Newton Developer Technical Information: Newton Programmer's Guide: 2.1 OS Addendum /

Chapter 7 - Sound / About Sound

Devices and Channels

The Newton 2.1 OS now supports multiple output devices for playback and multiple input devices for recording. The system uses a default output device which can be overridden by the sound channel. The system also uses a default input device which can similarly be overridden by the channel.

Despite this flexibility, current hardware cannot send two simultaneous sounds to different devices: all concurrent or overlapping output must go to the same device(s). This means that if you have a sound playing on the external speaker, and you request a sound on the internal speaker, it is routed to the external speaker instead. The same is true of input: all simultaneously active input channels have the same source.

The number of simultaneous sounds that can be played is limited by the processing power of the CPU, the codecs in use, and memory constraints. On the eMate 300 and MessagePad 2000, the number is about 4, depending on the exact nature of the sounds being played.

The Newton 2.1 OS supports the following output devices:

 kDefaultDevice    0x00  // default output device

kInternalSpeaker  0x01  // the internal speaker
 kLineOut          0x08  // line out on the interconnect

and the following input devices:

 kDefaultDevice    0x00  // default input device

kInternalMic      0x04  // the internal microphone
 kLineIn           0x10  // line in on the interconnect bus

Notice that each device is represented by a single bit, so that the devices can theoretically be OR'ed together. In the 2.1 OS, however, more than one input or output device at a time is not supported.

It is possible to have multiple recording sessions running simultaneously, if you want to record the same input on multiple channels.