+++ /dev/null
-
-/*
- * Question: I need to display a live camera image via VNC. Until now I just
- * grab an image, set the rect to modified and do a 0.1 s sleep to give the
- * system time to transfer the data.
- * This is obviously a solution which doesn't scale very well to different
- * connection speeds/cpu horsepowers, so I wonder if there is a way for the
- * server application to determine if the updates have been sent. This would
- * cause the live image update rate to always be the maximum the connection
- * supports while avoiding excessive loads.
- *
- * Thanks in advance,
- *
- *
- * Christian Daschill
- *
- *
- * Answer: Originally, I thought about using seperate threads and using a
- * mutex to determine when the frame buffer was being accessed by any client
- * so we could determine a safe time to take a picture. The probem is, we
- * are lock-stepping everything with framebuffer access. Why not be a
- * single-thread application and in-between rfbProcessEvents perform a
- * camera snapshot. And this is what I do here. It guarantees that the
- * clients have been serviced before taking another picture.
- *
- * The downside to this approach is that the more clients you have, there is
- * less time available for you to service the camera equating to reduced
- * frame rate. (or, your clients are on really slow links). Increasing your
- * systems ethernet transmit queues may help improve the overall performance
- * as the libvncserver should not stall on transmitting to any single
- * client.
- *
- * Another solution would be to provide a seperate framebuffer for each
- * client and use mutexes to determine if any particular client is ready for
- * a snapshot. This way, your not updating a framebuffer for a slow client
- * while it is being transferred.
- */
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <rfb/rfb.h>
-
-
-#define WIDTH 640
-#define HEIGHT 480
-#define BPP 4
-
-/* 15 frames per second (if we can) */
-#define PICTURE_TIMEOUT (1.0/15.0)
-
-
-/*
- * throttle camera updates
-*/
-int TimeToTakePicture() {
- static struct timeval now={0,0}, then={0,0};
- double elapsed, dnow, dthen;
-
- gettimeofday(&now,NULL);
-
- dnow = now.tv_sec + (now.tv_usec /1000000.0);
- dthen = then.tv_sec + (then.tv_usec/1000000.0);
- elapsed = dnow - dthen;
-
- if (elapsed > PICTURE_TIMEOUT)
- memcpy((char *)&then, (char *)&now, sizeof(struct timeval));
- return elapsed > PICTURE_TIMEOUT;
-}
-
-
-
-/*
- * simulate grabbing a picture from some device
- */
-int TakePicture(unsigned char *buffer)
-{
- static int last_line=0, fps=0, fcount=0;
- int line=0;
- int i,j;
- struct timeval now;
-
- /*
- * simulate grabbing data from a device by updating the entire framebuffer
- */
-
- for(j=0;j<HEIGHT;++j) {
- for(i=0;i<WIDTH;++i) {
- buffer[(j*WIDTH+i)*BPP+0]=(i+j)*128/(WIDTH+HEIGHT); /* red */
- buffer[(j*WIDTH+i)*BPP+1]=i*128/WIDTH; /* green */
- buffer[(j*WIDTH+i)*BPP+2]=j*256/HEIGHT; /* blue */
- }
- buffer[j*WIDTH*BPP+0]=0xff;
- buffer[j*WIDTH*BPP+1]=0xff;
- buffer[j*WIDTH*BPP+2]=0xff;
- }
-
- /*
- * simulate the passage of time
- *
- * draw a simple black line that moves down the screen. The faster the
- * client, the more updates it will get, the smoother it will look!
- */
- gettimeofday(&now,NULL);
- line = now.tv_usec / (1000000/HEIGHT);
- if (line>HEIGHT) line=HEIGHT-1;
- memset(&buffer[(WIDTH * BPP) * line], 0, (WIDTH * BPP));
-
- /* frames per second (informational only) */
- fcount++;
- if (last_line > line) {
- fps = fcount;
- fcount = 0;
- }
- last_line = line;
- fprintf(stderr,"%03d/%03d Picture (%03d fps)\r", line, HEIGHT, fps);
-
- /* success! We have a new picture! */
- return (1==1);
-}
-
-
-
-
-/*
- * Single-threaded application that interleaves client servicing with taking
- * pictures from the camera. This way, we do not update the framebuffer
- * while an encoding is working on it too (banding, and image artifacts).
- */
-int main(int argc,char** argv)
-{
- long usec;
-
- rfbScreenInfoPtr server=rfbGetScreen(&argc,argv,WIDTH,HEIGHT,8,3,BPP);
- server->desktopName = "Live Video Feed Example";
- server->frameBuffer=(char*)malloc(WIDTH*HEIGHT*BPP);
- server->alwaysShared=(1==1);
-
- /* Initialize the server */
- rfbInitServer(server);
-
- /* Loop, processing clients and taking pictures */
- while (rfbIsActive(server)) {
- if (TimeToTakePicture())
- if (TakePicture((unsigned char *)server->frameBuffer))
- rfbMarkRectAsModified(server,0,0,WIDTH,HEIGHT);
-
- usec = server->deferUpdateTime*1000;
- rfbProcessEvents(server,usec);
- }
- return(0);
-}
projects / presencevnc / blobdiff