一、环境介绍
操作系统：ubuntu18.04 64位
摄像头：电脑自带摄像头+外置USB摄像头
ffmpeg版本：4.2.2
x264版本：x264-snapshot-20181217-2245
关于Linux下X264和FFMPEG库的编译安装方法参考这里：https://blog.csdn.net/xiaolong1126626497/article/details/104919095
二、代码介绍
代码在linux下运行，使用ffmpeg本身的接口读取摄像头的数据帧，并编码为MP4文件存储。
三、核心代码
#include <stdlib.h> #include <stdio.h> #include <string.h> #include <math.h> #include <libavutil/avassert.h> #include <libavutil/channel_layout.h> #include <libavutil/opt.h> #include <libavutil/mathematics.h> #include <libavutil/timestamp.h> #include <libavformat/avformat.h> #include <libswscale/swscale.h> #include <libswresample/swresample.h> #define STREAM_DURATION 50.0 /*录制视频的持续时间 秒*/ #define STREAM_FRAME_RATE 5 /* images/s 这里可以根据摄像头的采集速度来设置帧率 */ #define STREAM_PIX_FMT AV_PIX_FMT_YUV420P /* default pix_fmt */ #define SCALE_FLAGS SWS_BICUBIC //存放视频的宽度和高度 int video_width; int video_height; // 单个输出AVStream的包装器 typedef struct OutputStream { AVStream *st; AVCodecContext *enc; /*下一帧的点数*/ int64_t next_pts; int samples_count; AVFrame *frame; AVFrame *tmp_frame; float t, tincr, tincr2; struct SwsContext *sws_ctx; struct SwrContext *swr_ctx; }OutputStream; typedef struct IntputDev { AVCodecContext *pCodecCtx; AVCodec *pCodec; AVFormatContext *v_ifmtCtx; int videoindex; struct SwsContext *img_convert_ctx; AVPacket *in_packet; AVFrame *pFrame,*pFrameYUV; }IntputDev; static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt) { AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base; printf("pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n", av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base), av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base), av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base), pkt->stream_index); } static int write_frame(AVFormatContext *fmt_ctx, const AVRational *time_base, AVStream *st, AVPacket *pkt) { /* 将输出数据包时间戳值从编解码器重新调整为流时基 */ av_packet_rescale_ts(pkt, *time_base, st->time_base); pkt->stream_index = st->index; /*将压缩的帧写入媒体文件。*/ log_packet(fmt_ctx, pkt); return av_interleaved_write_frame(fmt_ctx, pkt); } /*添加输出流。 */ static void add_stream(OutputStream *ost, AVFormatContext *oc,AVCodec **codec,enum AVCodecID codec_id) { AVCodecContext *c; int i; /* find the encoder */ *codec = avcodec_find_encoder(codec_id); if (!(*codec)) { fprintf(stderr, "Could not find encoder for '%s'\n", avcodec_get_name(codec_id)); exit(1); } ost->st = avformat_new_stream(oc, NULL); if (!ost->st) { fprintf(stderr, "Could not allocate stream\n"); exit(1); } ost->st->id = oc->nb_streams-1; c = avcodec_alloc_context3(*codec); if (!c) { fprintf(stderr, "Could not alloc an encoding context\n"); exit(1); } ost->enc = c; switch((*codec)->type) { case AVMEDIA_TYPE_AUDIO: c->sample_fmt = (*codec)->sample_fmts ? (*codec)->sample_fmts[0] : AV_SAMPLE_FMT_FLTP; c->bit_rate = 64000; c->sample_rate = 44100; if ((*codec)->supported_samplerates) { c->sample_rate = (*codec)->supported_samplerates[0]; for (i = 0; (*codec)->supported_samplerates[i]; i++) { if ((*codec)->supported_samplerates[i] == 