Provided by: oss4-base_4.2-build2010-5ubuntu9_amd64 
NAME
oss_envy24 - ICE Envy24 audio device driver.
DESCRIPTION
Open Sound System driver for Envy24 based audio cards such as the M-Audio Delta Series,
Terratec EWS88 Series, Hoontech DSP24.
ENVY24 device characteristics:
· 8/16 bit playback/record
· mono/stereo/4ch/5.1ch/7.1ch playback
· mono/sterero recording
· 8KHz to 192Khz sample rate.
ENVY24 AUDIO DEVICES
Audio devices:
0: M Audio Delta 1010 out1/2
1: M Audio Delta 1010 out3/4
2: M Audio Delta 1010 out5/6
3: M Audio Delta 1010 out7/8
4: M Audio Delta 1010 S/PDIF out
5: M Audio Delta 1010 in1/2
6: M Audio Delta 1010 in3/4
7: M Audio Delta 1010 in5/6
8: M Audio Delta 1010 in7/8
9: M Audio Delta 1010 S/PDIF in
10: M Audio Delta 1010 input from mon. mixer
11: M Audio Delta 1010 (all outputs)
12: M Audio Delta 1010 (all inputs)
Synth devices:
Midi devices:
0: M Audio Delta 1010
Timers:
0: System clock
Mixers:
0: M Audio Delta 1010
The actual /dev/dsp# numbers may be different on your system. Check the right ones by
looking at the output procuced by "ossinfo -a" command. With the above configuration you
can use /dev/dsp0 to /dev/dsp4 for playback of stereo streams. If you play mono files the
signal will be output only from the left channel. /dev/dsp0 to /dev/dsp3 are connected to
the analog outputs while /dev/dsp4 is the S/PDIF output.
The /dev/dsp5 to /dev/dsp10 device files can be used for recording. /dev/dsp5 to /dev/dsp8
are the analog inputs. /dev/dsp11 and /dev/dsp12 are raw input/output device files. They
will be described in detail in the "Raw I/O devices" section below.
It's also possible to make OSS to create individual device files for every channel this
creates twice as many device files than the default setting. To do this just append
envy24_skipdevs=1 to the oss_envy24.conf file. This is useful only if you are working on
mono rather than stereo signals. However please note that setting envy24_skipdevs=1 does
_NOT_ lock the device files to one channel mode, the application can still set them to
stereo or multi channel mode if it likes.
It is possible to set all device files to mono only mode by setting envy24_skipdevs=1 and
envy24_force_mono=1. However this mode disables stereo and multi channel usage for all
devices so in general it should not be used.
By default the driver will create output devices before the input ones. By setting
envy24_swapdevs=1 in oss_envy24.conf you can ask OSS to create the device files in
opposite order i.e. input device files before the output ones. This may be useful when
using RealProducer.
As a workaround to a bug in RealProducer you also need to create some dummy mixer devices
by defining envy24_realencoder_hack=1 in oss_envy24.conf. Without these extra mixer
devices RealProducer will not be able to access other than the first input device.
DEVICE MANAGEMENT
By default OSS creates a large number of device files for each envy24 card. This
may be a problem when multiple cards need to be used in the same system. Adding
the envy24_devmask option to oss_envy24.conf should help in most cases because it
removes the devices that are actually not needed in the system.
The envy24_devmask number is the SUM of the following values:
1: Create primary (analog/ADAT/TDIF) outputs.
2: Create primary (analog/ADAT/TDIF) inputs.
4: Create S/PDIF outputs.
8: Create S/PDIF inputs.
16: Create monitor input device.
32: Create the raw input and output devices.
For example envy24_devmask=12 (4+8) creates only the S/PDIF devices. To enable all
possible (current or future) device files set envy24_devmask to 65535 (default).
If possible make your application to open the right device file (/dev/dsp0 to
/dev/dsp10) explicitly. It's also possible to use the default devicefile (/dev/dsp)
since OSS now supports automatic device allocation (it opens the first available
input or output devicefile depending on the open mode).
The channel allocation mechanism between device files is very flexible. Even there
is a device file for every stereo pair (or a mono channel) it's possible to use any
of the device file to access multiple channels. For example an application can
open /dev/dsp0 and set the number of channels to 10. In this way the application
can play all 10 channels (or any number between 1 and 10) simultaneously (the
samples will be interleaved).
