文章目录

代码
makefile

经过这几天的验证，终于走通了FFmpeg读取USB摄像头H264帧，然后用rtmp推流。使用的版本是4.0.2，网上的示例要么是命令形式的，要么是读取YUV格式的数据，然后在编码的，所以只能自己摸索了。
FFmpeg的源码在ubuntu16.04上的编译就不说了，这个网上的文章很多，这里我要说的是，好像FFmpeg对v4l2的封装，不能从摄像头多种输出格式数据中，选择V4L2_PIX_FMT_H264这种格式的数据输出，只能是默认的输出，这点还没有研究明白。
没办法只能写v4l2的操作，将数据保存到内存中，在用FFmpeg从内存中读取数据，最后用rtmp推流。
这里要非常感谢雷神的两篇博客：

可以说没有这两篇博客，我还要摸索很久，可惜他不在世了；他的贡献现在还在让我们受益。

代码

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <errno.h>#include <assert.h>#include <fcntl.h>#include <malloc.h>#include <math.h>#include <sys/types.h>#include <sys/stat.h>#include <sys/time.h>#include <sys/ioctl.h>#include <sys/mman.h>#include <sys/poll.h>#include <linux/types.h>#include <linux/videodev2.h>#include <libavutil/time.h>#include <libavutil/imgutils.h>#include <libavutil/mathematics.h>#include <libavcodec/avcodec.h>#include <libavformat/avformat.h>#include <libavdevice/avdevice.h>#define DEV_TYPE'video4linux2'#define DEV_NAME'/dev/video1'#define MAX_CHANNEL (4)#define AV_IO_BUF_SIZE(96*1024)#define CLEAR(x) memset(&(x), 0, sizeof(x))struct buffer {void *start;size_t length;};struct usbcamera_node{int channel;char id[32];int usb_port;//V4L2char devname[32];int fd;struct v4l2_format fmt;struct v4l2_streamparm parm;struct v4l2_requestbuffers req;struct buffer *buffers;int n_buffers;int poll_index[MAX_CHANNEL];};struct usbcamera_node usbcamra;struct pollfd usbcamra_poll_fd[MAX_CHANNEL];nfds_t usbcamra_poll_fd_num = 0;unsigned int frame_len = 0;unsigned int frame_cnt = 0;int avError(int errNum);static int xioctl(int fh, int request, void *arg){int r;do{r = ioctl(fh, request, arg);} while (-1 == r && EINTR == errno);return r;}static int video_init(struct usbcamera_node *camera_node){struct v4l2_capability cap;struct v4l2_fmtdesc fmtdesc;int ret = 0;// open the video device with the API of open()camera_node->fd = open(camera_node->devname, O_RDWR | O_NONBLOCK, 0);if (-1 == camera_node->fd){fprintf(stderr, 'Cannot open '%s': %d, %s\n', camera_node->devname, errno, strerror(errno));return -1;}// inquire video device capability with the API of ioctlif (-1 == xioctl(camera_node->fd, VIDIOC_QUERYCAP, &cap)){fprintf(stderr, '%s is no V4L2 device\n', camera_node->devname);return -1;}// Set video device settingsif (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)){fprintf(stderr, '%s is no video capture device\n', camera_node->devname);return -1;}if (!(cap.capabilities & V4L2_CAP_STREAMING)){fprintf(stderr, '%s does not support streaming i/o\n', camera_node->devname);return -1;}printf('\nVIDOOC_QUERYCAP\n');printf('the camera driver is: %s\n', cap.driver);printf('the camera card is: %s\n', cap.card);printf('the camera bus info is: %s\n', cap.bus_info);printf('the version is: %d\n', cap.version);printf('the capabilities is: 0x%x\n', cap.capabilities);printf('the device_caps is: 0x%x\n', cap.device_caps);fmtdesc.index = 0; //form numberfmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;//frame typewhile(ioctl(camera_node->fd, VIDIOC_ENUM_FMT, &fmtdesc) != -1){printf('VIDIOC_ENUM_FMT success! fmtdesc.index:%d, fmtdesc.type:%d, fmtdesc.flags:%d, ' 'fmtdesc.description:%s, fmtdesc.pixelformat:%d\n', fmtdesc.index, fmtdesc.type, fmtdesc.flags, fmtdesc.description, fmtdesc.pixelformat);fmtdesc.index ++;}if (-1 == xioctl(camera_node->fd, VIDIOC_S_FMT, &camera_node->fmt)){fprintf(stderr, '%s