Conventional read(2) interface. This mode is the easiest and slowest to use. This mode is great for capturing a single field at little programming cost.
In this mode, the user opens the device, sets the capture mode and size (see: METEORSETGEO ioctl(2) call), and uses the read(2) system call to load the data into a buffer.
meteor_read.c; read 400x300 RGB24 into a viewable PPM file
#include <sys/fcntl.h>
#include <machine/ioctl_meteor.h>
extern int errno;
#define ROWS 300
#define COLS 400
#define SIZE (ROWS * COLS * 4)
main()
{
struct meteor_geomet geo;
char buf[SIZE],b[4],header[16],*p;
int i,o,c;
if ((i = open("/dev/meteor0", O_RDONLY)) < 0) {
printf("open failed: %d\n", errno);
exit(1);
}
/* set up the capture type and size */
geo.rows = ROWS;
geo.columns = COLS;
geo.frames = 1;
geo.oformat = METEOR_GEO_RGB24 ;
if (ioctl(i, METEORSETGEO, &geo) < 0) {
printf("ioctl failed: %d\n", errno);
exit(1);
}
c = METEOR_FMT_NTSC;
if (ioctl(i, METEORSFMT, &c) < 0) {
printf("ioctl failed: %d\n", errno);
exit(1);
}
c = METEOR_INPUT_DEV0;
if (ioctl(i, METEORSINPUT, &c) < 0) {
printf("ioctl failed: %d\n", errno);
exit(1);
}
if ((c=read(i, &buf[0], SIZE)) < SIZE) {
printf("read failed %d %d %d\n", c, i, errno);
close(i);
exit(1);
}
close(i);
if ((o = open("rgb24.ppm", O_WRONLY | O_CREAT, 0644)) < 0) {
printf("ppm open failed: %d\n", errno);
exit(1);
}
/* make PPM header and save to file */
strcpy(&header[0], "P6 400 300 255 ");
header[2] = header[6] = header[10] = header[14] = ’\n’;
write (o, &header[0], 15);
/* save the RGB data to PPM file */
for (p = &buf[0]; p < &buf[SIZE]; ) {
b[2] = *p++; /* blue */
b[1] = *p++; /* green */
b[0] = *p++; /* red */
*p++; /* NULL byte */
write(o,&b[0], 3); /* not very efficient */
}
close(o);
exit(0);
}
Memory mapped single capture or unsynchronized continuous capture. The single capture mode is designed for conferencing tools such as nv. These tools need to control the starting of the image capture and also need several frames a second. The continuous capture mode is designed for applications that want free-running data.
In this mode, the user opens the device, sets the capture mode and size (see: METEORSETGEO ioctl(2) call), mmap 2 s the frame buffer memory into the user process space, and issues either the single-capture or the continuous capture call (see: METEORCAPTUR ioctl(2) call) to load the data into the memory mapped buffer.
As explained in the METEORCAPTUR ioctl(2) call, the single frame capture ioctl(2) will block until the capture is complete, the continuous capture will return immediately.
meteor_mmap_single_continuous.c
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/fcntl.h>
#include <machine/ioctl_meteor.h>
extern int errno;
#define ROWS 480
#define COLS 640
#define SIZE (ROWS * COLS * 2)
main()
{
struct meteor_geomet geo;
char buf[SIZE];
char *mmbuf;
int i,c;
if ((i = open("/dev/meteor0", O_RDONLY)) < 0) {
printf("open failed\n");
exit(1);
}
geo.rows = ROWS;
geo.columns = COLS;
geo.frames = 1;
geo.oformat = METEOR_GEO_RGB16 ;
if (ioctl(i, METEORSETGEO, &geo) < 0) {
printf("ioctl failed: %d\n", errno);
exit(1);
}
c = METEOR_FMT_NTSC;
if (ioctl(i, METEORSFMT, &c) < 0) {
printf("ioctl failed: %d\n", errno);
exit(1);
}
c = METEOR_INPUT_DEV0;
if (ioctl(i, METEORSINPUT, &c) < 0) {
printf("ioctl failed: %d\n", errno);
exit(1);
}
mmbuf=(char *)mmap((caddr_t)0, SIZE, PROT_READ,
MAP_SHARED, i, (off_t)0);
#ifdef SINGLE_MODE
/* single frame capture */
c = METEOR_CAP_SINGLE ;
ioctl(i, METEORCAPTUR, &c); /* wait for the frame */
/* directly access the frame buffer array data in mmbuf */
#else
/* continuous frame capture */
c = METEOR_CAP_CONTINOUS ;
ioctl(i, METEORCAPTUR, &c); /* returns immediately */
/* directly access the frame buffer array data in mmbuf */
c = METEOR_CAP_STOP_CONT ;
ioctl(i, METEORCAPTUR, &c); /* close will also stop capture */
#endif
close(i);
exit(0);
}
Memory mapped, multi-frame ring buffer synchronize capture. This continuous capture mode is synchronized with the application that processes up to 32 frames. This gives the advantages of both single and continuous capture modes.
