[gstreamer-bugs] [Bug 118142] need an interface for encoder quality

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-base | Ver: HEAD CVS




------- Comment #14 from Ronald Bultje  2008-06-17 15:45 UTC -------
As a complete outsider, I disagree with that. Limiting yourself to such an
uninteresting subset of codec features will ensure that nobody will use it or
take it seriously.

Take a look at win32/MacOSX graphical encoders. They go from the ground up to
provide control of all details. what kind of block do you use for quantization?
4x4? 4x8? Some codecs only support one, some multiple, etc. Quality of output
is very different in each case. Global Motion Compensation or only per-block?
Look at all options that high-quality MPEG-4 encoders provide. Look at h.264. A
float that describes "quality" is just insufficient.

What you want is layers, and your design needs to address this. At the basis,
you want control of all individual codec options, with selection boxes. I'm
sure GObject properties could be used for this, but you need flags that tell
you which ones affect codec quality.

On top of that, you could use a series of "presets" (in a different manner of
the word) that combine multiple codecs/filters plus pre-set properties to
describe a subset of a pipeline encoding a media.  Users could take a global
approach and select "high quality ogg/vorbis" or "low quality 8-bit PCM audio",
as in the current profiles in gnome-media. Or they could specify their own and
add GMC, 16x16 block encoding etc. in h/264 with AC3 audio at a 192bps bitrate,
5-channels etc.


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