分类: LINUX
2009-04-15 01:36:13
Linux摄像头编程小结 | |
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来源: ChinaUnix博客 日期: 2006.06.03 16:47 (共有0条评论) | |
这次是在linux下开发摄像头的程序,主要用的是video4linux来做的,界面用qt来实现,开始准备用frame buffer来直接写屏但是效果不怎么好,后来就用qt来做了,这样用起来效果还蛮好的,帧率也可以,可以上到30fps;运用v4l来编程主要掌握其 api,要提高帧率最重要的是用到内存映射,其实用qt和frame buffer的时候都要用到内存映射来做,只有这样才可以达到较高的帧率,不过要注意资源的利用问题.mmap后一定要munmap.对于frame buffer是很有意思的一个东西,特别是驱动的设计. 代码如下: 1.open device: video_dev = open("\dev\video0",O_RDWR)); 2.get the information of the video device struct video_capability video_cap; memset(&video_cap,0,sizeof(video_cap)); if(ioctl(video_dev,VIDIOCGCAP,&video_cap) == -1) { perror("Cann't get the information of the video device"); close(video_dev); exit(1); } 3.get the information of the channels struct video_channel video_chan; memset(&video_chan,0,sizeof(video_chan)); for(channel = 0;channel < video_cap.channels;channel++) { video_chan.channel = channel; if(ioctl(video_dev,VIDIOCGCHAN,&video_chan) == -1) { perror("Cann't get the information of the channels"); close(video_dev); exit(3); } if(video_chan.type == VIDEO_TYPE_TV) { #ifdef DEBUG printf("NO.%d channel is %s,type is tv!\n",channel,video_chan.name); #endif } if(video_chan.type == VIDEO_TYPE_CAMERA) { if(ioctl(video_dev,VIDIOCSCHAN,&video_chan) == -1) { perror("Cann't set the camera channel!"); close(video_dev); exit(4); } } } 4.get the capture attributes struct video_picture video_pic; memset(&video_pic,0,sizeof(video_pic)); if(ioctl(video_dev,VIDIOCGPICT,&video_pic) == -1) { perror("Cann't get the picture attributes of the device!"); close(video_dev); exit(5); } 5.set capture attributes video_pic.palette = VIDEO_PALETTE_*****;//different camera has different palette video_pic.brightness = 65535; video_pic.colour = 0; if(ioctl(video_dev,VIDIOCSPICT,&video_pic) == -1) { perror("Cann't set the picture attributs!"); close(video_dev); exit(6); } 6.mmap the device struct video_mbuf mbuf; unsigned char *frames; memset(&mbuf,0,sizeof(mbuf)); if(ioctl(video_dev,VIDIOCGMBUF,&mbuf) == -1) { perror("Cann't get the buffer information of the video device!"); close(video_dev); exit(7); } frames = (unsigned char *)::mmap(0,mbuf.size,PROT_READ|PROT_WRITE,MAP_SHARED,video_dev,0); if(!frames || frames == (unsigned char *)(long)(-1)) { perror("The device cann't be memory mapped!"); close(video_dev); exit(8); } 7.capture if(ioctl(video_dev,VIDIOCMCAPTURE,&mmap) == -1) { perror("Capture failed!"); close(video_dev); exit(9); } else { //display or save the picture file } |