Re: Fwd: [Ardour-Cvs] Ardour source branch meterbridge updated. 3.2-153-gf885622

On 07/06/2013 06:27 PM, Jörn Nettingsmeier wrote:
> hi robin, i'm not currently tracking the meterbridge branch, so i may be
> talking nonsense, but here goes:
> peaking should be defined as a configurable number of samples at full
> scale (or equal to or greater than 1.0f, in the case of floats) , not
> some arbitary level.


Hi Jörn,

Do you have a reference for this *should be* defined as? I don't think
that makes much sense.

Actually it's rather the other way 'round. Since the digital signal is
band-limited there can be peaks in the audio even if the digital samples
are not exceeding 0dbFS [1].

Either way this is not relevant yet. The meterbridge branch (which will
be merged back to master soonish) is currently mostly concerned with GUI
- not the actual calculations.

NTL, the level-metering in ardour will see a major rework in the not to
distant future - and doing that needs a rethink.

Your suggested approach has one major downside though: it cannot be
efficiently accelerated with SSE2 (thanks to Sampo, the current
max-peak-hold is accelerated).

Other level-meters standards/algorithms will have the same issue and
because every port in ardour has a peak-meter and you can have thousands
of ports this can become a major DSP-load bottleneck.

Anyway - this needs careful planning.

Thanks for kicking off this discussion..

Cheers!
robin


[1]
http://www.oofus.co.uk/ardour/TL%20Labs%20digital%20distortion%20white%20paper.pdf