Hi all, I am quite confused about how to save a video stream into a mp4 file. Let me explain the problem:
1. I connect to a network camera via RTSP (H.264 stream) with avformat_open_input(), avformat_find_stream_info(), av_read_play(), and I get frames with av_read_frame(). 2. Each time I get a frame with av_read_frame(), I store the corresponding AVPacket in a circular buffer. 3. In some points in my application, a range of this circular buffer is selected. I find a key frame used to start from. 4. Once I have a list of AVPacket's starting from a key frame, I write header, frames, and tail, as I described below in the code. The problem is that the resulting mp4 video has artifacts if I try to watch it using VLC, Windows Media Player, or another one. I have also realized that the pts of that packets are not continuous, while dts are continuous. I know about B frames, but is this a problem in my case? // Prepare the output AVFormatContext* oc = avformat_alloc_context(); oc->oformat = av_guess_format(NULL, "video.mp4", NULL); // Must write header, packets, and trailing avio_open2(&oc->pb, "video.mp4", AVIO_FLAG_WRITE, NULL, NULL); // Write header AVStream* stream = avformat_new_stream(oc, (AVCodec*) context->streams[video_stream_index]->codec->codec); avcodec_copy_context(stream->codec, context->streams[video_stream_index]->codec); stream->sample_aspect_ratio = context->streams[video_stream_index]->codec->sample_aspect_ratio; avformat_write_header(oc, NULL); // FOR EACH FRAME... ... av_write_frame(oc, circular[k]); ... // Write trailer and close the file av_write_trailer(oc); avcodec_close(stream->codec); avio_close(oc->pb); avformat_free_context(oc); Thank you so much, -- Dídac Pérez
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