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Old 22nd November 2017, 03:41   #1  |  Link
tppytel
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Is High@4.1 AVC safe at this point?

I reencode various videos for my Plex server and haven't paid close attention to AVC profiles in the past. Is High@4.1 a reasonable profile going forward? Or is it better to stick to Main@4.1? The server is just for me and my family, so I don't need to support every ancient smartphone out there. I'm only interested in current devices. I see various references stating that Main@4.1 is a better default, but most of them are at least a year or two old.
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Old 22nd November 2017, 13:17   #2  |  Link
froggy1
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Never had problems with High@4.1 on any of my devices. Most gear made in the past few or so years should have no issues supporting it
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Old 22nd November 2017, 14:46   #3  |  Link
Atak_Snajpera
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Some older devices do not support anything beyond High@4.0.
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Old 28th November 2017, 05:10   #4  |  Link
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Also, a number of portable devices don't support interlaced decode, which is a required feature of High Profile. So it's really HighP that is pretty much standard.
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Old 28th November 2017, 05:20   #5  |  Link
tppytel
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So it's really HighP that is pretty much standard.
HighP or MainP? I don't understand your comment. It seems to imply that MainP is standard because devices don't support deinterlacing.
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Old 29th November 2017, 17:06   #6  |  Link
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HighP or MainP? I don't understand your comment. It seems to imply that MainP is standard because devices don't support deinterlacing.
A number of devices support High Profile progressive only decode. iOS devices in particular.
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Old 30th November 2017, 19:20   #7  |  Link
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I have been using High 4 for 1080p24/p30 material for dog's years and never had any trouble with any display device I threw it at.

But you ask about High 4.1. I believe the only difference is that 4.1 has a maximum bitrate of 50 MBps compared 20 MBps for 4.

Not having run or seen any comparison, I do not know how much, if any, that improves quality for any given circumstances. Maybe extremely high action cuts? Opinions?

As for the impact on replay, I think that today there are some common use cases in which, for example, bandwidth/buffering is sufficiently limited that this alone could make a 50 MBps-peak video stutter where a 20 MBps-peak video wouldn't.
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Old 1st December 2017, 18:52   #8  |  Link
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But you ask about High 4.1. I believe the only difference is that 4.1 has a maximum bitrate of 50 MBps compared 20 MBps for 4.

Not having run or seen any comparison, I do not know how much, if any, that improves quality for any given circumstances. Maybe extremely high action cuts? Opinions?
For 1080p30, High 4.0 should be effectively transparent at 20 Mbps with high quality encoding. Blu-Ray can go up to Level 4.1 @ 40 Mbps, but it has other limitations that reduce compression efficiency like a 1 sec GOP, 4 slices, and some GOP and B-frame restrictions. 1080i30 is more likely to benefit from >20 Mbps for challenging content, since interlaced is inherently more complex to encode. But broadcast 1080i30 is still always Level 4.0 AFAIK; real-world broadcast bitrates for H.264 1080i never get to 20 Mbps.

High 4.2 is also 50 Mbps, but allows for 1080p60. In practice, I don't see content other than Blu-ray that uses Level 4.1. It's 4.2 for high frame rates, 4.0 otherwise.
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Old 1st December 2017, 20:06   #9  |  Link
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Even the xbox360 supported 4.1 interlaced but at max bitrates around 15Mbps with some other "hacks". I'm hard pressed to find a shittier decoder than the one in that god awful machine. If I remember correctly you had to enabled slicing like encoding for blu-rays when using 4.1. Those were the days, your file might have played fine on one xbox and not so fine on another one.

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Old 1st December 2017, 20:21   #10  |  Link
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Even the xbox360 supported 4.1 interlaced but at max bitrates around 15Mbps with some other "hacks". I'm hard pressed to find a shittier decoder than the one in that god awful machine. If I remember correctly you had to enabled slicing like encoding for blu-rays when using 4.1. Those were the days, your file might have played fine on one xbox and not so fine on another one.
It could actually do 1080i up to the HD DVD peak bitrate (28 Mbps or so?). The original release could just do 1080p, and there was a furious race to ship the 1080i capable decoder before the first 1080i HD DVD hit the market. And by the skin of pants, it barely made it.

