static int detect_standard(struct capture_device *c, int fd){
int found=0, i=0;
dprint(LIBVIDEO_SOURCE_CAP, LIBVIDEO_LOG_DEBUG,
"Trying to autodetect standard\n");
while(found==0 && i<4) {
if (try_std(fd, i)==0){
found=1;
if(i==WEBCAM) {
info("Adjusted standard to WEBCAM\n");
c->std = WEBCAM;
} else if (i==PAL) {
info("Adjusted standard to PAL\n");
c->std = PAL;
} else if (i==NTSC) {
info("Adjusted standard to NTSC\n");
c->std = NTSC;
} else {
info("Adjusted standard to SECAM\n");
c->std = SECAM;
}
}
i++;
}
return found==0 ? -1 : 0;
}
static int detect_standard(struct capture_device *c, int fd){
int found=0, i=0;
dprint(LIBV4L_LOG_SOURCE_CAPTURE, LIBV4L_LOG_LEVEL_DEBUG, "Trying to autodetect standard\n");
while(found==0 && i<4) {
if (try_std(fd, i)==0){
found=1;
if(i==WEBCAM) {
dprint(LIBV4L_LOG_SOURCE_CAPTURE, LIBV4L_LOG_LEVEL_DEBUG, "WEBCAM standard autodetected\n");
c->std = WEBCAM;
} else if (i==PAL) {
dprint(LIBV4L_LOG_SOURCE_CAPTURE, LIBV4L_LOG_LEVEL_DEBUG, "PAL standard autodetected\n");
c->std = PAL;
} else if (i==NTSC) {
dprint(LIBV4L_LOG_SOURCE_CAPTURE, LIBV4L_LOG_LEVEL_DEBUG, "NTSC standard autodetected\n");
c->std = NTSC;
} else {
dprint(LIBV4L_LOG_SOURCE_CAPTURE, LIBV4L_LOG_LEVEL_DEBUG, "SECAM standard autodetected\n");
c->std = SECAM;
}
}
i++;
}
return found==0 ? -1 : 0;
}
static int set_std(struct capture_device *c, int fd){
struct v4l2_standard s;
CLEAR(s);
//Linux UVC doesnt like to be ioctl'ed(VIDIOC_S_STD)
//even though v4l2 specs say nothing
//about usb cam drivers returning EINVAL...
//so we first try VIDIOC_ENUMSTD. if it returns EINVAL, then we
//assume it is a webcam
//otherwise, we need to set a standard
if(-1 != ioctl(fd, VIDIOC_ENUMSTD, &s)){
//driver says "I use standards" -
//check if it is the UNKNOWN one, only used by webcams
if(s.id != V4L2_STD_UNKNOWN) {
//driver says "not webcam", check what we want...
if(c->std == WEBCAM){
//we want webcam... try to autodetect
info("The specified standard (%d) is invalid.\n", c->std);
if(detect_standard(c, fd)!=0) {
//autodetect failed, so do we
info("libvideo could not autodetect a standard for this "
"input.\n");
return -1;
}
//autodetect suceeded keep going
} else {
//we want !WEBCAM, so try that standard
dprint(LIBVIDEO_SOURCE_CAP, LIBVIDEO_LOG_DEBUG,
"Trying standard (%d).\n", c->std);
if (-1 == try_std(fd, c->std)) {
//failed, try autodetect
info("The specified standard (%d) cannot be selected\n",
c->std);
if(detect_standard(c, fd)!=0) {
//failed, exit
info("libvideo could not autodetect a standard for this"
" input.\n");
return -1;
}
//autodetect succeeded, keep going
}
//given standard succeeded, keep going
}
} else {
//driver says webcam, check what we want
if(c->std != WEBCAM){
//we want !WEBCAM, so try that standard
if (-1 == try_std(fd, c->std)) {
//failed, try autodetect
info("The specified standard (%d) cannot be selected\n",
c->std);
if(detect_standard(c, fd)!=0) {
//failed, exit
dprint(LIBVIDEO_SOURCE_CAP, LIBVIDEO_LOG_ERR,
"CAP: Couldnt autodetect a standard for this "
"input.\n");
return -1;
}
//autodetect succeeded, keep going
}
} else {
//driver sais WEBCAM, so did we, keep going
}
}
} else {
//driver doesnt use standards - most likely a webcam
if(c->std!=WEBCAM){
info("The standard has been autodetected and set to WEBCAM \n");
c->std = WEBCAM;
}
}
return 0;
}