Digital Audio

Audio-Visual (AV) is one of the few art forms where one plus one equals four. AV, as the name implies, is made up of two main components, both of which are art forms in their own right. However, when combined in an AV sequence, the result is much more than just the sum of the parts. Everyone loves a slide-show. This was one reason for the huge success of the original "Magic Lantern" shows, the forerunners of today's cinema and also of today's AV shows, when they first appeared in Europe almost two centuries ago. We have come a long way since then, both in the movie world and also in the world of AV sequences or slide shows. It is possible with digital projection to simulate the effects of an unlimited number of projectors with a single projector.

The purpose of this article is not to provide an in-depth definition of “Audio-Visual”, nor to debate the merits of digital over analogue. Instead it is to provide some hopefully useful tips on various techniques associated with putting together a digital AV sequence. Suffice it to say, for purpose of this article, that an AV sequence is a presentation consisting of still images and accompanying music, sound effects or narration, usually synchronized with each other.

Please note that the ideas detailed in this article are based on my own opinions and experiences. Others may find that their techniques are different but equally, or even more, effective.

Preparation for an AV sequence should ideally start before picking up one’s camera. It is the nature of AV that the more images from which one can choose the more flexibility one will have in putting the AV sequence together. Digital technology has improved one’s chances in this area, as it is the general tendency of photographers (particularly of the amateur variety) to photograph many more images in digital than with film.

As with most endeavours in life, a good plan is the best starting-point in preparing an AV sequence. But before one can start planning the details, it helps if one has a solid theme or story in mind. This theme could be simply a poem, or a number of favourite music selections, or it could be a story about a trip one has taken, or an essay about a particular belief or idea. Generally it is most effective if it is based on a topic about which one has particularly strong emotions or beliefs or experiences and which one wishes to share with others. Since AV consists of both sound and images, either one could influence the selection of the other. The most common case is probably the selection of background music to reinforce a fairly well-developed theme or story.

The so-called “story-board”, common on movie sets, is useful in forcing one to think ahead about the types of images needed to complete the production. This doesn’t need to be an elaborate image-by-image description, but more likely a statement of the theme, how it will be broken down into different sections or components, and the types of images and music which will be used to achieve this theme. Of course, the more detailed the planning is, the more effective will be the result.

Digital images are easier to store, catalogue, and retrieve than the traditional transparencies. Gone are the problems of fingerprints, dust, scratches, etc., that plague miniature transparencies. There is no more danger of dropping a tray and scattering its contents. And searching for and sorting of images is made almost automatic.

Two excellent digital image management systems are “ACDSee” and “IMatch”. The latter is available as an inexpensive “shareware” download from the “Photools” website, while the former is an inexpensive Canadian-designed and slightly more professional system. Both are capable of management of images on a large scale. Two of the most valuable features of these programs are the ability to categorize images separately and independently from the folders in which they are located, and also to be able to search for them using many different criteria, from file name or category to other images that they resemble. It does not matter whether the original images are located on one’s immediate hard drive or on backup CD’s or DVD’s. Using these useful aids, one can search for images to fill in sections of a slide show without having to physically handle and sort through hundreds of transparencies, resulting in great savings in time, and also less wear and tear on one’s prize photos. Two other excellent photo management systems now available are Picasa (by Google) and Lightroom (by Adobe). The latter is considerably more expensive (and more rich in features, too) than the free Picasa system.

The better digital slideshow programs also have light-tables where one can readily sort thumbnails of the selected images into the order in which they belong in the show. Here, the entire show can be visualized and rearranged to fit the music if necessary. New images may be readily added to, or unwanted images removed from the mix.

It is useful to collect all the images and music selections to be used in the slideshow into a single folder to avoid having to associate them with particular pathnames which could prove awkward later on if one wishes to re-construct a show. It will also help to be able to view all available files together in one place.

At this point in time, the maximum image size which most affordable digital projectors will accommodate without automatically reducing the size for projection is 1024 by 768 pixels. This, therefore, is the ideal maximum size if the presentation is intended for projection or viewing on a number of different computer monitors. However, if one wishes to view it only on his or her own monitor, the image size can be whatever that monitor is capable of showing (e.g. even up to 1600 x 1200 pixels, for a very dramatic, high-quality slideshow). To view a slideshow, it goes without saying that for maximum effect, one's monitor should be set at the resolution at which the slideshow was created. I, personally, prefer the 15:9 wide-screen format of 1280x768 pixels. Both my laptop and digital projector were chosen with this aspect ratio and resolution in mind.

