Linux下C语言实现ffmpeg视频+音频推流

1.环境需求
①ffmpeg源码编译
https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu官网编译教程
一定要支持h264

②alsa支持

2.思路
①ffmpeg调用摄像头推流为主进程
②alsa录音并推流为线程
③利用信号量做互斥锁，让两个进程互斥推流。

3.源码

#include <alsa/asoundlib.h>
#include <stdio.h>
#include <sys/time.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavdevice/avdevice.h>
#include <libswresample/swresample.h>
#include <libswscale/swscale.h>
#include <pthread.h>
#include <sys/sem.h>
#include <sys/ipc.h>
#include <errno.h>
#include <unistd.h>
#include <math.h>
#define CHANNELS 2
#define FSIZE 2*CHANNELS

//设置初值结构体
union semun{
    int              val;    /* Value for SETVAL */
    struct semid_ds *buf;    /* Buffer for IPC_STAT, IPC_SET */
    unsigned short  *array;  /* Array for GETALL, SETALL */
    struct seminfo  *__buf;  /* Buffer for IPC_INFO(Linux-specific) */
};

//获取资源
int sem_p(int semid)
{
    struct sembuf buf;
    int ret=-1;
    buf.sem_num=0;
    buf.sem_op=-1;
    buf.sem_flg=SEM_UNDO;
    ret=semop(semid,&buf,1);
    if(ret==-1)
    {
        perror("sem get fail!");
        return -1;
    }
    return 0;
}


//释放资源
int sem_v(int semid)
{
    struct sembuf buf;
    int ret=-1;
    buf.sem_num=0;
    buf.sem_op=+1;
    buf.sem_flg=SEM_UNDO;
    ret=semop(semid,&buf,1);
    if(ret==-1)
    {
        perror("sem get fail!");
        return -1;
    }
    return 0;
}


void *thread_func(void *arg);

//关键输出封装器
AVFormatContext* outfmt_ctx = NULL;
//推流前准备标志
int video_ready=0,audio_ready=0;
//互斥锁
int semid=-1;
union semun sem_val;

int main()
{
    
    //初始化网络
    avformat_network_init();
    //初始化设备
    avdevice_register_all();
    //输入封装器
    AVFormatContext* infmt_ctx = NULL;
    
	
    //视频输入格式
    AVInputFormat* ifmt =NULL;
	
    //通过v4l2框架来获取视频输入格式
    ifmt = av_find_input_format("linux4video2");

    //视频输入设备
    char *in_filename  = "/dev/video0";
	
    //视频输出设备
    char *out_filename = "rtmp://47.101.62.167/live/stream";
    
    //打开视频设备
    if (0 > avformat_open_input(&infmt_ctx, in_filename, ifmt, NULL)) {
		printf("failed open input file\n");
		return -1;
	}
	
	//读取设备信息
	if (0 > avformat_find_stream_info(infmt_ctx, NULL)) {
		printf("failed find stream info\n");
		avformat_close_input(&infmt_ctx);
		return -1;
	}
	
	
	//对流（Stream）的封装和抽象
	AVStream *in_stream = NULL;
    AVStream *out_stream = NULL;
    
    //视频流和音频流的标志
    int videoindex=-1;
	
	int i=0;
	int ret;
	//查找视频||音频流
	for (i = 0; i < infmt_ctx->nb_streams; i++)
	{
		//Create output AVStream according to input AVStream
		
		if (infmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
		{
			videoindex = i;
		}
		else
		{
			break;
		}
	}
	
	if (videoindex == -1) 
	{
        printf("input video stream not exist\n");
        return -1;
    }
    
    
	AVCodec* encodec = NULL;
	AVCodec* decodec = NULL;
	
	
	//找到编码器
	encodec = avcodec_find_encoder(AV_CODEC_ID_H264);
	if (!encodec) 
	{
		printf("not find encoder\n");
		avformat_close_input(&infmt_ctx);
		return -1;
	}
	
	
	//创建解码器上下文
	AVCodecContext* decodec_ctx = NULL;
	decodec_ctx=infmt_ctx->streams[videoindex]->codec;
	//找到解码器
	decodec = avcodec_find_decoder(decodec_ctx->codec_id);
	if (!decodec) 
	{
		printf("not find decoder\n");
		avformat_close_input(&infmt_ctx);
		return -1;
	}
	
