Alofi(1)

NAME
Alofi - a network-transparent audio server for LoFi

SYNOPSIS

The AF audio server is a network transparent system developed at Digital CRL for using LoFi audio hardware in a distributed environment.

DESCRIPTION

Alofi is an AF server with LoFi/DECaudio device dependent support.

STARTING UP
Alofi [:portOffset] [options] &

OPTIONS

-help

    Use the help switch to determine device independent arguments.

-device device

    Specifies the name of the LoFi audio device. If this switch is not used, the Alofi audio server will default to the device specified by the AUDIO_DEVICE environment variable or the devlofi device. (In general, devlofi is a symbolic link to the devlofi0 device special file.)

-ukernel lodfile

    Specifies an alternate DSP56001 absolute lodfile. If ukernel is not specified, the server checks for the AF_UKERNEL environment variable. If neither the switch nor the AF_UKERNEL environment is used, the server looks for the path DIR/main.lod (Or DIR/mainteleport.lod in -teleport mode) where DIR is the LODPATH environment variable if it exists, otherise it is the config variable LODDIR.

-pcoeff coeff_file

    Specifies an alternate set of X filter coefficients for the primary/phone CODEC. coeff_file should be an ASCII file containing eight lines with two bytes per line representing the X filter coefficients for the AMD79C30A CODEC. Here are the contents of an example file containing the default coefficients used on LoFi's telephone CODEC.
      94 0F
      C2 AC
      94 FF
      22 AB
      36 EA
      4A B2
      A4 E2
      BC BA

-teleport

    When this switch is specified, the operation of the hifi parts of the server are customized to work well with the Ariel Teleport DSP port to telephone interface. In this mode, device 2 is a 16 bit mono path to Line 1 of the Teleport and device 3 is a 16 bit mono path to Line 2 of the Teleport. On device 2, the passthrough mode controls the "line" or "local" setting of the local telephone set. Device 2 also provides two "inputs". Input 0 connects the interface to the telephone line, while Input 1 connects the device to the Teleport local battery circuit. Along with -teleport, you must specify "-mode ext" "-hrate xxx" and "-dspc xxx".

    The Teleport mode replaces the low two client data bits on output with inband signalling to the Teleport. On input, the low two bits are inband signalling from the Teleport, which are observed, but not changed by the server.

-nohifi

    Disables HiFi support (devices 2, 3, and 4).

-daa_gain {0,1}

    Sets the state of the telephone DAA's gain control bit. Setting the bit to 1 (default) disables the power limiting circuitry in the DAA. Setting the bit to 0 enables the automatic power limiter.

-mode {int,ext}

    Sets the hi-fi operating mode: int selects the internal stereo DAC (44.1 kHz, two-channel output). ext selects an external device connected to the DSP port. NOTE: make sure the switch on the back of the distribution box is set to match the operating mode. Defaults to int.

-hrate <#>

    Informs the server of the hi-fi sample rate (in samples per second). This option does not set the rate for the hi-fi hardware. The internal DAC runs at 44100 samples per second. External devices may have fixed sample rates, be configurable with panel switches, or may be software configurable (see the -dspc parameter below); consult the device's manual for details. Defaults to 44100.

-dspc <#>

    Specifies a 3-bit DSP port value that sets the sample rate for some hi-fi devices; consult the device's manual for details. Only valid when the external operating mode is selected.

AUDIO DEVICES

The Alofi audio server presents five audio devices to client applications. These audio devices are the 8KHz mu-law telephone CODEC, the 8KHz local audio CODEC, left and right stereo HiFi device, mono HiFi left channel device, and finally the mono HiFi right channel device. These audio devices have device numbers of 0 to 4. In Teleport mode, there are 4 devices, numbered 0 to 3.

CONNECTION NAME

From the user's prospective, every AF server has an audio connection of the form:

hostname:portOffset

This information is used by the application to determine how it should connect to the server.

hostname
    The hostname specifies the name of the machine to which the audio device is physically connected.

portOffset
    The portOffset is used to identify the audio server's port on hostname. For example, to simultaneously run two audio servers on a given host, you might select 0 or 1 for portOffset.

If the connection name to an audio server is not specified, then the environment variables AUDIOFILE or DISPLAY will be used.

ACCESS CONTROL
The sample server provides two types of access control: an authorization protocol which provides a list of ``magic cookies'' clients can send to request access, and a list of hosts from which connections are always accepted.

EXAMPLES

Alofi has been used with the following three devices: the Ariel ProPort Model 656, the Ariel Teleport Model 214, the Ariel DM-N Digital Microphone, and the Applied Speech Technologies A/D16.

A "-mode ext" option selects external operation (disabling the DECaudio's built-in stereo DAC). The "-dspc #" option sets bits on the DSP port to set the external device's sample rate in some device specific way. The "-hrate #" informs the server of the sample rate (the actual sample rate is usually set by the external device). Ariel DM-N Digital Microphone settings:
        5.5 kHz: Alofi -mode ext -dspc 3 -hrate 5500
        11.02 kHz: Alofi -mode ext -dspc 2 -hrate 11020
        22.05 kHz: Alofi -mode ext -dspc 1 -hrate 22050
        44.1 kHz: Alofi -mode ext -dspc 7 -hrate 44100 Ariel ProPort Model 656 settings:
        8 kHz: Alofi -mode ext -dspc 6 -hrate 8000
        11.025 kHz: Alofi -mode ext -dspc 5 -hrate 11025
        16 kHz: Alofi -mode ext -dspc 4 -hrate 16000
        32 kHz: Alofi -mode ext -dspc 3 -hrate 32000
        44.1 kHz: Alofi -mode ext -dspc 2 -hrate 44100
        48 kHz: Alofi -mode ext -dspc 1 -hrate 48000 Applied Speech Technologies, A/D16: (fixed single channel, 16 kHz input)
        16 kHz: Alofi -mode ext -hrate 16000 Ariel Teleport Model 214 settings:
        7.2 KHz: Alofi -teleport -mode ext -dspc 2 -hrate 7200
        8.0 KHz: Alofi -teleport -mode ext -dspc 1 -hrate 8000
        9.6 KHz: Alofi -teleport -mode ext -dspc 0 -hrate 9600

BUGS
DECaudio's built-in DAC will not work if there is an external device plugged into the DSP port (regardless of the switch setting).

If you encounter a repeatable bug, please submit a problem report to () and include the source code if possible.

SEE ALSO

AF(1), Aaxp(1), Amaxine(1), Alofi(1), Ajv(1), Amsb(1), Aj300(1), aplay(1), arecord(1), apass(1), aset(1), abrowse(1), afft(1), ahost(1), aphone(1), aprop(1), ahs(1), axset(1), xpow(1), afxctl(1), aname2num(1), alsatoms(1), aevents(1), abob(1)

COPYRIGHT

See the COPYRIGHTS file.

Copyright 1991-1994, Digital Equipment Corporation and the Massachusetts Institute of Technology.

AUTHORS
Digital Cambridge Research Lab