private function normalizeConfig(array $embedConfig)
    {

        $config = $embedConfig;

        // apply deprecated configuration keys if exists:
        if (array_key_exists('video_player', $embedConfig)) {
            $config['video']['player'] = $embedConfig['video_player'];
        }
        if (array_key_exists('video_autoplay', $embedConfig)) {
            $config['video']['autoplay'] = $embedConfig['video_autoplay'];
        }
        if (array_key_exists('video_available_speeds', $embedConfig)) {
            $config['video']['available-speeds'] = $embedConfig['video_available_speeds'];
        }
        if (array_key_exists('audio_player', $embedConfig)) {
            $config['audio']['player'] = $embedConfig['audio_player'];
        }
        if (array_key_exists('audio_autoplay', $embedConfig)) {
            $config['audio']['autoplay'] = $embedConfig['audio_autoplay'];
        }
        if (array_key_exists('audio_available_speeds', $embedConfig)) {
            $config['audio']['available-speeds'] = $embedConfig['audio_available_speeds'];
        }
        if (array_key_exists('enable_pdfjs', $embedConfig['document'])) {
            $config['document']['enable-pdfjs'] = $embedConfig['document']['enable_pdfjs'];
        }

        return $config;
    }