Here a brief word about image dimensions is in order to help to defuse one of the most-widely held misconceptions about digital images. The size in pixels is all that is needed to define the dimensions of a digital image as long as it will be displayed only on a computer monitor or digitally projected. Some people insist on adding the number of “dpi” as well. First of all, “dpi” (dots per inch) is the wrong terminology to use here as Photoshop and other image editors refer to “ppi” (pixels per inch), but it can be readily demonstrated that a digital image at 300 or 72 “ppi” looks exactly the same on a monitor (or projected) as one at 2 “ppi”. The only other parameter that is significant, if the image is a jpeg, is the quality of the image (in percent, or a number from 1 to 12, depending on the software used for editing). The maximum quality selected is a function of the speed and processing capability of one’s computer system and whether the show will be viewed directly from a CD or transferred first to a hard-drive. Generally a value of from 50% to 75% is used to keep the size of the image files small (usually around a maximum of 150 to 300 Kb). However, if one is playing the slideshow on the latest high-speed multimedia computer (with top of the line video card, high-speed processor, and plenty of RAM), files much larger than this may be used quite successfully.

The other aspect of a digital slideshow that can become very technical is the music accompaniment. Generally, it is best to use music and sound files in “mp3” format due to their smaller size. Another format gaining popularity is “Ogg”. Wave files may be used, but generally their large file size hinders the smooth running and easy distribution of the finished product.

One final technical note about pc configuration is in order. Although some CD drives are fast enough to play the finished AV production directly from the CD, it is usually best to transfer the files first to one’s hard drive for playback. Also, it is usually recommended that all other programs playing in the background, such as email, web pages, anti-virus software, etc., be suspended while the playback is in progress to make sure that the maximum computer resources are available.

There are many digital slideshow programs available today (including Windows XP, and the various programs which are bundled together with new digital cameras as well as many others available as shareware downloads from the Internet), but only a few of them are recommended, particularly for the serious digital AV enthusiast. Some of the most popular of these are: PicturesToExe, ProShow, GlobeFx, and Adobe Premiere. MS "PowerPoint" and Macromedia "Flash" can also be used to develop a slideshow from one's images but the dissolves are not as smooth as those from the above-mentioned programs. My preference is PicturesToExe (PTE) on the basis of its price, its many professional features, the attention given by the developer to suggestions and complaints, its ease of synchronization to sound and music, and the large Forum of happy users who share experiences, knowledge, and slideshows. I will attach a list of links to websites for each of these programs at the end of the article.

A good image editor and a user-friendly sound editor are also important tools of the digital AV creator. Adobe "Photoshop" is probably the most popular image editor (and probably also the most expensive, unless you settle for the less-expensive, but adequate, "Photoshop Elements"). Corel "PhotoPaint", Roxio's "PhotoSuite", and Jasc Software's "Paint Shop Pro" are also good editors. The image editor is used for modifying images to make them suitable for the show as well as for creating titles.

For sound, the legendary free download, "Audacity", is one of the best, especially for its price. "dBpowerAMP Music Converter" is another excellent free download useful for converting sound and music files from one format to another. Other excellent, but more expensive sound editors are Acoustica, Adobe "Audition" (formerly "Cool Edit"), Sony's "Sound Forge", and Steinberg's "Cubase". They also tend to contain more high-end features such as noise reduction and the ability to combine MIDI and audio tracks. A sound editor is required in order to splice music selections together, truncate music that is too long, adjust volume levels, create fade-ins and fade-outs, record narration, and export (or "mix-down") the results in the format desired.

Depending on the AV software used, there are often other third-party free-ware and share-ware utilities for specific purposes.

There are other sources of information on how to go about developing one's AV masterpiece, so this section will deal with only a few important considerations.

One of the main things to remember when creating an AV sequence is to keep it simple. Too many fancy title slides and elaborate image borders actually detract from the impact of the overall production. Also, try to stick with just one main theme instead of trying to cover too many different topics or ideas in the same show. And make sure the music and sound accompaniment fit the theme.

Transitions should be used to lead the viewer from one image to the next. As with the titles and borders, it is possible to go overboard with too many different transitions. And, they should complement the images they are switching to and from. For example, one might use a circular transition between two images where circles predominate. Or horizontal "gates" between a vertical and a horizontal of the same height. Dissolves are the most common in slideshows, but their duration should be varied to suit the images, using a "cut" to inject drama into the show and wake up the audience, or a long dissolve for mood enhancement.

Music selection is important, too - in fact it can be as important to the final product as the images themselves. Both should work in harmony and reinforce each other. Sometimes the images are selected first, as is the case with most travelogues, but often the reverse is true. It is fun to take a song or a poem and then hunt for images which match the words or music.

A good AV is made even more effective if the image transitions are synchronized with the sound and music. Everyone can learn how to count the beats in a music selection. True, some music is more difficult to "read" than others, but synching the images can be as simple a matter as clapping ones hands to the beat of the music. However, here, too, it is important to inject some variety to the piece by interspersing some faster "cuts" periodically, or having some images stay on-screen twice as long as the average. Some AV software programs actually provide a view of the waveform of the music which can be useful in lining up the transitions more precisely.

This section will outline a few techniques useful in creating digital slideshows. Most are related specifically to PTE, but some will also apply to other digital AV software as well.

