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Old 6th February 2021, 20:38   #1  |  Link
YaBoyShredderson
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X265 high vs main tier??

In x264/H.264(AVC) high offers better quality than main, as far as i know anyway. Is the same true for x265? I ask as in staxrip i have to select an encoder level to use the high tier of that level. Selecting level 4 still uses main though? Im thinking at this point that its only a tag, like level, and doesnt actually affect quality as long i stay in range of the level/tier? Like it will only increase quality if i exceed the maximum bitrate of, say, level 4 main, and cross into level 4 high? I dont know if i explained that right but anyway. Is high tier better than main in x265?
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Old 7th February 2021, 10:25   #2  |  Link
rwill
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H.264 has a High Profile which allows the use of additional coding tools like 8x8 transform. This increases Quality/Rate most of the time.

H.265 has a High Tier for Levels which potentially requires additional decoder resources and speed but has no effect on the selected Profile which specifies the available coding tools.

So if you do not hit Level Limits with H.265 there is no impact to Quality. Or you can constrain your streams to a specific Level to target a specific Decoder Class which is recommended for playback compatibility.
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Old 7th February 2021, 13:08   #3  |  Link
YaBoyShredderson
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Quote:
Originally Posted by rwill View Post
H.264 has a High Profile which allows the use of additional coding tools like 8x8 transform. This increases Quality/Rate most of the time.

H.265 has a High Tier for Levels which potentially requires additional decoder resources and speed but has no effect on the selected Profile which specifies the available coding tools.

So if you do not hit Level Limits with H.265 there is no impact to Quality. Or you can constrain your streams to a specific Level to target a specific Decoder Class which is recommended for playback compatibility.
So i can leave the level on automatic and dont have to worry about quality? I believe everything i encode will be within level 4 anyway, so selecting level 4 high wont make any difference?
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Old 7th February 2021, 13:26   #4  |  Link
rwill
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Well maybe you should not let the encoder automatically decide the level but set a hard cap yourself.

You can always download the h.265 spec from here:
https://www.itu.int/rec/T-REC-H.265-201911-I
and check the level limits for a certain level. Then configure all relevant parameters of your encoder to match a specific level and set that level at the encoder so no magic things that are not wanted happen.
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Old 7th February 2021, 23:39   #5  |  Link
benwaggoner
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Originally Posted by rwill View Post
Well maybe you should not let the encoder automatically decide the level but set a hard cap yourself.

You can always download the h.265 spec from here:
https://www.itu.int/rec/T-REC-H.265-201911-I
and check the level limits for a certain level. Then configure all relevant parameters of your encoder to match a specific level and set that level at the encoder so no magic things that are not wanted happen.
That said, the default levels in HEVC are pretty sane for any given height * width * fps, and using the lowest content-compatible level maximizes decoder compatibility. x265 does a good job at automatically picking the optimal level for your content, and I only override it in rare and peculiar circumstances.

For reasonably slow presets and a broad range of content, the max bitrate/ref frames/ecetera of the default profile is almost always sufficient for excellent quality.
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Old 8th February 2021, 09:38   #6  |  Link
excellentswordfight
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Quote:
Originally Posted by benwaggoner View Post
For reasonably slow presets and a broad range of content, the max bitrate/ref frames/ecetera of the default profile is almost always sufficient for excellent quality.
Correct me if I'm wrong, but afaik x265 does only enforce vbv restrictions when level is set manually.

And for OP, level 4 @ main has max bitrate of 12Mbps, that could effect quality for 1080p. But as I said above, I'm pretty sure that its left unrestricted at auto, so in that case it wont effect your output.

Last edited by excellentswordfight; 8th February 2021 at 10:25.
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Old 23rd February 2021, 10:33   #7  |  Link
Tenkei
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But what about device compatibility? If specification for a device says it supports "Main 10 Profile Level 4.1", does that mean main tier and high tier or just main? AFAIK Main 10 profile does not mean main tier, so I'm a little confused. If it's just main, can I assume that device supporting 4.1 main tier would also run 4.0 high?
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Old 23rd February 2021, 19:23   #8  |  Link
benwaggoner
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Originally Posted by Tenkei View Post
But what about device compatibility? If specification for a device says it supports "Main 10 Profile Level 4.1", does that mean main tier and high tier or just main? AFAIK Main 10 profile does not mean main tier, so I'm a little confused. If it's just main, can I assume that device supporting 4.1 main tier would also run 4.0 high?
Assume it's Main Tier unless otherwise specified.

The primary exception I can think if is that UHD Blu-ray's peak bitrate is a lot higher than 40 Mbps, so that probably should be done at High Tier and then --vbv-bufsize and --vbv-maxrate specified per the BD spec.
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Old 23rd February 2021, 20:21   #9  |  Link
excellentswordfight
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Originally Posted by benwaggoner View Post
Assume it's Main Tier unless otherwise specified.

The primary exception I can think if is that UHD Blu-ray's peak bitrate is a lot higher than 40 Mbps, so that probably should be done at High Tier and then --vbv-bufsize and --vbv-maxrate specified per the BD spec.
Yes, the uhd blu-ray standard specify high tier, the lower max bitrate is set as other disk based media cause of the limitation of the read bandwidth from the disk. The decoder itself in those units can probably handle the full data rate of high teir.

Quote:
Originally Posted by Tenkei View Post
But what about device compatibility? If specification for a device says it supports "Main 10 Profile Level 4.1", does that mean main tier and high tier or just main? AFAIK Main 10 profile does not mean main tier, so I'm a little confused. If it's just main, can I assume that device supporting 4.1 main tier would also run 4.0 high?
I wouldn't assume that, 4.0 high specify a higher data rate then 4.1 main.
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Old 24th February 2021, 16:05   #10  |  Link
Tenkei
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Originally Posted by excellentswordfight View Post
I wouldn't assume that, 4.0 high specify a higher data rate then 4.1 main.
I'll have to manually set the profile then, because If I set the VBV constraints to eg. 19000, x265 will choose 4.0 high instead of 4.1 main.
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Old 25th February 2021, 00:43   #11  |  Link
benwaggoner
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Originally Posted by Tenkei View Post
I'll have to manually set the profile then, because If I set the VBV constraints to eg. 19000, x265 will choose 4.0 high instead of 4.1 main.
Profile or Tier?

I always specify Profile and Level, and it always defaults to Main Tier as long as my --vbv-maxrate and --vbv-bufsize are within Main Tier limits.
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