Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > Video Encoding > MPEG-4 AVC / H.264

Reply
 
Thread Tools Search this Thread Display Modes
Old 13th November 2008, 16:24   #1  |  Link
Selur
Registered User
 
Selur's Avatar
 
Join Date: Oct 2001
Location: Germany
Posts: 5,867
How to calculating max ref for level,....

Wanting to calculate the max number of refs allowed for a specific avc level I searched the forum and then based my calculation on http://forum.doom9.org/showthread.php?t=102048
which gave me
Quote:
/***
* Restrictions:
* MaxMBPS >= width*height*fps. (w&h measured in macroblocks, i.e. pixels/16 round up in each dimension)
* MaxFS >= width*height
* sqrt(MaxFS*8) >= width
* sqrt(MaxFS*8) >= height
* MaxDPB >= (bytes in a frame) * min(16, ref + (pyramid ? 2 : bframes ? 1 : 0))
* MaxBR >= vbv_maxrate.
* MaxCPB >= vbv_bufsize.
* MaxVmvR >= max_mv_range.
* MaxMvsPer2Mb, MinLumaBiPredSize, direct_8x8_inference_flag : are not enforced by x264. The only way to ensure compliance is to disable p4x4 at level>=3.1, or at level>=3 w/ B-frames.
* MinCR : is not enforced by x264. Won't ever be an issue unless you use lossless.
* SliceRate : I don't know what this limits.latexxx once posted the values needed for these factors:
* VALUES FOR LEVEL: http://forum.doom9.org/showthread.php?t=101345
*
* LEGEND:
* MaxDPB = max decoded picture buffer
* MaxMBPS = max macroblocks per second
* MaxFS = max frame size
* MaxBR = max bitrate
* MaxCPB = max vbv buffer
* MaxVmvR = max motion vetor range
***/
so taking
MaxDPB >= (bytes in a frame) * min(16, ref + (pyramid ? 2 : bframes ? 1 : 0))
as basis I rearranged it to
Min(this->maxDPB(level)/bytesPerFrame - bframeModifier, 16)
where:
maxDPB = 12582912 (for Level 4.1)
bytesPerFrame = (pixel width)*(pixel height)*1.5 (since x264 only support 4:2:0 atm) = 1920*1080*1.5
bframeModifier = 0 when no bframes are used, 1 when bframes are enabled and 2 when bframes&pyramid are enabled.

using this I get:

with bframes:
Min(this->maxDPB(level)/bytesPerFrame - bframeModifier, 16)
maxDPB = 12582912
bytesPerFrame = 3110401
maxDPB/bytesPerFrame = 4
bframeModifier = 0
-> maxRef = 4

with bframes:
Min(this->maxDPB(level)/bytesPerFrame - bframeModifier, 16)
maxDPB = 12582912
bytesPerFrame = 3110401
maxDPB/bytesPerFrame = 4
bframeModifier = 1
-> maxRef = 3

with bframes&pyramid:
Min(this->maxDPB(level)/bytesPerFrame - bframeModifier, 16)
maxDPB = 12582912
bytesPerFrame = 3110401
maxDPB/bytesPerFrame = 4
bframeModifier = 2
-> maxRef = 2


Trahald&Co nutzen die Formel:
min( 1024 * MaxDPB/(PicWidthInMbs * FrameHeightInMbs * 384), 16)
1024 * (12288) / (120 * (( 2 – frame_mbs_only_flag ) * PicHeightInMapUnits) * 384)
maxDPB / (Width/16 * ( 2 – frame_mbs_only_flag ) * Height/16 * 384)
wobei frame_mbs_only_flag = 0 heißt man encoded interlaced

But looking at http://forum.doom9.org/showthread.php?t=136258 Trahald uses a different formula.
Quote:
maxDPB / (PicWidth/16 * (( 2 – frame_mbs_only_flag ) * FrameHeight/16) * 384)
maxDPB = 12582912 (for Level 4.1)
and frame_mbs_only_flag = 1 assuming the material is progressive (iiirc frame_mbs_only_flag = 0 means material is interlaced)
1st thing about this formula that I registered was that:
a. it doesn't care about B-Frames
b. it cares about interlacing

Thanks for reading up to here.
Now here's my question/problem:

How does one calculate the maximum number of frames?
(I suspect that the 'real' formula is a mix of the two above. )



Cu Selur
__________________
Hybrid here in the forum, homepage
Selur is offline   Reply With Quote
Old 13th November 2008, 16:49   #2  |  Link
Manao
Registered User
 
Join Date: Jan 2002
Location: France
Posts: 2,856
First of all, any formula will depend on the encoder. For example, without MMCOs (explicit picture reordering messages, not used by x264), B-pyramid requires a DPB of 4 frames if you want each frame to be able to use the closest reference frame (which is a good thing to want). MMCO would cut that number down to 3.

