iPlayer streams at 50fps progressive?

[John Warburton]

Hello,

Is the BBC sending out live streams at 50fps progressive? FFprobe
seems to think so. And the pictures look like they're at 50fps, either
natively or de-interlaced.

When I pipe the output of get_iplayer watching BBC News 24 into
ffprobe, taking great care not to re-code to anything on the way out,
I get ffprobe showing me that the frame rate is 50fps.

This is the get_iplayer command line:

$ get_iplayer --stream --type=livetv "80002" --modes=hlsvhd
--hls-livetv-opts "-v quiet -c:v copy -c:a copy" --raw --player="mpv
--cache 20000 -"

The output informs me that the content provider is: "ll_hls_live", and
I see from watching the process status that ffmpeg is, indeed, using
the 'copy' flags to over-ride any get_iplayer tendency to recode the
incoming H.264 stream as mpeg2video.

And ffprobe tells me:

Input #0, mpegts, from 'pipe:':
  Duration: N/A, start: 1.400000, bitrate: N/A
  Program 1
    Metadata:
      service_name    : Service01
      service_provider: FFmpeg
    Stream #0:0[0x100], 252, 1/90000: Video: h264 (High), 2 reference
frames ([27][0][0][0] / 0x001B), yuv420p(tv, bt709, left), 1280x720
[SAR 1:1 DAR 16:9], 1/100, 50 fps, 50 tbr, 90k tbn, 100 tbc
    Stream #0:1[0x101], 232, 1/90000: Audio: aac (LC) ([15][0][0][0] /
0x000F), 48000 Hz, stereo, fltp, 130 kb/s