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Old 28th September 2015, 03:48   #1  |  Link
kotuwa
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Optimal 480p resolution for HEVC

480p for 16:9 is 853.33x480. right?

Since a pixel should be a whole number, ppl use 854 or 852 or 848 for width.
Ppl use 852x480 to get the width dividable by 4.
And 848x480 to it dividable by 16.

I would like to know how HEVC behaves among those 3 resolution. (854x480, 852x480, 848x480)
Sure it supports all 3... But what are the impacts of encoding...

Regarding the resolution factors and image stretch and A/R deviations when resizing, what could be the optimal for HEVC

In HEVC, is that, dividable by 4 and 16 factors are less important than in AVC?
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Old 28th September 2015, 14:23   #2  |  Link
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x265 pads the video out to min-cu size, generally 8x8 but can be set higher. The visual compression difference of any of the three sizes will probably be completely unnoticeable. (Frankly, the aspect ratio differences will also probably be unnoticeable in casual viewing.) Just use whatever you prefer.

HEVC won't gain you much at all at that resolution though; it barely even gains much at 1080p. It's tremendously better than x264 at 4K and up, but that's worlds away from 480p. Give it a shot, though, maybe your video works better.
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Old 28th September 2015, 14:52   #3  |  Link
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Typical process on DVD source is to crop 8 pixels on left and right side, and then resize to 854x480.
If you are looking for optimal width then you can try different cropping.
(For example, 10 pixels on each side and then 848x480, etc

Last edited by MeteorRain; 25th February 2016 at 04:18. Reason: Typo on numbers
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Old 28th September 2015, 16:15   #4  |  Link
HarryM
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Quote:
Originally Posted by MeteorRain View Post
Typical process on DVD source is to crop 4 pixels on left and right side, and then resize to 854x480.
If you are looking for optimal width then you can try different cropping.
(For example, 6 pixels on each side and then 848x480, etc
Its not true. "480p" compatible HW players support only 720 pixels in width as maximum. No more. Therefore, the best is 704x400px or 720x400px only.

Mod16 is preferable for ALL codecs.
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Last edited by HarryM; 28th September 2015 at 16:19.
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Old 28th September 2015, 17:30   #5  |  Link
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This is about HEVC, you will have a very hard time finding any hardware player that does not support 1920x1080 at the very least.
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Old 28th September 2015, 19:49   #6  |  Link
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Quote:
Originally Posted by MeteorRain View Post
Typical process on DVD source is to crop 4 pixels on left and right side, and then resize to 854x480.
If you are looking for optimal width then you can try different cropping.
(For example, 6 pixels on each side and then 848x480, etc
Quote:
Originally Posted by HarryM View Post
Its not true. "480p" compatible HW players support only 720 pixels in width as maximum. No more. Therefore, the best is 704x400px or 720x400px only.
"Best" (see rules about the word best, BTW) resolution is the original one. Crop only as much as is needed to get rid of black bars and keep it at that, encode anamorphically and use a proper display aspect ratio, for example what this calculator tells you.

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Mod16 is preferable for ALL codecs.
Don't say such things. It is hardly true for anything decent since x264 and thanks to myths like this, people ruin their videos by using wrong ARs, overcropping and such. The benefits of using mod16 resolution are basically zero. If you disagree, try to make a comparison of two encodes where rounding the resolution to mod16 would be improving quality! (And that would still ignore the issue that forcing mod16 harms quality in the first place by requiring resampling and/or overcrop.)

Last edited by mandarinka; 28th September 2015 at 19:52.
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Old 29th September 2015, 10:40   #7  |  Link
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Yes, there is no need anymore for mod16.

852x480 (assuming no crop was done) would be good. 854 is probably most accurate and "expected".

Last edited by kolak; 29th September 2015 at 10:43.
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Old 29th September 2015, 12:32   #8  |  Link
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I recently went through some of my old 720x480 (16:9 DAR) MPEG-2 disc sources and have re-encoded them to AVClossless at 856x480 pixels (ie: mod-8)
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Last edited by SeeMoreDigital; 2nd October 2015 at 17:33. Reason: Corrected AVClossless resolution
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Old 2nd October 2015, 17:28   #9  |  Link
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Originally Posted by SeeMoreDigital View Post
I recently went through some of my old 720x480 (16:9 DAR) MPEG-2 disc sources and have re-encoded them to AVClossless at 856x720 pixels (ie: mod-8)
Didn't that leave you will a bigger file that is less accurate than the source?

Now that non-square pixel support is pretty well universal, I'm a fan of just cropping to active image area and keeping all the pixels and the SAR. There's no benefit to throwing pixels out or to creating new ones.