There is simple automatic syncstart feature when using multiple applications at the
same time. Playback will not start before all currently open devices files have
started the playback operation. The same mechanism works for recording (recording
and playback operations are fully independent).
The Envy24 driver supports 8, 16 and 24/32 bit sample formats.
SAMPLING RATE
Envy24 based cards are multi channel devices and all the channels share the same
sampling rate. For this reason the sampling rate is normally locked to the value
selected using ossmix. However OSS supports some other methods for changing the
sampling rate. There are four ways to change the sampling rate.
BASIC METHOD:
Since all input and output channels of Envy24 work at the same sampling rate it's
not possible for the applications to select the rate themselves. Instead the
sampling rate is always locked to the currently selected rate. This rate selection
can be changed using the ossmix program shipped with OSS.
For example:
ossmix envy24.rate 48000
sets the sampling rate to 48000 Hz (default). The possible alternatives are
· 8000
· 9600
· 11025
· 12000
· 16000
· 22050
· 24000
· 32000
· 44100
· 48000
· 88200
· 96000
When using S/PDIF inputs/outputs only the sampling rates 32000, 44100, 48000, 88200
or 96000 should be used.
EXTERNAL SYNC
It's possible to lock the sampling rate to the S/PDIF or world clock inputs by
setting the envy24.sync setting in ossmix to SPDIF or WCLOCK. However the
envy24.rate setting should be set manually to match the rate being used (there is
no autodetection for that).
NONLOCKED METHOD
It's also possible to turn the envy24.ratelock setting to OFF using ossmix. After
that the first application that opens the device can change the sampling rate.
However great care should be taken that this application gets the
recording/playback process fully started before any of the other applications open
their devices. Otherwise all devices will be locked to 8Khz. Also keep in mind
that subsequent applications will be forced to use the sampling rate set by the
first one.
SOFTWARE SRC
OSS contains a very high quality software based sample rate converter. It can be
enabled by setting envy24.src to ON using ossmix.
After that OSS can do on-fly sample rate conversions between the actual "hardware"
sampling rate and the sampling rates used by the applications. In this way every
application may use different sampling rate. However there are some drawbacks in
this method:
· The hardware rate needs to be 44100, 48000 or 96000 Hz.
· The software SRC algorithm consumes some CPU time (1% to 20% per audio channel
depending on the CPU speed and sampling rates). For this reason this method may
be useless in multi channel use with anything else but the fastest high end
CPUs.
· Only mono and stereo (1 or 2 channel) streams are supported.
· The SRC algorithm does cause minor artifacts to the sound (SNR is around 60 dB).
RAW IO DEVICES
These device files provide an alternative way to access Envy24 based devices. With
these devices it's possible to bypass the dual buffering required by the "normal"
input-output device files described above. This means that also the mmap() feature
is available and that the latencies caused by dual buffering are gone. So these
device files work much like "ordinary" soundcards. However due to multi channel
professional nature of the Envy24 chip there are some very fundamental differences.
This means that these device files can only be used with applications that are
aware of them.
The differences from normal audio device files are:
1. The sample format will always be 32 bit msb aligned (AFMT_S32_LE). Trying to
use any other sample format will cause unexpected results.
2. Number of channels is fixed and cannot be changed. The output device has always
10 channels (0 to 7 are analog outputs and 8 to 9 are the digital outputs).
This assignment will be used even with cards that don't support digital (or
analog) outputs at all. If the actual hardware being used has less channels the
unused ones will be discarded (however they will be fed to the on board monitor
mixer).
The input device is fixed to 12 channels. Channels 0 to 7 are analog inputs.
Channels 8 to 9 are digital inputs. Channels 10 and 11 are for the result signal
from the on board monitor mixer.
DIGITAL MONITOR MIXER
All Envy24 based cards have a built in monitor mixer. It can be used to mix
allinput and output signals together. The result can be recorded from the "input
from mon mixer" device (device 10 in the /dev/sndstat example above). The monitor
mix signal can also be routed to any of the outputs (including S/PDIF and the
"consumer" AC97 output of Terratec EWS88MT/D and any other card that support s it).
