使用avilib封装MJPEG数据应用实例

    avilib 是一个很小的封装模块，它可以将一些图片数据封装成视频格式。在一些比较差的摄像头中，他们只支持V4L2_PIX_FMT_MJPEG 输出JPEG格式数据，以这种格式输出的数据，并不是标准的JPEG图片数据。因此，如果只是把MJPEG输出的所有文件存成一个文件，那么这个文件其实并不能播放。据网上的一些资料介绍，说是缺少Huffman 表，需要自己手动插入一个Huffman表。在一些嵌入式设备中，他们直接将MPEG模式下输出的数据，然后通过JPEG解码库解码成RGB数据，然后直接丢到LCD的BUFF中就可以了（这种方法我没有测试过，只是看网上资料这么介绍）。

    本人主要开发嵌入式设备，且刚接触图形编码时间不久，暂时还没有使用一些大的图片格式转换库，库文件是在网上找的，avilib只有一个文件编译之后的大小也只有几十K，他可以直接将v4l2 MPEG模式输出的数据封装成avi格式视屏。它提供的接口有：

void AVI_set_video(avi_t *AVI, int width, int height, double fps, char *compressor);void AVI_set_audio(avi_t *AVI, int channels, long rate, int bits, int format, long mp3rate);int  AVI_write_frame(avi_t *AVI, char *data, long bytes, int keyframe);int  AVI_dup_frame(avi_t *AVI);int  AVI_write_audio(avi_t *AVI, char *data, long bytes);int  AVI_append_audio(avi_t *AVI, char *data, long bytes);long AVI_bytes_remain(avi_t *AVI);int  AVI_close(avi_t *AVI);long AVI_bytes_written(avi_t *AVI);avi_t *AVI_open_input_file(char *filename, int getIndex);avi_t *AVI_open_fd(int fd, int getIndex);int avi_parse_input_file(avi_t *AVI, int getIndex);long AVI_audio_mp3rate(avi_t *AVI);long AVI_video_frames(avi_t *AVI);int  AVI_video_width(avi_t *AVI);int  AVI_video_height(avi_t *AVI);double AVI_frame_rate(avi_t *AVI);char* AVI_video_compressor(avi_t *AVI);int  AVI_audio_channels(avi_t *AVI);int  AVI_audio_bits(avi_t *AVI);int  AVI_audio_format(avi_t *AVI);long AVI_audio_rate(avi_t *AVI);long AVI_audio_bytes(avi_t *AVI);long AVI_audio_chunks(avi_t *AVI);long AVI_max_video_chunk(avi_t *AVI);long AVI_frame_size(avi_t *AVI, long frame);long AVI_audio_size(avi_t *AVI, long frame);int  AVI_seek_start(avi_t *AVI);int  AVI_set_video_position(avi_t *AVI, long frame);long AVI_get_video_position(avi_t *AVI, long frame);long AVI_read_frame(avi_t *AVI, char *vidbuf, int *keyframe);int  AVI_set_audio_position(avi_t *AVI, long byte);int  AVI_set_audio_bitrate(avi_t *AVI, long bitrate);long AVI_read_audio(avi_t *AVI, char *audbuf, long bytes);long AVI_audio_codech_offset(avi_t *AVI);long AVI_audio_codecf_offset(avi_t *AVI);long AVI_video_codech_offset(avi_t *AVI);long AVI_video_codecf_offset(avi_t *AVI);int  AVI_read_data(avi_t *AVI, char *vidbuf, long max_vidbuf,                               char *audbuf, long max_audbuf,                               long *len);void AVI_print_error(char *str);char *AVI_strerror();char *AVI_syserror();int AVI_scan(char *name);int AVI_dump(char *name, int mode);char *AVI_codec2str(short cc);int AVI_file_check(char *import_file);void AVI_info(avi_t *avifile);uint64_t AVI_max_size();int avi_update_header(avi_t *AVI);int AVI_set_audio_track(avi_t *AVI, int track);int AVI_get_audio_track(avi_t *AVI);int AVI_audio_tracks(avi_t *AVI);

