ffmpeg转封装格式

本文记录ffmpeg进行视频格式的转换。

ffmpeg视频格式转换主要流程

ffmpeg视频格式转换示例

#include extern "C" {
#include "libavformat\avformat.h"
#include "libavutil\avutil.h"
#include "libavcodec\avcodec.h"
}#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "avutil.lib")void printErr(char *info, int ret)
{char err[1024] = { 0 };av_strerror(ret, err, sizeof(err));std::cout <}int main(int argv, char *argc[])
{//打开输入封装格式char *inPath = "D:/video/Bilby.mp4";AVFormatContext *inFormatCtx = nullptr;int ret = avformat_open_input(&inFormatCtx, inPath, NULL, NULL);if (ret != 0) {printErr("avformat_open_input failed", ret);return -1;}//读取packet，获取stream信息avformat_find_stream_info(inFormatCtx, NULL);av_dump_format(inFormatCtx, 0, NULL, 0);//创建输出的封装格式char *outPath = "D:/video/Bilby.flv";AVFormatContext *outFormatCtx = nullptr;ret = avformat_alloc_output_context2(&outFormatCtx, NULL, NULL, outPath);if (ret != 0) {printErr("avformat_alloc_output_context2 failed", ret);return -1;}//为输出封装格式创建streamfor (int i = 0; i nb_streams; i++) {AVStream *inStream = inFormatCtx->streams[i];AVStream *outStream = avformat_new_stream(outFormatCtx, NULL);ret = avcodec_parameters_copy(outStream->codecpar, inStream->codecpar);if (ret != 0) {printErr("avcodec_parameters_copy failed", ret);return -1;}//如果不设置，某些格式转换会失败outStream->codecpar->codec_tag = 0;}av_dump_format(outFormatCtx, 0, NULL, 1);//打开io，创建输出文件ret = avio_open(&outFormatCtx->pb, outPath, AVIO_FLAG_WRITE);if (ret != 0) {printErr("avio_open failed", ret);return -1;}//写入stream头，会改变输出stream中的time_baseret = avformat_write_header(outFormatCtx, NULL);if (ret != 0) {printErr("avformat_write_header failed", ret);return -1;}//遍历输入文件中的packetAVPacket pkt;av_init_packet(&pkt);while (1) {//读取packetret = av_read_frame(inFormatCtx, &pkt);if (ret <0) {break;}//pts,dts,duration以输出format的time_base转换AVRational srcTb = inFormatCtx->streams[pkt.stream_index]->time_base;AVRational dstTb = outFormatCtx->streams[pkt.stream_index]->time_base;pkt.pts = av_rescale_q_rnd(pkt.pts, srcTb, dstTb, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));pkt.dts = av_rescale_q_rnd(pkt.dts, srcTb, dstTb, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));pkt.duration = av_rescale_q(pkt.duration, srcTb, dstTb);//packet写入文件av_interleaved_write_frame(outFormatCtx, &pkt);}//输出剩余的packet和stream尾部信息 av_write_trailer(outFormatCtx);//关闭输入输出avformat_close_input(&inFormatCtx);avio_close(outFormatCtx->pb);avformat_free_context(outFormatCtx);system("pause");return 0;
}