	//创建编码器上下文
	AVCodecContext* encodec_ctx = NULL;
	encodec_ctx = avcodec_alloc_context3(encodec);
	if (!encodec_ctx) 
	{
		printf("not alloc context3\n\n");
		avformat_close_input(&infmt_ctx);
		return -1;
	}
	
	//打开解码器
	ret = avcodec_open2(decodec_ctx, decodec, NULL);
    if (ret < 0) {
        fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
        return -1;
    }
	
	
    //配置编码器参数
    encodec_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; 
    encodec_ctx->codec_id = encodec->id;
    encodec_ctx->bit_rate = 400000;
    encodec_ctx->width = 640;
    encodec_ctx->height = 480;
    encodec_ctx->time_base = (AVRational){1, 30};    //5是编多少帧就发送，可根据编码速度改变
    encodec_ctx->framerate = (AVRational){30, 1};
    encodec_ctx->gop_size = 15;
    encodec_ctx->max_b_frames = 0;
    encodec_ctx->pix_fmt = AV_PIX_FMT_YUV420P;
	
    
    //编码质量和速度
    av_opt_set(encodec_ctx->priv_data, "preset", "ultrafast", 0);
    av_opt_set(encodec_ctx->priv_data, "tune", "zerolatency", 0);
    AVDictionary *opts = NULL;
    av_dict_set(&opts, "profile", "baseline", 0);
    //av_opt_set(encodec_ctx->priv_data, "crf", "18", 0);
	
    //打开编码器
    ret = avcodec_open2(encodec_ctx, encodec, &opts);
    if (ret < 0) {
        fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
        return -1;
    }
    
    //初始化输出封装器
    ret=avformat_alloc_output_context2(&outfmt_ctx, NULL, "flv",out_filename);
    if (ret != 0) {
        printf("failed alloc output context\n");
		avformat_close_input(&infmt_ctx);
        return -1;;
    }
    
    //添加视频流
    out_stream = avformat_new_stream(outfmt_ctx,NULL);
    if (!out_stream) {
		printf("failed new stream\n");
		avformat_close_input(&infmt_ctx);
		avformat_close_input(&outfmt_ctx);
		return -1;
    }
    out_stream->codecpar->codec_tag = 0;
    //复制参数
    avcodec_parameters_from_context(out_stream->codecpar, encodec_ctx);
	
    //查看输出封装内容
    av_dump_format(outfmt_ctx, 0, out_filename, 1);
    //创建音频推流线程
    pthread_t tid;            //线程ID
    int t_arg=100;            //传入参数
    if(pthread_create(&tid,NULL,thread_func,&t_arg))    //创建线程
    {
        perror("Fail to create thread");
    }
    //等待音频推流初始化
    while(!audio_ready)
    {
    
    }
    //打开rtmp的网络输出IO
    ret=avio_open(&outfmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
    if (ret!=0) 
    {
	printf("failed to open outfile\n");
	avformat_close_input(&infmt_ctx);
	avformat_close_input(&outfmt_ctx);
	return -1;
    }
	
    //写入封装头
    ret=avformat_write_header(outfmt_ctx, NULL);
    if (ret!=0) 
    {
	printf("failed to write header\n");
	avio_close(outfmt_ctx->pb);
	avformat_close_input(&infmt_ctx);
	avformat_close_input(&outfmt_ctx);
	return -1;
    }
	
	
	AVPacket *dec_pkt,enc_pkt;
	//包裹申请内存
	dec_pkt = (AVPacket *)av_malloc(sizeof(AVPacket)); 
	memset(&enc_pkt, 0, sizeof(enc_pkt));
	//像素格式转换YU420
	struct SwsContext *img_convert_ctx  = NULL;
	img_convert_ctx  = sws_getCachedContext(img_convert_ctx, decodec_ctx->width, decodec_ctx->height,decodec_ctx->pix_fmt, encodec_ctx->width, encodec_ctx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, 0, 0, 0);
	if (!img_convert_ctx)
	{
		printf("fail to sws_getCachedContext\n");
	} 
	