下面是一个简单的测试程序：

/*=============================================================================#     FileName: main.c#         Desc: this program aim to get image from USB camera,#               used the V4L2 interface.#       Author: Licaibiao#      Version: #   LastChange: 2016-12-10 #      History:=============================================================================*/#include <unistd.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>#include <sys/ioctl.h>#include <stdlib.h>#include <linux/types.h>#include <linux/videodev2.h>#include <malloc.h>#include <math.h>#include <string.h>#include <sys/mman.h>#include <errno.h>#include <assert.h>#include <sys/time.h>#include "avilib.h"#define FILE_VIDEO  "/dev/video0"#define JPG "./out/image%d.jpg"typedef struct{    void *start;int length;}BUFTYPE;BUFTYPE *usr_buf;static unsigned int n_buffer = 0;  avi_t *out_fd = NULL; struct timeval time;float get_main_time(struct timeval* start , int update){float dt;struct timeval now;gettimeofday(&now, NULL);dt = (float)(now.tv_sec  - start->tv_sec);dt += (float)(now.tv_usec - start->tv_usec) * 1e-6;if (update > 0) {start->tv_sec = now.tv_sec;start->tv_usec = now.tv_usec;}return dt;}/*set video capture ways(mmap)*/int init_mmap(int fd){/*to request frame cache, contain requested counts*/struct v4l2_requestbuffers reqbufs;memset(&reqbufs, 0, sizeof(reqbufs));reqbufs.count = 6;  /*the number of buffer*/reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;    reqbufs.memory = V4L2_MEMORY_MMAP;if(-1 == ioctl(fd,VIDIOC_REQBUFS,&reqbufs)){perror("Fail to ioctl 'VIDIOC_REQBUFS'");exit(EXIT_FAILURE);}n_buffer = reqbufs.count;printf("n_buffer = %d\n", n_buffer);//usr_buf = calloc(reqbufs.count, sizeof(usr_buf));usr_buf = calloc(reqbufs.count, sizeof(BUFTYPE));/*** (4) ***<span style="font-family: Arial, Helvetica, sans-serif;">/</span>if(usr_buf == NULL){printf("Out of memory\n");exit(-1);}/*map kernel cache to user process*/for(n_buffer = 0; n_buffer < reqbufs.count; ++n_buffer){//stand for a framestruct v4l2_buffer buf;memset(&buf, 0, sizeof(buf));buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;buf.index = n_buffer;/*check the information of the kernel cache requested*/if(-1 == ioctl(fd,VIDIOC_QUERYBUF,&buf)){perror("Fail to ioctl : VIDIOC_QUERYBUF");exit(EXIT_FAILURE);}usr_buf[n_buffer].length = buf.length;usr_buf[n_buffer].start = (char *)mmap(NULL,buf.length,PROT_READ | PROT_WRITE,MAP_PRIVATE, fd,buf.m.offset);if(MAP_FAILED == usr_buf[n_buffer].start){perror("Fail to mmap");exit(EXIT_FAILURE);}}}int open_camera(void){int fd;/*open video device with block */fd = open(FILE_VIDEO, O_RDONLY);if(fd < 0){fprintf(stderr, "%s open err \n", FILE_VIDEO);exit(EXIT_FAILURE);};return fd;}int init_camera(int fd){struct v4l2_capability cap;/* decive fuction, such as video input */struct v4l2_format tv_fmt; /* frame format */  struct v4l2_fmtdesc fmtdesc;  /* detail control value */struct v4l2_control ctrl;int ret;/*show all the support format*/memset(&fmtdesc, 0, sizeof(fmtdesc));fmtdesc.index = 0 ;                 /* the number to check */fmtdesc.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;/* check video decive driver capability */if(ret=ioctl(fd, VIDIOC_QUERYCAP, &cap)<0){fprintf(stderr, "fail to ioctl VIDEO_QUERYCAP \n");exit(EXIT_FAILURE);}/*judge wherher or not to be a video-get device*/if(!(cap.capabilities & V4L2_BUF_TYPE_VIDEO_CAPTURE)){fprintf(stderr, "The Current device is not a video capture device \n");exit(EXIT_FAILURE);}/*judge whether or not to supply the form of video stream*/if(!(cap.capabilities & V4L2_CAP_STREAMING)){printf("The Current device does not support streaming i/o\n");exit(EXIT_FAILURE);}printf("\ncamera driver name is : %s\n",cap.driver);printf("camera device name is : %s\n",cap.card);printf("camera bus information: %s\n",cap.bus_info);/*display the format device support*/while(ioctl(fd,VIDIOC_ENUM_FMT,&fmtdesc)!=-1){printf("\nsupport device %d.%s\n\n",fmtdesc.index+1,fmtdesc.description);fmtdesc.index++;}/*set the form of camera capture data*/tv_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;      /*v4l2_buf_typea,camera must use V4L2_BUF_TYPE_VIDEO_CAPTURE*/tv_fmt.fmt.pix.width = 320;tv_fmt.fmt.pix.height = 240;tv_fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_JPEG;/*V4L2_PIX_FMT_YYUV*/tv_fmt.fmt.pix.field = V4L2_FIELD_NONE;   /*V4L2_FIELD_NONE*/if (ioctl(fd, VIDIOC_S_FMT, &tv_fmt)< 0) {fprintf(stderr,"VIDIOC_S_FMT set err\n");exit(-1);close(fd);}init_mmap(fd);}int start_capture(int fd){unsigned int i;enum v4l2_buf_type type;/*place the kernel cache to a queue*/for(i = 0; i < n_buffer; i++){struct v4l2_buffer buf;memset(&buf, 0, sizeof(buf));buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;buf.index = i;if(-1 == ioctl(fd, VIDIOC_QBUF, &buf)){perror("Fail to ioctl 'VIDIOC_QBUF'");exit(EXIT_FAILURE);}}type = V4L2_BUF_TYPE_VIDEO_CAPTURE;if(-1 == ioctl(fd, VIDIOC_STREAMON, &type)){printf("i=%d.\n", i);perror("VIDIOC_STREAMON");close(fd);exit(EXIT_FAILURE);}return 0;}int process_image(void *addr, int length){#if 0FILE *fp;static int num = 0;char image_name[20];sprintf(image_name, JPG, num++);if((fp = fopen(image_name, "w")) == NULL){perror("Fail to fopen");exit(EXIT_FAILURE);}fwrite(addr, length, 1, fp);usleep(500);fclose(fp);return 0;#endifint res = 0;float ret = 0;//ret = get_main_time(&time , 1);res = AVI_write_frame(out_fd, addr, length,0);//ret = get_main_time(&time , 1);//printf("AVI write time = %f\n",ret);if(res < 0){perror("Fail to write frame\n");exit(EXIT_FAILURE);}return 0;}int read_frame(int fd){struct v4l2_buffer buf;unsigned int i;memset(&buf, 0, sizeof(buf));buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;//put cache from queueif(-1 == ioctl(fd, VIDIOC_DQBUF,&buf)){perror("Fail to ioctl 'VIDIOC_DQBUF'");exit(EXIT_FAILURE);}assert(buf.index < n_buffer);//read process space's data to a fileprocess_image(usr_buf[buf.index].start, usr_buf[buf.index].length);if(-1 == ioctl(fd, VIDIOC_QBUF,&buf)){perror("Fail to ioctl 'VIDIOC_QBUF'");exit(EXIT_FAILURE);}return 1;}int mainloop(int fd){int count = 400;while(count-- > 0){for(;;){fd_set fds;struct timeval tv;int r;float ret = 0;ret = get_main_time(&time , 1);FD_ZERO(&fds);FD_SET(fd,&fds);/*Timeout*/tv.tv_sec = 2;tv.tv_usec = 0;r = select(fd + 1,&fds,NULL,NULL,&tv);ret = get_main_time(&time , 1);//printf("AVI write time = %f\n",ret);if(-1 == r){ if(EINTR == errno)continue;perror("Fail to select");exit(EXIT_FAILURE);}if(0 == r){fprintf(stderr,"select Timeout\n");exit(-1);}if(read_frame(fd)){    break;}}}return 0;}void stop_capture(int fd){enum v4l2_buf_type type;type = V4L2_BUF_TYPE_VIDEO_CAPTURE;if(-1 == ioctl(fd,VIDIOC_STREAMOFF,&type)){perror("Fail to ioctl 'VIDIOC_STREAMOFF'");exit(EXIT_FAILURE);}}void close_camera_device(int fd){unsigned int i;for(i = 0;i < n_buffer; i++){if(-1 == munmap(usr_buf[i].start,usr_buf[i].length)){exit(-1);}}free(usr_buf);if(-1 == close(fd)){perror("Fail to close fd");exit(EXIT_FAILURE);}}void init_avi(void){ char *filename = "avi_test.avi";out_fd = AVI_open_output_file(filename);if(out_fd!=NULL){AVI_set_video(out_fd, 320, 240, 25, "MJPG");}else{perror("Fail to open AVI\n");exit(EXIT_FAILURE);}}void close_avi(void){AVI_close(out_fd);}void main(void){int fd;fd = open_camera();init_avi();init_camera(fd);start_capture(fd);mainloop(fd);stop_capture(fd);close_avi();close_camera_device(fd);}

