```
# ohos_camera_demo
GetUintParameter debug.bytrace.tags.enableflags error.
Options:
-h | --help Print this message
-o | --offline stream offline test
-c | --capture capture one picture
-w | --set WB Set white balance Cloudy
-v | --video capture Viedeo of 10s
-a | --Set AE Set Auto exposure
-f | --Set Flashlight Set flashlight ON 5s OFF
-q | --quit stop preview and quit this app
o
Options:
-h | --help Print this message
-o | --offline stream offline test
-c | --capture capture one picture
-w | --set WB Set white balance Cloudy
-v | --video capture Viedeo of 10s
-a | --Set AE Set Auto exposure
-f | --Set Flashlight Set flashlight ON 5s OFF
-q | --quit stop preview and quit this app
```
执行结果:输入u 报错:ERROR:main test:cannot open framebuffer /dev/fb0 file node
```
Options:
-h | --help Print this message
-p | --preview start preview on platform sensor
-c | --capture capture one picture
-w | --set WB Set white balance Cloudy
-e | --Set AE Set exposure time
-v | --video capture Viedeo of 10s
-u | --uvc start preview on uvc preview
-a | --Set ATE Set Auto exposure
-q | --quit stop preview and quit this app
INFO:please input command(input -q exit this app)
u
ERROR:main test:cannot open framebuffer /dev/fb0 file node
INFO:V4L2OpenDevice /dev/video10
```
```
# ls -l dev/fb0
ls: dev/fb0: No such file or directory
# find -name fb0
./dev/graphics/fb0
./sys/class/graphics/fb0
./sys/devices/platform/display-subsystem/graphics/fb0
```
```c
/**
* struct v4l2_buffer - video buffer info
* @index: id number of the buffer
* @type: enum v4l2_buf_type; buffer type (type == *_MPLANE for
* multiplanar buffers);
* @bytesused: number of bytes occupied by data in the buffer (payload);
* unused (set to 0) for multiplanar buffers
* @flags: buffer informational flags
* @field: enum v4l2_field; field order of the image in the buffer
* @timestamp: frame timestamp
* @timecode: frame timecode
* @sequence: sequence count of this frame
* @memory: enum v4l2_memory; the method, in which the actual video data is
* passed
* @offset: for non-multiplanar buffers with memory == V4L2_MEMORY_MMAP;
* offset from the start of the device memory for this plane,
* (or a "cookie" that should be passed to mmap() as offset)
* @userptr: for non-multiplanar buffers with memory == V4L2_MEMORY_USERPTR;
* a userspace pointer pointing to this buffer
* @fd: for non-multiplanar buffers with memory == V4L2_MEMORY_DMABUF;
* a userspace file descriptor associated with this buffer
* @planes: for multiplanar buffers; userspace pointer to the array of plane
* info structs for this buffer
* @length: size in bytes of the buffer (NOT its payload) for single-plane
* buffers (when type != *_MPLANE); number of elements in the
* planes array for multi-plane buffers
*
* Contains data exchanged by application and driver using one of the Streaming
* I/O methods.
*/
struct v4l2_buffer {
__u32 index;
__u32 type;
__u32 bytesused;
__u32 flags;
__u32 field;
struct timeval timestamp;
struct v4l2_timecode timecode;
__u32 sequence;
/* memory location */
__u32 memory;
union {
__u32 offset;
unsigned long userptr;
struct v4l2_plane *planes;
__s32 fd;
} m;
__u32 length;
__u32 reserved2;
__u32 reserved;
}
```