The kernel notifies the application of a new data by raising an application defined signal. The driver also shares a structure with the application that allows them to communicate which frame has been written by the kernel and which frame has been read by the application.
The shared structure starts on the first page after your data. The structure address can be found by calculation:
"(number_rows * number_columns * pixel_depth + 4095) & 0xfffff000"
or
"((number_rows * number_columns * pixel_depth + 4095)/4096) * 4096"
The shared structure is of type struct meteor_mem. The two most important fields are called active and num_active_buf. active is a bitmap of frames written by the kernel. num_active_bufs is a count of frames marked in the active field. When a frame is read in by the driver, the num_active_bufs count is tested, if this count is below the threshold of number of active frames (value in meteor_mem ’s hiwat variable), the bit representing frame number in the buffer is stored in the active variable, the num_active_bufs is incremented, the kernel then raises the specified signal to activate the user application. The user application’s responsibility when getting the signal is to check the active bitmap to determine the lowest active frame, use the data as the application desires, clear the bitmap entry for that frame, and decrement the num_active_bufs. If the threshold of number of active frames (hiwat) has been exceeded, no new frames or signal from the kernel will occur until the num_active_bufs is less than or equal to lowat.
The driver loads the frames in a round-robin fashion. It is expected that the user removes them in the same order. The driver does not check to see if the frame is already active.
The frame_size and number of frames in the buffer are also provided to the meteor_mem structure, but changing these fields in the application will not change the operation of the driver.
In programming for this mode, the user opens the device, sets the geometry, mmap 2 s the data/common control structure, then starts the continuous capture mode. A special signal catcher is required to process the frames as they are read by the kernel.
When specifying the geometry (see: METEORSETGEO ioctl(2) call), it is important that the number of frames is set greater than 1.
skeleton_capture_n.c
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/fcntl.h>
#include <sys/signal.h>
#include <machine/ioctl_meteor.h>
int video; /* made global if you wish to stop capture in signal handler */
caddr_t data_frames;
struct meteor_mem *common_mem;
extern int errno;
#define FRAME_MAX
void
usr2_catcher()
{
#ifdef SIGNAL_STOP
struct meteor_capframe capframe; /* for ioctl */
#endif
char *frame;
/* find frame */
frame = (char *) (data_frames + sig_cnt * common_mem->frame_size) ;
/* add frame processing here */
/* deactivate frame */
common_mem->active &= ~(1 << (sig_cnt % 16));
common_mem->num_active_bufs--;
/* process next frame on next interrupt */
sig_cnt = ((sig_cnt+1) % FRAME_MAX);
#ifdef SIGNAL_STOP
if (some_condition_requiring_stopping) {
capframe.command=METEOR_CAP_STOP_FRAMES;
if (ioctl(i, METEORCAPFRM, &capframe) < 0) {
printf("METEORCAPFRM failed %d\n", errno);
exit(1);
}
}
#endif
}
main()
{
struct meteor_geomet geo;
int height, width, depth, frames, size;
struct meteor_capframe capframe;
if ((i = open("/dev/meteor0", O_RDONLY)) < 0) {
printf("open failed\n");
exit(1);
}
printf("test %d %d\n", errno, i);
height = geo.rows = 120;
width= geo.columns = 320;
frames = geo.frames = FRAME_MAX;
depth = 2; /* 2 bytes per pixel for RGB*/
geo.oformat = METEOR_GEO_RGB16;
if (ioctl(i, METEORSETGEO, &geo) < 0) {
printf("METEORSETGEO failed %d\n", errno);
exit(1);
}
c = METEOR_FMT_NTSC;
if (ioctl(i, METEORSFMT, &c) < 0) {
printf("ioctl failed: %d\n", errno);
exit(1);
}
c = METEOR_INPUT_DEV0;
if (ioctl(i, METEORSINPUT, &c) < 0) {
printf("ioctl failed: %d\n", errno);
exit(1);
}
size = ((width*height*depth*frames+4095)/4096)*4096;
/* add one page after data for meteor_mem */
data_frames = mmap((caddr_t)0, size + 4096, PROT_READ | PROT_WRITE,
MAP_SHARED, i, (off_t)0);
if (data_frames == (caddr_t) MAP_FAILED) return (0);
/* common_mem is located at page following data */
common_mem = (struct meteor_mem *) (y + size);
signal(SIGUSR2, usr2_catcher); /* catch new frame message */
capframe.command=METEOR_CAP_N_FRAMES;
capframe.signal=SIGUSR2;
capframe.lowat=12; /* must be < hiwat */
capframe.hiwat=14; /* must be < FRAME_MAX */
/* start the sync capture */
if (ioctl(i, METEORCAPFRM, &capframe) < 0) {
printf("METEORCAPFRM failed %d\n", errno);
exit(1);
}
/* this is the background working area, or you can sleep */
/* to stop capture */
capframe.command=METEOR_CAP_STOP_FRAMES;
if (ioctl(i, METEORCAPFRM, &capframe) < 0) {
printf("METEORCAPFRM failed %d\n", errno);
exit(1);
}
}
