/// <summary>
        /// This function will embed the auto generated speech to the current slide.
        /// File names of generated audios will be returned.
        /// </summary>
        /// <param name="slide">Current slide reference.</param>
        /// <returns>An array of auto generated audios' name.</returns>
        private static string[] EmbedSlideNotes(PowerPointSlide slide)
        {
            String folderPath = Path.GetTempPath() + TempFolderName;
            String fileNameSearchPattern = String.Format("Slide {0} Speech", slide.ID);
            
            Directory.CreateDirectory(folderPath);
            
            // TODO:
            // obviously deleting all audios in current slide may not a good idea, some lines of script
            // may still be the same. Check the line first before deleting, if the line has not been
            // changed, leave the audio.

            // to avoid duplicate records, delete all old audios in the current slide
            var audiosInCurrentSlide = Directory.GetFiles(folderPath);
            foreach (var audio in audiosInCurrentSlide)
            {
                if (audio.Contains(fileNameSearchPattern))
                {
                    try
                    {
                        File.Delete(audio);
                    }
                    catch (Exception e)
                    {
                        Logger.LogException(e, "Failed to delete audio, it may be still playing. " + e.Message);
                    }
                }
            }

            bool isSaveSuccessful = OutputSlideNotesToFiles(slide, folderPath);
            string[] audioFiles = null;
            
            if (isSaveSuccessful)
            {
                slide.DeleteShapesWithPrefix(SpeechShapePrefix);

                audioFiles = GetAudioFilePaths(folderPath, fileNameSearchPattern);

                for (int i = 0; i < audioFiles.Length; i++)
                {
                    String fileName = audioFiles[i];
                    bool isOnClick = fileName.Contains("OnClick");

                    try
                    {
                        Shape audioShape = InsertAudioFileOnSlide(slide, fileName);
                        audioShape.Name = String.Format("PowerPointLabs Speech {0}", i);
                        slide.RemoveAnimationsForShape(audioShape);

                        if (isOnClick)
                        {
                            slide.SetShapeAsClickTriggered(audioShape, i, MsoAnimEffect.msoAnimEffectMediaPlay);
                        }
                        else
                        {
                            slide.SetAudioAsAutoplay(audioShape);
                        }
                    }
                    catch (COMException)
                    {
                        // Adding the file failed for one reason or another - probably cancelled by the user.
                    }
                }
            }

            return audioFiles;
        }
        //Delete existing animations
        private static void ProcessExistingHighlightSlide(PowerPointSlide currentSlide, List<PowerPoint.Shape> shapesToUse)
        {
            currentSlide.DeleteIndicator();
            currentSlide.DeleteShapesWithPrefix("PPTLabsHighlightBackgroundShape");

            foreach (PowerPoint.Shape tmp in currentSlide.Shapes)
                if (shapesToUse.Contains(tmp))
                    if (userSelection != HighlightTextSelection.kTextSelected)
                        currentSlide.DeleteShapeAnimations(tmp);
        }