Capturing Audio on BREW Handsets

oday's wireless handsets are veritable multimedia powerhouses; sporting more I/O options than the average desktop PC a mere decade ago. Because all users are comfortable talking to a wireless handset (it is, after all, first and foremost a phone!), having the ability to capture audio paves the way for a wide variety of applications, including voice command and speech recognition, audio note-taking, and multi-user chat and messaging in either stand-alone applications or integrated as part of a larger application. Qualcomm BREW makes it easy to capture audio, either as an audio recording you can package up, replay, and send to a remote server, or in real time by directly accessing the handset's vocoder. This article shows you both methods and arms you with the information you need to know to select which path is right for you.

Using the IMedia Interface to Capture Audio
The IMedia interface—which was covered in in the recent article "Playing Multimedia Using BREW's IMedia"—not only plays media, but can record media as well. Using the IMedia interface, you can capture audio to a file for storage, playback, and transmission to other hosts. The interface supports a variety of audio formats including PCM, although most handsets currently only support QCELP. (QCELP is a highly optimized format used by the CDMA network itself, and is very well suited for recording the human voice for playback to the human ear, but may not be suitable for other applications that require little or no compression artifacts.) By definition, you can't use the IMedia interface to directly capture audio off the microphone in real-time; to do this, you use the IVocoder interface, which is the subject of the next section.