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

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