Audio Hardware Considerations (Windows CE 5.0)

For information about developing device drivers for a specific type of device, see Windows CE Drivers.

Sample rates

You must support a sample rate of 44.1 kHz. Supporting other sample rates is not required because the audio manager up-converts or down-converts other sample rates to 44.1 kHz. When the audio manager up-converts or down-converts audio, it consumes microprocessor cycles, so it is advantageous to support as many sample rates as possible. The following list shows the sample rates that Microsoft recommends supporting in the audio controller, if you support each of these sample rates, you will also qualify for the PlaysForSure™ logo:

32.0 kHz
44.1 kHz
48.0 kHz
64.0 kHz
88.2 KHz
96.0 kHz

For more information about the PlaysForSure logo requirements, see this Microsoft Web site and this Microsoft Web site.

Bits per sample

16-bits per audio sample support is required.
24-bits per audio sample support is optional.

Surround sound audio

To provide a cinema-like audio experience, Microsoft recommends supporting Dolby Digital and DTS surround sound audio. If you implement surround sound audio, your device must down-mix the multi-channel surround sound audio to stereo, and then send the output through the RCA stereo connectors.

Audio decoder

A hardware audio decoder handles audio decoding, which allows the microprocessor to handle other tasks and process other data. Offloading audio decoding to a hardware audio decoder allows for a smoother and more robust audio playback experience.

To offload audio decoding to hardware, you must implement a DirectShow DirectX Media Object (DMO) filter driver for the audio decoder. The networked media device (NMD) software provides a DirectShow DMO filter driver, but if your hardware platform has a different hardware audio decoder, you must obtain the DirectShow DMO filter driver from the manufacturer of the hardware audio decoder or from a third party.

Microsoft recommends providing a hardware audio decoder for the following audio formats:

Dolby Digital/AC3 5.1, 6.1, 7.1
DTS 5.1
MP3
MPEG-2 Advanced Audio Coding (AAC)
MPEG-4 AAC
WMA 9
WMA 9 Professional
WMA 9 Lossless
WMA 9 Voice

Audio connections

Your networked media device (NMD) must have at least one RCA stereo audio connector. This RCA stereo connector allows the audio output to connect to a TV or stereo system.

An S/PDIF audio input/output connector is recommended. The S/PDIF audio connector allows the digital audio output to be directly sent to a surround sound receiver.

A headphone stereo audio connector is optional. The headphone stereo audio connector allows the user to connect a stereo headphone to the device for private listening.

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