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

[Zhao, Yakui]

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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>