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25th March 2008, 11:15 | #1 | Link |
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Blu-ray compliancy (x264): Number of B-frames?
Hi everyone,
I've had a look at the Blu-ray profile in meGUI and saw that the max. number of B-frames is set to 3 as well as the max. number of reference frames. Is this the absolute limitation for a 1080p Blu-ray video? |
25th March 2008, 12:56 | #4 | Link |
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For 4.1 level it's:
1/2/3 bframes without pyramidal bframe: 4 pref and 3 bref 3 bframes with pyramidal bframes: 3 pref and 2 bref --bframe 1/2/3 --ref 3 --bframe 3 --b-pyramid --ref 2
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25th March 2008, 18:14 | #6 | Link |
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--bframe 3 --b-pyramid --b-rdo --ref 2
really efficient for clean source and/or low motion --bframe 1 --ref 3 3 bframes with noise/grain is useless Anyway if bframe decision is good the encoder will never use in practice 3 pyramidal bframes with grainy/noisy source.
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25th March 2008, 23:52 | #7 | Link |
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@Sagittaire: Hm, weird, is it definitely fact that using pyramidal bframes limits the number of reference frames to 2? You always talk of a number of reference frames less than 4, while meisterlee says it was 4. I want to get the most out of x264 and thus don't care about encoding time. The source is pretty clean...
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26th March 2008, 16:51 | #10 | Link |
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Here are the settings of Elecard Converter Studio full quality profiles:
Blu-Ray: B-frames: 1 Ref. frames: 4 Blu-Ray HD: B-frames: 2 Ref. frames: 4 Use B-frames as reference/Pyramid coding is disabled for Blu-Ray SD and HD. How about these settings? |
26th March 2008, 17:36 | #11 | Link |
Wewkiee
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For some reason when I use ref = 4 i get jumpiness (thats with x264 or cinevision), but thats only with cyberlink and my 8500 (dont have standalone) ref = 3 works better. having said that...
bluray spec is max 3 b-frames and b-pyramid (in conjunction is 3 b-frames) is allowed. ref = 4 is correct to L4.1 w/1080p. so in spec.. yes.
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26th March 2008, 18:58 | #12 | Link | |
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Thanks, Trahald.
Does this mean that... with Pyramid coding B-frames: 3 Ref. frames: 3 (for more compatibility, otherwise 4) without Pyramid coding B-frames: 1 Ref. frames: 3 (for more compatibility, otherwise 4) If I set 2 or 3 B-frames here, I get the following AVC encoder message (Elecard Converter Studio): 2 B-frames: "It is recommended to use one B-frame or three B-frames with the following options for encoding: 'Adaptive B-frames', 'Use reference B-frames' and 'Pyramid coding'" 3 B-frames: "For encoding with three B-frames the following options must be enabled: 'Adaptive B-frames', 'Use reference B-frames' and 'Pyramid coding'" What amazes me is that XolocoTuxmaster recommends 3 B-frames and 3 Ref. frames for Blu-ray encoding without B-Pyramids. Quote:
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26th March 2008, 19:31 | #13 | Link |
Wewkiee
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you know what.. i did the math using the spec.. and i may be wrong.. but i get that 3 would be max... here is the math
Code:
min( 1024 * MaxDPB/(PicWidthInMbs * FrameHeightInMbs * 384), 16) 1024 * (11288) / (120 * (( 2 – frame_mbs_only_flag ) * PicHeightInMapUnits) * 384) 1024 * 11288 / (120 * (( 2 - 1 ) * 68 ) * 384 ) 1024 * 11288 / (120 * ( 68 ) * 384 ) 11558912 / (3133440) 3.688888888888 min(3.6888,16) = 3.368888
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26th March 2008, 19:46 | #14 | Link | |
Spielberger
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Quote:
Specification lists for Level 4.1: Picture Buffer 12288 kB (12582912 Bytes) Max MBs 8192 (1920x1088 -> 8160 Macroblocks) so 8192 (=Macroblocks) x 256 (=pixel per macroblock) x 1.5 (= 4:2:0 video uses 12 bit per pixel = 1.5 Byte) 8192 x 256 x 1.5 = 3145728 12582912 / 3145728 = 4 Level 4.1 certified Decoder can hold 4 Ref. Frames |
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26th March 2008, 19:57 | #15 | Link |
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Well in fact it's 4 pref and 3 bref for level 4.1 but x264 use the same value for pref and bref. If you use pyramidal bframe you must use 3 pref and 2 bref.
imply for x264 --bframe 1/2/3 --ref 3 --bframe 3 --b-pyramid --ref 2 Other setting are not BluRay compliant.
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26th March 2008, 20:24 | #18 | Link | |
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Quote:
imply for x264 --bframe 1/2/3 --ref 4 --bframe 3 --b-pyramid --ref 3
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26th March 2008, 20:49 | #19 | Link |
Wewkiee
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oops.. i copied the MaxDPB value wrong from the table.. here is the revised calc
Code:
min( 1024 * MaxDPB/(PicWidthInMbs * FrameHeightInMbs * 384), 16) 1024 * (12288) / (120 * (( 2 – frame_mbs_only_flag ) * PicHeightInMapUnits) * 384) 1024 * 12288 / (120 * (( 2 - 1 ) * 68 ) * 384 ) 1024 * 12288 / (120 * ( 68 ) * 384 ) 11558912 / (3133440) 4.0156862745098039215686274509804 but weird i see pro streams (streams that have are tweaked out different PPS settings per picture and adaptive inloop filter levels per frame etc) using 2 and 3 refs. i suppose its knowledge the hardware that should be able to handle it cant?
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...yeah...but...why on earth would I compare apples with apples? Last edited by Trahald; 26th March 2008 at 20:53. |
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