FFprobe.duration

You're seeing just the function duration, go back to FFprobe module for more information.

duration(file_path)

duration(binary() | format_map()) ::
  float() | :no_duration | {:error, :no_such_file}

Get the duration in seconds, as a float.

If no duration (e.g., a still image), returns :no_duration. If the file does not exist, returns { :error, :no_such_file }