The 360 decoder is actually a work of engineering genius. It's a multithreaded CPU/GPU design that can get 1080i playback without a HW decoder and on hardware that wasn't even designed for this kind of video playback. And it also does a pretty good 30i to 60p conversion as well (although not nearly as good as the 480i to 480p conversion mode which had way more MIPS/pixel to work with).

So what it does in practice may not be what's desired, but that it works as well as is does is VERY impressive.

The bigger problem is that the Greenlight (Silverlight on Xbox) stack artificially limited all H.264 decode to 720p for dumb reasons that I am still furious about.

But, back to the main thread, the Xbox 360 certainly can't be expected to play back anything that exceeds Level 4.0 capabilities. The PS3 (also without a HW decoder, but with the more media-friendly Cell processor) does support Level 4.1, but I'm not sure it could go up to 50 Mbps. It supports Level 4.2 for 60p to some degree, but also would need <50 Mbps peak bitrates.

I'm glad the current gen of consoles all have HW H.264 decoders!
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Old 1st December 2017, 21:00   #11  |  Link
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It could actually do 1080i up to the HD DVD peak bitrate (28 Mbps or so?).
On paper yes. The xbox360 profile in MeGUI uses 24Mbps but I sometimes got choppy playback with that. Its astonishing that they didn't have the forethought to include a hardware decoder. Maybe the inclusion of high profile to h.264 in 03/2005 was too near to launch or Microsoft put all of its bets on VC-1. It very much seems like the whole video playback issue was an afterthought because it didn't have HDMI either. What I'm furious about is that it didn't support AC3 playback for files.

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Old 1st December 2017, 21:57   #12  |  Link
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But you ask about High 4.1. I believe the only difference is that 4.1 has a maximum bitrate of 50 MBps compared 20 MBps for 4.
Quote:
Originally Posted by benwaggoner View Post
High 4.2 is also 50 Mbps
High 4.0 is vbv maxrate 25000, bufsize 31250.
High 4.1 and 4.2 are vbv maxrate 62500, bufsize 78125.
See Table A-2 for factor for High Profile (1,25 x value from Table A-1). (Blu-ray is different.)

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The PS3 (also without a HW decoder, but with the more media-friendly Cell processor) does support Level 4.1, but I'm not sure it could go up to 50 Mbps. It supports Level 4.2 for 60p to some degree, but also would need <50 Mbps peak bitrates.
PS3 needs slices for higher bitrates.
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Old 2nd December 2017, 19:06   #13  |  Link
benwaggoner
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On paper yes. The xbox360 profile in MeGUI uses 24Mbps but I sometimes got choppy playback with that. Its astonishing that they didn't have the forethought to include a hardware decoder. Maybe the inclusion of high profile to h.264 in 03/2005 was too near to launch or Microsoft put all of its bets on VC-1. It very much seems like the whole video playback issue was an afterthought because it didn't have HDMI either. What I'm furious about is that it didn't support AC3 playback for files.
The cost of a H.264 1080i/p ASIC would have pushed the price of a game console back then (Blu-ray and HD DVD launched quite a while after the 360, and at higher price points). It wasn't just a block on the GPUs of the era. HDMI was also quite new. Recall the PS3 came out quite a while after the 360, at a higher price point, and with lower game performance. The PS3 was much more focused on media originally, although that changed over the life of the 360.

The AC3 playback for files was because the console had to decode add system audio, and reencode. A passthrough mode of files would have disabled all other audio.

Reencoding to 640 Kbps AC-3 was essentially lossless in any case. The lack of support for 5.1 PCM output was my big frustration. I had a proposal for the "Xbox 365" that would have had an integrated HD DVD player, ASIC decoder, PCM audio out, and could disable the latency adding module that emulated the original multichip performance. It would have used 3-layer discs; two layers for DVD-9 and one of HD-DVD 15. Games could be optimized for 365 and access better textures and audio, while preserving perfect backwards compatibility.

