Re: [LAD] [PlanetCCRMA] FIxed alsa-tools' envy24control missing peak level meters and "Reset Peaks"

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To: Geoff King <gsking1@...>
Cc: <alsa-devel@...>, PlanetCCRMA mailinglist <planetccrma@...>, <linux-audio-dev@...>, fedora-music-list <fedora-music-list@...>
Date: Friday, July 16, 2010 - 10:57 pm

On Fri, Jul 16, 2010 at 5:27 AM, Geoff King wrote:

Geoff -- thank you for trying out the patch! (And, OT, thanks for
working w/ Rui to help fix
http://sourceforge.net/tracker/?func=detail&atid=733076&aid=3021645&grou...
:: "help fix qtractor crash on bus changing/configuration (3021645)" --
Envy24 and multichannel qtractor users, yes, it's time for a "svn up" ).

FYI, to try out the new levelmeters "easy", if you're running Fedora
x86_64, use the "envy24control" binary directly, or drop the
levelmeters.c file into your build:
http://nielsmayer.com/npm/Efficient-Meters-Envy24Control.tgz
( for details http://nielsmayer.com/npm/Efficient-Meters-Envy24Control.README )

........

On a completely different "note" the envy 24 manual (
http://alsa.cybermirror.org/manuals/icensemble/envy24.pdf )
has interesting info on the envy24 digital mixer that I've snapshotted:

Diagram: http://nielsmayer.com/npm/envy24mixer-architecture.png

Note the way it truncates in the mixer: the more inputs you "mix" at
once, the fewer bits each input source gets, and it's not clear what
kind of dither, or it's a straight truncate of 24... ultimately the
envy24 seems oriented towards producing a 16 bit, and not 24 bit
master (which makes sense given that the chip is well over a decade
old and HD audio production for "prosumer" was rare):
..........
4.5.5 Multi-Track Digital Monitoring
The Envy24 integrates a 36-bit resolution digital hardware mixer. The
width of the data path is strictly to
ensure that during processing of all the channels, under any
condition, no resolution is lost. The dynamic range
of the end user system will be limited by the range of the physical
output devices used. In order to maintain
identical gain to the input stream (i.e. 0dB), the resulting 24-bit is
not msb-aligned to the 36-bit. The overflow
bits correspond to the analog distortion due to saturation. The user
would need to reduce the overall attenuation
of the inputs to avoid clipping. Insertion of the digital mixer adds
only a single sample cycle delay with respect
to the original data. This extremely low latency all digital mixer
provides monitoring functionality and can
replace a traditional external analog input mixer. There are 20
independent audio data streams to mix and
control the volume. ...
..............

--Niels
http://nielsmayer.com
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Re: [LAD] [PlanetCCRMA] FIxed alsa-tools' envy24control miss..., Niels Mayer, (Fri Jul 16, 10:57 pm)