set fmt failed\n', camera_node->devname);return -1;}printf('VIDIOC_S_FMT success! width:%d, height:%d, pixelformat:%x, field:%d, bytesperline:%d, ' 'sizeimage:%d, colorspace:%d, priv:%d, flags:%x, ycbcr_enc:%d, quantization:%d, xfer_func:%d\n', camera_node->fmt.fmt.pix.width, camera_node->fmt.fmt.pix.height, camera_node->fmt.fmt.pix.pixelformat, camera_node->fmt.fmt.pix.field, camera_node->fmt.fmt.pix.bytesperline, camera_node->fmt.fmt.pix.sizeimage, camera_node->fmt.fmt.pix.colorspace, camera_node->fmt.fmt.pix.priv, camera_node->fmt.fmt.pix.flags, camera_node->fmt.fmt.pix.ycbcr_enc, camera_node->fmt.fmt.pix.quantization, camera_node->fmt.fmt.pix.xfer_func);struct v4l2_streamparm parm = {0};parm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;xioctl(camera_node->fd, VIDIOC_G_PARM, &parm);parm.parm.capture.timeperframe.numerator = 1;parm.parm.capture.timeperframe.denominator = camera_node->parm.parm.capture.timeperframe.denominator;ret = xioctl(camera_node->fd, VIDIOC_S_PARM, &parm);if(ret !=0 ){printf('line:%d parm set error, errno:%d, str:%s\n', __LINE__, errno, strerror(errno));return -1;}printf('fd %d ret %d set Frame rate %.3f fps\n', camera_node->fd, ret, 1.0 * parm.parm.capture.timeperframe.denominator / parm.parm.capture.timeperframe.numerator);// Require the Driver of V4L2 buffers for MMAPif (-1 == xioctl(camera_node->fd, VIDIOC_REQBUFS, &camera_node->req)){if (EINVAL == errno){fprintf(stderr, '%s does not support memory mapping\n', 'USBCAMERA');return -1;}else{return -1;}}// Make the buffers map to the user spacefor (camera_node->n_buffers = 0; camera_node->n_buffers < camera_node->req.count; ++camera_node->n_buffers){struct v4l2_buffer buf;CLEAR(buf);buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;buf.index = camera_node->n_buffers;if (-1 == xioctl(camera_node->fd, VIDIOC_QUERYBUF, &buf)){ret = -1;break;}camera_node->buffers[camera_node->n_buffers].length = buf.length;camera_node->buffers[camera_node->n_buffers].start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE ,MAP_SHARED, camera_node->fd, buf.m.offset);printf('mmap buffer index:%d buf %p length %d\n', camera_node->n_buffers, camera_node->buffers[camera_node->n_buffers].start, buf.length);if (MAP_FAILED == camera_node->buffers[camera_node->n_buffers].start){ret = -1;break;}}if((ret == -1) && (camera_node->n_buffers != 0)){for(ret = 0; ret < camera_node->n_buffers; ret++){munmap(camera_node->buffers[camera_node->n_buffers].start, camera_node->buffers[camera_node->n_buffers].length);printf('munmap buffer index:%d buf %p length %ld\n', camera_node->n_buffers, camera_node->buffers[camera_node->n_buffers].start, camera_node->buffers[camera_node->n_buffers].length);}return -1;}return 0;}static int start_capturing(struct usbcamera_node *camera_node){unsigned int i;enum v4l2_buf_type type;int n_buffers = 0;n_buffers = camera_node->n_buffers;printf('start_capturing fd %d n_buffers %d\n', camera_node->fd, n_buffers);for (i = 0; i < n_buffers; ++i){struct v4l2_buffer buf;CLEAR(buf);buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;buf.index = i;if (-1 == xioctl(camera_node->fd, VIDIOC_QBUF, &buf)){printf('fd %d VIDIOC_QBUF faild\n', camera_node->fd);return -1;}}printf('fd %d VIDIOC_QBUF OK!