[Libva] encoding text image in h264 at QP 1--what quality can be expected?

[Matt Pekar]

Comparing the NV12 image with the RGB I can readily see it is the
color-space conversion that causes the distortion--not libva or the intel
driver.  My apologies for the diversion.

On Wed, Oct 8, 2014 at 7:35 PM, Zhao, Yakui <yakui.zhao at intel.com> wrote:

> On Wed, 2014-10-08 at 10:02 -0600, Matt Pekar wrote:
> > I've examined the behavior on Intel(R) Core(TM) i3-4130 and Intel(R)
> > Core(TM) i5-2400.  We target resolutions as low as 224x64 and up to
> > 720P.
> >
> > Another thing I'm noticing is that the colors used seem to matter.  I
> > put some white on black text up and it looks great.  Maybe there is an
> > issue with how I do my colorspace conversion from BGR to NV12...
> >
>
> Hi, Matt
>
> In order to narrow down the issue, Will you please help to remove the
> extra color-space conversion of NV12 -> RGB and instead use the NV12
> image directly for the encoding?
>
> After the encoding is finished, you can calculate the corresponding PSNR
> with the original reference YUV and then see whether the PSNR can meet
> with your requirement.
>
> Thanks.
>     Yakui
>
> > I'm going to attempt to attach two pictures of what I'm seeing.  They
> > show the original .png image and what the encoder delivers side by
> > side.
> >
> >
> > On Wed, Oct 8, 2014 at 10:41 AM, Chris Healy <cphealy at gmail.com>
> > wrote:
> >         Hi Matt,
> >
> >
> >         I've been using the libva with the Intel driver to encode and
> >         stream myself for quite some time now.  There are a number of
> >         visual artifacts that I have encountered along the way, though
> >         the fuzziness you describe is not one of them.  With the Intel
> >         driver, I would expect different visual behaviour depending on
> >         the particular HW you are using as each one is different.  I'm
> >         using an i7-3517U to encode 1280x720 H.264 at 4Mbps.  What are
> >         you working with?
> >
> >         Chris
> >
> >
> >         On Wed, Oct 8, 2014 at 7:18 AM, Matt Pekar
> >         <mpekar at raineyelectronics.com> wrote:
> >
> >                 We use libva with the Intel driver to do live video
> >                 streaming.  In the encoding process we dynamically
> >                 ramp the QP up and down as different content flows
> >                 through.
> >
> >
> >                 There are cases where we display simple text messages
> >                 for many seconds.  In these cases I'd like to send my
> >                 QP down to 1--highest quality--and get as close to a
> >                 lossless encode as possible.
> >
> >
> >                 What I'm seeing is that on fonts and sharp lines a
> >                 little bit of encoding will be done regardless,
> >                 leaving the text slightly fuzzy.  I tried the
> >                 new VAEncMiscParameterTypeQualityLevel setting, but it
> >                 only had two levels (1 and 2) and they didn't seem to
> >                 affect the picture at all.
> >
> >
> >                 Are there any settings I might try to ramp the quality
> >                 up even further?  Is the fuzziness I'm seeing in the
> >                 text inherent to the h264 standard, or is this just
> >                 what Intel's implementation happens to do?
> >
> >
> >
> >
> >
> >                 _______________________________________________
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> >                 Libva at lists.freedesktop.org
> >                 http://lists.freedesktop.org/mailman/listinfo/libva
> >
> >
> >
> >
> >
>
>
>
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