CPS100 • INTRODUCTION TO COMPUTERS


SUMMER 2018 Semester • LAKELAND UNIVERSITY

Audio & Video

PowerPoint allows new dimensions that were not very easy to use in slideshows before computers: audio and video.

In terms of audio, you can add background music to your presentation, in addition to sound effects for both animations and slide transitions. You can also add videos, both small and full-screen.


File Formats & Codecs

Audio and Video come in various file formats. These are also called "containers," and are usually identified by their filename extension, the few letters after a period at the end of a filename. For example:

  1. .mp4
  2. .avi
  3. .mpg
  4. .mp3
  5. .aiff
  6. .au

These file formats are really just containers, or packaging—they are not the part of the file that handles the actual audio or video.

However, the file format sometimes will determine whether or not an audio or video file can be opened by a program at all. For example, in PowerPoint, while many types of audio can be used for inserted sounds, only .wav files can be used as sound effects for animations or slide transitions.

Next, there are codecs, which are the part of the file that do the really hard work. A "codec" does what its name suggests: it compresses and decompresses audio and video.

Compression is when you take a file and make it smaller, while trying not to lose much or any quality. Lossless compression keeps the exact quality of the original; lossy compression will lose some quality.

Older compression codecs are usually less efficient. When audio CDs came out, for example, they used a good codec for its time: the PCM audio codec, saved inside an .aiff file format. If you open an audio CD on a computer, you may note that each song is about 50 MB is size.

A more modern codec is mp3 (which is also the name of the container). Mp3 does a far better job of compression than older files using PCM. Mp3 files can reduce up to 95% of the file size. A feature of mp3 is that is has variable compression; you can compress a little, or a lot. This is usually measured in "bit rate," measured in kilobits per second, or kbps. 128kbps compression in an mp3 file is acceptable; too much less than that, and the quality loss is very easy to hear. Higher-quality compression is 256 or 320kbps, or higher.

If you take an older .aiff file from an audio CD and save it as an mp3, the file size may drop from 50 MB to only 5 MB.

The Problems with File Formats and Codecs

As stated above, some programs will only accept certain file formats. However, codecs can be trickier. Even if a file format is accepted, a program (or operating system) may not have the required codecs to read certain files.

If you have an audio or video file, it may not be readable by a program like PowerPoint even if it is the right file format.

If you run into this situation, a way to fix it is to re-encode the file—open the file, and then save it as a different format. Most people do not have the software for this, but there are online services such as this one that will do it for free.


Inserting Audio

After you prepare the media file, you will want to insert it into your presentation. When you use the "Insert" tab to put audio into your presentation, the audio file becomes an object. Most audio file formats may be used, including MP3, although PowerPoint likes WMV files as well.

As I warn above, it is best to have your sound files in the same folder as your presentation, all on a USB Flash drive. Make sure that you save the media file in the USB Flash, in the correct folder, BEFORE you insert it into your presentation.

Once the file is in the correct place, just go to the "Insert" tab in the Ribbon, go to the "Media" group on the right side, and then click on the "Audio" button. A short menu will appear; choose the "Audio on my PC" selection.

A dialog box will appear. Navigate to the folder which has the sound file you wish to use. Many sound formats will work, including mp3, mp4, m4a, wma, aiff, wav, midi, and au. Other sound files may work if their filename extensions are included in the "Audio Files" list to the right of the filename at the bottom of the dialog box. MP3 files are most common, and work reliably.

Once selected and inserted, the sound will appear as a sound icon in a placeholder, with audio controls in a bar below the icon.

In the Ribbon, you will see a new tab group, titled Audio Tools. Select the Playback tab.

In the Playback tab, there are several controls which help set the sound's options. The most useful controls:

  • Trim Audio: play only part of the audio file
  • Fade Duration: Create a sound fade at the start and/or end of the sound
  • Start: Play the sound only when clicked, or begin the sound automatically
  • Play Across Slides: Allow the sound to continue playing over more than one slide
  • Hide During Show: Does not show the audio file's icon on the slide during a presentation
  • Play in Background: Makes the audio file the background music for the slide show

To Trim Audio, click on the button, and a dialog box will appear:

Move the green marker to where you want the sound to begin, and the red to where the sound should end. You can hit the Play button to test whether the selection is correct. Click "OK" when done.

The Fade Duration should be easy to understand; it is useful when a trimmed audio is used, smoothing the sudden beginning or ending of the sound.

Under "Audio Options," the Start selection allows you to choose between "On Click" or "Automatically."

If you do not hide the icon during the show and wish to start the sound at exactly a desired time, then choose On Click. "On Click" means that the sound will begin when the start button in its control bar is clicked—it does not mean that any mouse click will start it. Make sure you do not select "Hide During Show" for the sound icon, otherwise clicking will not be possible.

If you want the sound to play Automatically, select that option. You can set the sequence and timing of the sound play using the Animation Pane in the Animations tab in the Ribbon. We will look at animations later.

Background Music

If you would like to use an audio file as background music for several slides, there are two ways to do it. The easiest way is to simply click the Play in Background button.

This will actually just change three other settings: Start (to "Automatically"), Play Across Slides, and Loop Until Stopped. The alternate way to play background music is simply to slect these yourself.

The effect of these settings is that the sound will start automatically in the order it was introduced to the slide, and will continue to play for 999 slides, repeating after the sound file completes.

You can turn off the "Loop" setting if you want the sound to play only once, and not repeat.

You can have better control if you go to the Animations tab in the Ribbon, and click on the Animation Pane button:

Clicking on the Animation Page button will make the pane appear at right. The sound should be listed as an animation:

Double-clicking on the listing in the pane will open a dialog box with controls:

Here, you can set various options, including the exact number of slides the sound will play across.

Many people want PowerPoint to automatically begin playing a new song exactly at the time the first one finishes. Unfortunately, PowerPoint cannot do this.


Inserting Video

Inserting video is very much the same as audio, except that the file appears as a still-frame ("Poster Frame") from the video:

When you select the movie, the Video Tools section will appear in the Ribbon, with a Playback tab, with mostly similar tools to that for audio:

Note the special settings under "Video Options" on the right side.

Also note that many movie files will not play; if that happens, you will either get an error message, or you will see a blank rectangle. Even with a blank screen, the sound may still play. This just means that your computer does not have the correct codec to play the video type.

Note: I would advise against using videos much in presentations. Do not use them unless it is necessary. A presentation is supposed to be your speech, with the slideshow assisting you. If you add too many videos, then you are just watching a video with your audience!


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