FFmpeg으로 트랜스코딩하는 프로그램 만들기

선행 학습

• FFmpeg으로 재생하는 프로그램 만들기
  

예제 코드

static AVFormatContext *fmt_ctx = NULL;
static AVCodecContext *dec_ctx = NULL;
static int vst_idx = -1;

void open_input_file()
{
    AVCodec *dec;

    /* open input streams */
    avformat_open_input(&fmt_ctx, filename, NULL, NULL);

    /* select the video stream */
    vst_idx = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
    dec_ctx = fmt_ctx->streams[vst_idx]->codec;

    /* init the video decoder */
    avcodec_open2(dec_ctx, dec, NULL);
}

void close_input_file()
{
    for (i = 0; i < fmt_ctx->nb_streams; i++) {
        AVStream *st = fmt_ctx->streams[i];
        avcodec_close(st->codec);
    }
    avformat_close_input(&fmt_ctx);
}

void encode_video()
{
    AVPacket pkt, outpkt;
    AVFrame *frm;
    int got_frame, got_output;

    AVCodec *enc;
    AVCodecContext *enc_ctx = NULL;

    /* find the h.264 video encoder */
    enc = avcodec_find_encoder(AV_CODEC_ID_H264);

    enc_ctx = avcodec_alloc_context3(codec);

    /* put sample parameters */
    enc_ctx->bit_rate = 400000;
    /* resolution must be a multiple of two */
    enc_ctx->width = 352;
    enc_ctx->height = 288;
    /* frames per second */
    enc_ctx->time_base= (AVRational){1,25};
    enc_ctx->gop_size = 10; /* emit one intra frame every ten frames */
    enc_ctx->max_b_frames=1;
    enc_ctx->pix_fmt = AV_PIX_FMT_YUV420P;

    /* init the video encoder */
    avcodec_open2(enc_ctx, enc, NULL);

    frm = av_frame_alloc();

    while (1) {
        av_read_frame(fmt_ctx, &pkt);

        if (pkt.stream_index == vst_idx) {
            avcodec_get_frame_defaults(frm);

            /* decode the frame */
            avcodec_decode_video2(dec_ctx, frm, &got_frame, &pkt);

            if (got_frame) {
                av_init_packet(&outpkt);
                outpkt.data = NULL;
                outpkt.size = 0;

                /* encode the frame */
                avcodec_encode_video2(c, &outpkt, frm, &got_output);
                if (got_output) {
                    /* write or send the frame */
                    av_free_packet(&outpkt);
                }
            }
        }

        av_free_packet(&pkt);
    }
    av_init_packet(&outpkt);
    outpkt.data = NULL;
    outpkt.size = 0;

    /* get the delayed frames */
    got_output = 1;
    while (got_output) {
        /* encode the frame */
        avcodec_encode_video2(c, &outpkt, frm, &got_output);
        if (got_output) {
            /* write or send the frame */
            av_free_packet(&outpkt);
        }
    }
    av_frame_free(&frm);
}

예제 코드에서 추가로 사용한 자료형과 함수

• Encoding/Decoding Library
• Encoding
  
• avcodec_encode_video2