Apple Newton Utilities User's Guide download pdf (Page 561)

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CHAPTER 14

Sound

Using Sound 14-7

Synchronous and Asynchronous Sound 14

When a sound is played asynchronously, the playback can be intermixed with other

tasks because the system does not wait for the sound to ﬁnish before beginning

another task (such as updating the user interface, allowing user feedback; for

example with buttons, or playing a subsequent sound).

When playback must be allowed to complete, use the

PlaySoundSync,

PlaySoundAtVolume, or PlaySoundIrregardless to guarantee

uninterrupted playback. Synchronous playback is generally preferred unless the

sound is so long as to be tedious or the application requires a high degree of

responsiveness to the user. The NewtonScript interpreter can do nothing else until

it completes synchronous playback.

Both approaches have beneﬁts and drawbacks: synchronous playback can block

other NewtonScript code from running when it’s inconvenient to do so; on the

other hand, asynchronous playback is never guaranteed to complete. Your use of

synchronous or asynchronous sound playback depends on your application’s needs.

Differences Between Synchronous Asynchronous Playback 14

The following code example demonstrates the difference between asynchronous

playback and synchronous playback. To hear the demonstration of the two types

of sound playback, type following code example into the Inspector as it is shown

here, select all of these lines, and press Enter:

print ("Synchronous sound demo");

call func()

begin

for i := 0 to 20 do

PlaySoundSync(ROM_simplebeep);

end with();

print ("Async sound demo");

call func()

begin

for i := 0 to 20 do

PlaySoundSync(ROM_simplebeep);

end with();

The synchronous sound playback example plays the ROM_simplebeep sound

twenty times; the sound plays its entire length each time. Twenty repetitions may

seem a bit laborious until you hear how quickly the same calls are made in

asynchronous mode.

Note that the asynchronous version can call the sound chip so fast that the sound

does not have enough time to ﬁnish playing; as a result, part of the playback is

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