44100) c->sample_rate = 44100; } } c->channels = av_get_channel_layout_nb_channels(c->channel_layout); c->channel_layout = AV_CH_LAYOUT_STEREO; if ((*codec)->channel_layouts) { c->channel_layout = (*codec)->channel_layouts[0]; for (i = 0; (*codec)->channel_layouts[i]; i++) { if ((*codec)->channel_layouts[i] == AV_CH_LAYOUT_STEREO) c->channel_layout = AV_CH_LAYOUT_STEREO; } } c->channels = av_get_channel_layout_nb_channels(c->channel_layout); ost->st->time_base = (AVRational){ 1, c->sample_rate }; break; case AVMEDIA_TYPE_VIDEO: c->codec_id = codec_id; c->bit_rate = 2500000; //平均比特率,例子代码默认值是400000 /* 分辨率必须是2的倍数。*/ c->width=video_width; c->height=video_height; /*时基：这是基本的时间单位（以秒为单位） *表示其中的帧时间戳。 对于固定fps内容， *时基应为1 /framerate，时间戳增量应为 *等于1。*/ ost->st->time_base = (AVRational){1,STREAM_FRAME_RATE}; //帧率设置 c->time_base = ost->st->time_base; c->gop_size = 12; /* 最多每十二帧发射一帧内帧 */ c->pix_fmt = STREAM_PIX_FMT; if(c->codec_id == AV_CODEC_ID_MPEG2VIDEO) { /* 只是为了测试，我们还添加了B帧 */ c->max_b_frames = 2; } if(c->codec_id == AV_CODEC_ID_MPEG1VIDEO) { /*需要避免使用其中一些系数溢出的宏块。 *普通视频不会发生这种情况，因为 *色度平面的运动与亮度平面不匹配。 */ c->mb_decision = 2; } break; default: break; } /* 某些格式希望流头分开。 */ if (oc->oformat->flags & AVFMT_GLOBALHEADER) c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; } static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height) { AVFrame *picture; int ret; picture = av_frame_alloc(); if (!picture) return NULL; picture->format = pix_fmt; picture->width = width; picture->height = height; /* 为帧数据分配缓冲区 */ ret = av_frame_get_buffer(picture, 32); if(ret<0) { fprintf(stderr, "Could not allocate frame data.\n"); exit(1); } return picture; } static void open_video(AVFormatContext *oc, AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg) { int ret; AVCodecContext *c = ost->enc; AVDictionary *opt = NULL; av_dict_copy(&opt, opt_arg, 0); /* open the codec */ ret = avcodec_open2(c, codec, &opt); av_dict_free(&opt); if (ret < 0) { fprintf(stderr, "Could not open video codec: %s\n", av_err2str(ret)); exit(1); } /* 分配并初始化可重用框架 */ ost->frame = alloc_picture(c->pix_fmt, c->width, c->height); if (!ost->frame) { fprintf(stderr, "Could not allocate video frame\n"); exit(1); } printf("ost->frame alloc success fmt=%d w=%d h=%d\n",c->pix_fmt,c->width, c->height); /*如果输出格式不是YUV420P，则为临时YUV420P *也需要图片。 然后将其转换为所需的 *输出格式。 */ ost->tmp_frame = NULL; if(c->pix_fmt != AV_PIX_FMT_YUV420P) { ost->tmp_frame = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height); if (!ost->tmp_frame) { fprintf(stderr, "Could not allocate temporary picture\n"); exit(1); } } /* 将流参数复制到多路复用器*/ ret=avcodec_parameters_from_context(ost->st->codecpar, c); if(ret<0) { fprintf(stderr, "Could not copy the stream parameters\n"); exit(1); } } /* *编码一个视频帧 *编码完成后返回1，否则返回0 */ static int write_video_frame(AVFormatContext *oc, OutputStream *ost,AVFrame *frame) { int ret; AVCodecContext *c; int got_packet=0; AVPacket pkt={0}; if(frame==NULL) return 1; c = ost->enc; av_init_packet(&pkt); /* 编码图像*/ ret = avcodec_encode_video2(c, &pkt, frame, &got_packet); if(ret<0) { fprintf(stderr, "Error encoding video frame: %s\n", av_err2str(ret)); exit(1); } printf("--------------video- pkt.pts=%s\n",av_ts2str(pkt.pts)); printf("----st.num=%d st.den=%d codec.num=%d codec.den=%d---------\n",ost->st->time_base.num,ost->st->time_base.den, c->time_base.num,c->time_base.den); if(got_packet) { ret = write_frame(oc, &c->time_base, ost->st, &pkt); }else { ret = 0; } if(ret<0) { fprintf(stderr, "Error while writing video frame: %s\n", av_err2str(ret)); exit(1); } return (frame || got_packet) ? 0 : 1; } static AVFrame *get_video_frame(OutputStream *ost,IntputDev* input,int *got_pic) { int ret, got_picture; AVCodecContext *c = ost->enc; AVFrame * ret_frame=NULL; if(av_compare_ts(ost->next_pts, c->time_base,STREAM_DURATION, (AVRational){1,1})>=0) return NULL; /*当我们将帧传递给编码器时，它可能会保留对它的引用 *内部,确保我们在这里不覆盖它*/ if (av_frame_make_writable(ost->frame)<0) exit(1); if(av_read_frame(input->v_ifmtCtx, input->in_packet)>=0) { if(input->in_packet->stream_index==input->videoindex) { ret = avcodec_decode_video2(input->pCodecCtx, input->pFrame, &got_picture, input->in_packet); *got_pic=got_picture; if(ret<0) { printf("Decode Error.\n"); av_packet_unref(input->in_packet); return NULL; } if(got_picture) { sws_scale(input->img_convert_ctx, (const unsigned char* const*)input->pFrame->data, input->pFrame->linesize, 0, input->pCodecCtx->height, ost->frame->data, ost->frame->linesize); ost->frame->pts =ost->next_pts++; ret_frame= ost->frame; } } av_packet_unref(input->in_packet); } return ret_frame; } static void close_stream(AVFormatContext *oc, OutputStream *ost) { avcodec_free_context(&ost->enc); av_frame_free(&ost->frame); av_frame_free(&ost->tmp_frame); sws_freeContext(ost->sws_ctx); swr_free(&ost->swr_ctx); } /* 采集摄像头数据编码成MP4视频 */ int main(int argc, char **argv) { OutputStream video_st = { 0 }, audio_st = { 0 }; const char *filename; AVOutputFormat *fmt; AVFormatContext *oc; AVCodec *audio_codec, *video_codec; int ret; int have_video = 0, have_audio = 0; int encode_video = 0, encode_audio = 0; AVDictionary *opt = NULL; int i; if(argc<3) { //./app /dev/video0 123.mp4 printf("用法: %s <摄像头设备节点> <文件名称> \n", argv[0]); return 1; } filename = argv[2]; printf("当前存储的视频文件名称:%s\n",filename); /*分配输出媒体环境*/ avformat_alloc_output_context2(&oc, NULL, NULL, filename); if(!oc) { printf("无法从文件扩展名推断出输出格式：使用MPEG。\n"); avformat_alloc_output_context2(&oc, NULL, "mpeg", filename); } if(!oc)return 1; //添加摄像头---------------------------------- IntputDev video_input={0}; AVCodecContext *pCodecCtx; AVCodec *pCodec; AVFormatContext *v_ifmtCtx; avdevice_register_all(); v_ifmtCtx = avformat_alloc_context(); //Linux下指定摄像头信息 AVInputFormat *ifmt=av_find_input_format("video4linux2"); if(avformat_open_input(&v_ifmtCtx,argv[1],ifmt,NULL)!=0) { printf("无法打开输入流.%s\n",argv[1]); return -1; } if(avformat_find_stream_info(v_ifmtCtx,NULL)<0) { printf("找不到流信息.