[CELT-dev] Audio Performance on solo instruments

[Gregory Maxwell]

On Mon, Mar 21, 2011 at 3:06 PM, Bob Bang <bob.bang2 at gmail.com> wrote:
> Hello everyone, I was curious if anyone has performed any listening tests or
> done work with solo instrument performances with the CELT codec?
>
> I experience quite a bit of noise coming up with a heavily tonal stimulus,
> the worst offender being a trumpet. I understand some of this behavior is to
> be expected, this is a perceptual codec afterall, but was curious if anyone
> was able to find an elegant solution.  (Jean-Marc: This may also be a good
> test file to throw into your routine listening)
>
> I know I am pushing the codec to its limits a bit: fixed point math, small
> frame size (100 samples on v0.7.1, 120 samples on v0.11.1) and a bitrate of
> around 200kbps for a stereo application. I understand I can throw more bits
> or a larger window at the problem, but then my system requirements would be
> blown. Would the complexity option help me at all? Has anyone worked around
> this some other way?

The pre/post filter (which is not enabled in the default builds because
the IPR for it may not be available until the opus process is completed)
helps _greatly_ for this kind of stimulus.

Though, as you're aware, you're somewhat pushing the limits. 200kbit/sec
should heal many sins however.

You should check with the pre/post filter enabled and see if the results
are more satisfactory.