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Need help to understand how/when VP8 updates reference frames
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minyi yang  
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 More options Aug 1 2012, 1:14 pm
From: minyi yang <minyi.y...@oovoo.com>
Date: Wed, 1 Aug 2012 10:14:19 -0700 (PDT)
Local: Wed, Aug 1 2012 1:14 pm
Subject: Need help to understand how/when VP8 updates reference frames
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VP8 encoder uses force_update and no_update flags to specify whether or not
to update the Golden and/or AltRef frames.
Case 1: force_update = 0, no_update = 1; the specified ref frame will NOT
be updated with the current frame.  
Case 2: force_update = 1, no_update = 0; the specified ref frame WILL be
updated with the current frame.
Case 3: force_update = 1, no_update = 1; encoder reports “invalid
parameter” and give error.
Case 4: force_update = 0; no_update = 0; how does the encoder handle this?
Does the encoder make its own decision (so it may or may not update the ref
frame) or always take one flag over the other?


 
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Rajesh Pamula  
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 More options Aug 1 2012, 2:18 pm
From: Rajesh Pamula <rajeshpam...@gmail.com>
Date: Wed, 1 Aug 2012 20:18:22 +0200
Local: Wed, Aug 1 2012 2:18 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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I am not in possession of the reference code, but my guess is that in such
case GF and AltRef remain unchanged. As far as I can remember there is no
adaptive frame buffer update logic in reference encoder implementation.

Also for the sake of completeness, I like to mention that the last decoded
frame also forms one of the reference frames apart from  GF and Alt ref.
(Last decoded not necessarily the last frame to be decoded in temporal
order).

--
Rajesh Pamula
Post Graduate Student
Analogue and Digital Integrated Circuit Design
Imperial College London.
Residence Phone: +44-20-78522056

 
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sonicwi...@gmail.com  
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 More options Aug 2 2012, 4:13 pm
From: sonicwi...@gmail.com
Date: Thu, 2 Aug 2012 13:13:19 -0700 (PDT)
Local: Thurs, Aug 2 2012 4:13 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Hi Rajesh

Thanks for the help!


 
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sanjeev verma  
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 More options Aug 7 2012, 1:25 pm
From: sanjeev verma <sanjeev1...@gmail.com>
Date: Tue, 7 Aug 2012 22:55:12 +0530
Local: Tues, Aug 7 2012 1:25 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Hi,
In VP8, Can Coeff and MV decoding happen completely in  parallel
without any dependency?
Reg,
San

 
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Rajesh Pamula  
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 More options Aug 7 2012, 1:31 pm
From: Rajesh Pamula <rajeshpam...@gmail.com>
Date: Tue, 7 Aug 2012 19:31:19 +0200
Local: Tues, Aug 7 2012 1:31 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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As far as I remember, MVDs are part of control partition along with frame
level and MB level information and MVP computation does not depend on
coeffs either and hence the answer is yes. Parallel decoding should be
possible.

--
Rajesh Pamula
Post Graduate Student
Analogue and Digital Integrated Circuit Design
Imperial College London.
Residence Phone: +44-20-78522056

 
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sanjeev verma  
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 More options Aug 7 2012, 1:36 pm
From: sanjeev verma <sanjeev1...@gmail.com>
Date: Tue, 7 Aug 2012 23:06:23 +0530
Local: Tues, Aug 7 2012 1:36 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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thanks.
I mean does coeff decoding depend on the "MV partition decoding" in
any way(any dependency likeon  MB modes etc). I want to decode the
coeff and the partition that contains MV in parallel using two
different processors on the same chip?


 
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Rajesh Pamula  
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 More options Aug 7 2012, 1:42 pm
From: Rajesh Pamula <rajeshpam...@gmail.com>
Date: Tue, 7 Aug 2012 19:42:59 +0200
Local: Tues, Aug 7 2012 1:42 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Well, let me put it in a perhaps more clear way. By decode I mean, entropy
decode (which some may prefer calling as mere parsing). In order to be able
to apply inverse transform, the knowledge of the MB type is required and
for inverse quantization Qp value of the MB is required.

So parsing or rather entropy decode can be made parallel, reconstruction is
sequential.

--
Rajesh Pamula
Post Graduate Student
Analogue and Digital Integrated Circuit Design
Imperial College London.
Residence Phone: +44-20-78522056

 
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John Koleszar  
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 More options Aug 8 2012, 12:48 pm
From: John Koleszar <jkoles...@google.com>
Date: Wed, 8 Aug 2012 09:48:59 -0700
Local: Wed, Aug 8 2012 12:48 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Decoding the mode/mv partition ("partition 0") has no dependencies,
but decoding the residual partitions does depend on the mode/mv
partition. The number of coefficients to decode depends on the block
mode, for example.


 
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Rajesh Pamula  
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 More options Aug 8 2012, 4:06 pm
From: Rajesh Pamula <rajeshpam...@gmail.com>
Date: Wed, 8 Aug 2012 22:06:19 +0200
Local: Wed, Aug 8 2012 4:06 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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But I thought one could entropy decode all the tokens and keeps them in
blocks and associate with respective MBs even at a later stage based on its
MB_TYPE. Isnt it true?

--
Rajesh Pamula
Post Graduate Student
Analogue and Digital Integrated Circuit Design
Imperial College London.
Residence Phone: +44-20-78522056

 
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John Koleszar  
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 More options Aug 8 2012, 4:35 pm
From: John Koleszar <jkoles...@google.com>
Date: Wed, 8 Aug 2012 13:35:39 -0700
Local: Wed, Aug 8 2012 4:35 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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No, the context model is dependent on which plane and band the token
being decoded belongs to, and whether there are 24 or 25 blocks per MB
depends on the block mode, which is in the other partition. I don't
see any way to decode them independently.


