ffmpeg入门之Windows开发之二（视频转码）-编程知识

添加ffmpeg windows编译安装及入门指南-CSDN博客的头文件和依赖库如下：

main 函数如下：

extern "C"
{
#ifdef __cplusplus
#define __STDC_CONSTANT_MACROS

#endif

}
extern "C" {

#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>
#include <libavutil/mem.h>

}

static void log_packet(const AVFormatContext* fmt_ctx, const AVPacket* pkt, const char* tag)
{
AVRational* time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;

   /*printf("%s: pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
       tag,
       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);*/
}

int main()
{
   AVOutputFormat* ofmt = NULL;
   AVFormatContext* ifmt_ctx = NULL, * ofmt_ctx = NULL;
   AVPacket pkt;
   const char* in_filename, * out_filename;
   int ret;
   unsigned int i;
   int stream_index = 0;
   int* stream_mapping = NULL;
   int stream_mapping_size = 0;

   /*if (argc < 3) {
       printf("usage: %s input output\n"
           "API example program to remux a media file with libavformat and libavcodec.\n"
           "The output format is guessed according to the file extension.\n"
           "\n", argv[0]);
       return 1;
   }*/

in_filename = "../resources/video.avi";
out_filename = "../resources/video.mp4";

   if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
       fprintf(stderr, "Could not open input file '%s'", in_filename);
       goto end;
   }

   if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
       fprintf(stderr, "Failed to retrieve input stream information");
       goto end;
   }

av_dump_format(ifmt_ctx, 0, in_filename, 0);

   avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
   if (!ofmt_ctx) {
       fprintf(stderr, "Could not create output context\n");
       ret = AVERROR_UNKNOWN;
       goto end;
   }

   stream_mapping_size = ifmt_ctx->nb_streams;
   stream_mapping = (int*)av_malloc_array(stream_mapping_size, sizeof(*stream_mapping));
   if (!stream_mapping) {
       ret = AVERROR(ENOMEM);
       goto end;
   }

ofmt = (AVOutputFormat * )ofmt_ctx->oformat;

   for (i = 0; i < ifmt_ctx->nb_streams; i++) {
       AVStream* out_stream;
       AVStream* in_stream = ifmt_ctx->streams[i];
       AVCodecParameters* in_codecpar = in_stream->codecpar;

       if (in_codecpar->codec_type != AVMEDIA_TYPE_AUDIO &&
           in_codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
           in_codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE) {
           stream_mapping[i] = -1;
           continue;
       }

stream_mapping[i] = stream_index++;

       out_stream = avformat_new_stream(ofmt_ctx, NULL);
       if (!out_stream) {
           fprintf(stderr, "Failed allocating output stream\n");
           ret = AVERROR_UNKNOWN;
           goto end;
       }

       ret = avcodec_parameters_copy(out_stream->codecpar, in_codecpar);
       if (ret < 0) {
           fprintf(stderr, "Failed to copy codec parameters\n");
           goto end;
       }
       out_stream->codecpar->codec_tag = 0;
   }
   av_dump_format(ofmt_ctx, 0, out_filename, 1);

   if (!(ofmt->flags & AVFMT_NOFILE)) {
       ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
       if (ret < 0) {
           fprintf(stderr, "Could not open output file '%s'", out_filename);
           goto end;
       }
   }

   ret = avformat_write_header(ofmt_ctx, NULL);
   if (ret < 0) {
       fprintf(stderr, "Error occurred when opening output file\n");
       goto end;
   }

while (1) {
AVStream* in_stream, * out_stream;

       ret = av_read_frame(ifmt_ctx, &pkt);
       if (ret < 0)
           break;

       in_stream = ifmt_ctx->streams[pkt.stream_index];
       if (pkt.stream_index >= stream_mapping_size ||
           stream_mapping[pkt.stream_index] < 0) {
           av_packet_unref(&pkt);
           continue;
       }

       pkt.stream_index = stream_mapping[pkt.stream_index];
       out_stream = ofmt_ctx->streams[pkt.stream_index];
       log_packet(ifmt_ctx, &pkt, "in");

       /* copy packet */
       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;
       log_packet(ofmt_ctx, &pkt, "out");

       ret = av_interleaved_write_frame(ofmt_ctx, &pkt);
       if (ret < 0) {
           fprintf(stderr, "Error muxing packet\n");
           break;
       }
       av_packet_unref(&pkt);
   }

av_write_trailer(ofmt_ctx);
end:

avformat_close_input(&ifmt_ctx);

   /* close output */
   if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
       avio_closep(&ofmt_ctx->pb);
   avformat_free_context(ofmt_ctx);

av_freep(&stream_mapping);

   if (ret < 0 && ret != AVERROR_EOF) {
       //fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
       return 1;
   }
   system("pause");
   return 0;
}

最后video.avi的格式转换为output.avi文件。