Transcoding for Mobile

OTTAWA—As more wireless devices hit the market—Androids, iPads, iPhones, Blackberrys, and soon Amazon's Kindle Fire—the more transcoded streams that broadcasters have to create, serve, and store. This explosion of mobile devices can induce headaches for broadcasters trying to keep up with the latest format du jour.

Bruce Devlin, CTO, Amberfin Even though H.264 is supported by many mobile devices, the fact remains that broadcasters have to create separate streams for iPhone/iPad, Blackberry and Android platforms, according to Wayne Andrews, product manager for Matrox, which has designed a faster-than-real-time H.264 hardware-based transcoder for broadcasters. "This means that you cannot just put out one stream for mobile and serve everyone, because one size does not fit all," he said.

In addition, different mobile devices use different screen aspect ratios, and indeed different-sized screens. So what looks good on an iPad will not necessarily look good on an iPhone. This fact also extends to metadata, according to John Pallett, director of product marketing for Telestream, which makes a range of software-based transcoding products for broadcasters. "The graphics, file information and other metadata that is attached to an Android feed may not be right for someone using an iPad," he said. "So you have to be able to serve up the right metadata for each platform you support... which means more work for broadcasters."


If this isn't enough, broadcasters now need to provide different bit-rate versions of each stream. "By offering different bit-rate versions of the same feed, a viewer's device can access the best quality when the network permits, and then switch to a lower bit-rate version to prevent interruptions during congested periods," said Tom Lattie, vice president of product management at Harmonic, which provides a family of video management tools to the broadcast industry. "The problem is that each bit-rate version is a separate feed," Lattie says. "For one customer this means transcoding 8,000 incoming assets into 40,000 assets each month just to serve the Apple platforms."

More feeds also means more quality control issues. In particular, "Visual quality issues are important to check for, given the lower bit-rates used for mobile devices," said Mike Nann, director of marketing and communications for Digital Rapids, a maker of scalable software and hardware transcoding products. "You can't manually check every output you make, so it's important to incorporate such checks into your automated workflows."

Broadcasters selling content to subscribers must factor in digital rights management to their transcoding workflows, according to Adrian Giuhat, CTO and senior vice president of product development for Viewcast, which provides end-to-end streaming media solutions to broadcasters. "Another 'problem' is ad insertion," Giuhat says. "Each of the broadcasters use different ad insertion systems. Integrating those with different transcoding solutions needs to make sure the ads are served and accounted for."

"Finally, you have to serve and store all of these various mobile feeds, and be ready to respond to new products that likely won't be compatible with anything else," concludes Bruce Devlin, CTO of AmberFin, which provides end-to-end content management solutions for broadcasters. "As new formats arise, you have to be prepared to cope!"


The days of doing transcoding casually are over. To keep up with consumer trends, a broadcaster must create a dedicated, factory-like transcoding department that specializes in ingesting feeds, editing them for all platforms to be served (mobile and Web), and serving them out as efficiently as possible.

To streamline the transcoding factory flow, quality review must be conducted as soon in the production process as possible. Ideally, a "master feed" should be created that can then be transcoded to serve all necessary platforms. Spot checks of the finished feeds can then be done as time permits, but the process should be structured to minimize errors as soon as transcoding begins.

"This is why we have invested R&D cycles developing automated quality control into the transcoding workflow," says Harmonic's Lattie. "The only way to scale is to automate tasks previously received for 'eye ball' verification."

On a larger scale, "transcoding needs to be automated and flexible, with upgrades executed through software upgrades without having to replace hardware," says ViewCast's Giuhat. "An end-to-end fulfilment mechanism that covers ad insertion—including static ads or clips—DRM playback for encrypted content, and a system verification mechanism also needs to be integrated in the workflow."

All transcoding solutions should be software-upgradeable, so that new formats can be supported with a minimum of hassle. If possible, such upgrades should be able to be done 'on the fly,' so that the factory can keep pumping out feeds without interruption.

"New viewing devices are coming out constantly, and while some can be supported immediately with simply minor adjustments to transcoding parameters, others may require a software upgrade to support new formats, metadata structures or protocols," says Nann at Digital Rapids. "Such upgrades need to be transparent operationally, as if you're putting hundreds or thousands of clips through the transcoding system each day—even short maintenance disruptions can be costly."

Given the storage demands of so many feeds, it's crucial for broadcasters to use a cloud-based, off-premises server solution. Trying to keep up by adding servers in-house will cost too much, consume too many tech resources, and open the door to mistakes that can directly affect the entire playout chain.

"The main point you have to accept is that transcoding is now a full-time function of broadcasting," says Devlin. "Embrace this fact, and you can master the transcoding monster—instead of letting it master you."

James Careless

James Careless is an award-winning journalist who has written for TV Technology since the 1990s. He has covered HDTV from the days of the six competing HDTV formats that led to the 1993 Grand Alliance, and onwards through ATSC 3.0 and OTT. He also writes for Radio World, along with other publications in aerospace, defense, public safety, streaming media, plus the amusement park industry for something different.