SGS SRC ALGORITHM USER GUIDE¶

REVISION HISTORY¶

Revision No.	Description	Date
1.0	Initial release	09/12/2020
1.1	Modified API	10/15/2020
1.2	Added new low pass filter	06/01/2021
1.21	Added some details about point number	08/18/2022
1.22	Added some details about channel number	12/15/2022
1.3	Add 24kHz sample rate	12/20/2023
1.31	Add Json API description	12/09/2024
1.32	Update file description and copyright	04/24/2025
1.33	Remove copyright	05/14/2025

1. Overview¶

1.1. Algorithm Description¶

SRC (short for Sample Rate Conversion) is used to convert the sampling frequency from audio stream to obtain different sampling frequencies audio streams.

1.2. Keyword¶

Sampling frequency: The number of samples sampled from a continuous signal per second.

1.3. Note¶

In order to facilitate debugging and confirm the effect of the algorithm, the user application needs to implement replacement algorithm parameter and grab audio data.

2. API Reference¶

2.1. API List¶

API name	Features
IaaSrc_GetBufferSize	Get the memory size required for Src algorithm running
IaaSrc_Init	Initialize Src algorithm
IaaSrc_Run	Src algorithm processing
IaaSrc_Release	Release Src algorithm resources
IaaSrc_GetJsonFileSize	SRC get size of json file
IaaSrc_StructReadFromJson	Set json parameter into SRC structure.

2.2. IaaSrc_GetBufferSize¶

Features

Get the memory size required for Src algorithm running.

Syntax

unsigned int IaaSrc_GetBufferSize(SrcConversionMode mode);

Parameters

Parameter Name Description Input/Output

SrcConversionMode mode Sample rate conversion type Input
Return value

Return value is the memory size required for Src algorithm running.
Dependency
- Header: AudioSRCProcess.h
- Library: libSRC_LINUX.so/ libSRC_LINUX.a
Note

This interface only returns the required memory size. To apply and release the memory, you need to use other APIs.
Example

Please refer to IaaSrc_Run example.

2.3. IaaSrc_Init¶

Features

Initialize Src algorithm.

Syntax

SRC_HANDLE IaaSrc_Init(char *workingBufferAddress,
SRCStructProcess *src_struct);

Parameters

Parameter Name Description Input/Output

working_buffer_address Memory address used by Src algorithm Input

SRCStructProcess Src algorithm initialization structure pointer Input
Return value

Return value Result

Not NULL Successful

NULL Failed
Dependency
- Header: AudioSRCProcess.h
- Library: libSRC_LINUX.so/ libSRC_LINUX.a
Example

Please refer to IaaSrc_Run example.

2.4. IaaSrc_Run¶

Features

Src algorithm processing.

Syntax

ALGO_SRC_RET IaaSrc_Run(SRC_HANDLE handle, short *audio_input, short
*audio_output, int* output_size);

Parameters

Parameter Name	Description	Input/Output
handle	Src algorithm handle	Input
audio_input	Data pointer before resampling	Input
audio_output	Resampled output data pointer	Output
output_size	Resampled output data length. According to SRC mode and point_number, this data length will increase or decrease with the ratio of sampling rate change. Example: if the SRC mode is convert 8K to 48K, the output_size will be 6 times of point_number.	Output

Return value

Return value Result

0 Successful

Non-zero Failed, refer to Error code
Dependency
- Header: AudioSRCProcess.h
- Library: libSRC_LINUX.so/ libSRC_LINUX.a
Note
- The buffer stored in audio_output needs to be passed in by the application
- Npoints range: ≤1536

Example

#include <stdio.h>
#include <stdlib.h>

#include "AudioSRCProcess.h"

