No decoder could be found for codec ttml

[svnpenn]

using FFplay I get this:

  libavutil      59.  1.100 / 59.  1.100
  libavcodec     61.  1.100 / 61.  1.100
  libavformat    61.  0.100 / 61.  0.100
  libavdevice    61.  0.100 / 61.  0.100
  libavfilter    10.  0.100 / 10.  0.100
  libswscale      8.  0.100 /  8.  0.100
  libswresample   5.  0.100 /  5.  0.100
  libpostproc    58.  0.100 / 58.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'out.mp4':=    0B
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.16.100
  Duration: 01:38:48.75, start: 0.000000, bitrate: 3957 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 1200x720 [SAR 1:1 DAR 5:3], 3822 kb/s, 24 fps, 24 tbr, 19200 tbn (default)
      Metadata:
        handler_name    : USP Video Handler
        vendor_id       : [0][0][0][0]
        encoder         : AVC Coding
  Stream #0:1[0x2](zho): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 127 kb/s (default)
      Metadata:
        handler_name    : USP Sound Handler
        vendor_id       : [0][0][0][0]
  Stream #0:2[0x3](eng): Subtitle: ttml (stpp / 0x70707473), 1 kb/s (default)
      Metadata:
        handler_name    : USP Subtitle Handler
No decoder could be found for codec ttml
   1.45 A-V: -0.028 fd=   0 aq=   23KB vq=  744KB sq=    0B