Level 2 Audio Requirements

The audio subsystem of a PC satisfying the Level 2 specification includes the following items:

    A CD-ROM driver with CD-DA (Red Book audio) outputs and volume control

    A 16-bit DAC with the following characteristics:

    Linear PCM (Pulse Code Modulation) sampling

    DMA or FIFO buffered transfer capability with interrupt on buffer empty

    Mandatory sample rates of 44.1, 22.05, and 11.025 kHz

    Stereo channels

    CPU bandwidth usage of 10 percent or less when outputting audio of 22.05 or 11.025 kHz sample rate, or a CPU bandwidth of 15 percent or less when outputting audio of 44.1 kHz sample rate

    A 16-bit ADC with the following characteristics:

    Linear PCM sampling

    DMA or FIFO buffered transfer capability with interrupt on buffer empty

    Mandatory sample rates of 44.1, 22.05, and 11.025 kHz

    Microphone input

    Internal synthesizer capabilities with multivoice, multitimbral, six simultaneous melody notes plus two simultaneous percussive notes

    Internal mixing with the following capabilities:

    Can combine three audio sources and present the output as a stereo, line-level audio signal at the back panel

    Mixing sources are CD Red Book audio, synthesizer, and DAC

    Each mixing source has 3-bit volume control with a logarithmic taper