Installing a Wave Driver

Playback and recording of audio required by voice modems is done by the Windows Multimedia System (MMSystem), which uses digitized wave files (.WAV files). There are the two basic types of voice modem wave devices, each requiring a different interface with Unimodem/V:

• Serial wave device driver.
• Wave wrapper.

Serial port modems send and receive wave input/output data through the Windows 95 computer's communications port. SERWVDRV.DRV is used by Unimodem/V as the serial wave device driver. SERWVDRV.DRV supports the following formats:

• 4-bit Rockwell ADPCM 7200 Hz
• 4-bit IMA ADPCM 4800 Hz
• 4-bit IMA ADPCM 7200 Hz
• 4-bit IMA ADPCM 8000 Hz

Modems with a separate audio hardware interface require synchronization between the modem and audio through AT commands (to set the mode, etc.). For these modems, the wave driver wrapper performs all synchronization. It is called by MMSystem, and calls Unimodem to send any needed AT commands to the modem. After the AT commands are completed, the wave driver wrapper calls back into MMSystem, and MMSystem then calls the modem wave device. The modem wave device interfaces only to the audio hardware interface. Your modem wave driver must not directly access to the COMM port (let the wave wrapper send all AT commands to the modem).

You must decide which wave device driver to use, the serial wave device driver or the wave wrapper.

For either one to be installed, the following item must be added to an AddReg section in your modem INF file:

   HKR,, Enumerator, ,serwave.vxd
 

This item must be in every voice modem INF file, regardless of whether your voice modem uses the serial wave driver or wave wrapper to play audio. Do not change the value of this entry, it is always SERWAVE.VXD. SERWAVE.VXD has the ability to connect either type of wave device to your modem when your modem is detected.

You must also provide a wave driver INF in addition to your modem INF file. Sample INF files are in the MDK for both types of wave drivers:

• SMPSERWV.INF is a sample INF file the installs the serial wave driver.
• SMPWRAP.INF is a sample INF file that installs the wave wrapper.

When either the serial driver or wave wrapper are installed, the game-compatible device is installed automatically to ensure compatibility with Windows games. Three multimedia devices are usually installed:

• The line device, which allows audio to be recorded from and/or played to the phone line during an active call.
• The handset device, which allows audio to be recorded from and/or played to the local telephone handset. If the modem does not support a handset device, this device will not be installed.
• A game compatible device, which ensures compatibility with Windows games and other multimedia applications. Many Windows multimedia applications hard code using device 0 for their wave out device. When the serial wave device or wave wrapper is installed, it is always device 0. The game compatible device was added to the serial wave and wave wrapper devices to "pass through" calls to device 0 to the other wave driver device installed.