Video FAQ

If you merely want to know how to decide which link to use to download one of our videos, click on Video Links in the side bar. This page has no videos, it’s just a collection of questions and answers on mostly boring subjects, but it might appeal to you if you’re really interested in some of these details.

Why does DaffTube use Dropbox for some of its videos? 

Video files are generally a lot larger than PDF files. If a lot of people download videos directly from DaffTube at about the same time, this will generate an enormous amount of outgoing traffic from DaffTube. DaffTube instead relies on Dropbox’s ability to limit the amount of traffic on DaffTube’s Dropbox account to 20GB per day, not just to a particular file but to all of DaffTube’s files combined.  It does this by disabling links to the files for a day. If your browser gets an error message about the file not being there, that is probably what happened. Dropbox will notify us when this happens so that we won’t panic when you tell us our files seem to have disappeared from Dropbox. Note that we are protecting DaffTube from excessive download traffic when you are saving videos on your computer or mobile device. When you click on the viewer to view a video, DaffTube is sending you data stored on its own server, not on Dropbox. So DaffTube and Dropbox are both protecting themselves from excessive download traffic while DaffTube serves users who wish to view its videos on demand.

What’s the difference between streaming and progressive download?

Both of these refer to how a video file is delivered to your browser for viewing as the data arrive. In a progressive download there is one file that the DaffTube server starts sending from the beginning and works progressively through the file. You can’t jump ahead unless the data for that part of the video has already arrived. You might see a colored horizontal bar showing how much of the video you’ve viewed and a gray bar showing how much more of the video has arrived and could be played. In a streaming video, the browser can ask the server to stop what it’s sending and jump to another part of the video to send. The server and the browser must use the RTMP protocol for this version of streaming to work. DaffTube’s viewer first offers your browser an .mp4 file and then a .webm file for progressive download. If your browser can’t handle either of those formats, the viewer offers an Apple HTTP Live Stream (HLS). As the name implies, it uses the ordinary HTTP protocol, not RTMP. It’s not quite as fancy as RTMP, but DaffTube uses HLS to support either low CPU powered iOS devices (e.g. older iPhones) or iOS devices connected by low bandwidth networks. In particular what’s streamed are multiple versions (different resolutions and bandwidth requirements) of a video. This is called adaptive streaming because it allows your iOS device to choose which version will work and to change versions if network congestion or other bottlenecks arise. Each version or stream is made up of many segments, each only a few seconds long. That allows switching streams at the end of any segment. In Apple HTTP Live Streaming, the server sends your browser an index file so that your browser can see what’s available and request the appropriate segment of one of the versions. Apple iOS devices and certain applications know how to do this. Version 10 of the QuickTime Player (but not version 7) knows how to handle Apple HTTP Live Streaming. If none of the first three options is acceptable to your browser, the viewer asks your browser to use the Adobe Flash Player plugin to play an MP4 video. Some versions of the Android system claimed to handle HLS, but they were not reliable.

What do you mean by the single word download?

There are two different ways you can see a video. One way is for your browser or one of its helper applications to decompress it and display it on your screen as it arrives. Normally, there is nothing left on your disk or phone memory when the video has finished playing although for a progressive download, the entire video is stored temporarily. There are many reasons why you might want to save the video on your device. Keeping a copy on your device is what we mean by downloading. You might want to view it multiple times without having to use up your data plan by repeating the transmission. You might want to view the video when you don’t have Internet access. You might want to view the video a little at a time and not all at once. You might have the screen and CPU power to see a high resolution video but not the bandwidth to receive it fast enough to play smoothly. In these latter cases, you want to download the file so that you can view it later without any network issues.

Why doesn’t the ADS just put its videos on YouTube?

YouTube would require the ADS to grant them a worldwide license to use, host, store, reproduce, modify, create derivative works, communicate, publish, publicly perform, publicly display, and distribute whatever content the ADS uploads to YouTube’s site. And the license continues even if we quit using YouTube. The ADS is reluctant to give up that much, so we’re putting our videos on our own site. A second reason is that some of our videos have a much longer running time than YouTube allows. A third reason is that we wanted to make it easier for you to download our videos.