I think Mod-4 is pretty well universally compatible today in released decoders. The only exception I can think of will have that fixed in a mandatory firmware update within a week.
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Old 5th October 2015, 04:12   #10  |  Link
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Most time when we are talking about non-anamorphic, or mod XX, we are talking about compatibilities.
For a "normal" player, these features are all well supported, and keep the original resolution + crop only the margin + mod 4 + anamorphic should be a very good option.
However when dealing with buggy decoders (who may crash on non mod 8/16), buggy subtitle filters (who may ignore ARs), extra care should be taken when making decision.
You never know what soft/hardware user is gonna use.
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Old 5th October 2015, 18:46   #11  |  Link
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Again, this is HEVC. All of that is much less likely on something that can play HEVC. I also prefer encoding the original pixels if possible.
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Old 6th October 2015, 04:11   #12  |  Link
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Again, this is HEVC. All of that is much less likely on something that can play HEVC. I also prefer encoding the original pixels if possible.
TBH, hevc player != well designed / developed / tested player.
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Old 13th October 2015, 19:57   #13  |  Link
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TBH, hevc player != well designed / developed / tested player.
Well, except HEVC player = recently updated player. I suspect most HEVC decoding is being doing in players/OSes/SoCs that already had anamorphic nailed. I certainly feel more comfortable that anamorphic HEVC will work on an arbitrary HEVC compatible player than anamorphic HEVC will work on a arbitrary compatible H.264 player.
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Old 5th January 2016, 19:28   #14  |  Link
movmasty
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Originally Posted by MeteorRain View Post
Typical process on DVD source is to crop 4 pixels on left and right side, and then resize to 854x480.
If you are looking for optimal width then you can try different cropping.
(For example, 6 pixels on each side and then 848x480, etc
I thought we were talking about BR source?

However, 712x 40/33 ~ 863....

Remember that DVD frames are 720, but mpeg frames are ~704

in fact 704x 40/33 = 853.333
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Old 9th January 2016, 12:34   #15  |  Link
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I tested x264 codec and non-mod16 and mod16 resolution coding... in many scenarios.... and my conclusion is, that non-mod16 resolution is generally possible, but with significant filesize penalty - plus +2-4% on bitrate/framepixel.
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Old 10th January 2016, 08:29   #16  |  Link
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but with significant filesize penalty - plus +2-4% on bitrate/framepixel.
Significant, is really relative.
May be I'm wrong, but with a bit rate of 10 MBit/s and a resolution of 1920x1080 one would have a bit/framepixel value of 10000000 / 2073600 = 4.8225308641975308641975308641975 bit/framepixel.
4% of that would be 0.1929012345679012345679012345679 bit/frame pixel, which would be 400 bit/frame.

Given a 3hr ( = 240min = 14400 sec) movie with a frame rate of 24fps we would have 345 600 (= 14400*24) frames and thus a file increase of (345 600*400) 138 240 000 bit = 17 280 000 byte = 16.4794921875 MB.
Normal file size would be (10MBit/s = 10 000 000 = 1 250 000 byte/s =) 1.1920928955078125 MB/s time 14400 sec = 17 166.1376953125 MB.

Less than 1% file increase doesn't sound that significant to me,...
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Old 10th January 2016, 10:06   #17  |  Link
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Given a 3hr ( = 240min,...
...Is the hour? It is 80 minutes.
A good movie is 2 hours, and this 3 hours are 240 minutes

If its +2-4% on bitrate/framepixel, its +2-4% on bitrate or size as well.
I like numbers, but there are too many in your post.
what is the distance of Centauri? 4Ly, 480 days in a year, 32 hours in a day, 80 mins in a hour, 80 secs in a min.....very big!

The difference exist, but is very smaller mod16xmod8 is still very good

If you really seek for total compatibly and universal rendering should use mod64xmod64.
that gives few res available
for 4:3 256x192 and multiples
for 16:9 1024x576 and multiples
for 2.35 2560x1088 and multiples.

Last edited by movmasty; 10th January 2016 at 12:49.
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Old 10th January 2016, 10:08   #18  |  Link
vivan
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4% of that would be 0.193 bit/frame pixel, which would be 400 bit/frame.
How do you do that?

And I'm pretty sure he meant just 4% increase in bitrate or bpp.

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If you really seek for compatibily and universal rendering should use mod64xmod64.
Compatibility? What kind of decoder can't decode 720p because it's not mod64?

Last edited by vivan; 10th January 2016 at 10:11.
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Old 10th January 2016, 12:51   #19  |  Link
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Compatibility? What kind of decoder can't decode 720p because it's not mod64?
Amiga? Commodore
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Old 10th January 2016, 13:39   #20  |  Link
vivan
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Amiga? Commodore
Yet they can decode 576p because it's mod64 resolution?
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