/*  0:Fixed input file  1:User input file   */
#define IN_PARAMETER 1

int main(int argc, char *argv[])
{
    SRCStructProcess src_struct;
    /*********************User change section start*******************/
    /*
    *  Audio file bit wide:The user modifies as needed,
    *  for example:16, 8
    */
    int srcFileBitWide = 16;
    /*
    *  The user modifies as needed,for example:1, 2
    */
    src_struct.channel = 1;
    /*
    *  The user modifies as needed,for example:
    *  SRATE_8K, SRATE_16K, SRATE_32K, SRATE_48K
    */
    src_struct.WaveIn_srate = SRATE_8K;
    /*
    *  The user modifies as needed,for example:
    *  SRC_8k_to_16k, SRC_8k_to_32k, SRC_48k_to_8k ...
    */
    src_struct.mode = SRC_8k_to_48k;
    /*
    *  The user modifies as needed,for example:
    *  256, 512, 1024 and 1536 (Please select among these values)
    */
    src_struct.point_number = 1536;
    /*************User change section end************/
    src_struct.mode = SRC_8k_to_48k;
    src_struct.order = ORDER_HIGH;
    src_struct.point_number = 1536;

    SrcConversionMode mode = src_struct.mode;
    SRC_HANDLE handle;
    ALGO_SRC_RET ret;
    int output_size;
    unsigned int workingBufferSize;
    char *workingBufferAddress = NULL;
    int freadBufferSize;
    char *freadBuffer = NULL;
    int fwriteBufferSize;
    char *fwriteBuffer = NULL;
    int nBytesRead;
    int nPoints = src_struct.point_number;
    int MaxFactor = SRATE_48K / SRATE_8K;//The biggest factor
    FILE* fpIn;  //input file
    FILE* fpOut; //output file
    char src_file[128] = {0};
    char dst_file[128] = {0};

#if IN_PARAMETER
    if(argc < 3)
    {
        printf("Please enter the correct parameters!\n");
        return -1;
    }
    sscanf(argv[1], "%s", src_file);
    sscanf(argv[2], "%s", dst_file);
#else
    sprintf(src_file, "%s", "./8K_16bit_MONO_30s.wav");
    if(argc < 2)
    {
        printf("Please enter the correct parameters!\n");
        return -1;
    }
    sscanf(argv[1], "%s", dst_file);
#endif

    fpIn = fopen(src_file, "rb");
    if(NULL == fpIn)
    {
        printf("fopen in_file failed !\n");
        return -1;
    }
    printf("fopen in_file success !\n");
    fpOut = fopen(dst_file, "wb");
    if(NULL == fpOut)
    {
        printf("fopen out_file failed !\n");
        return -1;
    }
    printf("fopen out_file success !\n");
    //(1)IaaSrc_GetBufferSize
    workingBufferSize =  IaaSrc_GetBufferSize(mode);
    workingBufferAddress = (char *)malloc(sizeof(char) * workingBufferSize);
    if(NULL == workingBufferAddress)
    {
        printf("malloc SRC workingBuffer failed !\n");
        return -1;
    }
    printf("malloc SRC workingBuffer success !\n");
    //(2)IaaSrc_Init
    handle = IaaSrc_Init(workingBufferAddress, &src_struct);
    if(NULL == handle)
    {
        printf("SRC:IaaSrc_Init  failed !\n");
        return -1;
    }
    printf("SRC:IaaSrc_Init  success !\n");
    freadBufferSize = src_struct.channel * nPoints * srcFileBitWide / 8;
    freadBuffer = (char *)malloc(freadBufferSize);
    if(NULL == freadBuffer)
    {
        printf("malloc freadBuffer failed !\n");
        return -1;
    }
    printf("malloc freadBuffer success !\n");
    fwriteBufferSize = MaxFactor * freadBufferSize;
    fwriteBuffer = (char *)malloc(fwriteBufferSize);
    if(NULL == fwriteBuffer)
    {
        printf("malloc fwriteBuffer failed !\n");
        return -1;
    }
    printf("malloc fwriteBuffer success !\n");
#if 0
    /*Consider whether the input file has a header*/
    fread(freadBuffer, sizeof(char), 44, fpIn); //Remove the 44 bytes header
#endif
    while(1)
    {
        nBytesRead = fread(freadBuffer, 1, freadBufferSize, fpIn);
        if(nBytesRead != freadBufferSize)
        {
            printf("needBytes =%d      nBytesRead = %d\n", freadBufferSize, nBytesRead);
            break;
        }
        //(3)IaaSrc_Run
        ret = IaaSrc_Run(handle, (short *)freadBuffer, (short *)fwriteBuffer, &output_size);
        if(ret < 0)
        {
            printf("SRC:IaaSrc_Run  failed !\n");
            return -1;
        }
        fwriteBufferSize = src_struct.channel * output_size * srcFileBitWide / 8;
        fwrite(fwriteBuffer, 1, fwriteBufferSize, fpOut);
    }
    fclose(fpIn);
    fclose(fpOut);
    //(4)IaaSrc_Release
    ret = IaaSrc_Release(handle);
    if(ret)
    {
        printf("IaaSrc_Release failed !\n");
        return -1;
    }
    printf("IaaSrc_Release success !\n");
    free(workingBufferAddress);
    free(freadBuffer);
    free(fwriteBuffer);