	AVFrame *pFrameYUV,*pFrame ;
	//原始帧
	pFrame = av_frame_alloc();
	//输出帧
	pFrameYUV = av_frame_alloc();
	pFrameYUV->format = AV_PIX_FMT_YUV420P;
	pFrameYUV->width = 640;
	pFrameYUV->height = 480;
	pFrameYUV->pts = 0;
	
	ret = av_frame_get_buffer(pFrameYUV, 1);
	if (ret != 0)
	{
		printf("fail to frame get buffer\n");
		return -1;
	}
	//开始计时
	int64_t start_time = av_gettime();
	//标记
    int got_picture=0,enc_got_frame=0;
    //每一帧编号
    int vpts = 0;
    
    //创建信号量
    semid=semget(1234,1,0666|IPC_CREAT);
    if(semid==-1)
    {
        perror("create sem fail!");
        return -1;
    }
    
    //设置信号量初值
    sem_val.val=1;
    ret=semctl(semid,0,SETVAL,sem_val);
    if(ret==-1)
    {
        perror("semctl set sem val fail!");
        return -1;
    }

    video_ready=1;
    
	while(1)
	{
	    //每一帧加1
	    pFrameYUV->pts = vpts;
		vpts+=1;
		//获取摄像头帧
	    ret=av_read_frame(infmt_ctx,dec_pkt);
		if (ret != 0)
        {    
            printf("fail to read_frame\n");
            break;
        }
        
		//解码获取初始图片
        ret = avcodec_decode_video2(infmt_ctx->streams[dec_pkt->stream_index]->codec, pFrame, &got_picture, dec_pkt);
        if(!got_picture)
        {
            printf("123\n");
            continue;
        }
        //h264格式转换
        ret=sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, encodec_ctx->height, pFrameYUV->data, pFrameYUV->linesize);
        if (ret <= 0)
		{
			printf("123\n");
			continue;
		}
		
        //输出帧编码
        ret = avcodec_send_frame(encodec_ctx, pFrameYUV);
		if (ret != 0)
		{
		    printf("123\n");
			continue;
		}
        //打包到输出包裹
		ret = avcodec_receive_packet(encodec_ctx, &enc_pkt);
		if (ret != 0 || enc_pkt.size > 0)
		{
				//cout << "*" << pack.size << flush;
		}
		else
		{
				continue;
		}
		
		//推流
		enc_pkt.pts = av_rescale_q(enc_pkt.pts, encodec_ctx->time_base, out_stream->time_base);
		enc_pkt.dts = av_rescale_q(enc_pkt.dts, encodec_ctx->time_base, out_stream->time_base);
		enc_pkt.duration = av_rescale_q(enc_pkt.duration, encodec_ctx->time_base, out_stream->time_base);
		
        
        ret=sem_p(semid);
        if(ret==-1)
        {
            perror("sem_p fail!");
            break;
        }
            
        
        //发送到服务器
	    ret = av_interleaved_write_frame(outfmt_ctx, &enc_pkt);
		if (ret < 0) {
            fprintf(stderr, "Error muxing packet\n");
            break;
        }	
        
        
	    av_packet_unref(&enc_pkt);
        //释放信号量资源
        ret=sem_v(semid);
        if(ret==-1)
        {
            perror("sem_p fail!");
            break;
        }

    }
    avio_close(outfmt_ctx->pb);
    avformat_close_input(&infmt_ctx);
    avformat_close_input(&outfmt_ctx);
    return 0;
}


void *thread_func(void *arg)    //线程函数
{
    int fd;

    int ret=0;
    snd_pcm_t *handle;
    //以录音模式打开设备
    ret = snd_pcm_open(&handle, "default",SND_PCM_STREAM_CAPTURE, 0);
	if (ret < 0) 
	{
		printf("unable to open pcm device!\n");
		exit(1);
	}
	
	//配置硬件参数结构体
    snd_pcm_hw_params_t *params;
    //params申请内存
    snd_pcm_hw_params_malloc(&params);
    //使用pcm设备初始化hwparams
    ret=snd_pcm_hw_params_any(handle, params);
	if (ret < 0) 
	{
		printf("Can not configure this PCM device!\n");
		exit(1);
	}
	
	//设置多路数据在buffer中的存储方式
	//SND_PCM_ACCESS_RW_INTERLEAVED每个周期(period)左右声道的数据交叉存放
	ret=snd_pcm_hw_params_set_access(handle, params,SND_PCM_ACCESS_RW_INTERLEAVED);
	if (ret < 0) 
	{
		printf("Failed to set PCM device to interleaved!\n");
		exit(1);
	}
	
