从USB摄像头接收YUV帧 SDL播放
SDL学习教程：http://lazyfoo.net/SDL_tutorials/index.php
代码下载：http://download.csdn.net/download/jinchaoqi/6953321
代码：
main.c
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/ioctl.h> #include <sys/time.h> #include <unistd.h> #include <fcntl.h> #include <errno.h> #include <sys/mman.h> #include <linux/videodev2.h> #include <linux/fb.h> #include <pthread.h> #include <libavcodec/avcodec.h> #include <libavformat/avformat.h> #include <libswscale/swscale.h> #include <SDL/SDL.h> #include <SDL/SDL_thread.h> #include "gather_picture.h" #define PRINT printf("LINE: %d\n",__LINE__) int main(int argc, char **argv) { int n = 1, i; unsigned char frmrate; unsigned char *p = NULL; char* status = NULL; SDL_Overlay *bmp = NULL; SDL_Surface *screen = NULL; SDL_Rect rect; SDL_Event event; struct SwsContext *sws_ctx = NULL; if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) { fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError()); exit(1); } #ifndef __DARWIN__ screen = SDL_SetVideoMode(WIDTH, HEIGHT, 0, 0); #else screen = SDL_SetVideoMode(WIDTH, HEIGHT, 24, 0); #endif if(!screen) { fprintf(stderr, "SDL: could not set video mode - exiting\n"); exit(1); } bmp = SDL_CreateYUVOverlay(WIDTH, HEIGHT, SDL_YUY2_OVERLAY, screen); p = (unsigned char *) bmp->pixels[0]; rect.x = 0; rect.y = 0; rect.w = WIDTH; rect.h = HEIGHT; init_V4L2(); gather_picture_init(); gather_on(); while(1){ for(i = 0; i < 4; i++){ video_getframe(i); //write(sock, frame_buf[i].start, frame_buf[i].length); SDL_LockYUVOverlay(bmp); memcpy(p, frame_buf.start[i], WIDTH* HEIGHT* 2); SDL_UnlockYUVOverlay(bmp); SDL_DisplayYUVOverlay(bmp, &rect); if(video_enqueue(i) < 0){ printf("video_enqueue() failed\n"); return -1; } SDL_PollEvent(&event); switch(event.type) { case SDL_QUIT: SDL_FreeYUVOverlay(bmp); SDL_Quit(); return 0; break; default: break; } } } return 0; }
gather_picture.h:
#ifndef GATHER_PICTURE_H #define GATHER_PICTURE_H #define VIDEO_DEV "/dev/video0" //视频设备 #define WIDTH 640 #define HEIGHT 480 struct frame_buf{ //一帧图像缓冲区 int length[4]; void * start[4]; }; struct frame_buf frame_buf; int init_V4L2(); int gather_picture_init(); int gather_on(); int gather_off(); int video_getframe(int i); int video_enqueue(int i); #endif
gather_picture.c:
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/ioctl.h> #include <fcntl.h> #include <errno.h> #include <sys/mman.h> #include <linux/videodev2.h> #include "gather_picture.h" int g_videofd = -1; //设备描述符 struct v4l2_buffer buf; //驱动中的一帧图像缓存，对应命令VIDIOC_QUERYBUF //投放一个空的视频缓冲区到视频缓冲区输入队列中 ； int video_enqueue(int i) { buf.index = i; if(ioctl(g_videofd, VIDIOC_QBUF, &buf) < 0){ perror("enqueue failed"); return -1; } return 0; } //摄像头设备信息查询及配置 int init_V4L2() { struct v4l2_capability cap ;//视频设备的功能，对应命令VIDIOC_QUERYCAP struct v4l2_fmtdesc stfmt; //当前视频支持的格式，对应命令VIDIOC_ENUM_FMT struct v4l2_format fmt; //当前驱动的频捕获格式式，对应命令VIDIOC_G_FMT、VIDIOC_S_FMT //1).打开摄像头设备 g_videofd = open(VIDEO_DEV, O_RDWR); if(g_videofd == -1){ perror("open"); return -1; } //2).查询摄像头设备的基本信息及功能 if(ioctl(g_videofd, VIDIOC_QUERYCAP, &cap) < 0){ perror("ioctl"); return -1; } else{ printf("driver:\t\t%s\n",cap.driver); printf("card:\t\t%s\n",cap.card); printf("bus_info:\t%s\n",cap.bus_info); printf("version:\t%d\n",cap.version); printf("capabilities:\t%#x\n",cap.capabilities); if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == V4L2_CAP_VIDEO_CAPTURE) { printf("Device %s: supports capture.\n", VIDEO_DEV); } if ((cap.capabilities & V4L2_CAP_STREAMING) == V4L2_CAP_STREAMING) { printf("Device %s: supports streaming.\n", VIDEO_DEV); } } //3).列举摄像头所支持像素格式。 memset(&stfmt, 0, sizeof(stfmt)); stfmt.index = 0; stfmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; printf("device support:\n"); while(ioctl(g_videofd, VIDIOC_ENUM_FMT, &stfmt) != -1){ printf("\t%d: %s \n\n", stfmt.index++, stfmt.description); //stfmt.index++; } //4).设置当前驱动的频捕获格式 memset(&fmt, 0 ,sizeof(fmt)); fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; fmt.fmt.pix.height = HEIGHT; fmt.fmt.pix.width = WIDTH; fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; ioctl(g_videofd, VIDIOC_S_FMT, &fmt); printf("Size: %d,%d\n", fmt.fmt.pix.width, fmt.fmt.pix.height); printf("Video stored type: %d\n",fmt.fmt.pix.pixelformat); if(fmt.fmt.pix.height != 480){ printf("%s,%d: Unable to set format\n",__func__,__LINE__); return -1; } return 0; } //采集初始化 int gather_picture_init() { struct v4l2_requestbuffers reqbuf;//申请帧缓存，对应命令VIDIOC_REQBUFS int i = 0; //1).向驱动申请帧缓存 reqbuf.count = 4;// 缓存数量，也就是说在缓存队列里保持多少张照片 reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; reqbuf.memory = V4L2_MEMORY_MMAP; if(ioctl(g_videofd, VIDIOC_REQBUFS, &reqbuf)==-1) { perror("VIDEO_REQBUFS"); return -1; } //2).获取申请的每个缓存的信息，并mmap到用户空间 for (i = 0; i < reqbuf.count; i++) { buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = i; if (ioctl (g_videofd, VIDIOC_QUERYBUF, &buf) == -1) { printf("query buffer error\n"); return -1; } frame_buf.length[i] = buf.length; frame_buf.start[i] = mmap(NULL, buf.length, PROT_READ |PROT_WRITE, MAP_SHARED, g_videofd, buf.m.offset); if(frame_buf.start[i] == MAP_FAILED) { printf("buffer map error:%s,%d\n", __func__, __LINE__); return-1; } video_enqueue(i);//帧缓存入队 } return 0; } //开始采集 int gather_on() { enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if(ioctl(g_videofd, VIDIOC_STREAMON, &type) < 0){ perror("stream on"); return -1; } return 0; } //采集结束 int gather_off() { enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if(ioctl(g_videofd, VIDIOC_STREAMOFF, &type) < 0){ perror("stream on"); return -1; } return 0; } //取出视频缓冲区的输出队列中取得一个已经 //保存有一帧视频数据的视频缓冲区； int video_getframe(int i) { buf.index = i; if(ioctl(g_videofd, VIDIOC_DQBUF, &buf) < 0){ perror("release failed"); return -1; } return 0; }
