Join Richard Harrington for an in-depth discussion in this video The need for compression and essential terminology, part of Producing Professional Podcasts.
- Now, when it comes to files, they often need to be optimized for delivery to mobile devices. You see, professional quality video can get pretty big. Earlier, we made a Quick Video Tip podcast. Here it is. That's that export from ScreenFlow. And it's only a minute long. And one minute of video, almost a gigabyte. Well, that's not going to work for most people. First up, it's going to take a long time to download that file. Secondly, it's going to fill up the internal hard drive.
And, in fact, the device likely doesn't have the processing power to play back that full-quality professional video. Here's another example. You see here, this is an episode from another show, clocking in at 3.3 gigabytes for a ten minute video. Well, this particular episode was from a show called "Power to Create". Myself and fellow lynda.com author Al Shapiro were teaching people how to use high-dynamic-range photography to put together some content.
This is Pro video. And if we look at the file here, you'll see that it uses the professional Apple ProRes codec. It was cut at 720P and 24 frames a second. Well, that's pretty big. What we need to do, is really optimize this. So, the goal here is to get the files smaller, both so they're more convenient and they're easy to deliver. Now this is going to make it simpler and more likely that the files will work on people's devices. Let's go through a couple of key terms for a second and then we'll explore this process.
First up, there's the Architecture. This is the overall global family, or classification, of a file. This is things like MPEG, Flash, QuickTime, Windows. In our case, MPEG is the architecture that we use for most podcasts. The 'big' picture here. We then apply a specific Compressor/Decompressor. This is often referred to as a Codec. C O D E C This algorithm allows for the shrinking of the files.
When done correctly, compressors can create visually pleasing results with dramatically smaller file sizes. Do keep in mind that many of these compressors and decompressors will cost you extra money. Now, a lot of professional video editing tools have these built in. And if you have QuickTime Player, same thing. Fortunately, you're going to be using MPEG-4. This is a widely compatible codec that's likely already installed on your system. The decompressor is also installed on devices like the IPad and the IPhone. In fact, many of these devices have a dedicated H.264 decoding chip.
This means that the battery and the processor don't get hit very heavily when they're playing back this high-quality HD video. Fortunately, by following these specific standards, devices like mobile phones and tablets can play back podcast files without sucking up a lot of processor, generating heat and consuming the battery. Now, Ideally, what we're going to do here is shrink the file using these mathematical algorithms. But, don't worry, you don't have to do any math. It's all done by the computer.
And modern compression techniques have come a long way. I've been delivering video over the web for a very long time. In fact, I delivered my first web video back in 1995. Well, that's a lot of different changes that we've gone through. And video used to be about that big and looked pretty awful. But, it was still amazing, and great to be publishing things around the world. Well now, high-definition video just comes right to the IPad, it's so easy to do. To the smartphone, to mobile devices, to set top boxes.
With podcasting, it is so easy to get high-quality audio and video. But, you do need to know what you're doing. A couple more things, the Bit Rate. This is how much data there is, per second, in the file. Higher bit rates tend to lead to clearer image quality, but you have to keep them below certain thresholds if they're going to work. The higher the number, the larger the file. Now, larger often means more quality, but it is dependent upon the codec. Many codecs are very efficient at keeping the file size down.
Similar to bit rate, is the Sample Rate. This is the number of audio samples captured per second. Audio CDs are 44 kilohertz. Digital videos 48. Most of the time, for podcasting, we're going to go with 44.1, the same quality as an audio CD. This conversion will likely happen on output. But, it's becoming less and less important as 48 kilohertz and 44.1 are becoming very commonly used. Another concept that's important is the active Variable Bit Rate Compression, or VBR.
This means that the video file is made as small as possible while maintaining a certain quality threshold. Essentially, the computer will analyze the file, taking two passes, and then, where it can, it will compress the video to the smallest size while maintaining certain quality standards. This way of encoding is a lot slower, but it produces much higher quality files with much smaller file sizes. So as such, whenever possible, I strongly suggest using this method.
Finally, look for the ability of Batch Processing, and trust me, it's as good as those cookies look. With batch processing, you have the ability to load up a bunch of files into your system, pick a preset and a setting, and click a button and walk away. Video compression, takes some time. The older your computer, the longer your show, the more it's going to take. This is not the sort of job you want to sit there doing by hand. Fortunately, with batch encoding, you can load up a bunch of files, start them up and walk away.
This will allow you to set those files up to run, and let the computer work without you being present. It also ensures consistency across the board. Now that you understand some of these key terms, let's move on to Essential Tools for compressing audio and video files to optimize them for podcasting.
In this course, you'll learn how to create a podcast to match any budget, using proven techniques that get listeners and results. You'll learn how to set up a small studio; record audio, video, and even group video chats; edit your podcast; and create a podcast feed (aka an RSS feed). This class is taught by Rich Harrington, who's produced, hosted, or consulted on several podcasts that are routinely featured as the best of iTunes. Watch and learn how to get your own podcast up and running in less than a day.
- What is podcasting
- Leveraging existing content
- Analyzing the competition
- Outlining a podcast budget
- Setting up a studio
- Setting up an RSS feed
- Recording interviews, screencasts, and Google Hangouts
- Editing podcasts with Adobe Audition and other audio editing software
- Optimizing audio and video for podcast delivery
- Hosting podcast files
- Branding and promoting your podcast feed