transcode:cropdetect

Full documentation of the tool`s crop detection can be found here: [ffmpeg - cropdetect](https://ffmpeg.org/ffmpeg-all.html#cropdetect)

This implementation covers accurate detection of black bars across entire movies, with predefined parameters. The output output will be stored as environment variable "cropdetect"
which can be used for cropping instructions in subsequent ffmpeg commands.


Example:

    {
      "parameters": {
        "inputfile": "movie.mov"
      },
      "tool": "transcode:cropdetect"
    },

Returns frame dimensions without black bars, width:height:columns_indent:rows_indent, for example:

    crop=1920:1072:0:4


Example for cropping instructions with that output in a later ffmpeg command:


    {
      "tool": "ffmpeg:cmd",
      "parameters": {
        "ignore_decoding_errors": "false",
        "arguments": [
          "-i",
          "{input}",
          "-filter_complex", ""[0:v]{cropdetect}[cropped];[cropped]scale='(trunc((ih*((16/9)/2))*2))':ih,setsar=1[cropped]"",
          "-map", "[cropped]
          "-f",
          "mp4",
          "{output}"
        ]
      }
    },