| chnical considerations come into play when deploying | | | | 320x240 |
| online video content. It can be difficult to weed | | | | 384x288 |
| through all the techno-babble around video formats | | | | 448x336 |
| and codecs. Fortunately, the tools in the Flash | | | | 512x384 |
| platform make it relatively easy to set up videos and | | | | These are excellent targets for downsizing such |
| compress them for online use. In addition, all of the | | | | videos. |
| video software in the Adobe Creative Suite has | | | | Video quality can be, as you see, quite a balancing |
| features that support processing and delivering online | | | | act. It requires a careful examination of the content, |
| videos. | | | | the dimensions of the video image, the audio quality, |
| In fact, the meteoric rise of YouTube, Vimeo, and | | | | and other factors. |
| other hosting sites can be traced in part to Flash, | | | | Playback and Security |
| which is the best platform for delivering video to | | | | Flash videos can be delivered to viewers through. |
| different users, on various platforms, in multiple ways. | | | | Embedded video |
| The Flash format is also widely supported across | | | | Progressive download and playback |
| browsers, is fully customizable, and offers many | | | | Streaming server |
| interactivity options. | | | | Embedded Video |
| This article summarizes the technical issues and | | | | The well-known Shockwave Flash (.swf) video files |
| tradeoffs that you will encounter when developing | | | | are played directly by Flash Players. This |
| and deploying course videos, including: | | | | method’s advantages include: |
| Image and audio quality | | | | Playback requires only one file. |
| Smooth playback | | | | Videos and animations are easily synchronized. |
| Content security | | | | But there are some disadvantages as well: |
| Quality | | | | Files are limited to 16,000 frames. |
| Every video requires different compression levels, | | | | Audio/video synchronization may prove |
| depending on its content. A typical | | | | problematic. |
| talking-head video, for instance, requires less | | | | An entire video file must be downloaded before |
| compression than a fast-action video of an air show. | | | | playback begins. |
| Also, a video with a simple narrative is easier to | | | | This method is usually practical only for videos that |
| compress than one that combines or layers a | | | | area less than a minute long. |
| narrative and music track. Another key compression | | | | Progressive Download and Playback |
| factor is the amount of motion in the video, plus how | | | | A standard called Flash MX 2004 made it |
| much of it comes from the subject and how much | | | | possible to play externally stored video files. Its |
| from camera movements, zooms, and pans. This is | | | | proprietary .flv file format has built-in components for |
| an important factor because only the content that | | | | handling them. The .swf file basically points to a |
| changes from frame-to-frame needs to be updated | | | | specific .flv file via a Flash Video Playback component, |
| by the player using keyframes. If nothing changes | | | | which has built-in features for playing, stopping, |
| between keyframes, less data must be compressed | | | | scrubbing, and other operations. This method’s |
| and sent to the viewer. | | | | advantages include: |
| Uncompressed video files are normally huge. For | | | | Videos are easy to deploy and view, without |
| example, a 1-minute, 640x480-pixel movie with a | | | | special software or plug-ins. |
| stereo audio track could easily reach 1 GB in size. And | | | | Videos start playing only when enough of their |
| delivering this low-resolution file uncompressed over | | | | files are downloaded. |
| the web won’t normally work well. There | | | | Videos are streamed from the local disk, with no |
| usually will be playback problems, and people viewing | | | | performance limitations on file size. |
| the video across the web will wait a long time for | | | | Disadvantages are: |
| the file to download. Therefore, even this small video | | | | Video seeks can be done only to |
| will need to undergo both video and audio | | | | already-downloaded keyframes. So viewers |
| compression, to play back acceptably on user | | | | can’t advance through a video until its |
| computers. | | | | yet-to-be-viewed content has arrived in cache. |
| This compression is done through different | | | | Content is downloaded to, and stored in, the |
| compression/decompression (codec) systems for | | | | viewer PC’s disk cache, from which it could be |
| video and audio. A video player reads the | | | | copied or even re-distributed. |
