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Old 7th December 2017, 17:49   #22  |  Link
benwaggoner
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Join Date: Jan 2006
Location: Portland, OR
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Quote:
Originally Posted by sneaker_ger View Post
That's a contradiction. If your Samsung player and your video card cannot play maxrate&bufsize >50000 they are not 4.1 compliant. High 4.1 is vbv maxrate 62500, bufsize 78125.

What usually happens is we use CRF encoding and barely reach high bitrates so we make wrong conclusions about level compliance of a device. You did the right thing by deliberately testing these high bitrates.
Exactly. Most real-world Level 4.1 use cases are actually Level 4.1 subsets. There certainly are chipsets that support the full Level 4.1, but all of the format specs generally only handle a subset of those.

Also, there are many Blu-ray players that will play out-of-spec bitstreams. Just because something plays on one test device doesn't make it spec compliant, or indicate that it is going to be broadly compatible. And even in those cases, using Level 4.0 often is more flexible. For example, Blu-ray Level 4.1 requires 4 slices and 40 Mbps maxrate. Blu-ray Level 4.0 doesn't have a slice requirement, and the maxrate is the same as the Level 4.0 max of 25 Mbps. You still have the 1 sec GOP, max 3 ref, strictly hierarchical b-frame, and some other requirements, but it gets looser with the lower level.

And with modern H.264 encoders, a 25 Mbps cap for 1080p24 or even 1080i30 is quite generous. The 40 Mbps max bitrate for Blu-ray was primarily for MPEG-2; double that of ATSC.

Of course, a lot of this gets back to the intended use for content. If it's just for personal use on the devices you have, whatever works, works. For those of us focused on broad compatibility across diverse devices, we really want to stick to published specs, so if there's a problem we know it isn't from out of spec encodes.

There was a significant problem 5-10 years ago with x264 --veryslow encodes using WAYmore reference frames than allowed by the specified level, which caused all kind of issues on hardware decoders. Fortunately most GUI encoders will automatically reduce parameters to those compatible with the specified Profile @ Level now, not just treat --level as metadata with no impact on encoding settings.
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