v4l2 debug

v4l2 디버깅을 위해서는 아래와 같이 설정해주면 dmesg에 출력되게 된다.

# echo 0x1f > /sys/class/video4linux/video1/dev_debug

[링크 : https://stackoverflow.com/questions/24330671/v4l2-kernel-space-debugging]

 

guvcview 유틸리티를 이용해서 테스트.

하단의 exposure, auto / (absolute) / Auto Priority 관련 설정을 바꿀때 나오는 값 확인

 

Exposure, Auto - Aperture Priority Mode

[ 1041.346246] video2: VIDIOC_DQEVENT: type=0x3, pending=0, sequence=13, id=10094850, timestamp=1040.623934215 [ 1041.346259] changes=0x3, type=1, value=3216, flags=0x10, minimum=39, maximum=10000, step=1, default_value=156 [ 1041.346272] video2: VIDIOC_DQEVENT: error -2: type=0x0, pending=0, sequence=0, id=0, timestamp=0.000000000

 

Exposure, Auto - Manual / 3216

[ 1128.312839] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0901/0x3 [ 1128.312866] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0901/0x3

 

Exposure (Absolute)

[  621.732496] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xe55 [  621.733321] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xe55 [  621.749803] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xe56 [  621.750586] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xe56 [  621.784790] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xcbf [  621.785731] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xcbf [  621.802333] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xcc0 [  621.803150] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xcc0 [  621.833353] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xc90 [  621.834204] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xc90 [  621.849972] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xc90 [  621.850772] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0902/0xc90

 

Exposure, Auto Priority (선택)

[ 1464.855961] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0903/0x1 [ 1464.855989] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0903/0x1

 

Exposure, Auto Priority (미선택)

[ 1519.669796] video2: VIDIOC_S_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0903/0x0 [ 1519.669856] video2: VIDIOC_G_EXT_CTRLS: which=0x9a0000, count=1, error_idx=0, request_fd=0, id/val=0x9a0903/0x0