protected function ensureFormatProperties(array $properties)
	{
		// defaults keys for transforming
		$properties += [
			'bit_rate'    => 0,
			'duration'    => 0.0,
			'format_name' => '',
			'tags'        => [],
			'codecs'      => []
		];
		
		if ( ! empty($this->options[ServiceFactoryInterface::OPTION_TEST_CODECS]))
		{
			$properties['codecs'] = $this->getAvailableCodecs();
		}
		
		$properties['metadata'] = (array) $properties['tags'];
		$properties['format'] = $properties['format_name'];
		$properties['bitrate'] = $properties['bit_rate'];
		
		unset($properties['tags'], $properties['bit_rate']);
		
		return $properties;
	}