[FFmpeg-user] how to copy a video file using ffmpeg

[hainei]

hi my friends.
i open a video file, then url_fopen a new file, just read the packet and
write the stream packet using the av_read_frame and av_write_frame.

but the program don't work, when the program run to the av_write_frame it
stop.

maybe the pts and dts have not set to the right value, but i don't know how
to set it.

	/* 11-24 now, we start to transcode */
    if(av_write_header(oFmtctx) < 0)
		return -1;

	//定位到起始值
	av_q.num = 1;
	av_q.den = AV_TIME_BASE;
	if(video_index>=0){
		st= iFmtctx->streams[video_index];
		timestamp= av_rescale_q(timestamp, av_q, video_st->time_base);
	}
	av_seek_frame(iFmtctx, video_index, timestamp, AVSEEK_FLAG_BACKWARD);


	while(av_read_frame(iFmtctx,&packet) >= 0)
	{
	/*	if(packet.stream_index == video_index)
		{

		}
		if(packet.stream_index == audio_index)
		{

		}*/
		AVPacket opkt;
		av_init_packet(&opkt);

		data_buf = packet.data;
		data_size = packet.size ;

		opkt.stream_index = packet.stream_index ;
/*
		if(packet.pts != AV_NOPTS_VALUE)
			opkt.pts= av_rescale_q(packet.pts,
iFmtctx->streams[video_index]->time_base,
			video_st->time_base);
		else
			opkt.pts= AV_NOPTS_VALUE;

		if (packet.dts == AV_NOPTS_VALUE)
			opkt.dts = av_rescale_q(packet.dts, av_q, video_st->time_base);
		else
			opkt.dts = av_rescale_q(packet.dts,
iFmtctx->streams[video_index]->time_base, 
			video_st->time_base);
*/
		opkt.pts= av_rescale_q(packet.pts,
iFmtctx->streams[video_index]->time_base,
			video_st->time_base);
		opkt.dts = av_rescale_q(packet.dts,
iFmtctx->streams[video_index]->time_base, 
			video_st->time_base);
		opkt.duration = av_rescale_q(packet.duration,
iFmtctx->streams[video_index]->time_base, 
			video_st->time_base);

		opkt.flags= packet.flags;

		opkt.data = data_buf;
		opkt.size = data_size;


		if (av_write_frame(oFmtctx, &opkt) != 0) {
			fprintf(stderr, "Error while writing audio frame\n");
			exit(1);
		}
		av_free_packet(&packet);
	}

	// write the trailer, if any
	av_write_trailer(oFmtctx);


please give me help.

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