ffmpeg -i input.ts output.webm
ffmpeg version 2.8.4 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  configuration: --prefix=/home/stuff/keep/ff2
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
input.ts: could not find codec parameters
prompt>