使用FFMPEG库封装264视频和acc音频数据到MP4文件中_ffmpeg 将aac 和 h264合并成mp4

准备

ffmepeg 4.4

一段H264的视频文件

一段acc格式的音频文件

封装流程

1.使用avformat_open_input分别打开视频和音频文件，初始化其AVFormatContext，使用avformat_find_stream_info获取编码器基本信息

2.使用avformat_alloc_output_context2初始化输出的AVFormatContext结构

3.使用函数avformat_new_stream给输出的AVFormatContext结构创建音频和视频流，使用avcodec_parameters_copy方法将音视频的编码参数拷贝到新创建的对应的流的codecpar结构中

4.使用avio_open打开输出文件，初始化输出AVFormatContext结构中的IO上下文结构

5.使用avformat_write_header写入流的头信息到输出文件中

6.根据时间戳同步原则交错写入音视频数据，并对时间戳信息进行设置和校准

7.写入流预告信息到输出文件中（moov）

8.释放空间，关闭文件

源码

 
 
#include <stdio.h>
 
#define __STDC_CONSTANT_MACROS
 
#ifdef _WIN32
 //Windows
extern "C"
{
#include "libavformat/avformat.h"
};
#else
 //Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavformat/avformat.h>
#ifdef __cplusplus
};
#endif
#endif
 
 
 
int main(int argc, char* argv[]) {
    AVOutputFormat* ofmt = NULL;
    //Input AVFormatContext and Output AVFormatContext
    AVFormatContext* ifmt_ctx_v = NULL, * ifmt_ctx_a = NULL, * ofmt_ctx = NULL;
    AVPacket pkt;
    int ret, i;
    int videoindex_v = -1, videoindex_out = -1;
    int audioindex_a = -1, audioindex_out = -1;
    int frame_index = 0;
    int64_t cur_pts_v = 0, cur_pts_a = 0;
    int writing_v = 1, writing_a = 1;
 
    const char* in_filename_v = "D:/测试工程/sound/ffmpeg_demo.h264";
    const char* in_filename_a = "D:/测试工程/sound/ffmpeg_demo.aac";
 
    const char* out_filename = "D:/测试工程/sound/muxing.mp4";//Output file URL
 
 
    if ((ret = avformat_open_input(&ifmt_ctx_v, in_filename_v, 0, 0)) < 0) {
        printf("Could not open input file.");
        goto end;
    }
    if ((ret = avformat_find_stream_info(ifmt_ctx_v, 0)) < 0) {
        printf("Failed to retrieve input stream information");
        goto end;
    }
 
    if ((ret = avformat_open_input(&ifmt_ctx_a, in_filename_a, 0, 0)) < 0) {
        printf("Could not open input file.");
        goto end;
    }
    if ((ret = avformat_find_stream_info(ifmt_ctx_a, 0)) < 0) {
        printf("Failed to retrieve input stream information");
        goto end;
    }
    //Output
    avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
    if (!ofmt_ctx) {
        printf("Could not create output context\n");
        ret = AVERROR_UNKNOWN;
        goto end;
    }
    ofmt = ofmt_ctx->oformat;
 
 
 
    for (i = 0; i < ifmt_ctx_v->nb_streams; i++) {
        //Create output AVStream according to input AVStream
        if (ifmt_ctx_v->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
 
            AVStream* out_stream = avformat_new_stream(ofmt_ctx, nullptr);
            videoindex_v = i;
            if (!out_stream) {
                printf("Failed allocating output stream\n");
                ret = AVERROR_UNKNOWN;
                goto end;
            }
            videoindex_out = out_stream->index;
            //Copy the settings of AVCodecContext
            if (avcodec_parameters_copy(out_stream->codecpar, ifmt_ctx_v->streams[i]->codecpar) < 0) {
                printf("Failed to copy context from input to output stream codec context\n");
                goto end;
            }
 
 
            break;
        }
    }
 
    for (i = 0; i < ifmt_ctx_a->nb_streams; i++) {
        //Create output AVStream according to input AVStream
        if (ifmt_ctx_a->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
 
            AVStream* out_stream = avformat_new_stream(ofmt_ctx, nullptr);
            audioindex_a = i;
            if (!out_stream) {
                printf("Failed allocating output stream\n");
                ret = AVERROR_UNKNOWN;
                goto end;
            }
            audioindex_out = out_stream->index;
 