\n', camera_node->fd);type = V4L2_BUF_TYPE_VIDEO_CAPTURE;if (-1 == xioctl(camera_node->fd, VIDIOC_STREAMON, &type)){printf('fd %d VIDIOC_STREAMON faild\n', camera_node->fd);return -1;}printf('fd %d VIDIOC_STREAMON Ok!\n', camera_node->fd);return 0;}static int stop_capturing(struct usbcamera_node *camera_node){enum v4l2_buf_type type;type = V4L2_BUF_TYPE_VIDEO_CAPTURE;if (-1 == xioctl(camera_node->fd, VIDIOC_STREAMOFF, &type)){printf('fd %d VIDIOC_STREAMOFF faild\n', camera_node->fd);return -1;}printf('fd %d VIDIOC_STREAMOFF Ok!\n', camera_node->fd);return 0;}static int read_frame(struct usbcamera_node *camera_node, unsigned char *pbuf, unsigned int ch, struct timeval *tvl){struct v4l2_buffer buf;int count = 0;int n_buffers = 0;n_buffers = camera_node->n_buffers;CLEAR(buf);buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;if (-1 == xioctl(camera_node->fd, VIDIOC_DQBUF, &buf)){switch (errno) {case EAGAIN:return 0;case EIO:/* Could ignore EIO, see spec. *//* fall through */default:{printf('VIDIOC_DQBUF faild\n');return -1;}}}if(buf.index > n_buffers){printf('buf.indx < n_buffers %d %d\n', buf.index, n_buffers);return -1;}memcpy(pbuf, camera_node->buffers[buf.index].start, buf.bytesused);tvl->tv_sec = buf.timestamp.tv_sec;tvl->tv_usec = buf.timestamp.tv_usec;count = buf.bytesused;if (-1 == xioctl(camera_node->fd, VIDIOC_QBUF, &buf)){printf('VIDIOC_QBUF faild\n');}return count;}void free_camra_resource(struct usbcamera_node *camera_node){int cnt = 0;for(cnt = 0; cnt < camera_node->n_buffers; cnt++){munmap(camera_node->buffers[cnt].start, camera_node->buffers[cnt].length);printf('munmap buffer index:%d buf %p length %ld\n', cnt, camera_node->buffers[cnt].start, camera_node->buffers[cnt].length);}}int read_buffer(void *opaque, uint8_t *pbuf, int buf_size){struct timeval tvl;if(poll(usbcamra_poll_fd, usbcamra_poll_fd_num, -1) == -1){printf('usbcamra poll failed !!!!!!!!!!!!!\n');return AVERROR_EXTERNAL;}if((usbcamra_poll_fd[0].revents & POLLERR) == POLLERR){printf('usbcamra_poll_fd[0].revents 0x%x\n', usbcamra_poll_fd[0].revents);return AVERROR_EXTERNAL;}if(usbcamra_poll_fd[0].revents && POLLIN){frame_len = read_frame(&usbcamra, pbuf, 0, &tvl);printf('frame_cnt:%d, frame_len:%d, tvl.tv_sec:%ld ', frame_cnt, frame_len, tvl.tv_sec);printf('%02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x ' '%02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x \n', pbuf[0],pbuf[1],pbuf[2],pbuf[3],pbuf[4],pbuf[5],pbuf[6],pbuf[7],pbuf[8],pbuf[9],pbuf[10],pbuf[11], pbuf[12],pbuf[13],pbuf[14],pbuf[15],pbuf[16],pbuf[17],pbuf[18],pbuf[19],pbuf[20],pbuf[21],pbuf[22], pbuf[23],pbuf[24],pbuf[25],pbuf[26],pbuf[27],pbuf[28],pbuf[29],pbuf[30],pbuf[31]);}frame_cnt++;usbcamra_poll_fd[0].revents = 0;if(frame_len > buf_size){printf('frame_len is too big then buf_size\n');return buf_size;}return (int)frame_len;}//ffmpeg -f v4l2 -list_formats all -i /dev/video0//程序执行：./ffmpeg_usb_rtmp /dev/video0 1280 720 30 1500000int main(int argc, char* argv[]){ int videoindex = -1; unsigned int frame_rate = 0; //所有代码执行之前要调用av_register_all和avformat_network_init //初始化所有的封装和解封装 flv mp4 mp3 mov。