As for interlacing, MBAff doesn't change the DPB size (provided everything else is handled like in the progressive case). PAff does, if you want to have for each pair of fields the same available references, in addition to the cross field reference (the second field can reference the first field, which is a very good thing, but it adds one frame to the DPB).
__________________
Manao is offline   Reply With Quote
Old 13th November 2008, 17:23   #3  |  Link
Selur
Registered User
 
Selur's Avatar
 
Join Date: Oct 2001
Location: Germany
Posts: 5,867
Quote:
First of all, any formula will depend on the encoder.
Okay, didn't know that.
I rephrase the question then:
How does one calculate the maximum number of frames for x264?

Cu Selur

Ps.: btw. for those who are wondering I'm working on a hobby-project which is linux&windows gui for x264 where I want to limit the number of references one can choose when a specific level is specified.
__________________
Hybrid here in the forum, homepage
Selur is offline   Reply With Quote
Old 13th November 2008, 17:28   #4  |  Link
Manao
Registered User
 
Join Date: Jan 2002
Location: France
Posts: 2,856
Code:
    sps->vui.i_num_reorder_frames = param->b_bframe_pyramid ? 2 : param->i_bframe ? 1 : 0;
    /* extra slot with pyramid so that we don't have to override the
     * order of forgetting old pictures */
    sps->vui.i_max_dec_frame_buffering =
    sps->i_num_ref_frames = X264_MIN(16, X264_MAX(param->i_frame_reference, 1 + sps->vui.i_num_reorder_frames));
So it's your formula.
__________________
Manao is offline   Reply With Quote
Old 13th November 2008, 17:46   #5  |  Link
Selur
Registered User
 
Selur's Avatar
 
Join Date: Oct 2001
Location: Germany
Posts: 5,867
Thanks!

So encoding for level 4.1 with 1080p, bframes and pyramid would mean:
maxref = Min(this->maxDPB(level)/bytesPerFrame - bframeModifier, 16)
= Min(this->maxDPB(level)/bytesPerFrame - bframeModifier, 16)
= Min(12582912 / (1920*1080*1,5)
= Min(12582912/3110400 - 2, 16)
= Min(4 - 2, 16)
= 2

Thanks a lot for the help!

Cu Selur
__________________
Hybrid here in the forum, homepage
Selur is offline   Reply With Quote
Old 13th November 2008, 17:54   #6  |  Link
Dark Shikari
x264 developer
 
Dark Shikari's Avatar
 
Join Date: Sep 2005
Posts: 8,689
Quote:
Originally Posted by Selur View Post
So encoding for level 4.1 with 1080p, bframes and pyramid would mean:
maxref = Min(this->maxDPB(level)/bytesPerFrame - bframeModifier, 16)
= Min(this->maxDPB(level)/bytesPerFrame - bframeModifier, 16)
= Min(12582912 / (1920*1080*1,5)
= Min(12582912/3110400 - 2, 16)
= Min(4 - 2, 16)
= 2
Nope.

MIN(16,MAX(4,3)) is still 4.
Dark Shikari is offline   Reply With Quote
Old 13th November 2008, 17:56   #7  |  Link
Selur
Registered User
 
Selur's Avatar
 
Join Date: Oct 2001
Location: Germany
Posts: 5,867
Care to explain? Where did I go wrong?
__________________
Hybrid here in the forum, homepage
Selur is offline   Reply With Quote
Old 13th November 2008, 17:56   #8  |  Link
Dark Shikari
x264 developer
 
Dark Shikari's Avatar
 
Join Date: Sep 2005
Posts: 8,689
Quote:
Originally Posted by Selur View Post
Care to explain? Where did I go wrong?
You subtracted "bframemodifier."
Dark Shikari is offline   Reply With Quote
Old 13th November 2008, 18:02   #9  |  Link
Selur
Registered User
 
Selur's Avatar
 
Join Date: Oct 2001
Location: Germany
Posts: 5,867
Okay, now I'm confused. What should I do with it when not subtract?

looking at the start point:
MaxDPB >= (bytes in a frame) * min(16, ref + (pyramid ? 2 : bframes ? 1 : 0))
for fixed a MaxDPB and fixed "bytes in a frame" ref should get smaller if pyramid and/or bframes are enabled.

