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

[Matt Pekar]

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...

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?
>>
>>
>> _______________________________________________
>> Libva mailing list
>> Libva at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/libva
>>
>>
>
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