How to programmatically determine bpp and pixel color format of android screen?

Question

I am trying to stream compressed raw framebuffer data to my Client application on the PC, from my Server service on Android. On the PC I want to display this raw data as streamed video in my Client's view, giving real-time view of the Android device's screen. I know how to get the resolution of the screen, but not the Bits-Per-Pixel(BPP) nor the Pixel's Color Format of the raw data programmatically at Android(Server) side. Please help.

All I could find over the Internet is native code. But I really wish to maintain the application as Java defined as possible.

From FBIOGET_VSCREENINFO over ioctl get BPP(bits-per-pixel) as follows

int main () {
    int fbfd;
    struct fb_var_screeninfo variable_info;

    fbfd=open("/dev/fb0", O_RDWR);
    //in real life, check every ioctl if it returns -1

    ioctl (fbfd, FBIOGET_VSCREENINFO, &variable_info);

    //This is the required BPP value
    switch(variable_info.bits_per_pixel) {
        case 16: //pixel format is RGB_565
            break;
        case 24: //pixel format is RGB_888
            break;
        case 32: //pixel format is RGBX_8888
            break;
    }
}

Answer 1

Finally figured out how to determine

• BPP(bits-per-pixel) of the frame
• Actual RGB byte orientation in the Pixel

• Size of the framebuffer & individual frames

  int main() {
      //Structs defined in "linux/fb.h"
      struct fb_var_screeninfo vscreeninfo;
      struct fb_fix_screeninfo fscreeninfo;
  
      //Open the framebuffer
      fbfd=open("/dev/graphics/fb0",O_RDONLY);
      if(fbfd==-1) {
          __android_log_print(ANDROID_LOG_ERROR,ERR,
                  "Could not open framebuffer fbfd=%d errno=%d",fbfd,errno);
          return errno;
      }
  
      //Fetch variable screen info
      ioct=ioctl(fbfd,FBIOGET_VSCREENINFO,&vscreeninfo);
      if(ioct==-1) {
          __android_log_print(ANDROID_LOG_ERROR,ERR,
                  "VSCREEN-IOCTL failed ioct=%d errno=%d",ioct,errno);
          return errno;
      }
  
      //Fetch fixed screen info
      ioct=ioctl(fbfd,FBIOGET_FSCREENINFO,&fscreeninfo);
      if(ioct==-1) {
          __android_log_print(ANDROID_LOG_ERROR,ERR,
                  "FSCREEN-IOCTL failed ioct=%d errno=%d",ioct,errno);
          return errno;
      }
  
      close(ioct);
  
      /**********************************VSCREEN DATA************************************/
      printf("\nVscreen Info:-\n");
      printf(" Xres   = %4ld | Yres   = %4ld\n",vscreeninfo.xres,vscreeninfo.yres);
      printf(" BPP    = %4ld | Height = %4ld | Width = %4ld\n",vscreeninfo.bits_per_pixel,
                                                               vscreeninfo.height,
                                                               vscreeninfo.width);
      printf(" Xres_V = %4ld | Yres_V = %4ld\n",vscreeninfo.height,vscreeninfo.width);
      printf(" Pixel format : RGBX_%ld%ld%ld%ld\n",vscreeninfo.red.length,
                                                   vscreeninfo.green.length,
                                                   vscreeninfo.blue.length,
                                                   vscreeninfo.transp.length);
      printf(" Begin of bitfields(Byte ordering):-\n");     //In my case :
      printf("  Red    : %ld\n",vscreeninfo.red.offset);    //Red    : 16
      printf("  Blue   : %ld\n",vscreeninfo.blue.offset);   //Blue   : 0
      printf("  Green  : %ld\n",vscreeninfo.green.offset);  //Green  : 8
      printf("  Transp : %ld\n",vscreeninfo.transp.offset); //Transp : 24
                //Hence orientation is : BGRT => (BGR4)RGB32 packed format
      /********************************~VSCREEN DATA************************************/
  
      /*********************************FSCREEN DATA************************************/
      printf("\nFscreen Info:-\n");
      printf(" Device ID : %s\n",fscreeninfo.id);
      printf(" Start of FB physical address : %ld\n",fscreeninfo.smem_start);
      printf(" Length of FB : %ld\n",fscreeninfo.smem_len); //Size of framebuffer in bytes
      printf(" Length of Line : %ld\n",fscreeninfo.line_length);
      printf(" Start of MMIO physical address : %ld\n",fscreeninfo.mmio_start);
      printf(" Length of MMIO : %ld\n",fscreeninfo.mmio_len);
      /********************************~FSCREEN DATA************************************/
  
      close(fbfd);
      return 0;
  }
  

References :-

• Framebuffer data http://www.ummon.eu/Linux/API/Devices/framebuffer.html
• Packed RGB formats http://linuxtv.org/downloads/v4l-dvb-apis/packed-rgb.html#V4L2-PIX-FMT-RGB565