The Transformation Transcoding

For ease of workflow replication for the inaugural transcoding report, Transitions invited primarily enterprise- and carrier-class solution providers rather than desktop- or workgroup-level transcoding tools.

Why limit testing to just two market segments? On the lower-end solutions, Jan Ozer and others have done a good job of examining those products, running most desktop and a few workgroup solutions through their paces. We felt that workflow integration was lacking in many of these products, though, which makes comparisons to mid- and high-level transcoding tools difficult. Likewise, on the online SaaS front, our initial reviews showed a lack of robust workflow integration-short
of highly customised programming-that allow online transcoding solutions to compete with enterprise workflow scenarios.

Transcoding or Protocol Conversion?
The biggest issues facing today's attempts to deliver a single video to every device-the mantra of media delivery, whether it be streaming or progressive download-is the sheer proliferation of devices. What once was a twofold decision (laptop/desktop versus set-top box) is now a 50-fold headache.

Between the myriad delivery protocols, the plethora of video screen sizes and the varying bandwidths needed to address each, the problem is as much about threading one's way through the device labyrinth as it is about choosing the best content to deliver.

Consider, for instance, the number of devices we used for testing: besides nine web-based profiles, we used 23 mobile-based profiles, encompassing numerous devices from Apple's iPhone and iPad to Google's Nexus One, Motorola's Droid, the Palm Pre and Samsung's Omnia. These devices represent the primary mobile operating systems-iOS, Android, webOS, and Windows Mobile-on the market today.

Even within the operating system categories, device sizes, screen sizes and pixel density all vary widely, meaning that each device needed profiles to properly compare content output.

Fortunately, with the exception of the Windows Mobile devices, each device's operating system supported the MP4 container format, with the AAC or MP3 audio codecs and H.264 video codec. The upcoming Windows Phone 7 operating system will also support MP4/AAC/H.264 within the year.

The benefit of the common thread of the MP4 container format is the ability to offload a bit of the transcoding workflow, in return for increasing the server workflow.

"What's that?" you're probably thinking. "I understand transcoding workflows, but what are protocol workflows?"

The reasoning behind protocols has to do with two of the biggest shifts in transcoding to date: the industry's settling-well, almost settling-on a single codec and the re-emergence of multibitrate transcoding.

Early transcoding solutions, in a trend that continues with simple transcoding tools, focused on conversion of a single bitrate video, encoded in a particular codec, to a video with the same bitrate but with a different codec.

Also known as transmuxing, given the need to multiplex files for easier delivery, protocol conversion began in the broadcast world but is finding its way into streaming and progressive download delivery. A move is underway to use standard MP4 files to deliver to any and all of the devices and operating systems listed above.

To do so, the generic MP4 file is converted-at time of delivery-into multiple protocols, from Adobe's RTMP to the more generic RTP/RTSP and on to the ubiquitous HTTP protocol. Protocol conversion by the media delivery server eliminates the need to convert a single video file into HTTP fragments for each of the three protocols, simplifying the transcoding process as well as the content management headache that comes with delivery to a multitude of devices.

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