359 lines
14 KiB
Groff
359 lines
14 KiB
Groff
." Automatically generated text
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.TH 7 "August 31, 2006" "OSS" "OSS Devices"
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.SH NAME
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oss_envy24 - ICE Envy24 audio device driver.
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.SH DESCRIPTION
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Open Sound System driver for Envy24 based audio cards such as the
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M-Audio Delta Series, Terratec EWS88 Series, Hoontech DSP24.
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ENVY24 device characteristics:
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.IP \(bu 3
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8/16 bit playback/record
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.IP \(bu 3
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mono/stereo/4ch/5.1ch/7.1ch playback
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.IP \(bu 3
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mono/sterero recording
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.IP \(bu 3
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8KHz to 192Khz sample rate.
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ENVY24 AUDIO DEVICES
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Audio devices:
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0: M Audio Delta 1010 out1/2
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1: M Audio Delta 1010 out3/4
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2: M Audio Delta 1010 out5/6
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3: M Audio Delta 1010 out7/8
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4: M Audio Delta 1010 S/PDIF out
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5: M Audio Delta 1010 in1/2
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6: M Audio Delta 1010 in3/4
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7: M Audio Delta 1010 in5/6
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8: M Audio Delta 1010 in7/8
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9: M Audio Delta 1010 S/PDIF in
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10: M Audio Delta 1010 input from mon. mixer
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11: M Audio Delta 1010 (all outputs)
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12: M Audio Delta 1010 (all inputs)
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Synth devices:
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Midi devices:
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0: M Audio Delta 1010
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Timers:
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0: System clock
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Mixers:
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0: M Audio Delta 1010
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The actual /dev/dsp# numbers may be different on your system. Check the right
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ones by looking at the output procuced by "ossinfo -a" command. With the
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above configuration you can use /dev/dsp0 to /dev/dsp4 for playback of stereo
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streams. If you play mono files the signal will be output only from the left
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channel. /dev/dsp0 to /dev/dsp3 are connected to the analog outputs while
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/dev/dsp4 is the S/PDIF output.
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The /dev/dsp5 to /dev/dsp10 device files can be used for recording. /dev/dsp5
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to /dev/dsp8 are the analog inputs. /dev/dsp11 and /dev/dsp12 are raw
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input/output device files. They will be described in detail in the "Raw I/O
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devices" section below.
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It's also possible to make OSS to create individual device files for every
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channel this creates twice as many device files than the default setting. To
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do this just append envy24_skipdevs=1 to the oss_envy24.conf file. This is useful
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only if you are working on mono rather than stereo signals. However please
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note that setting envy24_skipdevs=1 does _NOT_ lock the device files to one
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channel mode, the application can still set them to stereo or multi channel
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mode if it likes.
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It is possible to set all device files to mono only mode by setting
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envy24_skipdevs=1 and envy24_force_mono=1. However this mode disables stereo
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and multi channel usage for all devices so in general it should not be used.
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.SH
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By default the driver will create output devices before the input ones. By
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setting envy24_swapdevs=1 in oss_envy24.conf you can ask OSS to create the device
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files in opposite order i.e. input device files before the output ones. This
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may be useful when using RealProducer.
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As a workaround to a bug in RealProducer you also need to create some dummy
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mixer devices by defining envy24_realencoder_hack=1 in oss_envy24.conf. Without
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these extra mixer devices RealProducer will not be able to access other than
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the first input device.
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.SH DEVICE MANAGEMENT
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By default OSS creates a large number of device files for each envy24 card.
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This may be a problem when multiple cards need to be used in the same system.
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Adding the envy24_devmask option to oss_envy24.conf should help
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in most cases because it removes the devices that are actually not needed in
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the system.
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The envy24_devmask number is the SUM of the following values:
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1: Create primary (analog/ADAT/TDIF) outputs.
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2: Create primary (analog/ADAT/TDIF) inputs.
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4: Create S/PDIF outputs.
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8: Create S/PDIF inputs.
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16: Create monitor input device.
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32: Create the raw input and output devices.
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For example envy24_devmask=12 (4+8) creates only the S/PDIF devices.
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To enable all possible (current or future) device files set envy24_devmask
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to 65535 (default).
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If possible make your application to open the right device file
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(/dev/dsp0 to /dev/dsp10) explicitly. It's also possible to use the
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default devicefile (/dev/dsp) since OSS now supports automatic device
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allocation (it opens the first available input or output devicefile
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depending on the open mode).
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The channel allocation mechanism between device files is very flexible.
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Even there is a device file for every stereo pair (or a mono channel)
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it's possible to use any of the device file to access multiple channels.
