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 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#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) ***/
	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 frame
		struct 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 0
	FILE *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;
#endif
	int 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 queue
	if(-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 file
	process_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 clean
rm -f *.o a.out test core *~ *.avi
root@ubuntu:/home/share/test/v4l2_MJPEG_AVI# make
gcc    -c -o main.o main.c
gcc    -c -o avilib.o avilib.c
gcc  -o test main.o  avilib.o 
root@ubuntu:/home/share/test/v4l2_MJPEG_AVI# ./test 

camera driver name is : gspca_zc3xx
camera device name is : PC Camera
camera bus information: usb-0000:02:00.0-2.1

support device 1.JPEG

n_buffer = 6
root@ubuntu:/home/share/test/v4l2_MJPEG_AVI# ls
avilib.c  avilib.h  avilib.o  avi_test.avi  main.c  main.o  Makefile  test
root@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