Chapter 3 Sound playback method

3.1 Sound types

There are the following three methods for sound. In addition, there are advantages and disadvantages as shown in the table below, so please select the optimal playback method that matches the content of the game and each scene.

1. Sequence playback
2. PCM stream playback
3. CD-DA playback

Sequence playback


How to pronounce	Unzip sequence data using sound data (waveform data) in the sound memory as a sound source This is a way to play.
Features	How to treat waveform data as a sound source (single instrument) and Saturn itself as a multi sound source instrument > Law.
Advantages	・ Since the song data is small, you can have many songs. -Easy to change and modify songs. -Real-time tempo change is possible. -No need for CD access. -Main only issues a request. (The sound driver controls everything)
Disadvantages	There is a restriction of 4Mbit (512KB) on the waveform capacity that can be held at once.

PCM stream playback


Sound generation method	Loop playback of waveform data and transfer the next waveform data to the end of the sound Repeat to continuously play back long waveform data.
Features	This is a method to play back the long waveform data recorded in advance. However, the waveform data must be transferred so that the sound is not interrupted.
Advantages	-Long waveform data exceeding 4M bits can be played. ・ Various playback patterns can be edited with a special transfer mechanism. (Editing and synthesis are possible) -Data width can be selected from 8 bits / 16 bits, and the frequency can be changed freely. (Memory efficiency is good and the pitch can be changed during recording and playback) -Multiple channels can be played simultaneously.
Disadvantages	Transfer of waveform data puts a considerable load on the main system and the sound CPU.