SND_SetupChannelPcm

Syntax

#include <nitro/snd.h>

void SND_SetupChannelPcm(
int chNo,
SNDWaveFormat format,
const void* dataAddr,
SNDChannelLoop loop,
int loopStart,
int loopLen,
int volume,
SNDChannelDataShift shift,
int timer,
int pan );

Arguments

chNo	Channel number. Takes a value between 0 and 15.
format	Format of the waveform data.
dataAddr	Starting address of the waveform data. Must have 4-byte alignment.
loop	Loop playback setting.
loopStart	Loop-start position. Expressed in units of words. Takes a value of 0 to `0xffff`.
loopLen	Length of the loop. Expressed in units of words. Takes a value of 0 to `0x3fffff`.
volume	Volume. Takes a value between 0 and 127.
shift	Data shift setting.
timer	Timer. Takes a value between 0x10 and 0xffff.
pan	Pan. Takes values in the range of 0 (left) to 64 (center) to 127 (right).

Return Values

None.

Description

Sets up channels for PCM playback.

The function sets the parameters for the channel specified by chNo. The channel must first be locked by the SND_LockChannel function. Once the parameters have been set, call the SND_StartTimer function to begin actual playback.

Choose from among these values for the waveform data format format.

Table. SNDWaveFormat

Label	Description
`SND_WAVE_FORMAT_PCM8`	8-bit PCM
`SND_WAVE_FORMAT_PCM16`	16-bit PCM
`SND_WAVE_FORMAT_ADPCM`	IMA-ADPCM

The waveform data's starting address dataAddr must have 4-byte alignment.

Choose from among these values for the loop playback setting loop.

Table. SNDChannelLoop

Label	Description
`SND_CHANNEL_LOOP_MANUAL`	Continues playing, regardless of the loop setting.
`SND_CHANNEL_LOOP_REPEAT`	When playback has reached the end of the loop (loopStart + loopLen), continues playing from the start of the loop at loopStart.
`SND_CHANNEL_LOOP_1SHOT`	When playback has reached the end of the loop (loopStart + loopLen), playback stops automatically.

The loop starting position loopStart and the loop length loopLen are specified in word units. The value is ignored when the loop playback setting loop is set to SND_CHANNEL_LOOP_MANUAL.

Choose from among these values for the data shift setting shift.

Table. SNDChannelDataShift

Label	Description
`SND_CHANNEL_DATASHIFT_NONE`	Do not perform a data shift.
`SND_CHANNEL_DATASHIFT_1BIT`	Shift data 1 bit right.
`SND_CHANNEL_DATASHIFT_2BIT`	Shift data 2 bits right.
`SND_CHANNEL_DATASHIFT_4BIT`	Shift data 4 bits right.

The timer argument specifies the number of clock ticks for outputting one sample. The number of ticks per second is approximately 16.757 MHz with SND_TIMER_CLOCK. Thus, if you want to play the waveform data without changing the pitch, and the sampling rate is rate Hz, then you calculate timer as follows.

timer = SND_TIMER_CLOCK / rate

Note

This function is an ARM7 reserved function. After this function is called, its processing occurs only after the command is issued with the SND_FlushCommand function.

If program execution must be synchronized with process completion, first use the SND_GetCurrentCommandTag function to get the command tag immediately after calling this function. Then, after the command is issued, use the command tag and call the SND_IsFinishedCommandTag or SND_WaitForCommandProc function to confirm that processing has finished or to wait for it to complete.

Revision History

2008/11/19 Corrected mistaken explanation of loop length as data length.
2005/02/17 Added precaution about ARM7 command processing.
2004/10/07 Corrected SND_CHANNEL_LOOP_REPAET to read SND_CHANNEL_LOOP_REPEAT.
2004/07/20 Initial version.