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meteor - video capture driver 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); }
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)Nss 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); }
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)Nss 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); } }
Bf -symbolic IT IS VERY IMPORTANT TO CHECK FOR ERRORS ON THESE RETURNING IOCTLs. Ef Errors indicate that something is very wrong with the ioctl(2) and the application should not attempt to proceed further with capturing. The capture driver still makes attempts to stop the next capture step if an error occurred in a previous step but was ignored by the application programmer.
METEORSETGEO and METEORGETGEO are used to set and read the input size, input device, and output format for frame capture.
These ioctl(2) routines use the meteor_geomet structure that has the following entries:
Note: if rows , columns or frames is not changed, then the existing values are used. The system defaults is 640x480x1.
The METEORSETGEO ioctl(2) will fail if more than one entry from a category is selected. It is highly recommended that a METEORSETGEO is done before capturing data because you cannot guarantee the initial mode the card.
The METEORSETGEO will also attempt to reallocate a new contiguous kernel buffer if the new geometry exceeds the old geometry. On other hand, if the new geometry will fit in the existing buffer, the existing buffer is used.
If METEORSETGEO fails the ioctl(2) will return a value of -1 and the external variable errno will be set to:
METEORSFMT and METEORGFMT are used to set and read the camera input standard format.
Possible formats are:
METEORSINPUT and METEORGINPUT are used to set and read the camera input device. Using the DB9 connector on the Meteor card, 4 input devices can be connected and an input camera can be selected with this ioctl(2).
Possible formats are:
METEORSTATUS is used to read the status of the Meteor capture card and returns the following information:
METEORCAPTUR is used to single frame capture or unsynchronized continuous capture.
The single frame capture ioctl(2) request will return only after a frame has been captured and transfered to the frame buffer.
The unsynchronized continuous capture will return immediately and data is directly deposited into the buffer when it is available. Since this is unsynchronized, it is possible the data is being written by the kernel while being read by the application.
These ioctl(2) routines use the following settings:
If METEORCAPTUR fails the ioctl(2) will return a value of -1 and the external variable errno will be set to:
METEORCAPFRM is used for synchronous capture of multiple frames.
This ioctl(2) routine uses the meteor_capture structure that has the following entries:
When a new frame is completed, the driver checks the current unread frame count stored in shared variable (the shared variable is stored in the meteor_mem structure) num_active_buf if the count is larger than hiwat the driver will not store any new frames and will not send capture signal to the user application until the num_active_buf is lower than lowat
If METEORCAPFRM fails the ioctl(2) will return a value of -1 and the external variable errno will be set to:
METEORSCHCV and METEORGCHCV are used to set and get the chrominance gain control and effects the UV output amplitude.
If METEORSCHCV or METEORGCHCV fails the ioctl(2) will return a value of -1 and the external variable errno will be set to:
METEORGHUE and METEORSHUE are used to get and set the hue. The signed character has legal values are from +127 which represent +178.6 degrees to -128 which represents -180 degrees.
If METEORGHUE or METEORSHUE fails the ioctl(2) will return a value of -1 and the external variable errno will be set to:
METEORGCOUNT is used to get the count of frame errors, DMA errors and count of the number of frames captured that have occurred since the device was opened. METEORSCOUNT can be used to reinitialize the counters.
This ioctl(2) routines use the meteor_counts structure that has the following entries:
If METEORSCOUNT or METEORGCOUNT fails the ioctl(2) will return a value of -1 and the external variable errno will be set to:
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