[FFmpeg-devel] [PATCH v2 3/6] doc: update for libsvtav1 encoder

[Jan Ekström]

On Sat, Sep 18, 2021 at 4:27 AM <lance.lmwang at gmail.com> wrote:
>
> From: Limin Wang <lance.lmwang at gmail.com>
>
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---

Hi,

"doc/encoders: add available values for libsvtav1 options"

would possibly be better as a commit message?

>  doc/encoders.texi | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
>
> diff --git a/doc/encoders.texi b/doc/encoders.texi
> index 8fccd73..64d604e 100644
> --- a/doc/encoders.texi
> +++ b/doc/encoders.texi
> @@ -1750,12 +1750,56 @@ You need to explicitly configure the build with @code{--enable-libsvtav1}.
>  @table @option
>  @item profile
>  Set the encoding profile.
> + at table @samp
> + at item main
> + at item high
> + at item professional
> + at end table
>
>  @item level
>  Set the operating point level.
> + at table @samp
> + at item 2.0
> + at item 2.1
> + at item 2.2
> + at item 2.3
> + at item 3.0
> + at item 3.1
> + at item 3.2
> + at item 3.3
> + at item 4.0
> + at item 4.1
> + at item 4.2
> + at item 4.3
> + at item 5.0
> + at item 5.1
> + at item 5.2
> + at item 5.3
> + at item 6.0
> + at item 6.1
> + at item 6.2
> + at item 6.3
> + at item 7.0
> + at item 7.1
> + at item 7.2
> + at item 7.3
> + at end table
> +

The levels list is somewhat long, and it's specific to AV1 and not
this encoder. I don't think we list H.264/HEVC etc levels, either?

So I'm not 100% sure on this bit, possibly just noting "Set the
operating point level, f.ex. '4.0'." is good enough?

> + at item hielevel
> +Set the Hierarchical prediction levels.
> + at table @samp
> + at item 3level
> + at item 4level, This is the default.

You probably mean this to be on a separate line. Right now it ends up
as part of the entry on the list a la: ‘4level, This is the default.’

Noticed through the HTML documentation output (ffmpeg-codecs.html).

> + at end table
>
>  @item tier
>  Set the operating point tier.
> + at table @samp
> + at item main
> +The main tier was designed for most applications. This is the default.
> + at item high
> +The high tier was designed for very demanding applications.
> + at end table
>

Looking at https://aomediacodec.github.io/av1-spec/av1-spec.pdf , it
seems like the high tier only enable higher bit rates/lower
compression ratios in levels.

I think explaining it like that is probably more understandable than
vague references for "most applications" and "very demanding
applications". Or only explaining which one is the default, as I would
expect a person who needs to set this flag to know what the tier flags
in AV1 bit stream mean.

Jan