[FFmpeg-devel] [PATCH] liavcodec: add bit-rate support to RoQ video encoder

[Tomas Härdin]

> > 
> > >  -    if (frame->quality)
> > > -        enc->lambda = frame->quality - 1;
> > > -    else
> > > -        enc->lambda = 2*ROQ_LAMBDA_SCALE;
> > > +    if (avctx->bit_rate <= ROQ_DEFAULT_MIN_BIT_RATE) {
> > > +        /* no specific bit rate desired, use frame quality */
> > > +        if (frame->quality)
> > > +            enc->lambda = frame->quality - 1;
> > > +        else
> > > +            enc->lambda = 2*ROQ_LAMBDA_SCALE;
> > > +    }
> > 
> > This looks like a bit of a janky way to switch between qscale and
> > bitrate. Isn't there a way to detect whether an option has been set
> > explicitly? At the very least this behavior should be documented in
> > doc/encoders.texi
> > 
> 
> Originally, the code just checked for bit_rate !=
> AV_CODEC_DEFAULT_BITRATE,
> which required including options_table.h, which in turn produced a
> bunch
> of compilation warnings about certain fields being deprecated. None
> of the
> other codecs include that file + many simply check the bit_rate field
> against
> magic constants.

grepping for 200000 didn't reveal anything like that. Do you have a
specific example of an encoder that does this?

Perhaps we could move AV_CODEC_DEFAULT_BITRATE somewhere else, to avoid
pulling in a bunch of unrelated stuff. Maybe that doesn't need to hold
up this patch though. Tbh the way bitrate is defaulted to a value,
which makes it impossible to differentiate between a user-supplied -b
200k an no -b at all, is even more janky. The default is also
ridiculously low..

I know some encoders like libvpx allow specifying both quality (-crf)
and bitrate at the same time

/Tomas