[x265] x265-devel Digest, Vol 40, Issue 26

[Deepthi Nandakumar]

We just need a basic predictor for slice QP - this could be the first cut
QP estimates from Ratecontrol::rateEstimateQscale. These are very easy to
compute and likely to be more correlated to sliceQP. The ratecontrol team
should be able to help.

On Wed, Sep 28, 2016 at 8:35 AM, chen <chenm003 at 163.com> wrote:

> Hello Xuefeng,
>
> I understand your concept, I just said your algorithm output result close
> to average of slice base QP, but through complicated compute.
>
> Regards,
> Min
>
>
> At 2016-09-28 13:59:13，xuefeng <xuefeng at multicorewareinc.com> wrote：
>
> hello Min,
> Thanks for your reply.
>
> a）
> deltaQp = sliceQp - ppsQp
> ppsQp is saved in PPS and deltaQp is saved in bitstream.
> In fact, I don't calculate new QP, but calculate a best delta for ppsQP
> and deltaQp without changing sliceQp.
> For example,  deltaQp = 14(cost 4 bits),  sliceQp = 40, and ppsQp = 26
> If we set deltaQp = 14 - 14 = 0 ( cost 1 bits)  and ppsQp = 26 + 14 = 40,
>  sliceQp is still 40.  Then we save 3 - 1 = 2 bits in bitstream for each
> slice.
>
> b)
> I have change QP Range with range extension. Please see this patch.
>
> ------------------------------
> Regards,
>
>              Xuefeng Jiang
>
> xuefeng at multicorewareinc.com
>
>
> Message: 3
> Date: Wed, 28 Sep 2016 00:02:33 +0800 (CST)
> From: chen  <chenm003 at 163.com>
> To: "Development for x265" <x265-devel at videolan.org>
> Subject: Re: [x265] Optimize slice QP in PPS for x265
> Message-ID: <2e196b48.110e.1576c622432.Coremail.chenm003 at 163.com>
> Content-Type: text/plain; charset="gbk"
>
> Hello Xuefeng,
>
>
> Your idea is good, in low bitrate environment, the MV, header are most
> important part in bitstream.
> I take a look your code, it sounds some problems.
>
>
> Your calculate correlation between sliceQp and QP Range (it is [0, 51]
> without range extension), so you will got a constant correlative array for
> every QP value.
> In the final, your algorithm output a QP close to average value of sliceQP.
> It is right, just spending more time on compute.
>
>
> Regards,
> Min
>
>
> At 2016-09-27 14:46:14,xuefeng <xuefeng at multicorewareinc.com> wrote:
>
> All,
> hello!
>
>
> x265 set the slice QP in PPS to 26.  Bits can be saved by calculating a
> closer approximation to the actual slice QP values utilized to encode the
> bitstream at different quality levels. The delta QP in each slice header is
> huge especially at low bit rate and quality levels.
>
>
> My test command is as follows.
> --repeat-headers --hash 1  --input-res 1280x720 --keyint 30 --min-keyint
> 30 --input "Johnny_1280x720.y4m" --fps 30 --output "test_new.mp4"
>
>
> There is a patch in the attachment for this method based on "Changeset:
> 11587 (d20b78d6d138)".
> There is information for x265 coding to see that bitrate goes down.
> There is informations for HM decoding to see that MD5 and QP are the same
> with the method.
>
>
>
>
>
>
> Regards,
>              Xuefeng Jiang
> xuefeng at multicorewareinc.com
>
>
> _______________________________________________
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>
>


-- 
Deepthi
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