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
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