ffmpeg-视频操作

__int64 index_context = 0, last_start_pts=0;
std::list<AVFormatContext*> ifmt_ctx_lst;
AVFormatContext *ofmt_ctx = nullptr, *ifmt_ctx = nullptr;
void BeginSplitFile(const char* file, const char* out_file)
{
	index_context = 0;
	AVFormatContext* ifmt_ctx_item = nullptr;
	if ((avformat_open_input(&ifmt_ctx_item, file, 0, 0)) < 0)
		return;
	ifmt_ctx_lst.push_back(ifmt_ctx_item);
	if ((avformat_find_stream_info(ifmt_ctx_item, 0)) < 0)
		return;
	if (ofmt_ctx != nullptr) return;
	avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_file);
	if (!ofmt_ctx)	return;
	for (unsigned int i = 0; i < ifmt_ctx_item->nb_streams; i++) {
		AVStream *out_stream, *in_stream = ifmt_ctx_item->streams[i];
		AVCodecParameters *in_codecpar = in_stream->codecpar;
		out_stream = avformat_new_stream(ofmt_ctx, NULL);
		if (!out_stream) return;
		if (avcodec_parameters_copy(out_stream->codecpar, in_codecpar) < 0)
			return;
		out_stream->codecpar->codec_tag = 0;
	}
	if (!(ofmt_ctx->oformat->flags & AVFMT_NOFILE)){
		if (avio_open(&ofmt_ctx->pb, out_file, AVIO_FLAG_WRITE) < 0)
			return;
	}
	if (avformat_write_header(ofmt_ctx, NULL) < 0)
		return;
}
void SplitFile(double from, double to)
{
	std::list<AVFormatContext*>::iterator it = ifmt_ctx_lst.begin();
	std::advance(it, index_context);
	AVFormatContext* ifmt_ctx_item = *it;
	index_context++;
	if (!ifmt_ctx_item || av_seek_frame(ifmt_ctx_item, -1, (__int64)from * AV_TIME_BASE, AVSEEK_FLAG_ANY) < 0)
		return;

	__int64 start_pts = -1;
	for (int i = 0;; i++){
		AVPacket pkt;
		AVStream *in_stream, *out_stream;
		if (!ifmt_ctx_item || av_read_frame(ifmt_ctx_item, &pkt) < 0)
			break;
		in_stream = ifmt_ctx_item->streams[pkt.stream_index];
		out_stream = ofmt_ctx->streams[pkt.stream_index];

		double time_stamp = av_q2d(in_stream->time_base) * pkt.pts;
		if (time_stamp > to){
			last_start_pts = pkt.pts - start_pts;
			break;
		}
		if (start_pts == -1)	start_pts = pkt.pts;
		pkt.pts = av_rescale_q_rnd(pkt.pts - start_pts + last_start_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 - start_pts + last_start_pts, 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;
		if (!ofmt_ctx || av_interleaved_write_frame(ofmt_ctx, &pkt) < 0)
			break;
		av_packet_unref(&pkt);
	}
	
}
void EndSplitFile()
{
	index_context--;
	AVFormatContext* it = ifmt_ctx_lst.front();
	if (it) avformat_close_input(&it);
	ifmt_ctx_lst.pop_front();

	if (ifmt_ctx_lst.size() == 0){
		if (ofmt_ctx) av_write_trailer(ofmt_ctx);
		if (ofmt_ctx && !(ofmt_ctx->oformat->flags & AVFMT_NOFILE))
			avio_closep(&ofmt_ctx->pb);
		if (ofmt_ctx) {
			avformat_free_context(ofmt_ctx);
			ofmt_ctx = nullptr;
		}
	}
}

__int64 GetFileTimeSpan(const char* file)
{
    AVFormatContext *ifmt=avformat_alloc_context();
    if(avformat_open_input(&ifmt,file,NULL,NULL)<0)
        return -1;
    __int64 tduration=ifmt->duration;
    avformat_close_input(&ifmt);
    avformat_free_context(ifmt);
	return tduration / AV_TIME_BASE;
}