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uvc摄像头代码解析3

6.uvc解析uvc视频流
6.1 重要结构体
6.1.1 uvc数据流
[cpp]  
struct uvc_streaming {  
    struct list_head list;  //uvc视频流链表头  
    struct uvc_device *dev; //uvc设备  
    struct video_device *vdev;  //V4L2视频设备  
    struct uvc_video_chain *chain;  //uvc视频链  
    atomic_t active;  
    struct usb_inte易做图ce *intf; //usb接口设备  
    int intfnum;    //usb接口号  
    __u16 maxpsize; //最大包尺寸  
    struct uvc_streaming_header header; //uvc视频流头部  
    enum v4l2_buf_type type;    //V4L2缓冲区类型 输入/输出  
    unsigned int nformats;  //uvc格式个数  
    struct uvc_format *format;  //uvc格式指针  
    struct uvc_streaming_control ctrl;  //uvc数据流控制  
    struct uvc_format *cur_format;  //当前uvc格式指针  
    struct uvc_frame *cur_frame;    //当前uvc帧指针  
    struct mutex mutex;  
    unsigned int frozen : 1;  
    struct uvc_video_queue queue;   //uvc视频队列  
    void (*decode) (struct urb *urb, struct uvc_streaming *video,struct uvc_buffer *buf);//解码函数  
    struct {  
        __u8 header[256];  
        unsigned int header_size;  
        int skip_payload;  
        __u32 payload_size;  
        __u32 max_payload_size;  
    } bulk;  
    struct urb *urb[UVC_URBS];//urb数组  
    char *urb_buffer[UVC_URBS]; //urb缓冲区  
    dma_addr_t urb_dma[UVC_URBS];//urb DMA缓冲区  
    unsigned int urb_size;    
    __u32 sequence;  
    __u8 last_fid;  
};  
 
6.1.2 uvc格式
[cpp]  
struct uvc_format { //uvc格式  
    __u8 type;  //类型  
    __u8 index; //索引  
    __u8 bpp;   //bits per pixel 每像素位数  
    __u8 colorspace;    //颜色空间  
    __u32 fcc;  //压缩格式  
    __u32 flags;    //标记  
    char name[32];  //名字  
    unsigned int nframes;   //所含uvc帧个数  
    struct uvc_frame *frame;    //uvc帧指针  
};  
 
6.1.3 uvc帧
[cpp] 
struct uvc_frame {  //uvc帧  
    __u8  bFrameIndex;  //帧索引号  
    __u8  bmCapabilities;   //uvc帧兼容性  
    __u16 wWidth;   //宽度  
    __u16 wHeight;  //高度  
    __u32 dwMinBitRate; //最新位流  
    __u32 dwMaxBitRate; //最大位流  
    __u32 dwMaxVideoFrameBufferSize;    //最大视频帧缓冲区  
    __u8  bFrameIntervalType;   //间隙类型  
    __u32 dwDefaultFrameInterval;   //默认帧间隙  
    __u32 *dwFrameInterval; //帧间隙指针  
};  
 
6.2 uvc_parse_streaming函数
[cpp]  
static int uvc_parse_streaming(struct uvc_device *dev,struct usb_inte易做图ce *intf)  
{  
    struct uvc_streaming *streaming = NULL; //uvc数据流  
    struct uvc_format *format;  //uvc格式  
    struct uvc_frame *frame;    //uvc帧  
    struct usb_host_inte易做图ce *alts = &intf->altsetting[0];  //获取usb接口第一个usb_host_inte易做图ce (Alt.Setting 0)  
    unsigned char *_buffer, *buffer = alts->extra;   //获取额外描述符  
    int _buflen, buflen = alts->extralen;    //获取额外描述符长度  
    unsigned int nformats = 0, nframes = 0, nintervals = 0;  
    unsigned int size, i, n, p;  
    __u32 *interval;  
    __u16 psize;  
    int ret = -EINVAL;  
    if (intf->cur_altsetting->desc.bInte易做图ceSubClass != UVC_SC_VIDEOSTREAMING) { //判读usb接口描述符子类是否为视频数据流接口子类  
        uvc_trace(UVC_TRACE_DESCR, "device %d inte易做图ce %d isn't a video streaming inte易做图ce\n", dev->udev->devnum,intf->altsetting[0].desc.bInte易做图ceNumber);  
        return -EINVAL;  
    }  
    if (usb_driver_claim_inte易做图ce(&uvc_driver.driver, intf, dev)) {    //绑定uvc设备的usb驱动和usb接口  
        uvc_trace(UVC_TRACE_DESCR, "device %d inte易做图ce %d is already claimed\n", dev->udev->devnum,intf->altsetting[0].desc.bInte易做图ceNumber);  
        return -EINVAL;  
    }  
    streaming = kzalloc(sizeof *streaming, GFP_KERNEL); //分配uvc数据流内存  
    if (streaming == NULL) {  
        usb_driver_release_inte易做图ce(&uvc_driver.driver, intf);  
        return -EINVAL;  
    }  
    mutex_init(&streaming->mutex);  
    streaming->dev = dev;    //uvc数据流和uvc设备易做图  
    streaming->intf = usb_get_intf(intf);    //uvc数据流和usb接口易做图,并增加引用计数  
    streaming->intfnum = intf->cur_altsetting->desc.bInte易做图ceNumber;  //设置接口号  
    /* The Pico iMage webcam has its class-specific inte易做图ce descriptors after the endpoint descriptors. */  
    if (buflen == 0) {  //Pico iMage webcam 特殊处理  
        for (i = 0; i < alts->desc.bNumEndpoints; ++i) {  
            struct usb_host_endpoint *ep = &alts->endpoint[i];  
            if (ep->extralen == 0)  
                continue;  
            if (ep->extralen > 2 && ep->extra[1] == USB_DT_CS_INTERFACE) {  
                uvc_trace(UVC_TRACE_DESCR, "trying extra data from endpoint %u.\n", i);  
                buffer = alts->endpoint[i].extra;  
                buflen = alts->endpoint[i].extralen;  
       
补充:软件开发 , C++ ,
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