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For example an application can open /dev/dsp0 and set the number of
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channels to 10. In this way the application can play all 10 channels
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(or any number between 1 and 10) simultaneously (the samples will be
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interleaved).
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There is simple automatic syncstart feature when using multiple
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applications at the same time. Playback will not start before all
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currently open devices files have started the playback operation.
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The same mechanism works for recording (recording and playback
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operations are fully independent).
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The Envy24 driver supports 8, 16 and 24/32 bit sample formats.
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.SH SAMPLING RATE
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Envy24 based cards are multi channel devices and all the channels share the
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same sampling rate. For this reason the sampling rate is normally locked to the
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value selected using ossmix. However OSS supports some other methods for
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changing the sampling rate. There are four ways to change the sampling rate.
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BASIC METHOD:
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Since all input and output channels of Envy24 work at the same sampling rate
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it's not possible for the applications to select the rate themselves. Instead
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the sampling rate is always locked to the currently selected rate. This rate
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selection can be changed using the ossmix program shipped with OSS.
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For example:
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ossmix envy24.rate 48000
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sets the sampling rate to 48000 Hz (default). The possible alternatives are
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- 8000
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- 9600
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- 11025
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- 12000
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- 16000
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- 22050
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- 24000
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- 32000
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- 44100
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- 48000
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- 88200
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- 96000
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When using S/PDIF inputs/outputs only the sampling rates 32000, 44100, 48000, 88200 or 96000 should be used.
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.SH EXTERNAL SYNC
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It's possible to lock the sampling rate to the S/PDIF or world clock inputs
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by setting the envy24.sync setting in ossmix to SPDIF or WCLOCK. However
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the envy24.rate setting should be set manually to match the rate being used
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(there is no autodetection for that).
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.SH NONLOCKED METHOD
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It's also possible to turn the envy24.ratelock setting to OFF using ossmix.
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After that the first application that opens the device can change the sampling
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rate. However great care should be taken that this application gets the
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recording/playback process fully started before any of the other
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applications open their devices. Otherwise all devices will be locked to 8Khz.
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Also keep in mind that subsequent applications will be forced to use the
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sampling rate set by the first one.
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.SH SOFTWARE SRC
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OSS contains a very high quality software based sample rate converter.
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It can be enabled by setting envy24.src to ON using ossmix.
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After that OSS can do on-fly sample rate conversions between the actual
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"hardware" sampling rate and the sampling rates used by the applications. In
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this way every application may use different sampling rate. However there are
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some drawbacks in this method:
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.IP \(bu 3
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The hardware rate needs to be 44100, 48000 or 96000 Hz.
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.IP \(bu 3
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The software SRC algorithm consumes some CPU time (1% to 20% per audio
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channel depending on the CPU speed and sampling rates). For this reason this
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method may be useless in multi channel use with anything else but the fastest
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high end CPUs.
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.IP \(bu 3
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Only mono and stereo (1 or 2 channel) streams are supported.
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.IP \(bu 3
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The SRC algorithm does cause minor artifacts to the sound (SNR is around 60 dB).
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.SH RAW IO DEVICES
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These device files provide an alternative way to access Envy24 based devices.
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With these devices it's possible to bypass the dual buffering required by the
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"normal" input-output device files described above. This means that also the
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mmap() feature is available and that the latencies caused by dual buffering
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are gone. So these device files work much like "ordinary" soundcards. However
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due to multi channel professional nature of the Envy24 chip there are some very
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fundamental differences. This means that these device files can only be used
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with applications that are aware of them.
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The differences from normal audio device files are:
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1. The sample format will always be 32 bit msb aligned (AFMT_S32_LE). Trying to
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use any other sample format will cause unexpected results.
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2. Number of channels is fixed and cannot be changed. The output device has
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always 10 channels (0 to 7 are analog outputs and 8 to 9 are the digital
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outputs). This assignment will be used even with cards that don't support
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digital (or analog) outputs at all. If the actual hardware being used has
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less channels the unused ones will be discarded (however they will be fed to
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the on board monitor mixer).
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The input device is fixed to 12 channels. Channels 0 to 7 are analog inputs.
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Channels 8 to 9 are digital inputs. Channels 10 and 11 are for the result
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signal from the on board monitor mixer.
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.SH DIGITAL MONITOR MIXER
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All Envy24 based cards have a built in monitor mixer. It can be used to mix
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allinput and output signals together. The result can be recorded from the
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"input from mon mixer" device (device 10 in the /dev/sndstat example above).
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The monitor mix signal can also be routed to any of the outputs (including
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S/PDIF and the "consumer" AC97 output of Terratec EWS88MT/D and any other card
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that support s it).
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The settings in the gain.* group of ossmix are used to change the levels of all
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inputs and outputs in the digital monitor mixer. The possible values are
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between 0 (minimum) and 144 (maximum).
