Hi,
I have seen a few examples such as transcoding.c, muxing.c, but I couldn't
understand how to directly take a frame from a certain video stream (Of type
AVStream) to another stream in another video file. av_read_frame reads the
frame from the whole AVFormatContext, which I don't understand why it doesn't
take AVStream as a parameter? Or does it take all the frames from all streams
at the same elapsed time? I have tried this code to read frame from a video
file and write it to another (After initializing both AVFrameContext for input
and output, and also writing the header to the output file):
*************************************************
AVFrame *rawFrame = av_frame_alloc();
AVPacket *pkts = av_packet_alloc();
av_init_packet(pkts);
AVPacket *pktr = av_packet_alloc();
av_init_packet(pktr);
while(av_read_frame(input_ctx, pkts) == 0)
{
//decoding
int ret1 = avcodec_send_packet(input_codecCtx, pkts);
int ret2 = avcodec_receive_frame(input_codecCtx, rawFrame);
//encoding
avcodec_send_frame(output_codecCtx, rawFrame);
avcodec_receive_packet(output_codecCtx, pktr);
int ret = av_interleaved_write_frame(output_ctx, pktr);
}
*************************************************
But it doesn't work, no frames are written into the output file, and ret1 and
ret2 return error "invalid argument'.
Thanks.
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