (Handbrake)

[MovingParts]

Hi,

I thought, when you have a 16:9 source, it gets stored as 4:3 (squished left+right) and then for ourput stretched back to 16:9.
But here it is stored as 4:3 source, then anamorphic: strechted (perhaps 16:9), output: same as source.

Does it make any sene?

I attached Handbrake, Quicktime and MediaInfo all telling different stuff.

I looke into this https://trac.handbrake.fr/wiki/AnamorphicGuide but am still puzzled.

[jagabo]

In general, any frame size can encode any display aspect ratio. DVD supports 720x480 (3:2, NTSC) and 720x576 (5:4, PAL) frame sizes. Those can be 4:3 or 16:9 display aspect ratio. DVD does not support any 4:3 frame size.

The equation that relates display aspect ratio with the frame size and sampling AR:

DAR = FAR * SAR

Where DAR is the display aspect ratio, FAR is the frame aspect ratio, and SAR is the sample aspect ratio (distance between samles, or shape of individual pixels).

[MovingParts]

OK, so I get, that there is nothing wrong with the above movie file? OK; then I just don't bother anymore. I thought Handbrake might have picked a wrong handling of the file regarding picture size.


PS: there is another source, where Handbrake says "source: 1280x720 / output: 1280x720 / anamorphic: 1280x720". Why does it need anamorphic, when anamorphic is the same? I thought anamoprhic is used to save space on a medium and not the real viewing ratio.

[hello_hello]

I'm pretty sure the anamorphic method is up to the user, Handbrake doesn't select it. I don't use Handbrake much myself but I think it defaults to anamorphic loose, modulus 2, but that's not necessarily bad.

Anamorphic none = resize to square pixels.

Anamorphic strict = anamorphic without any resizing. The pixel aspect ratio of the output will be the same as the pixel aspect ratio of the input. For video that's not anamorphic, (PAR 1:1) the output won't be anamorphic as the PAR will still be 1:1. You can crop but you can't resize.

Anamorphic loose is the anamorphic option that resizes. Unlike anamorphic strict the PAR might change. The idea being that you could (for example) take a video that's 1280x720 and crop a few pixels off the top to make it 1280x712, then re-size it back to 1280x720 if you needed mod16 (width and height evenly divisable by 16). Normally that'd stretch the picture a little, but with anamorphic loose Handbrake would adjust the PAR a little to compensate, so it'd display as 1.79 as it should (it's no longer exactly 16:9) but it's still encoded at 1280x720.

There's a potential benefit to using anamorphic loose if the source has square pixels and you resize, although for anamorphic loose with a modulus of 2 it's probably quite small, as with a modulus of two the resizing can be quite accurate (width and height only need to be evenly divisible by 2). Still, 720x405 is exactly 16:9, yet if you resize a 1280x720 video you can only resize to 720x404 or 720x406 with a modulus of two, so where "anamorphic none" would result in a very small aspect error, "anamorphic loose" should let Handbrake adjust the PAR to compensate.

If the source isn't anamorphic and you don't resize (only crop), anamorphic none with a modulus of 2, anamorphic strict, and anamorphic loose with a modulus of 2, should all give you the same output.

[MovingParts]

Wow! Thanks that was well explained.

You say

If the source isn't anamorphic and you don't resize (only crop), anamorphic none with a modulus of 2, anamorphic strict, and anamorphic loose with a modulus of 2, should all give you the same output.

Does that mean, if the source was anamorphic (like on a DVD?) it is important to have in mind what the three anamorphic types (you listed and of which you explained the consequences and benefits) do and if not anamorphic I basically can do whatever as long I don't resize (only crop)?

If the source is non-anamorphic and I DO resize (lets say from a 1280x720 movie down to 640x360, I would have to make a decision on what anamorphic type and modulus to choose. In this case the loose @ modulus 2 would be the one I could do the least wrong?

[jagabo]

I highly recommend against using mod2. Use at least mod4. These forums are full of posts from people with mod2 videos that don't play properly on some devices or don't decompress properly in some editors. And don't worry about small AR errors. You won't notice a 1 or 2 percent AR error unless you get out a ruler and measure it.

