4 Aug
2010
4 Aug
'10
3:36 a.m.
FYI, I added the following since
http://nielsmayer.com/envy24control/mudita24-1.0.1.tar.gz
... shall I release a 1.0.2 with the following additions (?):
* fixed --card and --device to allow valid ALSA names and numbers
( https://bugzilla.redhat.com/show_bug.cgi?id=602900 ).
* Add display of "Delta IEC958 Input Status" under "Hardware
Settings."
* Updated and corrected manual page and README
Before I release, I'd like to know what happens on cards that don't
have this feature, or if it's universally supported, but badly named.
Can those with a Terratec or other card test the following command and
let me know the results of command "amixer -c M66 cget
iface=MIXER,name='Delta IEC958 Input Status'"
e.g.:
> amixer -c M66 cget iface=MIXER,name='Delta
IEC958 Input Status'
> numid=50,iface=MIXER,name='Delta IEC958 Input Status'
> ; type=BOOLEAN,access=r-------,values=1
> : values=on
.................................................................................................
Also, in case anybody ever wondered what this one, under "Analog
Volume" is for: "Volume Control Rate Register" I added it to the
README:
.........................
Notes on the Envy24's hardware Digital Mixer and hardware Metering,
by Niels Mayer ( http://nielsmayer.com ):
--------------------
The "Monitor Inputs" and "Monitor PCMs" tabs contain multiple scale
widgets
grouped into L/R pairs and an associated peak-level meter. Each scale
widget represents the 24 bit attenuation value of each input to the
ice1712-based soundcard's digital mixer. This mixer is typically used for
zero-latency monitoring of "live" inputs, alongside backing sounds and
effects coming from the eight channels of PCM feeding the digital mixer.
When many inputs are "hot" simultaneously these scale-widgets attenuate the
inputs going into the digital mixer to prevent the output from clipping.
For details see http://nielsmayer.com/npm/envy24mixer-architecture.png
(from http://alsa.cybermirror.org/manuals/icensemble/envy24.pdf )
This is what the above manual says about the Envy24's digital mixer:
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.
Adjustment of responsivity vs. "zipper noise" from the 1.5dB steps at
the top-range of
the digital mixer attenuators is achieved by the following control
under "Hardware Settings":
MT3B: Volume Control Rate Register
...
Volume update rate control (sampling rate, PSYNC)
This register allows gradual change of the digital mixer volume
setting. The value in MT3B specifies the number of samples to elapse (in
hex) between each 1.5dB increment/decrement in volume mixer. This gradual
volume update continues until the setting programmed into MT38 is
reached. The appropriate value to program may vary, but 00 or 01h are good
choices for most cases.
The peak metering data is displayed as 0 to -48dBFS in envy24control's
meters. This data is derived from the envy24's hardware peak metering:
Peak data derived from the absolute value of 9 msb.
00h min - FFh max
volume. Reading the register resets the meter to 00h.
This resolution of the hardware metering is descibed by Fons Adriaensen in
a mailing list discussion:
http://lists.linuxaudio.org/pipermail/linux-audio-dev/2010-August/029009.ht…
[...] You have 128 steps between 0 and -6dB...
And even at -24dB the next step is 1.3dB lower. Below that
it gets worse radipdly. For a meter that is just supposed
to keep a check on peak levels it's OK.
Note that hardware metering data is also available from the command-line:
amixer -c M66 cget iface=PCM,name='Multi Track
Peak',numid=45
numid=45,iface=PCM,name='Multi Track Peak'
; type=INTEGER,access=r-------,values=22,min=0,max=255,step=0
: values=63,62,51,49,56,60,63,62,59,54,0,0,0,0,0,0,0,0,0,0,113,112
....................................................................
Niels
http://nielsmayer.com