Bug#810224: /usr/bin/avconv: ogg format: unable to use pass and quality? options together

[Carl Eugen Hoyos]

On Friday 26 February 2016 10:42:14 pm you wrote:
> Hi Carl,
>
> On Thu, 25 Feb 2016 13:55:52 +0100 Carl Eugen Hoyos <cehoyos at ag.or.at>
>
> wrote:
> > Hi!
> >
> > When encoding with FFmpeg, you can either use fixed quality or fixed
> > bitrate (size), if you decide to use fixed bitrate, two-pass encoding
> > improves the output quality.
> > It makes no sense to use two-pass constant quality encoding, the result
> > of using two contradicting options is undefined.
> >
> > Please close this ticket as invalid.
>
> I think if two options a contradicting then ffmpeg should refuse
> accepting them instead of starting the conversion of the file.
> IMHO this is a valid upstream bug, but upstream can decide to leave it
> unfixed, of course.
>
> What do you think?

That my original comment was simply wrong.

Using two-pass encoding for constant quality is not undefined behaviour, it 
works fine here with all native encoders I tested producing two identical 
output files. I don't think this should be changed: While it makes little 
sense, I don't think it is an issue that FFmpeg accepts two-pass constant 
quality encoding.

When using libtheora, two-pass encoding only accepts constand bitrate, trying 
two-pass encoding with constant quality leads to an error.
I believe this is exactly what you requested.

Carl Eugen