[x264-devel] Getting the quantization stepsize (not QP)

[Eymen Kurdoglu]

Thanks for your quick reply. I've been told that what I've referred to as
QS might be the qscale in x264.

Essentially I'm interested in the quantity given by 4+6*log2( QP ).

If getting this quantity for each MB is not possible/difficult, it would
also help me to just record the mean QP used in each MB of each frame.

On Wed, Dec 7, 2016 at 12:39 PM BugMaster <BugMaster at narod.ru> wrote:

> On Wed, 07 Dec 2016 17:31:48 +0000, Eymen Kurdoglu wrote:
> > Hi all,
>
> > Is there a way to get the mean value of the quantization stepsize
> > (QS) used in a frame, instead of the mean value of the QP used
> > (which is the one that the debug log outputs)? Due to the non-linear
> > mapping between the quantization stepsize and the QP, finding the QS
> > equivalent of the mean QP is not equal to the actual mean value of the
> QS.
>
> > I would appreciate it if someone can direct me to the part of the code
> that might change this.
>
> > Here are the specific settings I'm using in my app.
> > High profile, veryfast, zerolatency, single thread, no scene-cuts,
> > no weighted prediction and the RC parameters are:
> > param.rc.i_rc_method = X264_RC_ABR;
> > param.rc.i_bitrate = i_target;
> > param.rc.i_vbv_max_bitrate = param.rc.i_bitrate;
> > param.rc.i_vbv_buffer_size = param.rc.i_bitrate/10;
>
> > Thanks a lot, and have a nice day!
>
> > Eymen
>
> Hi. What do you mean exactly by quantization stepsize (QS)? This is
> the first time I see this term used especially with H.264 encoding.
>
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