MI SRC API

1. Overview¶

1.1. Algorithm Description¶

SRC (short for Sample Rate Conversion) is used to convert the sampling frequency 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¶

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

  The interface only returns the required memory size, and the application and release of memory need to be processed by the application.

• 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: 128, 512, 1024.

• 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*******************/  
      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;  
          }  
          //printf("ret = %d\n", ret);  
          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.

3. SRC Data Type¶

3.1. SRC data type list¶

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
  
  }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

• 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;
  
      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
  point_number Input point number for SRC. The output_size of IaaSrc_Run will change according to the ratio of sampling rate conversion and point_number. For example: when point_number is 128 and SRC mode is SRC_8k_to_48k, output_size is 128×6=768. It is recommended that you should set the point number as your need. Setting value: [256, 512, 1024, 1536, 2880].

• Related data types and interfaces

  IaaSrc_Init

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
  
  }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

• 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

4. Error Code¶

SRC API error codes are shown as follow: