簡單查看流程，如有錯誤請指出。

CameraNativePreview.ets--> ?這里開始進入uvc_camera庫

(CameraDevice.ets/CameraManager.ets) ?--> CameraUtils.ets-->

-->CameraNativeMethods(index.d.ts文件，路徑:

uvc_camera\src\main\cpp\types\libuvc_camera\index.d.ts)

-->camera_uvc.cpp-->(camera_factory_helper.h,camera->getUserStream())

其中camera->getUserStream()在ICameraDevice?中，是base類，有倆實現：

class CameraDeviceUsbImpl : public ICameraDevice

在camera_device_usb.h中，路徑camera/usb，實現camera_device_usb.cpp

class CameraDeviceV4L2Impl : public ICameraDevice

在camera_device_v4l2.h中，路徑camera/v4l2

這里分析camera_device_usb.cpp

-->CameraStreamUsbImpl(camera_stream_usb.cpp)-->(prepare_preview,do_preview):

prepare_preview-->(uvc_get_stream,uvc_get_frame_desc，這倆方法都指向stream.c，路徑:

uvc_camera\src\main\cpp\libuvc\src\stream.c)

do_preview-->uvc_start_streaming-->stream.c-->uvc_start_streaming-->

(uvc_stream_open_ctrl,uvc_stream_start):

uvc_stream_open_ctrl-->(_uvc_get_stream_if,uvc_claim_if,uvc_stream_ctrl)

uvc_stream_start-->(uvc_find_frame_desc_stream,

libusb_fill_iso_transfer/libusb_fill_bulk_transfer,

pthread_create(&strmh->cb_thread, NULL, _uvc_user_caller, (void *)strmh);

libusb_submit_transfer)

-------------------------------------------------------------------------------------------------------------

這里根據紅綠藍三顏色分別分析：

一：

libusb_fill_iso_transfer-->_uvc_stream_callback-->(

_uvc_process_payload??或者

(pthread_cond_broadcast(&strmh->cb_cond);

pthread_mutex_unlock(&strmh->cb_mutex);))

這里根據LIBUSB_TRANSFER_XXX狀態不同會走不同的路徑，而libusb_fill_bulk_transfer和libusb_fill_iso_transfer一樣都會走_uvc_stream_callback，路徑一致

二:

pthread_create(&strmh->cb_thread, NULL, _uvc_user_caller, (void*)strmh

-->_uvc_user_caller--->(_uvc_populate_frame,

pthread_mutex_unlock(&strmh->cb_mutex);
strmh->user_cb(&strmh->frame, strmh->user_ptr);

)。

三：libusb_submit_transfer-->io.c-->libusb_submit_transfer

其中:_uvc_process_payload-->_uvc_swap_buffers

-->(pthread_cond_broadcast(&strmh->cb_cond);
pthread_mutex_unlock(&strmh->cb_mutex);)

數據是從linux_usbfs.c 中來的，從打開流到關閉流的整個過程，這里都會不停地打印：

op_submit_transfer:2

submit_bulk_transfer

handle_bulk_completion

op_submit_transfer:2

submit_bulk_transfer

_uvc_user_caller

而在獲取參數的過程中：

就會開始不停地打印：

op_submit_transfer:0

submit_control_transfer

handle_control_completion

直到打開后突然就變成：

op_submit_transfer:2

submit_bulk_transfer

然后:?_uvc_user_caller

而_uvc_user_caller方法見下：

do {
????LOG_D("_uvc_user_caller");
????pthread_mutex_lock(&strmh->cb_mutex);
????while (strmh->running && last_seq == strmh->hold_seq) {
????????pthread_cond_wait(&strmh->cb_cond, &strmh->cb_mutex);
????}
????if (!strmh->running) {
????????pthread_mutex_unlock(&strmh->cb_mutex);
????????break;
????}
????last_seq = strmh->hold_seq;
????_uvc_populate_frame(strmh);
????pthread_mutex_unlock(&strmh->cb_mutex);
????strmh->user_cb(&strmh->frame, strmh->user_ptr);
} while (1);

這里能否繼續執行取決于&strmh->cb_cond，搜索&strmh->cb_cond發現多出調用了：

pthread_cond_broadcast(&strmh->cb_cond);
pthread_mutex_unlock(&strmh->cb_mutex);

如：_uvc_swap_buffers

_uvc_stream_callback

uvc_stream_stop

而在linux_usbfs.c中的執行是：

op_handle_events-->reap_for_handle-->r = ioctl(hpriv->fd, IOCTL_USBFS_REAPURBNDELAY, &urb);

-->handle_bulk_completion(itransfer, urb);-->usbi_mutex_unlock(&itransfer->lock);

或者是

op_submit_transfer-->submit_bulk_transfer-->ioctl(hpriv->fd, IOCTL_USBFS_SUBMITURB, urb);

然后通過itransfer的數據和狀態變化，或者喚醒？調用_uvc_stream_callback??? 這樣就會和下面這段連接起來

而在stream.c中一般是通過：uvc_stream_start(開始執行一次)-->

_uvc_stream_callback

-->_uvc_process_payload

(_uvc_process_payload(strmh, transfer->buffer, transfer->actual_length);)-->

(

????????if (header_info & UVC_STREAM_EOF || ?strmh->got_bytes == strmh->cur_ctrl.dwMaxVideoFrameSize) {
????????????//來交換緩沖區，表示已接收完整幀
????????????_uvc_swap_buffers(strmh);
????????}

)

-->_uvc_swap_buffers

-->_uvc_user_caller

uvc_camera\src\main\cpp\libusb\os\linux_usbfs.c

這個包括了基本的usb操作

uvcCamera\uvc_camera\src\main\cpp\libusb\io.c

這個包括了io

uvc_camera\src\main\cpp\libuvc\src\stream.c

這里封裝了基本的相機流操作

然后關于

pthread_cond_broadcast(&strmh->cb_cond)

pthread_mutex_unlock(&strmh->cb_mutex)

以及close流程 ？？