	//设置16位采样格式
	ret=snd_pcm_hw_params_set_format(handle, params,SND_PCM_FORMAT_S16_LE);
	if (ret < 0) 
	{
        printf("Failed to set PCM device to 16-bit signed PCM\n");
		exit(1);
	}
	
	//设置声道数
	ret=snd_pcm_hw_params_set_channels(handle, params, CHANNELS);
	if (ret < 0) 
	{
        printf("Failed to set PCM device CHANNELS\n");
		exit(1);
	}
	
	unsigned int val=44100;
	int dir;
	//设置采样率,如果采样率不支持，会用硬件支持最接近的采样率
	ret=snd_pcm_hw_params_set_rate_near(handle, params,&val, &dir);
	if (ret < 0) 
	{
		printf("Failed to set PCM device to sample rate\n");
		exit(1);
	}
	
	unsigned int buffer_time,period_time;
	//获取最大的缓冲时间,buffer_time单位为us,500000us=0.5s
	snd_pcm_hw_params_get_buffer_time_max(params, &buffer_time, 0);
	//printf("buffer_time:%d\n",buffer_time);
	if ( buffer_time >500000)
		buffer_time = 500000;
	
	//设置缓冲时间
	ret = snd_pcm_hw_params_set_buffer_time_near(handle, params, &buffer_time, 0);
	if (ret < 0) 
	{
		printf("Failed to set PCM device to sample rate\n");
		exit(1);
	}
	
	//设置周期时间，设置为37帧/s，1/37=0.023219
	period_time = 23219;
	ret = snd_pcm_hw_params_set_period_time_near(handle, params, &period_time, 0);
	if (ret < 0) 
	{
		printf("Failed to set PCM device to period time\n");
		exit(1);
	}
	
	//让这些参数作用于PCM设备
	ret = snd_pcm_hw_params(handle, params);
	if (ret < 0) 
	{
		printf("unable to set hw parameters\n");
		exit(1);
	}
	
	snd_pcm_uframes_t frames;
	snd_pcm_hw_params_get_period_size(params,&frames, &dir);
	printf("period_size:%ld\n",frames);
	int size;
	// 1 frame = channels * sample_size.
	size = frames * FSIZE; /* 2 bytes/sample, 1 channels */
	printf("size:%d\n",size);
	char *buffer;
	buffer = (char *) malloc(size);
	
	AVFrame *pframePCM;
	pframePCM = av_frame_alloc();

	pframePCM->format = AV_SAMPLE_FMT_S16;
    pframePCM->channel_layout = AV_CH_LAYOUT_STEREO;
    pframePCM->sample_rate = 44100;
    pframePCM->nb_samples = frames;
    pframePCM->channels = CHANNELS;
    av_frame_get_buffer(pframePCM, 0);
    
    AVFrame *pframeAAC;
	pframeAAC = av_frame_alloc();

	pframeAAC->format = AV_SAMPLE_FMT_FLTP;
    pframeAAC->channel_layout = AV_CH_LAYOUT_STEREO;
    pframeAAC->sample_rate = 44100;
    pframeAAC->nb_samples = 1024;
    pframeAAC->channels = CHANNELS;
    av_frame_get_buffer(pframeAAC, 0);

    struct SwrContext *aac_convert_ctx  = swr_alloc();
    if (!aac_convert_ctx) 
    {
        fprintf(stderr, "Could not allocate resampler context\n");
        return -1;
    }
    
	swr_alloc_set_opts(aac_convert_ctx, 
	                   AV_CH_LAYOUT_STEREO, 
	                   AV_SAMPLE_FMT_FLTP,
	                   44100, 
	                   AV_CH_LAYOUT_STEREO, 
	                   AV_SAMPLE_FMT_S16, 
	                   44100, 
	                   0, 
	                   NULL);
    
	
	if ((ret = swr_init(aac_convert_ctx)) < 0) 
	{
        fprintf(stderr, "Failed to initialize the resampling context\n");
        return -1;
    }
    
    
    AVCodec* encodec = NULL;
    //找到编码器
	encodec = avcodec_find_encoder(AV_CODEC_ID_AAC);
	if (!encodec) 
	{
		printf("not find encoder\n");
		return -1;
	}
	