- With digital technology, animation effects in slideshows are easy to create. First of all you need two or more images in precise registration containing the motion you wish to show. For example, this could be several images of a vehicle moving along a road through the field of view. When these images are loaded into a digital AV program and played one after the other in quick succession, the vehicle will appear to move through the frame. If all images were photographed in perfect registration, the effect would be very realistic. However, it is not always possible to achieve perfect registration. With digital technology this is not a problem. Using "layers" in Photoshop, the background in one of the images is selected as prime, and erased in all other images, leaving only the moving vehicle. Then, using "save for web", each layer is saved, against the selected background, to individual jpeg files for use in the show. If medium file-sizes are used, they can be displayed as successive "cuts" as quickly as 15 images per second on a fast pc to achieve fast-motion effects. The following Flash demo is an animation based on a series of images I used in a little PTE slide show which I put together for fun at Christmas last year. Notice how only the figures in each image seem to move, leaving the background stationary.

- When synching slow dissolves it is necessary to start the dissolve several milliseconds before the beat to which one is synchronizing that transition. The reason for this is that several milliseconds elapse after the start of the transition before the viewer notices it. Thus one either has to predict the timing of the beats of the music or else go back in and move the transitions forward slightly on the timeline. The time of this perceived delay will depend on the length of the dissolve in question.

- It is better to use one single music/sound file when synchronizing the show to background music/sound effects. All the sound and music files may be combined into a single file using a music editor. It also helps to add three or four seconds of silence to the start of the music to allow time for the slideshow to start exactly where one wishes it to, and to facilitate synchronizing the first couple of slides.

- A black slide at the beginning and end of the show allows one to control the start of the show and also to fade to black at the end. To conserve file size, this black slide need only be one pixel by one pixel in size.

- Titles may be created in Photoshop and saved as transparent GIF's or in "png" format. They can then be overlaid as objects in some AV software such as PTE. With GIF's, if the background is dark and the titles are created against a light or transparent background, or if the background is light and the titles are created against a dark background there can be a problem with anti-aliasing (smoothing around the image) leaving unsightly artifacts around the edges of the text, as illustrated in the following demo. Therefore, it is best to turn anti-aliasing off when creating the text if it is to be used in transparent-GIF format and avoid the use of drop-shadows, as this also adds anti-aliasing effects. The effects of this are demonstrated in the following Flash demo. "Png" files can now be used in version 5 of PTE and result in much smoother transparent text overlays than do the GIF files.

- Digital AV lends itself marvelously to exploitation of the "Third Image", that pot of gold that all AV creators aspire to achieve in their presentations. The "Third Image" is simply the fleeting glimpse that is viewed during a slow dissolve that is the combination of the outgoing image and the incoming image. It can be reinforced in digital AV by creating an actual third image from a combination of the other two images in Photoshop and then introducing it into the slideshow between the other two images. This way, it can be embellished if one wishes, and held on-screen as long as desired.

The main value of AV competitions is that they offer a forum for the artist to display his or her work, as well as an opportunity for other photographers to view excellent material. Personally, I don't enjoy all that much the competitive aspect of AV competitions, or ordinary photo competitions, either, for that matter. (Sour grapes, maybe?) I feel that AV in particular is really too subjective for competition, and who can really say that one good slideshow or photograph is better than another, anyway, since each one is the result of an artist at work telling a story or describing his or her mood or feelings? Thus, by definition, it will strike a chord in the minds and hearts of those viewers who can relate to that particular idea, or mood, and will leave other viewers more or less cold. Of course, it gives one a warm feeling to have one's work selected over that of others, but what does it really mean? Granted, there are some technical aspects which can be considered to be handled in a more or less effective manner. But the very fact that judges tend to vary so much in their ranking of the same slideshows is evidence that in the end it is the first impressions and the subjective aspects that really count. However, I do participate in competitions because they are excellent ways to show off one's work which would otherwise not be seen by so many other people. Every artist needs an audience as one of the main purposes of art is to communicate. One can also usually benefit from the judges' critique.

The international digital SuperCircuit AV competition organized each year by a group in France is an excellent forum for showing one's AV productions. In November, 2005, Ottawa hosted the first-ever North American Festival as part of SuperCircuit.2005. This was be a wonderful opportunity for AV enthusiasts in Canada to have their work shown and for all local photographers, and others willing to travel to Ottawa, to view the best AV productions in the world. There is information in the linked web pages in the next section on how to submit AV shows and how to attend the Festival.

The following are some useful links related to AV software, events, and techniques.

Digital SuperCircuit:	- international digital AV competition (rules, etc.)
PicturesToExe (PTE):	- digital AV software
PTE Forum:	- forum for PTE users
Beechbrook Cottage:	- PTE slideshows and tutorials
ProShow:	- digital AV software
ACDSee:	- digital image management software
IMatch:	- digital image management software
Audacity:	- audio-editing software
dBpowerAMP:	- audio-conversion software
Other AV sites	- miscellaneous personal sites from around the world

Digital Audio-Visual Techniques