[Libav-user] XDCAM setting produces only P frame

[francesco at bltitalia.com]

Hi to all
I've used libavcodec library in order to generate XDCAM mxf files closed GOP.

My settings are:

   pCodecCtx->rc_max_rate = pCodecCtx->rc_min_rate =pCodecCtx->bit_rate =
50000000;

   pCodecCtx->time_base.num =  1;
   pCodecCtx->time_base.den =  25;
   pCodecCtx->pix_fmt = (AVPixelFormat) PIX_FMT_YUV422P;  ///< planar YUV
4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)
   pCodecCtx->thread_count = 4;
   pCodecCtx->flags2 =0;
   pCodecCtx->rc_buffer_size = 2000000;
pCodecCtx->rc_initial_buffer_occupancy = 2000000;
   pCodecCtx->flags =  CODEC_FLAG_INTERLACED_DCT | CODEC_FLAG_CLOSED_GOP |
CODEC_FLAG_INTERLACED_ME;
   pCodecCtx->qmin = 1; // pCodecCtx_xd->qmax = 4;
   pCodecCtx->b_frame_strategy = 1;
   pCodecCtx->vbv_delay = 1;
   pCodecCtx->scenechange_threshold = 2000000000;
   vform.num = 1;     vform.den = 1;   
   pCodecCtx->gop_size =  12;    pCodecCtx->max_b_frames= 8;
   pCodecCtx->sample_aspect_ratio = vform;

All seems to work fine, output file is ok, I can display on nonlinear editor,
but if I unwrap the file I saw that the essence is composed only of one I
frame and 11 P frames, while I will expect the sequence : I B B P B B P B B
P B B.
There is some other parameters that shoiuld be set ?
regards
Francesco