[theora] Additional encoding options for theora

Benjamin M. Schwartz bmschwar at fas.harvard.edu
Wed Nov 18 08:48:31 PST 2009

Basil Mohamed Gohar wrote:
> On 11/18/2009 11:16 AM, Benjamin M. Schwartz wrote:
>> Basil Mohamed Gohar wrote:
>>> Hey all,
>>> I've been using the example reference encoder that comes with Theora
>>> reference implementation from SVN, but there are very few options to
>>> tweak encoding parameters in contrast to other codecs utilities such as
>>> x264, mpeg2enc, etc.
>> This is deliberate.  libtheoraenc is designed with the philosophy that the
>> user should specify constraints on the output bitrate and encode CPU time,
>> and the encoder should produce the highest possible quality given the
>> constraints.
>> What other parameters do you wish for?
>> --Ben
> Well, without knowing exactly what's possible, I am not sure.  I am sure
> some time-quality trade-off decisions can still be made, and some of
> these can be exposed through the example encoder or another utility, if
> it's more appropriate.

As I said, libtheoraenc allows the user to specify their tradeoff between
encode time and output quality, using the --speedlevel argument in

> This would help people like me test various
> parameters and help the developers further refine the code, for
> example. 

Tuning of libtheoraenc is definitely valuable, and there is much to be
done.  So far, the "development tunables" have been kept far from the user
interfaces, on the grounds that "actual users" shouldn't have to set any
parameters.  Also, the parameters that could most use tuning, such as the
quantization matrices, are not simple to specify.  Nonetheless, it's a
good point: we don't have any easy way for tuners to experiment with the
innards unless they're willing to write a bit of C.

> As an enthusiast, I love to be able to fiddle the knobs and
> switches myself to see their impact, even if only minor.

I've had this feeling too, but of course, libtheoraenc is not a toy.

> Incidentally, why did you reply to me directly, and then CC the list? 
> Wouldn't replying to this message and addressing the list be
> sufficient?  I've noticed this behavior before when I've posted
> sometimes, and it messes up my filtering...

This list doesn't set a reply-to, so that's Thunderbird's default behavior
on "reply-all".

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