[FFmpeg-devel] [PATCH 1/2] libavcodec/libaomenc.c: Add a libaom command-line opton 'tune'

[Wang Cao]

Let me reply again with the correct posting form.
On Tue, Mar 3, 2020 at 2:50 PM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:

> Am Di., 3. März 2020 um 22:43 Uhr schrieb Wang Cao <doubleecao at gmail.com>:
>
> > + at item tune (@emph{tune})
> > +Set the distortion metric tuned with for encoder. Default is PSNR.
> > +
> > + at table @samp
> > + at item psnr (@emph{0})
> > +PSNR as distortion metric
> > +
> > + at item ssim (@emph{1})
> > +SSIM as distortion metric
> > + at end table
>
> My knowledge of video encoding is limited but I would have
> expected (actually I was sure) that the default would be
> "visual" or similar and not an artificial metric.
>
 Yes. I share the share hope as you do. The default should be a metric that
reflects actual human perception of a video. As far as I understand the
current status for now, PSNR and SSIM is the metric that libaom is by
default compiled with. Other metrics are being added support. For example,
VMAF and other metrics are also supported now as you can find them in
https://aomedia.googlesource.com/aom/+/refs/heads/master/aom/aomcx.h. I
added those two metrics trying to be conservative here because I don't know
if some require special configs.

> Does this mean libaom is only made to please automatic
> comparison tests?
>
> Carl Eugen
>
> As I mentioned above, libaom continues to add support for optimizing for
different metrics. I personally do not know if there is a perfect visual
quality metric for now. I will continue to add more options to ffmpeg if I
can make sure those metrics can be used in ffmpeg command-line easily.

-- 

Wang Cao |  Software Engineer |  wangcao at google.com |  650-203-7807