    return 0;
}

2.5. IaaSrc_Release¶

Features

Release Src algorithm resources.

Syntax

ALGO_SRC_RET IaaSrc_Release(SRC_HANDLE handle);

Parameters

Parameter Name Description Input/Output

handle Src algorithm handle Input
Return value

Return value Result

0 Successful

Non-zero Failed, refer to Error code
Dependency
- Header: AudioSRCProcess.h
- Library: libSRC_LINUX.so/ libSRC_LINUX.a
Example

Please refer to IaaSrc_Run example.

2.6. IaaSrc_GetJsonFileSize¶

Features

SRC get size of json file.

Syntax

unsigned int IaaSrc_GetJsonFileSize(char* jsonfile);

Parameters

Parameter name Description Input/Output

jsonfile name of json file Input
Return value

Return value is the memory size required for decoding json file.
Dependency
- Header: AudioSrcProcess.h
- Library: libSRC_LINUX.so/ libSRC_LINUX.a

2.7. IaaSrc_StructReadFromJson¶

Features

Set json parameter into SRC structure.

Syntax

ALGO_SRC_RET IaaSrc_StructReadFromJson(SRCStructProcess* src_struct, char* jsonBuffer, char* jsonfile, unsigned int buffSize);

Parameters

Parameter name	Description	Input/Output
src_struct	src parameter structure	Input
jsonBuffer	json buffer memory address	Input
jsonfile	name of json file	Input
buffSize	size of json file	Input

Return value

Return value Result

0 Successful

Non-zero Failed, refer to Error code
Dependency
- Header: AudioSrcProcess.h
- Library: libSRC_LINUX.so/ libSRC_LINUX.a

3. SRC Data Type¶

3.1. SRC data type list¶

DATA TYPE	Description
SrcConversionMode	Src algorithm sampling rate conversion type
SRCStructProcess	Src algorithm initialization parameter structure type
SrcInSrate	Src algorithm sampling rate type
SRC_HANDLE	Src algorithm handle type
SrcFilterOrder	Define low pass filter order

3.2. SrcConversionMode¶

Description

Define Src algorithm sampling rate conversion type.

Definition

typedef enum{

    SRC_8k_to_16k,

    SRC_8k_to_32k,

    SRC_8k_to_48k,

    SRC_16k_to_8k,

    SRC_16k_to_32k,

    SRC_16k_to_48k,

    SRC_32k_to_8k,

    SRC_32k_to_16k,

    SRC_32k_to_48k,

    SRC_48k_to_8k,

    SRC_48k_to_16k,

    SRC_48k_to_32k,

    SRC_24k_to_8k,

    SRC_24k_to_16k,

    SRC_24k_to_32k,

    SRC_24k_to_48k,

    SRC_8k_to_24k,

    SRC_16k_to_24k,

    SRC_32k_to_24k,

    SRC_48k_to_24k

}SrcConversionMode;

