## Storage Device Driver Reference

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### Audio Control Determination

At initialization time, the CD-ROM Device Manager will issue a series of Mode Select commands with various Audio Control Parameter Pages. The Output Port Channel Select and Volume Level fields will be varied to determine the audio control capabilities of the drive. For example, an Audio Control Parameter Page is sent with volume levels different for Channel 0 and Channel 1 to determine if the drive supports independent volume levels for each channel.

If the Adapter Device Driver receives a Mode Select command with an Audio Control Parameter Page which is not supported by the drive, it should return an error with a Sense Key of 05h (Illegal Request) and the Additional Sense Code set to 26h (Invalid field in parameter list). This allows the CD-ROM Device Manager to determine the audio capabilities of the drive.