The settings in the gain.* group of ossmix are used to change the levels of all
inputs and outputs in the digital monitor mixer. The possible values are between 0
(minimum) and 144 (maximum).
OSS permits using all 10 possible output channels of the monitor mixer even with
cards that have less physical outputs. These "virtual" outputs are only sent to the
monitor mixer and their signal is only present in the monitor mixer output. To
enable these "virtual" channels set the envy24_virtualout parameter to 1 in
oss_envy24.conf. This option has no effect with Delta1010, EWS88MT and other cards
that have 10 "real" outputs.
SYNC SOURCE
On cards with S/PDIF and/or World Clock inputs it's possible to select the sync
source using
ossmix envy24.sync
The possible choices are:
· INTERNAL: Use the internal sampling rate as defined by envy24.rate
· SPDIF: Use the S/PDIF input as the clock source. The envy24.rate setting must be
set manually to match the actual input sampling rate.
· WCLOCK: Like SPDIF but uses the world clock input signal (Delta 1010 only).
OUTPUT ROUTINGS
Output routing of output ports can be changed by changing the route.* settings
using ossmix. The possible choices are:
· DMA: Playback from the associated /dev/dsp# device.
· MONITOR: Output of the digital mixer (only out1/2 and S/PDIF).
· IN1/2 to IN9/10 or IN1 to IN10: Loopback from the analog inputs
· SPDIFL or SPDIFR or SPDIF: Loopback from the S/PDIF input.
PEAK METERS
Envy24 based cards have peak meters for the input and output ports of the digital
monitor mixer. ossmix can show these values under the peak.* group (these settings
are read only). The values are between 0 (minimum) and 255 (maximum). At this
moment the only applications that supports these peak meters are ossmix and
ossxmix.
AUDIO LATENCY
IDE disk and CD-ROM drives may cause some interrupt latency problems which may
cause dropouts in recording/playback with Envy24 based cards. For this reason
ensure that DMA is turned on for the disk drive.
Another method to solve the dropout problems is making the fragment size used by
the driver longer. This can be done by adding envy24_nfrags=N to the
oss_envy24.conf file. By default N is 16. Values 2, 4 or 8 make the fragments
longer which should cure the dropout problems. However this may cause latency
problems with some applications. Values 32 and 64 decrease the latencies but may
cause dropouts with IDE.
OPTIONS
· envy24_skipdevs: It's also possible to make OSS to create individual device files for
every channel. This creates twice as many device files than the
default setting.
Values: 1, 0 Default: 0
· envy24_swapdevs: By default the driver will create output devices before the input
ones. You can force the input devices to be configured before output devices. Values:
1, 0 Default: 0
· envy24_realencoder_hack: RealProducer wants to see a mixer device in /dev/mixer. This
option allows you to define a dummy /dev/mixer mixer device. Envy24 Mixer device
doesn't provide any consumer level soundcard compatibility so this dummy mixer fools
RealProducer into thinking it's running on a consumer soundcard like SB Pro or SBLive.
Values: 1, 0 Default: 0
· envy24_gain_sliders: With some devices it's possible to change the gain controllers to
be continuous sliders instead of just enumerated ones. Values: 1, 0 Default: 0
· envy24_nfrags: To solve the dropout problems make the fragment size used by the driver
longer. By default is 16. Values 2, 4 or 8 make the fragments longer which should cure
the dropout problems. However this may cause latency problems with some applications.
Values 32 and 64 decrease the latencies but may cause dropouts with IDE drives.
Values: 2-64 Default: 16
· envy24_virtualout: OSS permits using all 10 possible output channels of the monitor
mixer even with cards that have less physical outputs. These "virtual" outputs are only
sent to the monitor mixer and their signal is only present in the monitor mixer output.
This has no effect for Delta1010 or Terratec EWS88MT. Values: 1, 0 Default: 0
· envy24_force_mono: It is possible to set all device files to mono only mode by setting
envy24_skipdevs=1 and envy24_force_mono=1. However this mode disables stereo and multi
channel usage for all devices so in general it should not be used. Values: 1, 0
Default: 0
FILES
/etc/oss4/conf/oss_envy24.conf Device configuration file
AUTHOR
4Front Technologies
29 November 2021 oss_envy24(7)