MIPI RAW图像数据与RAW图像数据的区别

在ISP图像处理中经常需要面对MIPI RAW数据和RAW数据，这里简单说明一下二者的差别。

传感器采集的RAW数据通常为10bit，存储RAW数据需要两个Byte，而其中有6个bit位是空着的，这样就有存储空间浪费。

MIPI RAW数据充分利用了这个特性，采用5个Byte，共40bit存储4个RAW数据。

这里以大端存储方式，给出这样存储的示意图。如下图所示：

从MIPI RAW数据恢复RAW数据的方法：

//b1,b2,b3,b4,b5分别为连续读出的五个uint8类型的数据，p1,p2,p3,p4为四个像素点的像素值，那么
p1 = (b1 << 2) + ((b5     ) & 0x3);
P2 = (b2 << 2) + ((b5 >> 2) & 0x3);
P3 = (b3 << 2) + ((b5 >> 4) & 0x3);
P4 = (b4 << 2) + ((b5 >> 6) & 0x3);

再贴上自己写的格式转换code

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

char raw_array[3840*2160*2];
short pixel_array[3840*2160*2];

static const char *format_array[5] = {"RAW8", "RAW10", "RAW12", "RAW14", "RAW16"};
static const char *help = "help";

int main(int argc, char *argv[]){
    char *file_name = argv[1];
    char *format = argv[2];
    int width = atoi(argv[3]);
    int height = atoi(argv[4]);
    char out_file[256];
    int format_index;
    int byte_index = 0;
    int pixel_index = 0;
    int in_size = 0;
    int out_size = 0;
    printf("Usage: <filename> <format: RAW8/RAW10/RAW12/RAW14/RAW16> <width> <height>\r\n");
    printf("file name: %s \r\n", file_name);
    printf("format: %s \r\n", format);

    printf("width: %d \r\n", width);
    printf("height: %d \r\n", height);

    FILE *raw_fb = fopen(file_name, "rb" );
    if(!raw_fb) {
        printf("open input file faile \r\n");
        return -1;
    }

    sprintf(out_file, "out_%s_%s", format, file_name);
    printf("open input file name: %s\r\n", out_file);
    FILE *pixel_fb = fopen(out_file, "wb");

    if(!pixel_fb) {
        printf("open output file faile \r\n");
        return -1;
    }

    for(int i=0; i<5; i++) {
        if(0 == strcmp(format_array[i], format)) {
            format_index = i;
            break;
        }
        format_index = 5;

    }

    printf("start convertion format_index: %d \r\n", format_index);
    switch(format_index) {
    case 0:
        in_size = width*height;
        out_size = width*height;
        break;
    case 1:
        in_size = width*height*10/8;
        out_size = width*height*2;
        break;
    case 2:
        in_size = width*height*12/8;
        out_size = width*height*2;
        break;
    case 3:
        in_size = width*height*14/8;
        out_size = width*height*2;
        break;
    case 4:
        in_size = width*height*2;
        out_size = width*height*2;
        break;
    default:
        printf("format is unsupport !!! \r\n");
        break;
    }

    fread(raw_array, 1, in_size, raw_fb);

    switch(format_index) {
    case 0:
        // RAW8 don't need convert
        break;
    case 1:
        // RAW10
        for(byte_index=0, pixel_index=0; byte_index < (in_size-5); ) {
            pixel_array[pixel_index+0] = (((short)(raw_array[byte_index+0]))<<2) & 0x03FC;
            pixel_array[pixel_index+0] = pixel_array[pixel_index+0] | (short)((raw_array[byte_index+4]>>0) & 0x0003);
            pixel_array[pixel_index+1] = (((short)(raw_array[byte_index+1]))<<2) & 0x03FC;
            pixel_array[pixel_index+1] = pixel_array[pixel_index+1] | (short)((raw_array[byte_index+4]>>2) & 0x0003);
            pixel_array[pixel_index+2] = (((short)(raw_array[byte_index+2]))<<2) & 0x03FC;
            pixel_array[pixel_index+2] = pixel_array[pixel_index+2] | (short)((raw_array[byte_index+4]>>4) & 0x0003);
            pixel_array[pixel_index+3] = (((short)(raw_array[byte_index+3]))<<2) & 0x03FC;
            pixel_array[pixel_index+3] = pixel_array[pixel_index+3] | (short)((raw_array[byte_index+4]>>6) & 0x0003);
            byte_index = byte_index + 5;
            pixel_index = pixel_index + 4;
        }
        break;

    case 2:
        // RAW12
        for(byte_index=0, pixel_index=0; byte_index < (in_size-3); ) {
            pixel_array[pixel_index+0] = (((short)(raw_array[byte_index+0]))<<4) & 0x0FF0;
            pixel_array[pixel_index+0] = pixel_array[pixel_index+0] | (short)((raw_array[byte_index+2]>>0) & 0x000F);
            pixel_array[pixel_index+1] = (((short)(raw_array[byte_index+1]))<<4) & 0x0FF0;
            pixel_array[pixel_index+1] = pixel_array[pixel_index+1] | (short)((raw_array[byte_index+2]>>4) & 0x000F);
            byte_index = byte_index + 3;
            pixel_index = pixel_index + 2;
        }
        break;

    case 3:
        //RAW14
        for(byte_index=0, pixel_index=0; byte_index < (in_size-7); ) {
            pixel_array[pixel_index+0] = (((short)(raw_array[byte_index+0]))<<6) & 0x3FC0;
            pixel_array[pixel_index+0] = pixel_array[pixel_index+0] | (short)((raw_array[byte_index+4]>>0) & 0x003F);
            pixel_array[pixel_index+1] = (((short)(raw_array[byte_index+1]))<<6) & 0x3FC0;
            pixel_array[pixel_index+1] = pixel_array[pixel_index+1] | (short)((raw_array[byte_index+4]>>6) & 0x0003);
            pixel_array[pixel_index+1] = pixel_array[pixel_index+1] | (short)((raw_array[byte_index+5]>>0) & 0x000F);
            pixel_array[pixel_index+2] = (((short)(raw_array[byte_index+2]))<<6) & 0x3FC0;
            pixel_array[pixel_index+2] = pixel_array[pixel_index+2] | (short)((raw_array[byte_index+5]>>4) & 0x000F);
            pixel_array[pixel_index+2] = pixel_array[pixel_index+2] | (short)((raw_array[byte_index+6]>>0) & 0x0003);
            pixel_array[pixel_index+3] = (((short)(raw_array[byte_index+3]))<<6) & 0x3FC0;
            pixel_array[pixel_index+3] = pixel_array[pixel_index+3] | (short)((raw_array[byte_index+6]>>2) & 0x003F);
            byte_index = byte_index + 7;
            pixel_index = pixel_index + 4;
        }
        break;
    case 4:
        // RAW16 don't need convert
        break;
    default:
        printf("formt is unsupport !!! \r\n");
        break;
    }

    fwrite(pixel_array, 1, out_size, pixel_fb);
    fclose(raw_fb);
    fclose(pixel_fb);
    printf("convert finished !!! \r\n");
    return 0;
}