📄 spcaview_spcaserver源码详解（1） - legend - csdnblog.htm
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width=15 border=0> spcaview.spcaserver源码详解（1）</A> </DIV>
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<P>struct vdIn {<BR> int fd;<BR> char *videodevice
; <BR> struct
video_mmap
vmmap;
//内存影射<BR> struct video_capability videocap;<BR> int
mmapsize;<BR> struct video_mbuf videombuf;<BR> struct video_picture
videopict;<BR> struct video_window videowin;<BR> struct video_channel
videochan;<BR> struct video_param videoparam; <BR> int cameratype
;<BR> char *cameraname;<BR> char bridge[9];<BR> int
sizenative;
// available size in jpeg<BR> int
sizeothers;
// others palette <BR> int
palette; //
available palette<BR> int norme
;
// set spca506 usb video grabber<BR> int channel
;
// set spca506 usb video grabber<BR> int grabMethod
;<BR> unsigned char
*pFramebuffer;
//内存影射后指向数据指针<BR> unsigned char
*ptframe[4];
//frameconverse以后指向将要发送到网络的数据指针<BR> int
framelock[4];
//占用与否标识<BR> pthread_mutex_t
grabmutex;
<BR> int framesizeIn
;
//在init中确定<BR> volatile int
frame_cour;
//目前要传输到网络的frame<BR> int
bppIn;
//depth<BR> int hdrwidth;<BR> int
hdrheight;<BR> int
formatIn;
//palette<BR> int
signalquit; <BR> };<BR>在linux内核源代码中的/include/linux/videodev.h中定义了各个format格式的值</P>
<P>从main函数出发，跟踪int format</P>
<P>1.1 初始化int format</P>
<P>int format = VIDEO_PALETTE_YUV420P;</P>
<P>1.2 根据输入的参数识别用户要求的format</P>
<P>if (strcmp (argv[i], "-f") == 0) {<BR> if (i + 1 >= argc)
{<BR> printf ("No parameter specified with -f,
aborting.\n");<BR> exit
(1);<BR> }<BR> mode = strdup (argv[i +
1]);</P>
<P> if (strncmp (mode, "r32", 3) == 0) {<BR> format
= VIDEO_PALETTE_RGB32;<BR> } else if (strncmp (mode, "r24", 3)
== 0) {<BR> format =
VIDEO_PALETTE_RGB24;<BR> } else if (strncmp (mode, "r16",
3) == 0) {<BR> format =
VIDEO_PALETTE_RGB565;<BR> } else if (strncmp (mode,
"yuv", 3) == 0) {<BR> format =
VIDEO_PALETTE_YUV420P;<BR> } else if (strncmp (mode,
"jpg", 3) == 0) {<BR> format =
VIDEO_PALETTE_JPEG;<BR> }else
{<BR> format =
VIDEO_PALETTE_YUV420P;<BR> }<BR> }</P>
<P>2. 初始化设备的时候</P>
<P>init_videoIn (&videoIn, videodevice, width, height,
format,grabmethod)</P>
<P>2.1</P>
<P>vd->formatIn = format; <BR>vd->bppIn = GetDepth
(vd->formatIn);
//根据format值确定vd.depth</P>
<P>2.2 进入init_v4l (vd)</P>
<P>2.2.1</P>
<P>probePalette(vd
)
//将五个palette类型传到video_picture数据结构里面，set之后在get一次，比较前后palette值，如果两者一致，说明该palette类型为可用</P>
<P>probeSize(vd
)
//同上理，将7个width*height结构传到video_window里面，察看是否可用</P>
<P>check_palettesize(vd)
// 首先转换大小int needsize =
convertsize(vd->hdrwidth,vd->hdrheight)，convertsize(),根据w*h返回7个类型：VGA,PAL,SIF,CIF,QPAL,QSIF,QCIF，上述七个宏定义在spcav4l.h中：</P>
<P>#define MASQ 1<BR>#define VGA MASQ<BR>#define PAL (MASQ <<
1)<BR>#define SIF (MASQ << 2)<BR>#define CIF (MASQ << 3)<BR>#define