\n"); return -1; } int videoindex=-1; for(i=0; i<v_ifmtCtx->nb_streams; i++) if(v_ifmtCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) { videoindex=i; printf("videoindex=%d\n",videoindex); break; } if(videoindex==-1) { printf("找不到视频流。\n"); return -1; } pCodecCtx=v_ifmtCtx->streams[videoindex]->codec; pCodec=avcodec_find_decoder(pCodecCtx->codec_id); if(pCodec==NULL) { printf("找不到编解码器。\n"); return -1; } if(avcodec_open2(pCodecCtx, pCodec,NULL)<0) { printf("无法打开编解码器。\n"); return -1; } AVFrame *pFrame,*pFrameYUV; pFrame=av_frame_alloc(); pFrameYUV=av_frame_alloc(); unsigned char *out_buffer=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height,16)); av_image_fill_arrays((AVPicture *)pFrameYUV->data,(AVPicture *)pFrameYUV->linesize, out_buffer, AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height,16); printf("摄像头尺寸(WxH): %d x %d \n",pCodecCtx->width, pCodecCtx->height); video_width=pCodecCtx->width; video_height=pCodecCtx->height; struct SwsContext *img_convert_ctx; img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL); AVPacket *in_packet=(AVPacket *)av_malloc(sizeof(AVPacket)); video_input.img_convert_ctx=img_convert_ctx; video_input.in_packet=in_packet; video_input.pCodecCtx=pCodecCtx; video_input.pCodec=pCodec; video_input.v_ifmtCtx=v_ifmtCtx; video_input.videoindex=videoindex; video_input.pFrame=pFrame; video_input.pFrameYUV=pFrameYUV; //-----------------------------添加摄像头结束 fmt=oc->oformat; /*使用默认格式的编解码器添加音频和视频流并初始化编解码器。*/ printf("fmt->video_codec = %d\n", fmt->video_codec); if(fmt->video_codec != AV_CODEC_ID_NONE) { add_stream(&video_st,oc,&video_codec,fmt->video_codec); have_video=1; encode_video=1; } /*现在已经设置了所有参数，可以打开音频并视频编解码器，并分配必要的编码缓冲区。*/ if(have_video)open_video(oc, video_codec, &video_st, opt); av_dump_format(oc,0,filename,1); /* 打开输出文件(如果需要) */ if(!(fmt->flags & AVFMT_NOFILE)) { ret=avio_open(&oc->pb,filename,AVIO_FLAG_WRITE); if(ret<0) { fprintf(stderr, "打不开'%s': %s\n", filename,av_err2str(ret)); return 1; } } /* 编写流头(如果有)*/ ret=avformat_write_header(oc, &opt); if(ret<0) { fprintf(stderr, "打开输出文件时发生错误: %s\n",av_err2str(ret)); return 1; } int got_pic; while(encode_video) { /*选择要编码的流*/ AVFrame *frame=get_video_frame(&video_st,&video_input,&got_pic); if(!got_pic) { usleep(10000); continue; } encode_video=!write_video_frame(oc,&video_st,frame); } av_write_trailer(oc); sws_freeContext(video_input.img_convert_ctx); avcodec_close(video_input.pCodecCtx); av_free(video_input.pFrameYUV); av_free(video_input.pFrame); avformat_close_input(&video_input.v_ifmtCtx); /*关闭每个编解码器*/ if (have_video)close_stream(oc, &video_st); /*关闭输出文件*/ if (!(fmt->flags & AVFMT_NOFILE))avio_closep(&oc->pb); /*释放流*/ avformat_free_context(oc); return 0; }
四、Makefile文件
app1: gcc ffmpeg_video.c -I /home/wbyq/work_pc/x264-snapshot-20181217-2245/_install/include -L /home/wbyq/work_pc/x264-snapshot-20181217-2245/_install/lib -I /home/wbyq/work_pc/ffmpeg-4.2.2/_install/include -L /home/wbyq/work_pc/ffmpeg-4.2.2/_install/lib -lavcodec -lavfilter -lavutil -lswresample -lavdevice -lavformat -lpostproc -lswscale -lx264
五、运行示例