Don’t I download a video from YouTube when I view it?

For copyright or other reasons, YouTube does not want you to save a copy of their videos. They make it easy to view (progressively download) but difficult to save (download) what you’re viewing. In normal viewing, your browser will discard a YouTube video after you’ve viewed it. The ADS, as a non-profit organization that provides information to the public, wants to make it easier for you to study and learn from our programs by enabling you to retain a copy.

So, is downloading a simple operation?

Unfortunately, it’s not always simple. A lot depends on how your browser reacts to a link (URL) that takes it to an .mp4 (or .m4v) file. Some web browsers will start displaying a video and not give you the option to save it for later viewing. Browsers on computers have a  “Save as” command, but it sometimes doesn’t work on videos. For mobile devices, we know of at least one app, iCab Mobile, that allows saving as well as displaying, but for mobile devices you’ll generally need a separate app that’s called a download manager. You give the download manager the URL to the video, and it retrieves and saves it. There are a number of free download manager apps for mobile devices. You’ll have to download and install the app first and then use it to download videos.

What download managers do you recommend?

As a tax exempt, non-profit organization, the ADS cannot recommend any product or service. We can mention ones we’ve tried that worked, but we emphasize that there are others that may be as good or better. A workable one for iOS devices that you can get at the Apple App Store is MyMedia. For Android devices, the Play Store will show you at least three if you search for “download manager”. We tried the one named Download Manager for Android, and it worked. We don’t have any experience with Windows 8 mobile devices.

You don’t use Flash movies?

No, Apple didn’t want to allow Flash movies on iOS devices and therefore did not provide apps for viewing them. Flash movies are in a proprietary format designed by Adobe, and Adobe has been providing free plugins for web browsers that enable them to display Flash movies. What we’re providing are primarily .mp4 files because almost everyone can handle them. Flash movies have probably reached the peak of their popularity and will gradually fade from the scene now that HTML version 5 includes video.  By the way, the recent versions of the Flash player plugin can play MP4 videos as well as Flash movies. If you have an older web browser on your desktop or laptop computer that handles HTML 4 but not HTML 5, it very likely has the Flash Player plugin. As mentioned on our Video Links Details page, we deal with older browsers that can’t display MP4 videos directly by asking them to use the Flash Player plugin to display an MP4 video.

Okay, I installed Download Manager on my Android tablet, but instructions were sparse. How do I download one of your videos?

Just to the right the Recent Apps icon is the menu icon for Download Manager. Tap it and a plus sign appears for adding a download. Tap the plus sign, and you’ll get to the screen where you can type the URL of the video you want to download.

Great, but where did it go on my tablet?

Tap the icon for the Gallery app. The video should be stored as a movie there.

Okay, I installed MyMedia on my iPad, but instructions were sparse. How do I download one of your videos?

In the opening screen, type the URL of the desired video in the text box at the top of the screen, not the text box where it says “Search your files”.

I let MyMedia store the video in the Other category. So where is my video?

Under iOS, files have to be owned by an app, and you go to that app to get to the file. Since you downloaded the video with MyMedia, it belongs to MyMedia. Double tap the icon that looks like musical notes to get to the categories of files owned by MyMedia. You should find your downloaded movie there. When you run MyMedia subsequently, it may open to a screen showing the files it has downloaded, but if it restarts with the opening screen, tap the button labeled “Files”.

You say you can cite but not recommend products. You did mention iCab Mobile earlier. Can you say anything more about it?

You can get it at the Apple app store. It does both web browsing and downloading. When you start it, it’s in the browse mode. If you type in the URL for an ADS video iCab Mobile will start playing it for you. If you really meant to download it, you first need to tap the icon that looks like a gear. That takes you to the Tools screen where you tap the item labeled Downloads. That brings up a partial screen with a plus sign at the bottom. Tap the plus sign, and it will present you with the choice of making a new folder or a new download. Select new download, and you’ll get a screen where you can type the URL of the movie to download. When you run iCab Mobile later and tap the gear icon and Download in the Tools list, you’ll see the movie you downloaded.