Cu Selur
__________________
Hybrid here in the forum, homepage
Selur is offline   Reply With Quote
Old 13th November 2008, 18:03   #10  |  Link
Dark Shikari
x264 developer
 
Dark Shikari's Avatar
 
Join Date: Sep 2005
Posts: 8,689
Quote:
Originally Posted by Selur View Post
MaxDPB >= (bytes in a frame) * min(16, max(ref, 1 + (pyramid ? 2 : bframes ? 1 : 0)))
fixed
Dark Shikari is offline   Reply With Quote
Old 13th November 2008, 18:06   #11  |  Link
Selur
Registered User
 
Selur's Avatar
 
Join Date: Oct 2001
Location: Germany
Posts: 5,867
Okay, thanks. -> going to think about how to rearrange this to get maxRef
Doh, after thinking about it it's easier to do the max-brace after the calculation.

1. maxref = Min(this->maxDPB(level)/bytesPerFrame, 16)
2. if(maxref < bframeModifier+1) maxRef = bframeModifier+1;
__________________
Hybrid here in the forum, homepage

Last edited by Selur; 13th November 2008 at 18:34.
Selur is offline   Reply With Quote
Old 13th November 2008, 18:17   #12  |  Link
Sergey A. Sablin
Registered User
 
Join Date: Dec 2004
Location: Tomsk, Russia
Posts: 366
Quote:
Originally Posted by Selur View Post
MaxDPB >= (bytes in a frame) * min(16, max(ref + (pyramid ? 1 : 0), 1 + (pyramid ? 2 : bframes ? 1 : 0)))
refixed for x264
Sergey A. Sablin is offline   Reply With Quote
Old 13th November 2008, 18:33   #13  |  Link
Dark Shikari
x264 developer
 
Dark Shikari's Avatar
 
Join Date: Sep 2005
Posts: 8,689
Quote:
Originally Posted by Sergey A. Sablin View Post
refixed for x264
Every time you complain about it is one more day before it gets patched.

And yes, there's already a patch to resolve it
Dark Shikari is offline   Reply With Quote
Old 13th November 2008, 18:36   #14  |  Link
Selur
Registered User
 
Selur's Avatar
 
Join Date: Oct 2001
Location: Germany
Posts: 5,867
Quote:
MaxDPB >= (bytes in a frame) * min(16, max(ref + (pyramid ? 1 : 0), 1 + (pyramid ? 2 : bframes ? 1 : 0)))
which would result in:
Code:
maxref = Min(this->maxDPB(level)/bytesPerFrame, 16)
maxref = (pyramid) ? maxref-1 : maxref
if(maxref) < bframeModifier+1) maxref = bframeModifier+1
Quote:
And yes, there's already a patch to resolve it
Nice, hopefully I won't forget to remove the 'maxref = (pyramid) ? maxref-1 : maxref'-line then.

Cu Selur
__________________
Hybrid here in the forum, homepage
Selur is offline   Reply With Quote
Old 13th November 2008, 18:49   #15  |  Link
Sergey A. Sablin
Registered User
 
Join Date: Dec 2004
Location: Tomsk, Russia
Posts: 366
Quote:
Originally Posted by Dark Shikari View Post
Every time you complain about it is one more day before it gets patched.
the fact that you don't care about spec compliance doesn't change the spec.
and if you still didn't get it - I neither care about level compliance in x264, nor do I care about your humble opinion on this regard. I did answer original question and did it correctly, while x264 developer misinform x264 users (and seems did it knowingly):
Quote:
Originally Posted by Dark Shikari View Post
And yes, there's already a patch to resolve it
so you better beg your pardon to the users for your mistake instead of making pointless comments.
Sergey A. Sablin is offline   Reply With Quote
Old 13th November 2008, 18:53   #16  |  Link
Dark Shikari
x264 developer
 
Dark Shikari's Avatar
 
Join Date: Sep 2005
Posts: 8,689
Quote:
Originally Posted by Sergey A. Sablin View Post
the fact that you don't care about spec compliance doesn't change the spec.
and if you still didn't get it - I neither care about level compliance in x264, nor do I care about your humble opinion on this regard. I did answer original question and did it correctly, while x264 developer misinform x264 users (and seems did it knowingly):
I am referring to the DPB value written to the bitstream per the code above. I am merely explaining the C code. What I said, with regard to the code, is correct.

