ffmpeg:loudnorm_analyze

Full documentation of the tool can be found here:
[ffmpeg - loudnorm](https://ffmpeg.org/ffmpeg-filters.html#loudnorm)

Optionally, the tool can run a second pass to apply the normalization to the audio.
To do that, specify the "output" parameter with the desired ffmpeg arguments.

The data from the analysis pass will automatically be used to set the appropriate ffmpeg filter arguments.

Example:
    {
      "parameters": {
        "input_file": "input.mp4",
        "audio_selector": "0:a:0",
        "env_prefix": "my_audio_",
        "integrated_loudness_target: "-24.0",
        "maximum_true_peak": "-2.0",
        "loudness_range_target": "7.0",
        "output": {
          "ffmpeg_args": [
            "-c:a", "libfdk_aac",
            "-ar", "48000",
            "-b:a", "128k",
            "-ac", "2",
            "out.m4a"
            ]
          }
      },
      "tool": "ffmpeg:loudnorm_analyze"
    }

Returns analysis result in environment variables using the specified prefix.
The ffmpeg filter returns the following:
{
    "input_i" : "-27.61",
    "input_tp" : "-4.47",
    "input_lra" : "18.06",
    "input_thresh" : "-39.20",
    "output_i" : "-16.58",
    "output_tp" : "-1.50",
    "output_lra" : "14.78",
    "output_thresh" : "-27.71",
    "normalization_type" : "dynamic",
    "target_offset" : "0.58"
}

Given a prefix of "my_audio_" this tool sets the following environment variables:

my_audio_input_i: -27.61
my_audio_input_tp: -4.47
my_audio_input_lra: 18.06
my_audio_input_thresh: -39.20
my_audio_output_i: -16.58
my_audio_output_tp: -1.50
my_audio_output_lra: 14.78
my_audio_output_thresh: -27.71
my_audio_normalization_type: dynamic
my_audio_target_offset: 0.58