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2nd April 2023, 14:03 | #2501 | Link | |
Artem S. Tashkinov
Join Date: Dec 2006
Posts: 337
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3rd April 2023, 08:22 | #2502 | Link | |
Broadcast Encoder
Join Date: Nov 2013
Location: Royal Borough of Kensington & Chelsea, UK
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It's a shame, really... |
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3rd April 2023, 17:39 | #2503 | Link | |
Moderator
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Location: Portland, OR
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Real professional-grade live transcoding can get expensive quickly: https://aws.amazon.com/medialive/pricing/. |
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3rd April 2023, 17:49 | #2504 | Link | |
Artem S. Tashkinov
Join Date: Dec 2006
Posts: 337
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3rd April 2023, 18:24 | #2505 | Link | |
Moderator
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Location: Portland, OR
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VP9 was particularly poor for multithreading as frame encoding and decoding were (accidentally, I gather) serialized due to how in-loop filtering was structured. Shared entropy coding context across frames also limited decoder threading. VP9 was definitely a codec designed to run on a fast x86-64 core without a lot of consideration for multithreaded hardware or software implementations. AV1 is somewhat better, but is still more complex to decode than even VVC. HEVC's Wavefront Parallel Processing is great and elegant, allowing for one thread per 64 pixels tall of the video. WPP yields better compression efficiency than slices, tiles, and frame threading. The more traditional IPBb reference frame hierarchy of H.264 and HEVC makes for more straightforward frame threading, although there is always some risk of quality regressions. Some frame threading is feasible in AV1 doing tricks with golden frames. SVT-AV1 is a good demonstration of an AV1 encoder that can do a lot of threading (although quality isn't great). It'd be interesting to compare SVT-HEVC and SVT-AV1's parallelization. Fragment/GOP level threading has challenges due to higher latency and making sure VBV state is compliant across fragment boundaries. But the encoders are well optimized for that as that's YouTube's primary encoding model. I hope AV2 focuses more on architectural support for highly parallelized encoding and decoding. |
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4th April 2023, 12:25 | #2507 | Link | |
Registered User
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Location: New York, NY (USA)
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... but can be disabled by setting the frame-parallel bit in the header, and helps several percent (!!) in compression efficiency when enabled. In fact, this "tool" was (from what I hear) proposed for HEVC - but rejected. I can't comprehend why, and have heard similar (depressed) comments about this feature from other HEVC/MPEG contributing members. It should have made it in. |
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4th April 2023, 19:51 | #2509 | Link | |
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I believe a feature like that could be architected in a way that doesn't cause those issues (only follow context of frames that need to be referenced to decode the given frame anyway). |
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5th April 2023, 00:54 | #2510 | Link | |
Registered User
Join Date: May 2018
Posts: 182
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You can pick 1 of 3 speed settings in the youtube streamer dashboard. The setting with the highest delay offers the 'best' image quality. By default it is set to low latency, which is worse but most people don't change it. Last edited by takla; 5th April 2023 at 00:58. |
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5th April 2023, 22:55 | #2511 | Link | |
Registered User
Join Date: May 2009
Posts: 328
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There is far too much gatekeeping on the documentation, and far too much "why isn't this working". If they really want this to take over HEVC and in the future VVC, things need to fixed and addressed. Blindly defending it without addressing it's massive shortcomings and serious problems won't make it any better. |
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6th April 2023, 14:55 | #2513 | Link | ||
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Maybe part of the problem is that MPEG folks tend to like formalizing rules for this sort of stuff and picking at theoretical inconsistencies. I personally find that quite uninteresting once the problem itself is already solved. Quote:
To get more practical, I compared --frame-parallel=0/1 encodes at -q 30/40/50/60 to obtain BDRATE-PSNR differences, and observed a -2.5% average difference on the cif clipset from Xiph. These were only partially complexity-ordered. Husky, for example, gained "only" -1.0% on average, but football, soccer, foreman & harbour each gained -2.5%. Same on the easy end: clips like akiyo an students are "only" -2.0% each, whereas news and bowing are -2.5%. The best clips (around -4.0% each) are bridge_far, crew, sign_irene and highway, which are by no means the easiest clips in the set. I also checked for "bitrate" bias: gains are quite evenly distributed across all -q values for each clip. Based on this data, I don't accept the hypothesis that entropy carry-over between frames only help easy clips. |
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6th April 2023, 16:53 | #2515 | Link |
Registered User
Join Date: Aug 2009
Posts: 201
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https://www.anandtech.com/show/18805...-1w-per-stream
Xilinx based hardware encode for servers from AMD now supporting AV1. |
6th April 2023, 19:48 | #2517 | Link | |
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Join Date: Mar 2004
Posts: 1,120
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Last edited by hajj_3; 6th April 2023 at 20:34. |
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6th April 2023, 20:39 | #2518 | Link |
Moderator
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It is weird they are comparing to H.264 Baseline VeryFast, which is a lot faster than realtime these days. I presume the relative savings would be a lot lower compared to real world encodes.
Matching x265 slow with high density hardware encoding with AV1 is really impressive. High quality live AV1 has been a challenge so far. |
7th April 2023, 18:47 | #2519 | Link | |
Derek Prestegard IRL
Join Date: Nov 2003
Location: Los Angeles
Posts: 5,988
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I could see this being popular in the cloud IaaS providers soon. It would _smoke_ the older NVIDIA hardware that's usually available there e.g. Ampere in AWS g5 instances.
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These are all my personal statements, not those of my employer :) |
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8th April 2023, 01:25 | #2520 | Link |
Moderator
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Location: Portland, OR
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Premium quality ABR live streaming still requires a whole lot of fast cores. I doubt we'll ever see a fixed-function hardware encoder be quality-competitive again, given the ever-rising complexity of modern codecs.
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