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OSS permits using all 10 possible output channels of the monitor mixer even
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with cards that have less physical outputs. These "virtual" outputs are only
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sent to the monitor mixer and their signal is only present in the monitor mixer
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output. To enable these "virtual" channels set the envy24_virtualout parameter
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to 1 in oss_envy24.conf. This option has no effect with Delta1010, EWS88MT and
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other cards that have 10 "real" outputs.
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.SH SYNC SOURCE
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On cards with S/PDIF and/or World Clock inputs it's possible to select the
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sync source using
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ossmix envy24.sync
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The possible choices are:
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.IP \(bu 3
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INTERNAL: Use the internal sampling rate as defined by envy24.rate
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.IP \(bu 3
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SPDIF: Use the S/PDIF input as the clock source. The envy24.rate setting
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must be set manually to match the actual input sampling rate.
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.IP \(bu 3
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WCLOCK: Like SPDIF but uses the world clock input signal (Delta 1010 only).
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.SH OUTPUT ROUTINGS
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Output routing of output ports can be changed by changing the route.* settings
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using ossmix. The possible choices are:
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.IP \(bu 3
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DMA: Playback from the associated /dev/dsp# device.
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.IP \(bu 3
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MONITOR: Output of the digital mixer (only out1/2 and S/PDIF).
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.IP \(bu 3
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IN1/2 to IN9/10 or IN1 to IN10: Loopback from the analog inputs
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.IP \(bu 3
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SPDIFL or SPDIFR or SPDIF: Loopback from the S/PDIF input.
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.SH PEAK METERS
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Envy24 based cards have peak meters for the input and output ports of the
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digital monitor mixer. ossmix can show these values under the peak.* group
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(these settings are read only). The values are between 0 (minimum) and 255
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(maximum). At this moment the only applications that supports these peak meters
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are ossmix and ossxmix.
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.SH AUDIO LATENCY
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IDE disk and CD-ROM drives may cause some interrupt latency problems which
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may cause dropouts in recording/playback with Envy24 based cards. For this
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reason ensure that DMA is turned on for the disk drive.
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Another method to solve the dropout problems is making the fragment size used
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by the driver longer. This can be done by adding envy24_nfrags=N to the
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oss_envy24.conf file. By default N is 16. Values 2, 4 or 8 make the fragments
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longer which should cure the dropout problems. However this may cause
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latency problems with some applications. Values 32 and 64 decrease the
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latencies but may cause dropouts with IDE.
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.SH OPTIONS
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.IP \(bu 3
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envy24_skipdevs: It's also possible to make OSS to create individual device
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files for every channel. This creates twice as many device files than the
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default setting.
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Values: 1, 0 Default: 0
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.IP \(bu 3
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envy24_swapdevs: By default the driver will create output devices before the
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input ones. You can force the input devices to be configured before output
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devices.
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Values: 1, 0 Default: 0
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.IP \(bu 3
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envy24_realencoder_hack: RealProducer wants to see a mixer device in
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/dev/mixer. This option allows you to define a dummy /dev/mixer mixer device.
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Envy24 Mixer device doesn't provide any consumer level soundcard compatibility
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so this dummy mixer fools RealProducer into thinking it's running on a consumer
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soundcard like SB Pro or SBLive.
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Values: 1, 0 Default: 0
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.IP \(bu 3
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envy24_gain_sliders: With some devices it's possible to change the gain
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controllers to be continuous sliders instead of just enumerated ones.
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Values: 1, 0 Default: 0
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.IP \(bu 3
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envy24_nfrags: To solve the dropout problems make the fragment size used by
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the driver longer. By default is 16. Values 2, 4 or 8 make the fragments longer
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which should cure the dropout problems. However this may cause latency problems
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with some applications. Values 32 and 64 decrease the latencies but may cause
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dropouts with IDE drives.
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Values: 2-64 Default: 16
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.IP \(bu 3
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envy24_virtualout: OSS permits using all 10 possible output channels of the
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monitor mixer even with cards that have less physical outputs. These "virtual"
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outputs are only sent to the monitor mixer and their signal is only present in
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the monitor mixer output. This has no effect for Delta1010 or Terratec EWS88MT.
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Values: 1, 0 Default: 0
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.IP \(bu 3
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envy24_force_mono: It is possible to set all device files to mono only mode
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by setting envy24_skipdevs=1 and envy24_force_mono=1. However this mode
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disables stereo and multi channel usage for all devices so in general it should
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not be used.
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Values: 1, 0 Default: 0
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.SH FILES
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/usr/lib/oss/conf/oss_envy24.conf Device configuration file
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.SH AUTHOR
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4Front Technologies
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