Since Apple's decision to block Flash from iOS devices there has been much discussion of its strengths and weaknesses:mostly based on misinformation. As a developer I'd like to share my understanding of Flash with an eye towards providing a more balanced analysis of the platform's strengths and weaknesses. This will end up being a series of posts - I'll pick a single topic to focus on for each post.

Flash and Video

Misconception: Flash will drain your mobile device's battery much faster than native video.

Although this was true at the time of Steve Job's famous "Thoughts on Flash" open letter it's no longer the case. With Flash Player 10.3 video is decoded using the GPU, the same as native video - in some circumstances Flash's video decoding is marginally more efficient than video presented using HTML5 in the browser.

Misconception: Flash video uses a proprietary CODEC limiting deployment to the Flash Player.

This is no longer the case as the Flash Player supports H.264 video, the same as HTML5 in webkit browsers. It's possible to host an H.264 video on a server and play it through the Flash Player, or on an iOS device, play the same video through the HTML5 video player. The embed code will choose the player based on the presence or absence of the Flash Player - the viewer will be unaware of the switch.

Misconception: HTML5 video will replace Flash on Youtube and other video hosting sites

Although Youtube is experimenting with HTML5 video they will continue to use Flash video for the foreseeable future as the Flash Player allows them to superimpose ads on the video stream. I'm not a big fan of ads but they do allow Youtube to provide all the free content we see. If Youtube migrates to HTML5-only presentation then the ads will play before you can access the free content. I'd rather be able to dismiss the ads with a click rather than wait through them.

Little Known Facts About Flash Video

Close Captioning: Flash supports close captioning of video (HTML5 video players are beginning to offer this as well). The Flash solution allows the placement of the captions as metadata in the video file. At present the HTML5 solution requires the captions outside the video file (adding a layer of complication that can lead to broken links).

Alpha channel support: Flash video encoded using the ON2 CODEC supports alpha channels, the technology behind green screening. It's possible to superimpose a Flash video on a background image (or series of images), just like the TV weathermap. In an educational setting this allows a professor to produce a talking head podcast that can be superimposed over course content. The video data rate can be quite small while high resolution graphics are presented interactively with the video.

More on video in the next post ... all about streaming.