不包含编码和解码 av_register_all(); avformat_network_init(); if(argc != 5){usbcamra.fmt.fmt.pix.width = 1280;usbcamra.fmt.fmt.pix.height = 720;frame_rate = 30;}else{usbcamra.fmt.fmt.pix.width = atoi(argv[2]);usbcamra.fmt.fmt.pix.height = atoi(argv[3]);frame_rate = atoi(argv[4]);}sprintf(usbcamra.devname, '%s', argv[1]);printf('width:%d, height:%d, dev:%s', usbcamra.fmt.fmt.pix.width, usbcamra.fmt.fmt.pix.height, usbcamra.devname);usbcamra.fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;usbcamra.fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_H264;usbcamra.fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;CLEAR(usbcamra.parm);usbcamra.parm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;usbcamra.parm.parm.capture.timeperframe.numerator = 1;usbcamra.parm.parm.capture.timeperframe.denominator = frame_rate;CLEAR(usbcamra.req);usbcamra.req.count = 16;usbcamra.req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;usbcamra.req.memory = V4L2_MEMORY_MMAP;usbcamra.buffers = calloc(usbcamra.req.count, sizeof(struct buffer));if(!usbcamra.buffers){fprintf(stderr, 'calloc faild, errno:%d, str:%s\n', errno, strerror(errno));return -1;}video_init(&usbcamra);start_capturing(&usbcamra);usbcamra_poll_fd[0].fd = usbcamra.fd;usbcamra_poll_fd[0].events = POLLIN;usbcamra_poll_fd_num = 1; //输出的地址 const char *outUrl = 'rtmp://192.168.1.102:1935/live'; //AVFormatContext **ps 输入封装的上下文。包含所有的格式内容和所有的IO。如果是文件就是文件IO，网络就对应网络IOAVFormatContext *ifmt_ctx = NULL;ifmt_ctx = avformat_alloc_context();unsigned char* inbuffer=NULL;inbuffer = (unsigned char*)av_malloc(AV_IO_BUF_SIZE);if(inbuffer == NULL){avformat_free_context(ifmt_ctx);printf('line:%d av_malloc failed!\n', __LINE__);return -1;}AVIOContext *avio_in = avio_alloc_context(inbuffer, AV_IO_BUF_SIZE, 0, NULL, read_buffer, NULL, NULL);if(avio_in == NULL){avformat_free_context(ifmt_ctx);av_free((void*)inbuffer);printf('line:%d avio_alloc_context failed!\n', __LINE__);return -1;}ifmt_ctx->pb = avio_in;ifmt_ctx->flags = AVFMT_FLAG_CUSTOM_IO;//打开文件，解封文件头int ret = avformat_open_input(&ifmt_ctx, NULL, NULL, NULL);if (ret < 0){avformat_free_context(ifmt_ctx);av_free((void*)inbuffer);avio_context_free(&avio_in);return avError(ret);}printf('avformat_open_input success!\n');ret = avformat_find_stream_info(ifmt_ctx, NULL);if (ret != 0){avformat_free_context(ifmt_ctx);av_free((void*)inbuffer);avio_context_free(&avio_in);return avError(ret);}//打印视频视频信息//0打印所有 inUrl 打印时候显示，av_dump_format(ifmt_ctx, 0, NULL, 0);AVFormatContext * ofmt_ctx = NULL;//如果是输入文件 flv可以不传，可以从文件中判断。如果是流则必须传//创建输出上下文ret = avformat_alloc_output_context2(&ofmt_ctx, NULL, 'flv', outUrl);if (ret < 0){avformat_free_context(ifmt_ctx);av_free((void*)inbuffer);avio_context_free(&avio_in);avformat_free_context(ofmt_ctx);return avError(ret);}printf('avformat_alloc_output_context2 success!\n');printf('ifmt_ctx->nb_streams:%d\n', ifmt_ctx->nb_streams);//查找到当前输入流中的视频流，并记录视频流的索引unsigned int i;for (i = 0; i < ifmt_ctx->nb_streams; i++){//获取输入视频流AVStream *in_stream = ifmt_ctx->streams[i];if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO){videoindex = i;}//为输出上下文添加音视频流（初始化一个音视频流容器）AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);if (!out_stream){printf('未能成功添加音视频流\n');ret = AVERROR_UNKNOWN;}//将输入编解码器上下文信息 copy 给输出编解码器上下文//ret = avcodec_copy_context(out_stream->codec, in_stream->codec);ret = avcodec_parameters_copy(out_stream->codecpar, in_stream->codecpar);//ret = avcodec_parameters_from_context(out_stream->codecpar, in_stream->codec);//ret = avcodec_parameters_to_context(out_stream->codec, in_stream->codecpar);if (ret < 0){printf('copy 编解码器上下文失败\n');}out_stream->codecpar->codec_tag = 0;out_stream->codec->codec_tag = 0;if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER) {out_stream->codec->flags = out_stream->codec->flags | AV_CODEC_FLAG_GLOBAL_HEADER;}}printf('videoindex:%d\n', videoindex);av_dump_format(ofmt_ctx, 0, outUrl, 1);//打开IOret = avio_open(&ofmt_ctx->pb, outUrl, AVIO_FLAG_WRITE);if (ret < 0){avformat_free_context(ifmt_ctx);av_free((void*)inbuffer);avio_context_free(&avio_in);avformat_free_context(ofmt_ctx);return avError(ret);}//写入头部信息ret = avformat_write_header(ofmt_ctx, 0);if (ret < 0){avformat_free_context(ifmt_ctx);av_free((void*)inbuffer);avio_context_free(&avio_in);avformat_free_context(ofmt_ctx);avError(ret);}printf('avformat_write_header Success!\n');//推流每一帧数据//int64_t pts [ pts*(num/den) 第几秒显示]//int64_t dts 解码时间 [P帧(相对于上一帧的变化) I帧(关键帧，完整的数据) B帧(上一帧和下一帧的变化)] 有了B帧压缩率更高。AVPacket pkt;//获取当前的时间戳 微妙long long start_time = av_gettime();long long frame_index = 0;while (1){//输入输出视频流AVStream *in_stream, *out_stream;//获取解码前数据ret = av_read_frame(ifmt_ctx, &pkt);if (ret < 0) break;//PTS（Presentation Time Stamp）显示播放时间//DTS（Decoding Time Stamp）解码时间//没有显示时间（比如未解码的 H.264 ）if (pkt.pts == AV_NOPTS_VALUE){//AVRational time_base：时基。通过该值可以把PTS，DTS转化为真正的时间。AVRational time_base1 = ifmt_ctx->streams[videoindex]->time_base;//计算两帧之间的时间int64_t calc_duration = (double)AV_TIME_BASE / av_q2d(ifmt_ctx->streams[videoindex]->r_frame_rate);//配置参数pkt.pts = (double)(frame_index*calc_duration) / (double)(av_q2d(time_base1)*AV_TIME_BASE);pkt.dts = pkt.pts;pkt.duration = (double)calc_duration / (double)(av_q2d(time_base1)*AV_TIME_BASE);}if (pkt.stream_index == videoindex){AVRational time_base = ifmt_ctx->streams[videoindex]->time_base;AVRational time_base_q = { 1,AV_TIME_BASE };//计算视频播放时间int64_t pts_time = av_rescale_q(pkt.dts, time_base, time_base_q);//计算实际视频的播放时间int64_t now_time = av_gettime() - start_time;AVRational avr = ifmt_ctx->streams[videoindex]->time_base;printf('avr.num:%d, avr.den:%d, pkt.dts:%ld, pkt.pts:%ld, pts_time:%ld\n',avr.num, avr.den, pkt.dts, pkt.pts, pts_time);if (pts_time > now_time){//睡眠一段时间（目的是让当前视频记录的播放时间与实际时间同步）printf('pts_time:%ld, now_time:%ld\n', pts_time, now_time);av_usleep((unsigned int)(pts_time - now_time));}}in_stream = ifmt_ctx->streams[pkt.stream_index];out_stream = ofmt_ctx->streams[pkt.stream_index];//计算延时后，重新指定时间戳pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, (AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, (AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));pkt.duration = (int)av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);//字节流的位置，-1 表示不知道字节流位置,由程序自行探测pkt.pos = -1;if (pkt.stream_index == videoindex) {printf('Send %8lld video frames to output URL\n', frame_index);frame_index++;}ret = av_interleaved_write_frame(ofmt_ctx, &pkt);if (ret < 0){printf('发送数据包出错\n');break;}av_free_packet(&pkt);}stop_capturing(&usbcamra);free_camra_resource(&usbcamra);avformat_free_context(ifmt_ctx);av_free((void*)inbuffer);avio_context_free(&avio_in);avformat_free_context(ofmt_ctx);return 0;}int avError(int errNum) { char buf[1024]; av_strerror(errNum, buf, sizeof(buf)); printf('failed!\n'); return -1;}