 
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Rajesh Pamula  
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 More options Aug 8 2012, 4:45 pm
From: Rajesh Pamula <rajeshpam...@gmail.com>
Date: Wed, 8 Aug 2012 22:45:02 +0200
Local: Wed, Aug 8 2012 4:45 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Ah yes. You are absolutely right. I wasnt thinking about how I would get
probabilities.

Thanks for correcting me.

--
Rajesh Pamula
Post Graduate Student
Analogue and Digital Integrated Circuit Design
Imperial College London.
Residence Phone: +44-20-78522056

 
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sanjeev verma  
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 More options Aug 9 2012, 12:49 pm
From: sanjeev verma <sanjeev1...@gmail.com>
Date: Thu, 9 Aug 2012 22:19:12 +0530
Local: Thurs, Aug 9 2012 12:49 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Hi,
Does anybody has an idea, if VP8 decoder is able go decode 1080p
content on dual core A9 devices, If yes, then what bitrate can be
comfortably decoded?
Thanks and Regards,
Sanjeev


 
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sanjeev verma  
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 More options Aug 23 2012, 11:35 am
From: sanjeev verma <sanjeev1...@gmail.com>
Date: Thu, 23 Aug 2012 21:05:34 +0530
Local: Thurs, Aug 23 2012 11:35 am
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Hi,
In VP8, does loop filtering of the current MB depend upon neighbouring
MB's properties like neighbouring MB type or Motion vectors etc?
Regards,
Sanjeev

 
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Rajesh Pamula  
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 More options Aug 23 2012, 1:26 pm
From: Rajesh Pamula <rajeshpam...@gmail.com>
Date: Thu, 23 Aug 2012 19:26:26 +0200
Local: Thurs, Aug 23 2012 1:26 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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A quick scan of the spec did not indicate anything like loop filtering
being dependent on neighbor MB properties. To be honest, I am quite
surprised by that given other contemporary standards take MVs and Qps into
account while determining filter strength. Atleast I would have liked a Qp
dependence, although it is possible even now by setting LF adjustments per
segment ID, but that would leave the decision making to encoder, rather
than being specified in the standard.

I have been erroneous and rusty off-late wrt VP8. I am hoping more
experienced experts (John and others) would correct me, if I am wrong.

On Thu, Aug 23, 2012 at 5:35 PM, sanjeev verma <sanjeev1...@gmail.com>wrote:

--
Rajesh Pamula
Post Graduate Student
Analogue and Digital Integrated Circuit Design
Imperial College London.
Residence Phone: +44-20-78522056

 
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sanjeev verma  
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 More options Aug 23 2012, 1:31 pm
From: sanjeev verma <sanjeev1...@gmail.com>
Date: Thu, 23 Aug 2012 23:01:05 +0530
Local: Thurs, Aug 23 2012 1:31 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Thanks Rajesh.
Any other replies will also be appreciated.
Regards,
Sanjeev


 
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Attila Nagy  
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 More options Aug 24 2012, 3:18 am
From: Attila Nagy <attilan...@google.com>
Date: Fri, 24 Aug 2012 10:18:37 +0300
Local: Fri, Aug 24 2012 3:18 am
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Filtering depends on the actual reconstructed pixel values of the
above and left MB. These neighboring pixels can also be altered by the
filtering process of the current macroblock.
But yes, the neighbors' mode, mv or such properties are not used.


 
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Ben  
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 More options Dec 30 2012, 12:08 pm
From: Ben <ben.a...@outlook.com>
Date: Sun, 30 Dec 2012 09:08:20 -0800 (PST)
Local: Sun, Dec 30 2012 12:08 pm
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Hi Rajesh,

Need some help on VP8 partiton. My decoder pipeline is designed to operate
on MacroBlock (MB) basis. So my question is

1. With multiple partition, is it possible to decode the complete MB till
Loop Filter ?

What I understood from multiple partition is , for eg a frame with 4 MB
rows, and partition is 2. In this case the bitstream is packed with even
rows followed by odd rows.

BitStream:  MBrow0-MBRow2-MBRow1-MBRow3

If this is how it is received at the input of decoder, then Intra
Prediction and loop filter cannot start processing the MB Row2, because
MBRow1 is still not decoded.

How can MB based pipeline designs can work ?

-ben


 
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Ronald Bultje  
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 More options Dec 30 2012, 2:25 pm
From: Ronald Bultje <rbul...@google.com>
Date: Sun, 30 Dec 2012 11:25:00 -0800
Subject: Re: Need help to understand how/when VP8 updates reference frames
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Hi Ben,

you know the offsets of each data partition in advance. So although you
have a bitstream as you stated, you know the offsets/positions of the data
for MBrow0 and MBrow1 in advance. So really, you have two bitstreams:

bitstream1: MBRow0-MBrow2[-...]

and

bitstream2: MBrow1-MBrow3[-...]

to do a MB-based pipeline design, just use the two bitstreams
interchangeably for each mbrow you're decoding. I.e. use bitstream1 for
mbrow0, then bitstream2 for mbrow1, then bitstream1 again for mbrow2, and
lastly bitstream2 for mbrow3. You can also make this multithreaded, by
having two threads, where thread 1 decodes bitstream1 and thread2 decodes
bitstream2 in parallel.

Ronald


 
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