This is the last entry in the rough draft for my first book–Podcasting Church. I’ll be editing it now. I hope to release it on Amazon soon. I’ll keep you updated. I started writing on 11/2/10. Now, 40 days later, I have a rough draft of a book. It’s amazing how easily it came. Maybe I’ll write another soon 😉
The chapters weren’t written in order, so if you’re reading this in the final order, keep reading.
Resolutions about Codecs
For audio, there’s not much more than that. For video, it’s a little more to it. I’ve already said that video podcasts tend to be Quicktime video format because of the tendency for people to view them on iPods and iPhones. I wish that was all there was to it, but that’s not quite right.
At my church, we create everything on Macs. All video is edited in Final Cut Studio. We’ve noticed that sometimes videos didn’t play on computers that hadn’t been used to create them. At first, this was very confusing. At our satellite campus I noticed this with two identical computers–one that had Final Cut Pro and one that didn’t.
I opened up two videos (one that played and one that didn’t) on the computer that could play both. Both were Quicktime movies with the .mov extension, so neither of those pieces was the determining factor. They were both of similar size, so that wasn’t it. They were the same resolution, so that wasn’t it either.
Then I noticed the codec. A codec is a set of instructions that tells the computer how to display the video. The name is short for “COmpress DECompress”. It’s how the video is compressed and played back. In this case, the one that played used the H.264 codec and the one that didn’t had the DV/DVCPro codec.
The funny thing is that codecs aren’t format specific. A Quicktime movie can use the H.264 codec, but so can a Flash movie file. These formats can be thought of as wrappers that contain certain information about the video and within the wrapper is the actual video encoded using a certain codec.
Some codecs are better for editing (like Apple’s ProRes 422 or DV/DVDPro). Some are better for distribution and playback (like H.264). Some are better for animation and some are better for quick action.
Choosing the proper codec can dramatically reduce the size of the final file and ideally, the viewer wouldn’t know.
Depending on how the viewer will be watching the final podcast, you can also tweak the resolution. With the recent change from standard definition to HD, you probably know some of the terms. Whether it’s 720p, 1080i or 1080p, you probably remember seeing the clarity of HD for the first time. You don’t know how low resolution SD tv is until you see HD.
I used the metaphor of resolution earlier when talking about bit rate, but that wasn’t exactly right. There’s no number of dots that a speaker reproduces, but there is a number of lines and dots a display device reproduces when it comes to video.
Typically, SD is 480i. This means there are 480 lines of vertical resolution. The “i” means interlaced as opposed to “p” for progressive. An interlaced picture is drawn with odd numbered lines and followed by even. So, SD is actually drawn 240 lines at a time. Enhanced definition is a standard you don’t hear a lot about. It just takes those same 480 lines of resolution and draws them one after another (or progressive) so it’s also called 480p.
HD is 720p, 1080i and 1080p. You’ll notice that 1080p is around four times the resolution of a single 240 line field of an SD image. The sharpness of the image is what defines an HD image, but that’s not what most people notice.
Most people notice the aspect ratio. SD television is typically 4:3. It almost looks square. HD displays are usually around 16:9, although there are 4:3 HD displays, but they’re rare.
You can create a video that’s technically SD, but depending on what people are watching it on, they’ll think it’s HD if it’s 16:9. The sharpness of HD is device dependent. I can show a widescreen DVD on a wide-screen display and many people won’t know that it’s not a BluRay disc.
This is especially true for video embedded on websites. Because the video is only a section of the entire page, is scaled to fit in a section, and because computer resolutions vary so much, it’s even an easier mistake.
You can also adjust the playback frame rate to affect file size. Early web video was often 10-15 frames per second for this very reason. On the other end of the spectrum, 1080p video tends to run at 60 frames per second (not coincidently the same same rate as electricity’s 60 hertz). SD video ran at about 30 (actually 29.97, but let’s not get picky). Film was traditionally shot at 24 frames a second just like some DSLRs shoot today.
You can optimize video so that it takes the least amount of space and still plays fine by changing all three of these settings. If you transcode a video so that it uses H.264, 480p at 30 fps and you’ll get great results. Happily, there are programs that make all of this easier with presets.
iTunes itself has a menu album in the “Advanced section” to create iPod/iPhone or iPad/AppleTV versions. These are good general settings. Third-party software like iSquint also makes it possible create smaller video.
I personally use Compressor, Apple’s professional video compression utility. I’ve tried tweaking all sorts of settings, but found that the 720p h.264 preset for AppleTV creates a nice final product. I’ve already mentioned that I use it to create the weekly video for my church’s satellite campus and it works out to about 2 gb for an hour of beautiful 720p content that many people have mistaken for live.
If I were podcasting the sermon, I might create a couple of feeds–one for these larger videos and another that’s much smaller for people who aren’t watching it on a larger screen.
I’ve seen video podcasts that had half a dozen or more video feeds optimized for several devices. I’d encourage you to limit the number of devices that you specifically support. Instead, make no more than three feeds. Make one that works on everything even if it’s not the best quality. Start here. Add feeds as necessary, but you probably won’t want to create one that’s meant for one and only one device unless you have a really good reason.