2.Specifications

The specifications of this library are shown in the table below.

Table 2.1 Library specifications

Item	specification	remarks
sampling frequency	up to 44.1kHz
Quantization bit number	8bit,16bit
Number of channels	monaural, stereo
file format	AIFF format Specified ADPCM format1 ) CD-ROM XA Audio format2 ) SaturnPCM format 3)	PCM uncompressed ADPCM compression ADPCM compression PCM uncompressed
CD-ROM format	For CD-ROM XA Audio format Mode2Form2, Otherwise Model or Mode2Form1
play mode	Memory playback mode (playback data on memory) File playback mode (read and play from CD) Stream playback mode (read and play from CD)	Four) Use file system Use stream system
function	Branch playback, continuous playback, loop playback5 ) Multi playback (up to 4 videos can be played simultaneously) Specify pause, pause, volume/pan	Only one ADPCM
Continuous playback time	up to 1 hour
Library used	file system, stream system, DMA library, ADPCM decompression library	Specify to link these at the same time as this library 6)
CPU timer Use of (FRT)	This library uses the CPU timer (FRT) with a frequency division number of 128. is. Initialize it only once within the PCM_Init function. A user FRT initialization and settings on the side are prohibited.	It is possible to obtain the value using TIM_FRT_GET_16 etc.
Using DMA	CPU-DMA (channel 1), or Uses SCU-DMA (channel 0).	7)
sound driver	The user must perform initial settings (68000 reset, sound driver transfer, etc.) in advance. This library issues commands related to PCM playback (PCM start, stop, parameter change). All commands to the sound driver are issued using the sound I/F library .	See " SEGA Saturn Sound Driver 2.20 Programmer's Guide ".
Allocating a buffer	Work buffer: Work structure (approx. 530 bytes) Extended work buffer: 2048byte Ring buffer: Sector size *10 bytes ~ PCM buffer: 4096*2~4096*4sample/1ch Pose processing work: 4096 samples ~ PCM buffer size	fixed size 8) Only for SaturnPCM format 9) Ten) Required only when performing a pose
CPU load |After playback starts| |Task function| |CPU occupancy| 11)	PCM uncompressed 44kHz stereo 16bit: 10% PCM uncompressed 44kHz monaural 16bit: 6% ADPCM compression 44kHz stereo 16bit: 33% ADPCM compression 37.8kHz stereo 16bit: 29% ADPCM compression 22kHz stereo 16bit: 17% ADPCM compression 11kHz stereo 16bit: 8% ADPCM compression 11kHz monaural 16bit: 4%	This is the value measured for all processing times, including data transfer from CD to work memory to sound memory, including decompression processing in the case of ADPCM.
PCM_Task(Task function) specifications	- Call at a frequency equal to or higher than the V blank interrupt frequency (1 time/16ms). ・Maximum processing time for one task function PCM uncompressed stereo 16bit: 15ms PCM uncompressed monaural 16bit: 8ms ADPCM compression stereo 16bit: 34ms ADPCM compression monaural 16bit: 15ms	If you call it with appropriate frequency, the long processing time will only be once every few times.

1)

The specified ADPCM format corresponds to data output by CRC Research Institute's Audio Starck tool (AIFF → ADPCM conversion tool).

2)

CD-ROM XA Audio has 16bit PCM data compressed to 4bit ADPCM and has the following formats. For details, please refer to the CD-ROM XA standard document.

• B mode (37.8kHz) stereo/monaural
• C mode (18.9kHz) stereo/monaural

When playing CD-ROM XA Audio, only stream playback mode is available.

3) SaturnPCM format

SaturnPCM format files are created by converting AIFF files using the conversion tool AIF2SAP.
The characteristics of the SaturnPCM format are as follows.

• Data is transferred directly from the CD block to the sound memory using SCU-DMA, reducing the CPU load.
• Since no ring buffer is required, there is no pressure on main memory.

*For details on how to use the SaturnPCM format, please refer to " 4.Programming Notes/Section (8) ".

Four)

There are two ways to use memory playback mode.

Resident playback:

Play small files with the entire file preloaded into memory

Sequential supply regeneration:

The data read by the user from the CD is sequentially supplied to the ring buffer and played back.

Five)

The loop playback function can only be used in memory playback mode (resident playback method) or file playback mode.

6)

Some functions may not be linked depending on the functions you use.
The ADPCM decompression library will not be linked unless you declare PCM_DeclareUseAdpcm to use ADPCM.
In memory playback mode, file systems and stream systems are not linked.
In file playback mode, the stream system is not linked.
In stream playback mode, both the file system and stream system are linked.

7)

The default setting is to transfer data from the CD block to the ring buffer using CPU-DMA (except for the SaturnPCM format. In the SaturnPCM format, the default setting is to use SCU-DMA to transfer data from the CD block to the sound memory. Masu).
The function PCM_SetTrModeCd allows you to specify program transfer, CPU-DMA, or SCU-DMA.

8)

Extended work buffers are only required when using the SaturnPCM format.
The SaturnPCM format uses an extended work buffer but does not require a ring buffer.

9)

When a user supplies data to the ring buffer during branch playback or memory playback, making the ring buffer large reduces the risk of interruptions.
The larger the value, the higher the safety for PCM playback, but the disadvantage is that the processing time for one task may be somewhat unstable.
If the entire file is prepared in memory for memory playback, specify its address and file size. In this case, it does not need to be an integral multiple of the sector size.

Ten)

PCM buffer size of 4096*2 [sample/1ch] is sufficient unless there is a special reason.
By increasing this value, playback may not be disrupted even if the task function cannot be called at the specified frequency.

11)

The definition of CPU load (CPU occupancy rate of the task function after playback starts) is shown below.

R＝(100×Ttask)/Tplay
┌                                                                                  ┐
│ R    :CPU load[%]                                                                │
│ Ttask:Total processing time of PCM_Task from start of playback to end of playback│
│ Tplay:Playing time                                                               │
└                                                                                  ┘