You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
153 lines
4.5 KiB
153 lines
4.5 KiB
|
|
/*
|
|
* 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);
|
|
}
|