程序运行方式：./ffmpeg_usb_rtmp /dev/video0 1280 720 30 1500000
有些USB摄像头支持命令设置H264编码率，但是这里没有写出来，因为不同厂家，命令不同，貌似v4l2没有这样统一的命令去设置编码率。
以上代码仅仅是测试读取USB摄像头H264帧进行rtmp推流的验证，直接在readbuffer函数使用poll读取数据，当帧率设置为30 时，存在丢帧播放花屏，这是因为使用的单线程，发送rtmp流的时候，不能去读数据，因此会丢帧。
另外也没有添加音频合成，然后在推流，后面接着弄吧，最终验证完之后，还要移植到imx6平台上。

makefile

TARGET = ffmpeg_usb_rtmpLIB_PATH  = /usr/local/lib/FFMPEG_LIBS = -lavutil -lavdevice -lavformat -lavcodec -lswresample -lavfilter -lswscale SDL_LIBS= -lSDL2EXTRA_LIBS  = -lz -lm -lpthread -lstdc++ -lm -lrt -lpcreALL_LIBS= $(EXTRA_LIBS) $(SDL_LIBS) $(FFMPEG_LIBS)   COMPILE_OPTS = -v -g -Wall -Wno-deprecated-declarations C_COMPILER   = gccC_FLAGS  = $(CFLAGS) $(COMPILE_OPTS) LD_FLAGS  = -L$(LIB_PATH) $(LDFLAGS)SRC = ffmpeg_usb_rtmp.cALL:$(C_COMPILER) $(C_FLAGS) $(LD_FLAGS) $(SRC) -o $(TARGET) $(ALL_LIBS) clean:rm -rf $(TARGET) *.o *.mp4 *.wav *.h264 *.avi *.flv

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学习ffmpeg的路还有很长！

FFmpeg读取USB摄像头H264帧rtmp推流

文章目录

代码

makefile

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