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8th August 2022, 09:32 | #1 | Link |
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A list for the maximum allowed vbv-bufsize & vbv-maxrate per level
I forced ffmpeg to show me some values (by specifying way too high values it showed me the maximum)
Here you go, if anyone else needs this. https://docs.google.com/spreadsheets...z3mcwd/pubhtml Any reason why I shouldn't always use the highest allowed vbv-bufsize? After all, if a device supports a given level, it would also need to support the maximum possible bufsize. The reason why I do this in the first place is, I measured the difference in VMAF, and using the highest allowed vbv-bufsize always had better scores. In my tests (1920x1080p60 8000CBR preset medium), the worst frames improved by up to 5.5% at the cost of 1.3% encoding speed. That was a higher improvement then going from preset medium to preset slow. Medium: Average: 87.422148 Worst: 54.726831 Slow: Average: 87.610072 Worst: 54.896813 Medium+maximum vbv-bufsize: Average: 87.828082 Worst: 57.739257 Last edited by takla; 11th August 2022 at 03:37. |
9th August 2022, 16:49 | #2 | Link |
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What's wrong with the values from
https://en.wikipedia.org/wiki/Advanc..._Coding#Levels https://en.wikipedia.org/wiki/Advanc...ture_buffering ? |
9th August 2022, 17:43 | #3 | Link | |
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Quote:
There are a few reasons why someone would lower it
But for local file playback, yeah using the max values offers the most flexibility to the encoder to redistribute bits to minimize quality fluctuations. |
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10th August 2022, 01:18 | #4 | Link | ||
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My use case here was real-time streaming. In this case, I don't think device compatibility will be an issue with Level 4.2 in 2022😉 Last edited by takla; 10th August 2022 at 01:37. |
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10th August 2022, 02:19 | #5 | Link | |
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* High, maxBitrates should be multiplied by 1.25 * High10, maxBitrates should be multiplied by 3 * High422/High444, maxBitrates should be multiplied by 4 and Buffers should be multiplied by 3 |
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10th August 2022, 14:16 | #6 | Link | |
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The maximum allowed bitrate with Level 4.2 for Constrained Baseline, Baseline, Extended and Main is 50000 and 50000*1.25 is 62500 or 50000*3 is 150000, when in reality, the maximum vbv-bufsize for profile=high is 78125. You are just making numbers up. I already added all real max values for relevant levels as a link to the OP, which you seems to have missed. |
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10th August 2022, 16:50 | #7 | Link | |
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Last edited by rwill; 10th August 2022 at 17:00. |
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10th August 2022, 16:53 | #8 | Link | |
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I don't think I made them up (I collected that data 10+years ago), but to be sure I did a quick search.
According to the specification T-REC-H.264-200503-S (https://www.itu.int/rec/T-REC-H.264-200503-S; document was superseded but the restrictions stayed the same afaik.) A.3.1 Table A-1 for limits for the Baseline, Main, and Extended profiles A.3.3 Table A-2 for the "Specification of cpbBrVclFactor and cpbBrNalFactor" I should be correct, https://forum.doom9.org/showthread.p...09#post1215709 does seem to agree with me too. Quote:
Cu Selur Ps.: but maybe I understood you wrong for what you are looking for and you are looking for something totally different ¯\_(ツ)_/¯ Last edited by Selur; 10th August 2022 at 16:57. |
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11th August 2022, 03:19 | #9 | Link |
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If you use ffmpeg, and specify a vbv-bufsize, vbv-maxrate & bitrate of something ridiculous like 800k, as well as a profile and level, it will tell you the correct max values for bitrate and buffer. All of these values can be found in the google sheet link in the OP. I'm no longer looking for these values. Thanks anyways.
Last edited by takla; 11th August 2022 at 03:27. |
11th August 2022, 10:51 | #11 | Link | |
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1) There are dozens of pages labeled as "levels and profiles". 2) How should I have known to multiply those values by 1.25 (Why don't they show the values directly in the docs?) |
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11th August 2022, 13:46 | #12 | Link | ||
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But I dont see anything about 3x for buffsize, shoudlnt it just be MaxCPB table and x 1,25 there as well? Last edited by excellentswordfight; 11th August 2022 at 14:39. |
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