About a week ago, I received a request to change a video for a corporate client. "Send it here," I wrote, and then pasted a link to my Dropbox for uploading. My client quickly uploaded the file, and Dropbox sent me a notification letting me know the file was uploaded. I immediately opened my Dropbox folder and took a look at the video, only to discover...
...it was not a video.
What was it? It was a file with the extension .pptx, or a Microsoft PowerPoint file.
What's the difference?
Think of the very first motion picture ever made. It's called "The Horse in Motion", and it was literally a series of pictures placed in a turnstile, and then the turnstile was spun to create the motion. This one has a low frame rate, but even today, videos and movies are basically a series of still pictures played in rapid succession. I typically shoot my video clips in 4K at 30 frames per second. In other words, my camera is taking 30 digital 25" x 14" pictures every second.
When motion pictures were first created, they used film strips to create them. Since then, we had the advent of magnetic videotape, broadcast television, digital videotape, digital memory cards, high definition, digital video compression, and cloud video on demand. Video today looks very different than the video did when these things were first coming to life, thanks mostly to video compression, but the essence is still there. Video is still a series of pictures played in rapid succession. One example is pointed out with the video compression schemes. In MPEG type compression, one of the common units used is called GOP, or Group Of Pictures. MPEG-2 compression typically uses a Group Of Pictures of either 15 or 12, depending on the frame rate of the video.
Most of the video files I receive are Quicktime Movie files (.mov, .qt) or MPEG-4 files (.mp4, .m4v). Regardless of the compression used, those file types are merely wrappers that let my software know how to handle the information in the file. Others, like Windows Media (.wmv), Audio Video Interleave (.avi), MPEG-2 (.mpg, .ts, .mp2, .mpeg, .mts), Matroska (.mkv), Material Exchange Format (.MXF) can be used. There are many different video file types.
But .ppt, .pps, .pptx, etc., are not part of the list of video files. This is because they are not actually video files, but are another file format, called PowerPoint.
PowerPoint files are not a series of pictures played in rapid succession like a video file. Instead, they are mathematical algorithms that display the information you wish to convey. When you move your text around and add a little circle in your PowerPoint file, it is saved to the program as information such as, "font=Megaloonies, color=99EE67, size=48pt, style=bold, text=Hello%20World," etc. This may represent some green text across the screen that says:
Hello World
This type of information handling is called "vectorizing."
A video file, on the other hand, is saved as pixel by pixel, frame by frame. Instead of the above type of information, a video file information may look more like, "220/136=99EE76, 220/137=99EE77, 220/138=99EE76," etc. However, instead of that bit of code representing the line of text, it represents merely 3 pixels, and it takes 307,200 pixels to make up just 1 frame of standard definition video. 2,073,600 pixels are needed for each frame of high definition video, and 8,294,400 pixels are needed for each frame of video in the format I use. One second of standard definition of video will contain 9,216,000 pixels, and a minute will contain 552,960,000 pixels. For high definition, those numbers are 62,208,000 pixels for one second, and 3,732,480,000 pixels for a minute. What about 4K? Try 248,832,000 pixels for one second, and 14,929,920,000 pixels for a minute of 4K video. That's a lot of code.
This "pixel by pixel" way of saving the images is called "rasterizing."
Contrast that with the simple code of the text in the PowerPoint file, and one can clearly see that the PowerPoint file can be MUCH smaller than a video file. The file size is an obvious difference, but it's the style of the code that makes the biggest difference. Because of the way PowerPoint files are coded and saved, it is easy to make changes. No rendering is required, like it is when creating video files. Rendering is act of converting the cool graphics and animated text into that same code for video, or rasterizing the animation, i.e. "220/136=99EE76, 220/137=99EE77, 220/138=99EE76". PowerPoint doesn't need to do that, as the PowerPoint application processes the information differently.
But there is a MAJOR caveat with PowerPoint files. If you notice, in the first code sample, I chose the font Megaloonies. But the green text on the screen above doesn't use the font Megaloonies. This is because the computer you are using doesn't have the font that I chose. If I were to create a PowerPoint file using the Megaloonies font, you wouldn't be able to see that font. Instead, PowerPoint would choose your computer's default font and run with that. Unfortunately, Megaloonies is a very stretched out font, and now, since it's using your computer's default font, it's all squished up and it just doesn't look right. Video files NEVER have that problem, and that is because they are not encoded with font, size, and color information, but are encoded with pixel by pixel (rasterized) information, and that rasterized information can never be accidentally or arbitrarily changed when transferring to another computer simply because a font is missing. Vectorized information depends on your computer's installed resources and resources sent with the vector type file in an effort to save space.
Another significant difference is the way PowerPoint shows pause to allow the presenter to trigger the next slide or bit of text. Video files do not stop without the presenter stopping them, and they don't continue unless the presenter resumes playback.
Because of these differences, PowerPoint files need to be treated very differently from video files. In the case of the one I received, I had to open it in PowerPoint, make sure all the fonts were current and everything was placed correctly, and then export a video file from it. Fortunately, everything was there, but exporting the video file took nearly an hour to complete. After that, editing that file was difficult because there were no natural pauses that there would have been if a presenter was controlling it. Again, video files don't pause unless the presenter pauses them. I had to find every pause point, create my own pauses by freezing the frames, and extend them through the length of the voiceover with which I was editing.
These actions weren't really a problem, as I'm happy to do them. It's just important to know that if one is sending a PowerPoint presentation file to a video editor, one is NOT sending a video file, and it will take some extra time to get the presentation. It's also important to know that the editor may not have the proper fonts installed, which will change the look of the final video. If possible, instead of sending a PowerPoint presentation to a video editor to be used as a video, please consider exporting it as a video file (.mov, .wmv, .mp4), and sending that. It will take longer to upload and download, but it will be exactly how you see it on your screen, and the editor will thank you for providing a video instead of a PowerPoint presentation file.
-Brett Gentry
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