FFmpeg将mp4格式视频转为flv
#include <libavutil/>
#include <libavformat/>
#include ""
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 converterVideo(const char *in_filename, const char *out_filename) {
AVOutputFormat *outfmt = NULL; //输出格式
AVFormatContext *infmt_ctx = NULL, *outfmt_ctx = NULL;//输入、输出上下文
AVPacket pkt;
int ret , i;
int stream_index = 0;
int *stream_mapping = NULL;//数组用于存放输出文件流的Index
int stream_mapping_size = 0;//输入文件中流的总数量
av_register_all();
//打开输入文件为infmt_ctx分配内存
ret = avformat_open_input(&infmt_ctx, in_filename, 0, 0);
if (ret < 0) {
fprintf(stderr, "Could not open input file '%s'", in_filename);
goto end;
}
//检索输入文件的流信息
ret = avformat_find_stream_info(infmt_ctx, NULL);
if (ret < 0) {
fprintf(stderr, "Failed to retrieve input stream information");
goto end;
}
//打印输入文件相关信息
av_dump_format(infmt_ctx, 0, in_filename, 0);
//为输出上下文环境分配内存
avformat_alloc_output_context2(&outfmt_ctx, NULL, NULL, out_filename);
if (!outfmt_ctx) {
fprintf(stderr, "Could not create output context\n");
ret = AVERROR_UNKNOWN;
goto end;
}
//输入文件流的数量
stream_mapping_size = infmt_ctx->nb_streams;
//分配stream_mapping_size段内存，每段内存大小是sizeof(*stream_mapping)->如果有音频和视频，那就是，2段为整型的内存
stream_mapping = av_mallocz_array(stream_mapping_size, sizeof(*stream_mapping));
if (!stream_mapping) {
ret = AVERROR(ENOMEM);
goto end;
}
//输出文件格式
outfmt = outfmt_ctx->oformat;
//遍历输入文件中的每一路流，对于每一路流都要创建一个新的流进行输出
for (i = 0; i < infmt_ctx->nb_streams; i++) {
AVStream *out_stream = NULL;//输出流
AVStream *in_stream = infmt_ctx->streams[i];//输入流
AVCodecParameters *in_codecpar = in_stream->codecpar;//输入流的编解码参数
//只保留音频、视频、字幕流，其他流不要
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;
}
//对于输出流的index重新编号
stream_mapping[i] = stream_index++;
//创建一个对应的输出流
out_stream = avformat_new_stream(outfmt_ctx, NULL);
if (!out_stream) {
fprintf(stderr, "Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
//直接将输入流的编解码参数拷贝到输出流中
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;
}
//打印要输出的对媒体文件的详细信息
av_dump_format(outfmt_ctx, 0, out_filename, 1);
if (!(outfmt->flags & AVFMT_NOFILE)) {
ret = avio_open(&outfmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
if (ret < 0) {
fprintf(stderr, "Could not open output file '%s'", out_filename);
goto end;
}
}
//写入新的多媒体文件的头
ret = avformat_write_header(outfmt_ctx, NULL);
if (ret < 0) {
fprintf(stderr, "Error occurred when opening output file\n");
goto end;
}
while (1) {
AVStream *in_stream, *out_stream;
//循环读取每一帧数据
ret = av_read_frame(infmt_ctx, &pkt);
if (ret < 0) { //读取完后退出循环
break;
}
in_stream = infmt_ctx->streams[pkt.stream_index];
//如果当前包的流不是音频、视频、就不用做接下来的处理
if (pkt.stream_index >= stream_mapping_size ||
stream_mapping[pkt.stream_index] < 0) {
av_packet_unref(&pkt);
continue;
}
//按照输出流的index给pkt重新编号
pkt.stream_index = stream_mapping[pkt.stream_index];
//根据pkt的stream_index获取对应的输出流
out_stream = outfmt_ctx->streams[pkt.stream_index];
//对pts、dts、duration 进行时间基转换，不同格式时间基都不一样，不转换会导致音视频同步问题
pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX);
pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, 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(outfmt_ctx, &pkt, "out");
//将处理好的pkt写入输出文件
ret = av_interleaved_write_frame(outfmt_ctx, &pkt);
if (ret < 0) {
fprintf(stderr, "Error muxing packer\n");
break;
}
av_packet_unref(&pkt);
}
// 写入新的多媒体文件尾
av_write_trailer(outfmt_ctx);
end:
avformat_close_input(&infmt_ctx);
if(outfmt_ctx && !(outfmt->flags & AVFMT_NOFILE)) {
avio_closep(&outfmt_ctx->pb);
}
avformat_free_context(outfmt_ctx);
av_freep(&stream_mapping);
if (ret < 0 && ret != AVERROR_EOF) {
fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
return 1;
}
return 0;
}