Codecs

Codecs convert one audio format type to another format type. Typically, the conversions are performed between compressed formats and uncompressed formats in order to reduce the bandwidth requirements of transmitting the audio stream. The pluggable codec feature of Windows CE RTC utilizes codecs written to the Audio Compression Manager (ACM) interface. The ACM interface is a Microsoft-standard that, when supported by a codec, allows it to be plugged into the system.

By default, Windows CE includes the following codecs: G.711 (both A-law and mu-law encoding), GSM 610, G.722.1, and SIREN. Windows CE will also support other codecs, such as G.729 or G.723, if they are licensed and installed by the customer. Windows CE will also support your own custom codec, if it is wrapped in the ACM interface. For more information about the ACM interface, see Installing an ACM Driver.

Note   OEMs should consider the performance impact of the high bandwidth floating-point G.722.1 and SIREN codecs when selecting a default codec. If a device must emulate floating point, it is not recommended to enable any floating-point codecs on the hardware. These codecs add delays that can eventually become unacceptable.

The following illustration shows how codecs are handled within the Communications Service.

For more information, see Pluggable Codec Requirements and Installing an ACM Driver.

 Last updated on Saturday, April 10, 2004

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