[Bug 670108] New: vp8enc: better defaults, more presets/profiles

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=670108
  GStreamer | gst-plugins-bad | git

           Summary: vp8enc: better defaults, more presets/profiles
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: t.i.m at zen.co.uk
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Just some quick comments on our default values from an e-mail exchange with
Ronald:

>  mode                : Mode
>  Enum "GstVP8EncMode" Default: 0, "vbr"
>  (0): vbr  - Variable Bit Rate (VBR) mode
>  (1): cbr -  Constant Bit Rate (CBR) mode

You may want to look into CQ mode (2) also.

>  max-keyframe-distance: Maximum distance between key frames
>  Integer. Range: 0 - 9999 Default: 60

60 is quite low (for high-quality encodes), any particular reason for that?

I think in our tests and on webmproject.org, we recommend 120 frames
as kf interval.

>  multipass-mode      : Multipass encode mode
>  Enum "GstVP8EncMultipassMode" Default: 0, "one-pass"
>  (0): one-pass         - One pass encoding (default)
>  (1): first-pass       - First pass of multipass encoding
> (2): last-pass        - Last pass of multipass encoding

Can the default be changes to 2pass? We really do all our internal
testing for high-quality encodes on 2pass, it'll generate much better
output (in the range of >1dB difference).

(tpm: can't ever default to 2-pass, since that requires co-operation by the
application. 2-pass can only ever be opt-in)


>  auto-alt-ref-frames : Automatically create alternative
>     reference frames
>  Boolean. Default: false

This isn't a good idea, alt-refs by themselves will also cause several
tenths of dB difference (in a positive way), I'd highly recommend you
turn them on for high-quality (2pass) encodes.

(tpm: only for high-quality 2-pass encodes? BBB: yes)


>  lag-in-frames  : If set, this value allows the encoder to consume
> a number of input frames before producing output frames.
>  Unsigned Integer. Range: 0 - 64 Default: 0

Probably want to up this to e.g. 25 for high-quality encodes (unless 0
means 'don't touch').

(tpm: I think 0 means whatever the library default is, someone needs to check
this)


>  tune                : Tune
>  Enum "GstVP8EncTune" Default: 0, "psnr"
>  (0): psnr             - Tune for PSNR
>  (1): ssim             - Tune for SSIM

Minor nit, most people would claim ssim is a better default here, but
it's not that relevant.

I see you haven't mapped the ARNR options, which provide a quality
boost for noisy input (without affecting noiseless input much), are
you guys interested in exposing these options also? They affect the
way the alt-ref frame is used.

(tpm: might be good for input from webcams - though what would be even better
if we could detect that kind of input and switch to that mode automatically)

Other possibly interesting pages:
 http://www.webmproject.org/tools/encoder-parameters/

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