[MovingParts]

Oh, that's good info then. That might be a reason why my movie's I converted with Handbrake don't play, while other from the internet play. (I thought it had to do with profiles and lowered that, in the end I found out, that every movie that I encode above a resolution of 640x360, will stutter on a 1024x867 netbook. So maybe it is just because of using modulus2. I will try that tomorrow.)

[jagabo]

No, 640 is mod 128 and 360 is mod 8. So that's not the problem you were having.

[hello_hello]

You say

If the source isn't anamorphic and you don't resize (only crop), anamorphic none with a modulus of 2, anamorphic strict, and anamorphic loose with a modulus of 2, should all give you the same output.

Does that mean, if the source was anamorphic (like on a DVD?) it is important to have in mind what the three anamorphic types (you listed and of which you explained the consequences and benefits) do and if not anamorphic I basically can do whatever as long I don't resize (only crop)?

The main idea behind anamorphic encoding is to encode an anamorphic source "as-is", without any resizing. So ideally you'd use "anamorphic strict" and manually adjust the cropping if need be for your preferred modulus. If auto-cropping produces mod2 (for example) and you want mod4, you'd adjust the cropping to make it mod4 by increasing or decreasing it a little... it's up to you.

"Anamorphic loose" lets you resize, generally to achieve a desired modules without having to adjust the cropping. Of course you can resize much more if you want to, but that kind of defeats the purpose of anamorphic encoding.

"Anamorphic none" always resizes to square pixels. For DVD sources I'd consider Vidcoder rather than Handbrake if you want to resize that way. Handbrake won't let you upscale, but Vidcoder will, so for a 16:9 720x576 PAL DVD (as an example) Handbrake forces you to reduce the height when resizing, so the maximum resolution would be something like 720x404. Vidcoder lets you increase the width instead, so you can encode at 1024x576. More video to encode, so a higher bitrate for a given quality, but it'll retain more detail. For PAL DVDs I generally resize to 960x540 to keep the file size down a bit, but you're not limited to a width of 720.

Anamorphic encoding is technically the best method for anamorphic sources, but there's media players in two TVs in this house that don't obey aspect ratios in MKV or MP4 files (they just display them as though they have square pixels), so even for anamorphic sources I re-size to square pixels.

If the source is non-anamorphic and I DO resize (lets say from a 1280x720 movie down to 640x360, I would have to make a decision on what anamorphic type and modulus to choose. In this case the loose @ modulus 2 would be the one I could do the least wrong?

I can't say I've ever experienced hardware playback issues due to mod2 h264, although jagabo keeps making me paranoid so I usually stick to mod4. That's the beauty of anamorphic loose though, you could use a modulus of 4 and the resizing doesn't have to be exact because the PAR will be adjusted to compensate..... which is fine, assuming your player obeys MKV/MP4 aspect ratios.
The alternative is to pick your preferred square pixel resizing and adjust the cropping if need be so there'll be as little aspect error as possible. I don't think that's something Handbrake tells you though. Vidcoder might, or you can use this re-size calculator.
http://www.mediafire.com/download/09v9bldu9a6hm00/YodaResizeCalculator.exe
For anamorphic loose you wouldn't need to use it as there should be no aspect error (Handbrake should adjust the PAR as required), but for "anamorphic none" you could crop and resize with Handbrake and enter the cropping and resizing into the calculator. It'll tell you how much aspect error there is. Rather than change the resizing to minimize it, you could adjust the cropping a little instead.

[ackboo]

Handbrake won't let you upscale

That changed recently, couldn't locate the changelog so I don't know when that changed, but in handbrake 0.10.2 on linux you can take an anamorphic 720*576 and resize to square pixels to any resolution. I tried 1280*960, it did what I asked ^^.

[hello_hello]

Good to know. I've only got an older version of Handbrake installed as the newer flavors won't run on XP.

[mike20021969]

Good to know.

I never did understand why HandBrake's devs removed the ability to "upscale" (it remained in 0.9.3 though), yet RandomEngy kept that ability in VidCoder.
Although it is gimmicky and can/does ruin video quality. Upscaling is not a feature I use now anyway.
VidCoder 1.5.6 beta was last version to run on XP.