Kinda like the Xbox One X conceptually. But, it obviously went nowhere. I don't mind not working at Microsoft anymore .
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Old 2nd December 2017, 19:25   #14  |  Link
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The AC3 playback for files was because the console had to decode add system audio, and reencode. A passthrough mode of files would have disabled all other audio.
But what about playing AC3 on DVD's? Was there no system sounds then? It's been too long, I can't remember. Personally I don't seen much use of systems sounds during file playback so it would have been a sacrifice I would have been more than willing to make. I also didn't have a surround setup so decoding AC3 to stereo PCM and then adding system sounds to that would have also been no problem. The very reason I joined this forum was because of this problem.

Thanks for all this information btw. I can now settle my nerdrage and sleep a bit better at night.

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Old 2nd December 2017, 19:36   #15  |  Link
benwaggoner
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But what about playing AC3 on DVD's? Was there no system sounds then? It's been too long, I can't remember. Personally I don't seen much use of systems sounds during file playback so it would have been a sacrifice I would have been more than willing to make. I also didn't have a surround setup so decoding AC3 to stereo PCM and then adding system sounds to that would have also been no problem. The very reason I joined this forum was because of this problem.

Thanks for all this information btw. I can now settle my nerdrage and sleep a bit better at night.
I think passthrough was enabled (eventually?) for optical discs, since system audio isn't expected then (DVD players don't do it once a movie is playing). File playback is a lot more interactive.

But this is getting quite off topic from H.264 decoder support. One lesson that comes out of this is that Level 4.0 support is pretty well understood. But Level 4.1 has caveats on different implementations and formats. For example, on Blu-ray Level 4.1 requires 4 slices, but if you use Level 4.0, there isn't a slice requirement.

So, to answer the original question, I would say Level 4.1 is NOT safe at this point, although it's gotten a lot better.
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Old 4th December 2017, 10:58   #16  |  Link
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Indeed, and for most real-world use cases High @ 4.0 vs High @ 4.1 should have no real differences.

But please do use High Profile
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Old 7th December 2017, 00:21   #17  |  Link
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Indeed, and for most real-world use cases High @ 4.0 vs High @ 4.1 should have no real differences.

But please do use High Profile
Definitely! There was never a meaningful deployment of Level 4.0 decoders that were just Main. And the 8x8 blocks of high are very helpful for HD resolutions, and are never problematic. Main really never is needed for anything > 3.0. I don't think there are a meaningful number of internet connected devices that don't do High Profile anymore.

I still hear people talking about needing Baseline for backwards compatibility, but that strikes me as ridiculous.
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Old 7th December 2017, 04:39   #18  |  Link
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Ugh me too...

"YOU NEED BASELINE FOR ANDROID!"

Yeah... 7 years ago...

There's just a lot of crufty old documentation out there still, sadly... And lots of services that have been in production for years with zero budget for maintenance or R&D.
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Old 7th December 2017, 08:42   #19  |  Link
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I've been using High Profile, Level 4.1 for years and never had a problem with any device, except maybe an old hardware one such as an ipod or PS2, neither of which I own anyway. Both the Bluray players in our house happily play Level 4.1 via USB.

My other half owns a Sony Bluray player that's so old it has no USB input for playing video, but it'll play Level 4.1 in an MKV burned to disc.
.
I've often wondered if all the fuss about encoding for Bluray compliance is relevant any more, if it ever was required for the most part. The Bluray settings seem like "worse case scenario" that no Bluray player I know of requires in order to play video via USB.

I briefly tested our players by re-encoding a 1080p video using an extremely high bitrate and adjusting the VBV settings until each player could play the re-encoded video via USB without stuttering (30fps if I remember correctly). Aside from the Sony Bluray player which didn't care even when the peaks briefly hit 100Mbps, both Samsung players and my video card seemed to require around vbv_maxrate=50000 and vbv_bufsize=50000 to play the encoded video smoothly, so I use that, but in the real world bitrates probably never climb high enough to be an issue any more.

If I remember correctly Apple use High Profile, Level 3.1 for iTunes 720p downloads, and High Profile, Level 4 for 1080p.

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Old 7th December 2017, 11:21   #20  |  Link
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I've been using High Profile, Level 4.1 for years and never had a problem with any device
[...]
both Samsung players and my video card seemed to require around vbv_maxrate=50000 and vbv_bufsize=50000 to play the encoded video smoothly
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.
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