| compressed information and decompresses it in real | | | | This could be an solution for short videos. But if |
| time during playback. Several codecs are available for | | | | security is a concern, it isn’t a good choice. |
| different purposes. And the compression schemes | | | | Streaming Server |
| they use have recently narrowed to a few standard | | | | Flash Media Server (FMS), and other such Streaming |
| options for online delivery. | | | | Servers, can deliver both live and on-demand videos |
| Video formats have also changed. High Definition (HD) | | | | with interactive options, buffering support, and built-in |
| displays offer much more pixel information per frame | | | | security. This method’s advantages include: |
| than non-HD displays. And until Flash Player 9 arrived, | | | | Streaming videos start playing quicker. |
| Flash video were delivered through non-HD codecs. | | | | Live video feeds are easily handled. |
| But with Flash Player 9, the H.264 codec became | | | | Client-side and server-side API’s are |
| available for the MPEG-4 video format’s | | | | available. |
| high-def quality. | | | | Client-server interactions are controlled by Flash |
| CD-quality stereo audio also increases video-file size. | | | | itself, and video frames are transmitted only as they |
| So where possible, even it should be compressed | | | | are needed. |
| (using an appropriate codec), and converted to a | | | | Dynamic buffering detects a client’s |
| Mono signal. And in most cases, users deal much | | | | bandwidth and optimizes delivery quality around the |
| better with reduced audio quality than with reduced | | | | dynamic connection speed. |
| video quality. | | | | Since the server stores all video data, the |
| These factors must all be considered when deciding | | | | client’s Flash player can seek to any video |
| on the best video codec for a specific application. | | | | frame, at any time, through a simple server call. |
| During this step, you must also examine the pixel | | | | Video content can be stored on multiple servers, |
| dimensions of the video image. Usually, it too must | | | | to cope with potential bandwidth/demand issues. The |
| be trimmed down... to trim the file size. And when | | | | same video can be sent to many simultaneous |
| this is done, you might even be able to boost the | | | | viewers, without bottlenecks. This strategy optimizes |
| video quality by switching to lower compression | | | | bandwidth usage, because only the frames actually |
| levels or better compression methods. In effect, | | | | being watched are streamed to multiple clients. |
| cutting back the size of the video on-screen may | | | | Content is never fully cached in viewers’ |
| enable you to increase its quality through lower (or | | | | PCs, making this a highly secure approach. And extra |
| better) compression! | | | | security-management features are available. |
| For example, a client of ours had a 15-minute | | | | The only real disadvantage of streaming services can |
| talking-head movie of a man discussing a | | | | be their price. The cost of software, server storage, |
| business model. The image size was only 640x480 | | | | support, and other factors might dissuade you. But |
| pixels... old-time VGA resolution. But even at this, | | | | plenty of providers offer these services at a |
| strong compression was needed to reduce the file to | | | | reasonable monthly rate. I’ve used Internap |
| an acceptable size for web transmission/playback. | | | | and Upstream Networks, which both offer a variety |
| And when I squeezed the dimensions of the image | | | | of service plans and are simple to use. You can |
| down to 320x240 pixels, the strength of the | | | | upload your videos and send them to viewers’ |
| compression could also be reduced, and the overall | | | | Flash players very easily. |
| image quality actually improved. | | | | So if you are concerned about video quality, playback |
| If (and when) you decide to reduce the sizes of | | | | performance, and security, Streaming Server is |
| your own videos, you’ll probably achieve the | | | | perhaps the best way to deploy your videos. |
| best results if you target a fairly standard display | | | | Summary |
| size. Here, for example, are the best target | | | | I shouldn’t need to convince anyone that |
| dimensions (in pixels) for web videos with a 4:3 | | | | online videos benefit learners. The investment to |
| aspect ratio: | | | | deliver their content is worth it, because richer |
| 128x96 | | | | learning experiences come through videos
and not |
| 192x144 | | | | just text and images. |
| 256x192 | | | | |