编译运行结果：

root@ubuntu:/home/share/test/v4l2_MJPEG_AVI# make cleanrm -f *.o a.out test core *~ *.aviroot@ubuntu:/home/share/test/v4l2_MJPEG_AVI# makegcc    -c -o main.o main.cgcc    -c -o avilib.o avilib.cgcc  -o test main.o  avilib.o root@ubuntu:/home/share/test/v4l2_MJPEG_AVI# ./test camera driver name is : gspca_zc3xxcamera device name is : PC Cameracamera bus information: usb-0000:02:00.0-2.1support device 1.JPEGn_buffer = 6root@ubuntu:/home/share/test/v4l2_MJPEG_AVI# lsavilib.c  avilib.h  avilib.o  avi_test.avi  main.c  main.o  Makefile  testroot@ubuntu:/home/share/test/v4l2_MJPEG_AVI#

生成的avi_est.avi 文件，在迅雷播放器上播放如下：

     

    这里需要注意，可能是因为我的USB驱动问题，读取JPEG需要的时间过长，导致录制的视频，播放的时候会出现快进的问题。另外，如果在设置v4l2 内存映射的时候，如果申请的buff 块太少也是会导致数据采集过慢的问题。

    完整的工程代码可以这里下载：avilib将JPEG数据封装成AVI视频