    AVCodecContext* encodec_ctx = NULL;
    //创建编码器
	encodec_ctx = avcodec_alloc_context3(encodec);
	if (!encodec_ctx) 
	{
		printf("not alloc context3\n\n");
		return -1;
	}
	
    encodec_ctx->codec_id = encodec->id;
    encodec_ctx->codec_type = AVMEDIA_TYPE_AUDIO;
    encodec_ctx->sample_fmt  = AV_SAMPLE_FMT_FLTP;
    encodec_ctx->bit_rate    = 64000;
    encodec_ctx->sample_rate = 44100;
    encodec_ctx->channel_layout = AV_CH_LAYOUT_STEREO ;
    encodec_ctx->channels = av_get_channel_layout_nb_channels(AV_CH_LAYOUT_STEREO);
    
    //打开解码器
	ret = avcodec_open2(encodec_ctx, encodec, NULL);
    if (ret < 0) {
        fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
        return -1;
    }
    
    //服务器地址
    char *out_name="rtmp://47.101.62.167/live/stream";
    

    AVStream *out_stream = NULL;
    //添加音频流
    out_stream = avformat_new_stream(outfmt_ctx,NULL);
	if (!out_stream) {
		printf("failed new stream\n");
		return -1;
	}
	
    //复制参数
    avcodec_parameters_from_context(out_stream->codecpar, encodec_ctx);
	
    //查看输出封装内容
    av_dump_format(outfmt_ctx, 0, out_name, 1);
	

    AVPacket enc_pkt;
    memset(&enc_pkt, 0, sizeof(enc_pkt));
    
    int got_picture;
    int i,vpts=0;
    char *p;
    struct timeval start, end;
    gettimeofday( &start, NULL );
    
    audio_ready=1;
    while(!video_ready)
    {
        
    }
    
    while (1) 
    {
        ret = snd_pcm_readi(handle, buffer, frames);
        if (ret == -EPIPE) {
		// EPIPE means overrun 
			fprintf(stderr, "overrun occurred\n");
			ret=snd_pcm_prepare(handle);
			if(ret <0){
				printf("Failed to recover form overrun");
				exit(1);
			}
		}
		else if (ret < 0) {
			fprintf(stderr,"error from read: %s\n",snd_strerror(ret));
			exit(1);
		} 
		else if (ret != (int)frames) {
			fprintf(stderr, "short read, read %d frames\n", ret);
		
		}
		
		
        memcpy(pframePCM->data[0],buffer,size);
        
        ret=swr_convert(aac_convert_ctx,pframeAAC->data, pframeAAC->nb_samples,(const uint8_t **)pframePCM->data, pframePCM->nb_samples);
        
        avcodec_encode_audio2(encodec_ctx, &enc_pkt, pframeAAC, &got_picture);
	if(!got_picture)
        {
            printf("123\n");
            continue;
        }

        
	    //推流
	    enc_pkt.pts = av_rescale_q(enc_pkt.pts, encodec_ctx->time_base, out_stream->time_base);
        enc_pkt.dts = av_rescale_q(enc_pkt.dts, encodec_ctx->time_base, out_stream->time_base);
        enc_pkt.duration = av_rescale_q(enc_pkt.duration, encodec_ctx->time_base, out_stream->time_base);
        enc_pkt.stream_index=1;
        
        //获取信号量资源
        ret=sem_p(semid);
        if(ret==-1)
        {
            perror("sem_p fail!");
            break;
        }
            

        ret = av_interleaved_write_frame(outfmt_ctx, &enc_pkt);
	    if (ret < 0) {
            fprintf(stderr, "Error muxing packet\n");
            break;
        }	
        av_free_packet(&enc_pkt);
        
        //释放信号量资源
        ret=sem_v(semid);
        if(ret==-1)
        {
            perror("sem_p fail!");
            break;
        }

        pframeAAC->pts = vpts;
	    vpts+=pframeAAC->nb_samples;
                


        gettimeofday( &end, NULL );
        printf("%ld",end.tv_sec-start.tv_sec);
        printf("\r\033[k");
        fflush(stdout); 
	}
    
	printf("audio off\n");
	snd_pcm_drain(handle);
	snd_pcm_close(handle);
	free(buffer);
	
}

4.各种问题
①音频推流突然就卡住了
②音频与视频不同步，音频慢5秒