Detailed Description

sc68 audio mixer provides functions for computing audio data PCM.

Almost all functions work on 16 bit stereo PCM. Some functions require signed input to work properly. All functions allow to change PCM sign. Functions that require signed input perform a double sign change operation which allow to have any kind of input PCM.

Internaly PCM are read as 32bit integer. This implies that buffer must be properly aligned (depending on the architecture). Left channel is stored the less signifiant 16 bit and right the most signifiant 16 bit. Ensure the audio device use the same byte order.

Constants for PCM sign transformation.

#define MIXER68_SAME_SIGN   0x00000000

No channel.

#define MIXER68_CHANGE_LEFT_CHANNEL_SIGN   0x00008000

Left channel.

#define MIXER68_CHANGE_RIGHT_CHANNEL_SIGN   0x80000000

Right channel.

#define MIXER68_CHANGE_SIGN   0x80008000

Both channels.

Functions

void SC68mixer_stereo_16_LR (u32 *dest, u32 *src, int nb, const u32 sign)

Copy 16-bit-stereo PCM with optionnal sign change.

void SC68mixer_stereo_16_RL (u32 *dest, u32 *src, int nb, const u32 sign)

Copy 16-bit-stereo PCM with channel swapping and optionnal sign change.

void SC68mixer_stereo_FL_LR (float *dest, u32 *src, int nb, const u32 sign, const float norm)

Copy 16-bit-stereo PCM into normalized float-stereo (-norm..+norm).

void SC68mixer_dup_L_to_R (u32 *dest, u32 *src, int nb, const u32 sign)

Copy left channel of 16-bit stereo PCM into L/R channels with optionnal sign change.

void SC68mixer_dup_R_to_L (u32 *dest, u32 *src, int nb, const u32 sign)

Copy right channel of 16-bit stereo PCM into L/R channels with optionnal sign change.

void SC68mixer_blend_LR (u32 *dest, u32 *src, int nb, int factor, const u32 sign_r, const u32 sign_w)

Copy 16-bit-stereo PCM with L/R blending and optionnal sign change.

void SC68mixer_mult_LR (u32 *dest, u32 *src, int nb, const int ml, const int mr, const u32 sign_r, const u32 sign_w)

Copy 16-bit-stereo PCM with L/R amplitude factor and optionnal sign change.

void SC68mixer_fill (u32 *dest, int nb, const u32 sign)

Fill 16-bit-stereo buffer with sign value (RRRRLLLL).

Function Documentation

void SC68mixer_stereo_16_LR ( u32 * dest,

u32 * src,

int nb,

const u32 sign

)

Copy 16-bit-stereo PCM with optionnal sign change.

Parameters:

dest Destination PCM buffer

src Source PCM buffer (can be same as dest).

nb Number of PCM

sign Sign transformation.

void SC68mixer_stereo_16_RL ( u32 * dest,

u32 * src,

int nb,

const u32 sign

)

Copy 16-bit-stereo PCM with channel swapping and optionnal sign change.

Note:
Sign change occurs after channel swapping.

Parameters:

dest Destination PCM buffer

src Source PCM buffer (can be same as dest).

nb Number of PCM

sign Sign transformation.

void SC68mixer_stereo_FL_LR ( float * dest,

u32 * src,

int nb,

const u32 sign,

const float norm

)

Copy 16-bit-stereo PCM into normalized float-stereo (-norm..+norm).

Note:
Sign change occurs before float transformation.

Warning:
PCM are assumed to be signed after sign transform.

Parameters:

dest Destination PCM buffer

src Source PCM buffer (can be same as dest).

nb Number of PCM

sign Sign transformation.

norm float absolute range (normalization).

Note:
Minus norm causes a sign/phase inversion.

void SC68mixer_dup_L_to_R ( u32 * dest,

u32 * src,

int nb,

const u32 sign

)

Copy left channel of 16-bit stereo PCM into L/R channels with optionnal sign change.

Parameters:

dest Destination PCM buffer

src Source PCM buffer (can be same as dest).

nb Number of PCM

sign Sign transformation.

void SC68mixer_dup_R_to_L ( u32 * dest,

u32 * src,

int nb,

const u32 sign

)

Copy right channel of 16-bit stereo PCM into L/R channels with optionnal sign change.

Parameters:

dest Destination PCM buffer

src Source PCM buffer (can be same as dest).

nb Number of PCM

sign Sign transformation.

void SC68mixer_blend_LR ( u32 * dest,

u32 * src,

int nb,

int factor,

const u32 sign_r,

const u32 sign_w

)

Copy 16-bit-stereo PCM with L/R blending and optionnal sign change.
This function performs following transformations in this order :

Read 32 bit value from src.
Apply sign_r transformation; it is a bitwise EOR.
Apply blending (here PCM are asuumed to be signed).
Apply sign_w transformation; it is a bitwise EOR too.
Store 32 bit value.

Warning:
As the blending occurs on signed PCM the sign_r and the sign_w must be setted properly.

Parameters:

dest Destination PCM buffer

src Source PCM buffer (can be same as dest).

nb Number of PCM

factor Blending factor from [0..65536].

0, blend nothing.
65536, Swap L/R.
other value, linear blending.

sign_r sign transform for input PCM.

sign_w sign transform for output PCM.

void SC68mixer_mult_LR ( u32 * dest,

u32 * src,

int nb,

const int ml,

const int mr,

const u32 sign_r,

const u32 sign_w

)

Copy 16-bit-stereo PCM with L/R amplitude factor and optionnal sign change.
This function performs following transformations in this order :

Read 32 bit value from src.
Apply sign_r transformation; it is a bitwise EOR.
Apply signed modulation to both channels.
Apply sign_w transformation; it is a bitwise EOR too.
Store 32 bit value.

Warning:
As the modulation occurs on signed PCM the sign_r and the sign_w must be setted properly.

Note:
Amplitude factors (ml and mr) can be minus to invert phase.

Parameters:

dest Destination PCM buffer

src Source PCM buffer (can be same as dest).

nb Number of PCM

ml Left channel factor from [-65536..65536].

mr Like ml but for right channel.

sign_r sign transform for input PCM.

sign_w sign transform for output PCM.

void SC68mixer_fill ( u32 * dest,

int nb,

const u32 sign

)

Fill 16-bit-stereo buffer with sign value (RRRRLLLL).

Parameters:

dest Destination PCM buffer

nb Number of PCM

sign PCM value written (right channel is MSW).

audio mixer [api68 library documentation.]

Detailed Description

Constants for PCM sign transformation.

Functions

Function Documentation

audio mixer
[api68 library documentation.]