            //Copy the settings of AVCodecContext
            if (avcodec_parameters_copy(out_stream->codecpar, ifmt_ctx_a->streams[i]->codecpar) < 0) {
                printf("Failed to copy context from input to output stream codec context\n");
                goto end;
            }
            out_stream->codecpar->codec_tag = 0;
            if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
                ofmt_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
            break;
        }
    }
 
    /* open the output file, if needed */
    if (!(ofmt->flags & AVFMT_NOFILE)) {
        if (avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE)) {
            fprintf(stderr, "Could not open '%s': %d\n", out_filename,
                ret);
            goto end;
        }
    }
 
    //Write file header
    if (avformat_write_header(ofmt_ctx, NULL) < 0) {
        fprintf(stderr, "Error occurred when opening output file: %d\n",
            ret);
        goto end;
    }
 
    //写入数据
    while (writing_v || writing_a)
    {
        AVFormatContext* ifmt_ctx;
        int stream_index = 0;
        AVStream* in_stream, * out_stream;
 
        if (writing_v &&
            (!writing_a || av_compare_ts(cur_pts_v, ifmt_ctx_v->streams[videoindex_v]->time_base,
                cur_pts_a, ifmt_ctx_a->streams[audioindex_a]->time_base) <= 0))
        {
 
            ifmt_ctx = ifmt_ctx_v;
            stream_index = videoindex_out;
 
            if (av_read_frame(ifmt_ctx, &pkt) >= 0)
            {
                do {
                    in_stream = ifmt_ctx->streams[pkt.stream_index];
                    out_stream = ofmt_ctx->streams[stream_index];
 
                    if (pkt.stream_index == videoindex_v)
                    {
                        //FIX：No PTS (Example: Raw H.264)
                        //Simple Write PTS
                        if (pkt.pts == AV_NOPTS_VALUE)
                        {
                            //Write PTS
                            AVRational time_base1 = in_stream->time_base;
                            //Duration between 2 frames (us)
                            int64_t calc_duration = (double)AV_TIME_BASE / av_q2d(in_stream->r_frame_rate);
                            
                            //Parameters
                            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);
                            frame_index++;
                            printf("frame_index:  %d\n ", frame_index);
                        }
 
                        cur_pts_v = pkt.pts;
                        break;
                    }
                } while
                    (av_read_frame(ifmt_ctx, &pkt) >= 0);
            }
            else
            {
                writing_v = 0;
                continue;
            }
        }
        else
        {
            ifmt_ctx = ifmt_ctx_a;
            stream_index = audioindex_out;
            if (av_read_frame(ifmt_ctx, &pkt) >= 0)
            {
                do {
                    in_stream = ifmt_ctx->streams[pkt.stream_index];
                    out_stream = ofmt_ctx->streams[stream_index];
 
                    if (pkt.stream_index == audioindex_a)
                    {
 
                        //FIX：No PTS
                        //Simple Write PTS
                        if (pkt.pts == AV_NOPTS_VALUE)
                        {
                            //Write PTS
                            AVRational time_base1 = in_stream->time_base;
                            //Duration between 2 frames (us)
                            int64_t calc_duration = (double)AV_TIME_BASE / av_q2d(in_stream->r_frame_rate);
                            //Parameters
                            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);
                            frame_index++;
                        }
                        cur_pts_a = pkt.pts;
                        break;
                    }
                } while (av_read_frame(ifmt_ctx, &pkt) >= 0);
            }
            else
            {
                writing_a = 0;
                continue;
            }
        }
 
        //Convert PTS/DTS
        pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base,
            (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
        pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base,
            (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
        pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
        pkt.pos = -1;
        pkt.stream_index = stream_index;
 
        printf("Write 1 Packet. size:%5d\tpts:%lld\n", pkt.size, pkt.pts);
        //Write
        if (av_interleaved_write_frame(ofmt_ctx, &pkt) < 0) {
            printf("Error muxing packet\n");
            break;
        }
        av_packet_unref(&pkt);
    }
 
    printf("Write file trailer.\n");
    //Write file trailer
    av_write_trailer(ofmt_ctx);
 
end:
    avformat_close_input(&ifmt_ctx_v);
    avformat_close_input(&ifmt_ctx_a);
    /* close output */
    if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
        avio_close(ofmt_ctx->pb);
    avformat_free_context(ofmt_ctx);
    if (ret < 0 && ret != AVERROR_EOF) {
        printf("Error occurred.\n");
        return -1;
    }
    return 0;
}

小结

这里需要几个概念简单说明下：

tbr  表示每秒帧数

tbn 表示数据流的实际真实帧率的倒数

如：