QPAL (MASQ << 4)<BR>#define QSIF (MASQ << 5)<BR>#define QCIF (MASQ
<< 6)
int needsize的智应该为这七个值之一</P>
<P>int needpalette=0，needpalette =
checkpalette(vd)，在checkpalette(vd)中，convertpalette(vd->formatIn); see is
the palette available？ 根据vd->formatIn返回jpeg yuv420p rbg24 rgb565 and
rgb32</P>
<P>#define JPG MASQ //JPEG 1<BR>#define YUV420P (MASQ <<
1)<BR>#define RGB24 (MASQ << 2)<BR>#define RGB565 (MASQ <<
3)<BR>#define RGB32 (MASQ << 4) </P>
<P>根据needpalette的值察看是否available?将测试结果写入函数palette = paletteconvert(
needpalette)，if (palette)，对palette的返回将它赋值到vd->vmmap.height =
vd->hdrheight;<BR> vd->vmmap.width =
vd->hdrwidth;<BR> vd->vmmap.format =
palette;设置VIDIOCMCAPTURE，测试一下是否可以采集，ok的话vd->formatIn = palette;</P>
<P>根据needsize和vd.sizeother察看是否还有别的palettesize可以支持，test is palette and size are
available otherwhise return the next available palette and size palette is set
by preference order jpeg yuv420p rbg24 rgb565 and rgb32 </P>
<P>2.2.2</P>
<P>vd->videopict.palette = vd->formatIn; 设置video_picture数据结构</P>
<P>vd->videopict.depth = GetDepth (vd->formatIn);<BR>vd->bppIn =
GetDepth (vd->formatIn);</P>
<P>2.2.3</P>
<P>vd->framesizeIn = (vd->hdrwidth * vd->hdrheight * vd->bppIn)
>> 3; 设置framesize大小</P>
<P>erreur = SetVideoPict (vd);<BR>erreur = GetVideoPict (vd);<BR>if
(vd->formatIn != vd->videopict.palette ||<BR>vd->bppIn !=
vd->videopict.depth)<BR>exit_fatal ("could't set video palette Abort
!");<BR>if (erreur < 0)<BR>exit_fatal ("could't set video palette Abort
!");</P>
<P>2.2.4</P>
<P>开始采集两个frame的视频数据，指向数据的指针为pFramebuffer</P>
<P>3 打开采集视频线程 pthread_create (&w1, NULL, (void *) grab, NULL)，进入grab函数</P>
<P>3.1 vd->vmmap.format = vd->formatIn;</P>
<P>VIDIOCSYNC：开始check在init时候采集的数据是否已经完成</P>
<P>3.2 采集完成，进行jpeg压缩处理，里面大有文章</P>
<P>jpegsize= convertframe(vd->ptframe[vd->frame_cour]+ sizeof(struct
frame_t),<BR> vd->pFramebuffer +
vd->videombuf.offsets[vd->vmmap.frame],<BR> vd->hdrwidth,vd->hdrheight,vd->formatIn,qualite);</P>
<P>在 int convertframe(unsigned char *dst,unsigned char *src, int width,int
height, int formatIn, int qualite)中</P>
<P>switch
(formatIn)根据不同的palette值做不同的数据压缩处理，返回压缩后的数据大小值，如果是JPEG格式，意味着硬件采集近来的数据已经做了压缩，不需要再用软件进行压缩处理，而除了VIDEO_PALETTE_JPEG以外的palette，都需要进行encode,函数为UINT32
encode_image (UINT8 * input_ptr, UINT8 * output_ptr,UINT32 quality_factor,
UINT32 image_format,UINT32 image_width, UINT32 image_height)，UINT32
image_format为输入的palette，压缩使用huffman编码，详细代码在huffman.c和encode.c中</P>
<P>4. 打开数据远程网络传输线程，在accept阻塞处代开线程pthread_create(&server_th, NULL, (void
*)service, &new_sock)，</P>
<P>首先在连接处读取frame_t message数据结构的内容，read(sock,(unsigned
char*)&message,sizeof(struct
client_t)),根据message的内容决定如何传输，下一步做循环发送，根据frame_lock和frame_cour发送没有被占用的compressed
frame</P>
<P> </P> <BR><BR>
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