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-rw-r--r--Documentation/video4linux/v4lgrab.c25
1 files changed, 17 insertions, 8 deletions
diff --git a/Documentation/video4linux/v4lgrab.c b/Documentation/video4linux/v4lgrab.c
index 079b628481c..d6e70bef8ad 100644
--- a/Documentation/video4linux/v4lgrab.c
+++ b/Documentation/video4linux/v4lgrab.c
@@ -4,12 +4,21 @@
*
* Compile with:
* gcc -s -Wall -Wstrict-prototypes v4lgrab.c -o v4lgrab
- * Use as:
- * v4lgrab >image.ppm
+ * Use as:
+ * v4lgrab >image.ppm
*
* Copyright (C) 1998-05-03, Phil Blundell <philb@gnu.org>
- * Copied from http://www.tazenda.demon.co.uk/phil/vgrabber.c
- * with minor modifications (Dave Forrest, drf5n@virginia.edu).
+ * Copied from http://www.tazenda.demon.co.uk/phil/vgrabber.c
+ * with minor modifications (Dave Forrest, drf5n@virginia.edu).
+ *
+ *
+ * For some cameras you may need to pre-load libv4l to perform
+ * the necessary decompression, e.g.:
+ *
+ * export LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so
+ * ./v4lgrab >image.ppm
+ *
+ * see http://hansdegoede.livejournal.com/3636.html for details.
*
*/
@@ -24,7 +33,7 @@
#include <linux/types.h>
#include <linux/videodev.h>
-#define FILE "/dev/video0"
+#define VIDEO_DEV "/dev/video0"
/* Stole this from tvset.c */
@@ -90,7 +99,7 @@ int get_brightness_adj(unsigned char *image, long size, int *brightness) {
int main(int argc, char ** argv)
{
- int fd = open(FILE, O_RDONLY), f;
+ int fd = open(VIDEO_DEV, O_RDONLY), f;
struct video_capability cap;
struct video_window win;
struct video_picture vpic;
@@ -100,13 +109,13 @@ int main(int argc, char ** argv)
unsigned int i, src_depth;
if (fd < 0) {
- perror(FILE);
+ perror(VIDEO_DEV);
exit(1);
}
if (ioctl(fd, VIDIOCGCAP, &cap) < 0) {
perror("VIDIOGCAP");
- fprintf(stderr, "(" FILE " not a video4linux device?)\n");
+ fprintf(stderr, "(" VIDEO_DEV " not a video4linux device?)\n");
close(fd);
exit(1);
}