If I try other browsers or download managers and find one that works or doesn’t work, should I tell you about them?

Probably not. There are so many devices, browsers, and download managers that it would be hard to keep track of them and their various versions. Also the handling of Apple HTTP Live Streams is embedded in the iOS system. It would be too much work for us to keep track of exactly what combinations worked and which didn’t since they’re going to change over time. We just wanted to give you some examples to get you started. However, if future iOS or Android releases add significant capabilities that you think should be mentioned in this FAQ, let us know.

Aren’t movie files rather large to download? When I view movies on my home computer, it uses up a lot of my data allowance.

If your mobile device supports both cellular data and wi-fi connectivity, you should use wi-fi to download large files. We assume that you have a wi-fi base station at home connected to the Internet through cable or DSL (or you can go to a wi-fi hot spot). Your broadband connection will normally have a more generous data allowance than your cellular data plan. If you’re going to view our videos (or any other movies) more than once, it may make sense to download them once, play them as many times as you need, then delete them.

How did you decide what resolutions and bandwidths to support?

It’s a matter of deciding what devices our intended audience might have and then producing the files that can be displayed on them. There are several aspects we needed to consider. The two you mention are obvious. Computers usually have large monitors, but older smart phones have small screens. Cable and DSL generally provide fairly high data rates, but 3G cellular networks do not. Not so obvious is the compromise between degree of compression and the CPU power needed to decompress a video fast enough to display it in real time. A high degree of compression makes a smaller file that requires less bandwidth, but it also means a more complex compression that takes more CPU power to decompress. We want to make small files to send to older 3G mobile devices, but they may not have the power to decompress such videos in real time, even if that data arrives fast enough or has already been downloaded to the device. In this extreme situation, we have to lower the frame rate, and that’s been done in a couple of the streams in the Apple HTTP Live Stream (HLS) files we’ve produced. The HLS files are our method for dealing with low powered iOS devices connected at low bandwidth. The catch is that HLS video streams aren’t designed to be saved on the device. For more than you ever wanted to know about video compression, you can look at the two books we consulted to decide what file formats and compressions we should provide. They’re Video Compression for Flash, Apple Devices & HTML5 and Producing Streaming Video for Multiple Screen Delivery, both by Jan Ozer.

I see most of the downloadable files are .mp4 with only one .webm and one .m4v. Why is this?

.mp4 files are playable on almost all devices, so if we were to produce only one format, we’d make an assortment in various resolutions and bandwidths as we’ve actually done. The FireFox browser does not accept .mp4 files; it takes .webm files. We produce only one .webm file at a high resolution for people using FireFox on computers and the newer, higher resolution mobile devices.  The low resolution mobile devices might be able to handle the lower resolution .mp4 files, but, if they can’t and if they’re iOS devices, they can use the HLS stream files (which are made up of sequences of .ts files). One feature missing from all these is chapter markers. Movie DVDs usually have a scene index that allows you to jump to a scene, and this is handy if you want to view a video a little at a time and resume viewing in the middle. An .m4v file is a generalization of an .mp4 file that can also contain a table of time locations and chapter titles. The M4V format was defined by Apple and, not surprisingly, is the format Apple favors for its iOS devices, so all those devices know what to do with an .m4v file. In addition QuickTime Player version 10 (but not version 7) also know what to do with an .m4v file. Of course, you can’t jump to a later place in a video file unless you have the file, so it’s necessary to download the file first. As in the case of .webm files, we produce only one .m4v file at a high resolution for people with computers (and QuickTime Player 10) or a recent generation iOS device.

Are all DaffTube videos going to be available in the same resolutions and formats as on the Video Links page?

No. The first video we’re releasing was recorded in high definition so it made sense to prepare it and the sample videos with a vertical resolution of 720. We plan additional videos that will be salvaged from standard definition DVD or VHS tape, and there’s no point making them in resolutions higher than 480 for DVD or 360 for VHS. If we have a very long video, we might make only an .m4v file available since chapter marks might be needed for effective viewing.