DRM technology
Feb 1, 2009 12:00 PM, By David Austerberry
Frame Grab
IPTV subscription continues to increase worldwide
By 2013, there will be 57 million IPTV homes.
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Discuss digital rights management (DRM) with a group of people and you will most likely draw strong and opposing views. Unlike most engineering topics, the use of DRM is an emotive subject. On one side is a predominately younger group that abhors anything that obstructs the free sharing of content. On the other side are the content rights owners, who want fair payment to view their assets.
Whatever the philosophical issues, a broadcaster may be bound by contract to prevent the copying of content. The problem has existed since broadcasting was analog and copying used tape formats like VHS.
Conditional access (CA), DRM and copy protection are terms that are often used interchangeably. They each have separate roots. However, in the converged world of the connected home, they are being integrated into a unified system to protect the rights and revenues of content owners and distributors.
Traditional broadcast model
The traditional model used by broadcasters for revenue protection has been CA. It was designed to manage access to subscription services delivered via cable or satellite. The broadcaster scrambles all the pay channels. The set-top box (STB) is provided with the key to unscramble the channels that the viewer has chosen to pay for.
The problems for content owners started with the birth of the VCR. A viewer could make a copy of a program. Developments like Macrovision's analog copy protection (ACP) made copying to a VCR more difficult by distorting the sync signal. However, the generation loss of each VHS copy meant that many rights owners were content to put up with a certain leakage.
Digital television has changed all that. A clone of an HDTV broadcast is very good quality. It can be easily copied and distributed across the world, leading to substantial loss of market for subscription services and retail products such as Blu-ray and DVD.
Copy protection
With the introduction of HDTV, a solution to the problem of copying was devloped in the introduction of high-bandwidth digital content protection (HDCP). The STB forms a protected domain for the content. It can output downconverted SD through conventional connections, but HD signals are only available via a protected link, e.g., HDCP over HDMI or DVI. (See Figure 1.)
Figure 1. Conventional pay TV controls access to subscription channels. Protection must be employed to prevent copying to external devices.
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HDCP is a proprietary system, which is only licensed to trusted suppliers. An HD display manufacturer incorporates the technology to decrypt the link, extending the trusted domain to the display. Unlicensed devices cannot decode the video signal.
With the mass adoption of the DVR, viewers now expect to copy programs for later viewing at a convenient time. The DVR can also be designed as a trusted system, so that content can be recorded at will but not transferred to a third-party device.
The broadcast copy flag was intended to allow broadcasters to control redistribution of content, although currently the FCC has been deemed to be operating outside its remit in mandating that implementation.
New media
The broadcast landscape has been transformed with the introduction of new means to distribute and view video content. As streaming and progressive download became popular for the delivery of content to PCs, something equivalent to CA was needed to protect revenue. Unlike the controlled delivery of cable TV and the STB, streaming takes place over an open system, the public Internet. (See Figure 2, next page.)
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