Member

Member name	Description
SRC_8k_to_16k	8K resampling to 16K
SRC_8k_to_32k	8K resampling to 32K
SRC_8k_to_48k	8K resampling to 48K
SRC_16k_to_8k	16K resampling to 8K
SRC_16k_to_32k	16K resampling to 32K
SRC_16k_to_48k	16K resampling to 48K
SRC_32k_to_8k	32K resampling to 8K
SRC_32k_to_16k	32K resampling to 16K
SRC_32k_to_48k	32K resampling to 48K
SRC_48k_to_8k	48K resampling to 8K
SRC_48k_to_16k	48K resampling to 16K
SRC_48k_to_32k	48K resampling to 32K
SRC_24k_to_8k	24K resampling to 8K
SRC_24k_to_16k	24K resampling to 16K
SRC_24k_to_32k	24K resampling to 32K
SRC_24k_to_48k	24K resampling to 48K
SRC_8k_to_24k	8K resampling to 24K
SRC_16k_to_24k	16K resampling to 24K
SRC_32k_to_24k	32K resampling to 24K
SRC_48k_to_24k	24K resampling to 24K

Related data types and interfaces

IaaSrc_GetBufferSize

3.3. SRCStructProcess¶

Description

Define Src algorithm initialization parameter structure type.

Definition

typedef struct{

    SrcInSrate WaveIn_srate;

    SrcConversionMode mode;

    unsigned int channel;

    SrcFilterOrder order;

    unsigned int point_number;

}SRCStructProcess;

Member

Member name	Description
WaveIn_srate	Sampling frequency of source data
mode	Sampling frequency conversion mode, please choose according to the sampling frequency of source data and output data.
channel	Source data channels. Support 4 channel data.
order	Low pass filter order
point_number	Input data point number. Defult value must smaller than 1536, and it must be integer after conversion. User can use following command to check: `strings libSRC_LINUX.so \| grep PN`

Related data types and interfaces

IaaSrc_Init

IaaSrc_StructReadFromJson

3.4. SrcInSrate¶

Description

Define Src algorithm sampling rate type.

Definition

typedef enum{

    SRATE_8K = 8,

    SRATE_16K = 16,

    SRATE_32K = 32,

    SRATE_48K = 48,

    SRATE_24K = 24

}SrcInSrate;

Member

Member name	Description
SRATE_8K	8K sampling frequency
SRATE_16K	16K sampling frequency
SRATE_32K	32K sampling frequency
SRATE_48K	48K sampling frequency
SRATE_24K	24K sampling frequency

Related data types and interfaces

SRCStructProcess

3.5. SRC_HANDLE¶

Description

Define Src algorithm handle type.
Definition
```
typedef void* SRC_HANDLE;
```
Related data types and interfaces

IaaSrc_Init

IaaSrc_Run

IaaSrc_Release

3.6. SrcFilterOrder¶

Description

Define low pass filter order.

Definition

typedef enum{
    ORDER_LOW   =   0,
    ORDER_HIGH  =   1
}SrcFilterOrder;

Member

Member name Description

ORDER_LOW Low order

ORDER_HIGH High order
Related data types and interfaces

SRCStructProcess

4. Error Code¶

SRC API error codes are shown as follow:

Error code	Definition	Description
0x00000000	ALGO_SRC_RET_SUCCESS	Successful
0x10000601	ALGO_SRC_INIT_ERROR	Not initialized
0x10000602	ALGO_SRC_RET_INVALID_MODE	Parameter setting is invalid
0x10000603	ALGO_SRC_RET_INVALID_HANDLE	HANDLE is invalid
0x10000604	ALGO_SRC_RET_INVALID_CHANNEL	Channel number doesn`t support
0x10000605	ALGO_SRC_RET_INVALID_POINT_NUMBER	Points per frame doesn`t support
0x10000606	ALGO_SRC_RET_INVALID_SAMPLE_RATE	Sampling frequency doesn`t support
0x10000607	ALGO_SRC_RET_API_CONFLICT	Other APIs are running
0x10000608	ALGO_SRC_RET_INVALID_CALLING	Incorrect order of calling API
0x10000609	ALGO_SRC_RET_INVALID_JSONFILE	SRC Json related error

Parameter Name	Description	Input/Output
working_buffer_address	Memory address used by Src algorithm	Input
SRCStructProcess	Src algorithm initialization structure pointer	Input

Return value	Result
Not NULL	Successful
NULL	Failed

Return value	Result
0	Successful
Non-zero	Failed, refer to Error code

Return value	Result
0	Successful
Non-zero	Failed, refer to Error code

Return value	Result
0	Successful
Non-zero	Failed, refer to Error code