What you are saying is that the DPB value written to the bitstream is wrong. This is completely separate. I am not "misleading anyone"; rather, you are misleading people by trying to make both of the following true at the same time:

1. You need to lower ref by 1 when using pyramid to make x264 level-compliant.
2. x264 is, technically, never actually spec-compliant when using pyramid.

In all the threads you have trolled off-topic with your posts on this matter, you seem unable to decide which of these it is. Now, the correct answer is 2), but that hasn't stopped you from coming out and saying 1 when it fit the thread better or happened to make x264 look worse.

If you don't care about x264's level-compliance, stop posting about it. The fact that every single thread that uses the words "pyramid" and "reference frame" gets trolled by you is clearly a signal that you care a hell of a lot. If you didn't care, you wouldn't post about it.

Last edited by Dark Shikari; 13th November 2008 at 18:57.
Dark Shikari is offline   Reply With Quote
Old 13th November 2008, 21:46   #17  |  Link
Sergey A. Sablin
Registered User
 
Join Date: Dec 2004
Location: Tomsk, Russia
Posts: 366
Quote:
Originally Posted by Dark Shikari View Post
I am not "misleading anyone"; rather, you are misleading people by trying to make both of the following true at the same time:

1. You need to lower ref by 1 when using pyramid to make x264 level-compliant.
2. x264 is, technically, never actually spec-compliant when using pyramid.
This simply can't be true at the same time, and don't try to put words in my mouth. The only true statement here is 2. And this is exactly why 1 simply can't be true at all. This is obvious, isn't it?
And no, there is no such a term as "level-compliant" - there is only spec compliant or not. Providing incorrect value about memory needed for decoding process is non compliant with spec, even if the maximum value for specified level is enough for correct decoding of this stream. To optimize memory usage, decoder may allocate as much memory as specified by encoder - not by maximum value for a level.

If you thinking that providing correct information is "trolling" and off-topic, or were done specifically to make x264 look worse, then there is definitely something wrong with you. I pointed to the hole and this shall lead to make x264 better, but no - you always complain that I try to make it look worse, nevertheless that encoder still produces incorrect bitstreams. Probably you think that your comment a-la "I don't care about DPB" make things better.

One would probably want say thank, for at least to be in the know about non-compliance and how to get rid of it.

PS. And once again - I didn't use x264, I don't use it, and most probably won't use it at all. My interest in video compression is far from making home videos, rips of any kind etc. That's - I don't care how compliant x264 is. But if somebody wants to know - I'll let him know. These two do not contradict at all.
Sergey A. Sablin is offline   Reply With Quote
Old 13th November 2008, 23:50   #18  |  Link
shon3i
BluRay Maniac
 
shon3i's Avatar
 
Join Date: Dec 2005
Posts: 2,426
@Selur, why you make things so hard? when isn't

To calculate maximum references for choosen level you need to look into ITU-T Recommendation H.264 pdf document and Table A-1


Use MaxDBP from table and use this simple formula to calculate

numofrefs = int(MaxDPB * 1024 / 1.5 / (w * h))

Last edited by shon3i; 13th November 2008 at 23:52.
shon3i is offline   Reply With Quote
Old 14th November 2008, 10:32   #19  |  Link
Selur
Registered User
 
Selur's Avatar
 
Join Date: Oct 2001
Location: Germany
Posts: 5,867
you did read the rest of the thread didn't you?
__________________
Hybrid here in the forum, homepage
Selur is offline   Reply With Quote
Old 14th November 2008, 16:59   #20  |  Link
shon3i
BluRay Maniac
 
shon3i's Avatar
 
Join Date: Dec 2005
Posts: 2,426
Quote:
Originally Posted by Selur View Post
you did read the rest of the thread didn't you?
If i understood you correctly you want to calculate maximum number of reference frames for choosen level?

If yes, mine method, always give you maximum ref's for choosen level, but like Manao said everything depend on encoder, for example with Mainconcept, Ateme, you can count on this formula. With x264 because have broken b-pyramid, you must lower refs by one, and for totly safe encoding, turn b-pyramid completly off.
shon3i is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 12:34.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.