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22nd November 2017, 03:41 | #1 | Link |
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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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22nd November 2017, 14:46 | #3 | Link |
RipBot264 author
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Some older devices do not support anything beyond High@4.0.
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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. |
1st December 2017, 18:52 | #8 | Link | |
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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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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.
Last edited by Gser; 1st December 2017 at 20:09. |
1st December 2017, 20:21 | #10 | Link | |
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Quote:
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! Last edited by benwaggoner; 1st December 2017 at 20:28. Reason: More details. |
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1st December 2017, 21:00 | #11 | Link |
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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.
Last edited by Gser; 1st December 2017 at 21:18. |
1st December 2017, 21:57 | #12 | Link | |
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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.) PS3 needs slices for higher bitrates. |
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2nd December 2017, 19:06 | #13 | 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. 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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2nd December 2017, 19:25 | #14 | Link | |
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Thanks for all this information btw. I can now settle my nerdrage and sleep a bit better at night. Last edited by Gser; 2nd December 2017 at 19:32. |
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2nd December 2017, 19:36 | #15 | Link | |
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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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7th December 2017, 00:21 | #17 | Link | |
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I still hear people talking about needing Baseline for backwards compatibility, but that strikes me as ridiculous. |
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7th December 2017, 04:39 | #18 | Link |
Derek Prestegard IRL
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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. |
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. Last edited by hello_hello; 7th December 2017 at 08:45. |
7th December 2017, 11:21 | #20 | Link | |
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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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