File syn_adpcm.h¶

FileList > audio > syn_adpcm.h

IMA/DVI ADPCM Speech and Audio Codec (Encoder & Decoder). More...

#include "../common/syn_defs.h"
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

Classes¶

Type	Name
struct	SYN_ADPCM_State IMA-ADPCM Encoder and Decoder State.

Public Functions¶

Type	Name
size_t	syn_adpcm_decode_block (SYN_ADPCM_State * state, const uint8_t * in, int16_t * out, size_t sample_count) Decode a buffer of packed 4-bit ADPCM bytes into 16-bit PCM samples.
int16_t	syn_adpcm_decode_sample (SYN_ADPCM_State * state, uint8_t nibble) Decode a single 4-bit ADPCM nibble to a 16-bit PCM sample.
size_t	syn_adpcm_encode_block (SYN_ADPCM_State * state, const int16_t * in, uint8_t * out, size_t sample_count) Encode 16-bit PCM samples into packed 4-bit ADPCM bytes.
uint8_t	syn_adpcm_encode_sample (SYN_ADPCM_State * state, int16_t sample) Encode a single 16-bit PCM sample to a 4-bit ADPCM nibble.
void	syn_adpcm_init (SYN_ADPCM_State * state) Initialize or reset an IMA-ADPCM state context.

Detailed Description¶

Implements a lightweight, zero-heap, integer-only IMA-ADPCM codec. Achieves 4:1 compression ratio (16-bit linear PCM <-> 4-bit ADPCM nibbles). Fully compatible with standard WAV IMA-ADPCM files and tools (ffmpeg, Audacity).

** **

SYN_ADPCM_State state;
syn_adpcm_init(&state);
syn_adpcm_decode_block(&state, adpcm_data, pcm_output, sample_count);

Public Functions Documentation¶

function syn_adpcm_decode_block¶

Decode a buffer of packed 4-bit ADPCM bytes into 16-bit PCM samples.

size_t syn_adpcm_decode_block (
    SYN_ADPCM_State * state,
    const uint8_t * in,
    int16_t * out,
    size_t sample_count
)

Parameters:

state State context pointer.
in Input packed ADPCM byte buffer (2 nibbles per byte, low nibble first).
out Output 16-bit PCM sample buffer.
sample_count Total number of samples to decode.

Returns:

Number of samples successfully decoded.

function syn_adpcm_decode_sample¶

Decode a single 4-bit ADPCM nibble to a 16-bit PCM sample.

int16_t syn_adpcm_decode_sample (
    SYN_ADPCM_State * state,
    uint8_t nibble
)

Parameters:

state State context pointer.
nibble 4-bit ADPCM code (lower 4 bits used).

Returns:

Decoded 16-bit PCM sample.

function syn_adpcm_encode_block¶

Encode 16-bit PCM samples into packed 4-bit ADPCM bytes.

size_t syn_adpcm_encode_block (
    SYN_ADPCM_State * state,
    const int16_t * in,
    uint8_t * out,
    size_t sample_count
)

Parameters:

state State context pointer.
in Input 16-bit PCM sample buffer.
out Output packed ADPCM byte buffer (requires at least (sample_count + 1)/2 bytes).
sample_count Number of samples to encode.

Returns:

Number of packed bytes produced.

function syn_adpcm_encode_sample¶

Encode a single 16-bit PCM sample to a 4-bit ADPCM nibble.

uint8_t syn_adpcm_encode_sample (
    SYN_ADPCM_State * state,
    int16_t sample
)

Parameters:

state State context pointer.
sample 16-bit linear PCM sample.

Returns:

Encoded 4-bit ADPCM nibble (in bits 0-3).

function syn_adpcm_init¶

Initialize or reset an IMA-ADPCM state context.

void syn_adpcm_init (
    SYN_ADPCM_State * state
)

Parameters:

state State context pointer.

The documentation for this class was generated from the following file src/syntropic/audio/syn_adpcm.h