1.3.7 Required Codecs
The DirectPlay Voice Protocol requires communication using one of the codecs listed in the following table. The codecs are opaque to the DirectPlay Voice Protocol, with the exception that in a voice session, the voice client and voice server need to use the same codec. The following table lists the codecs, the frame size used with the protocol, and the approximate amount of time (in milliseconds) that each frame represents.
|
Required codec |
Frame size (bytes) |
Frame size (milliseconds of data) |
Approximate bit rate (bits/second) |
|---|---|---|---|
|
Voxware VR12 (*) |
Variable (Max 21) |
90 |
Variable (max 1822) |
|
Voxware SC03 (*) |
40 |
100 |
3200 |
|
Voxware SC06 (*) |
80 |
100 |
6400 |
|
Truespeech (*) |
96 |
90 |
8536 |
|
Global System for Mobile Communications (GSM) (*) |
130 |
80 |
13000 |
|
Microsoft Adaptive Delta Pulse Code Modulation (MS ADPCM) (**) |
256 |
63 |
32768 |
|
Pulse Code Modulation (PCM) - 8 Kilohertz, 8-bit, and Mono (*) |
394 |
50 |
64000 |
(*) = This codec is licensed through a third party.
(**) = Microsoft Adaptive Delta Pulse Code Modulation (MS ADPCM) is included with the Microsoft Windows Development Kit (WDK). For more information about the MS ADPCM codec, see [MSDN-AUDIOFORMAT].