MICHAEL ACER /
05.01.2007 12:00 PM
Scopus' DPI system

Local ad insertion has long been a method used by television networks and service providers to supplement revenues. It allows them to combine national programming with local advertising, thus profiting from airing commercials for local businesses.

The growth of digital television content via satellite and cable transmission has brought about the need for ad insertion into digital programs. Digital program insertion can enhance the potential for additional income if done effectively. On top of performing ad insertion, digital program insertion allows network operators to switch programs seamlessly, as in moving from a national feed to a local feed, for example.

Digital satellite and cable systems deliver an ever-growing number of channels to their viewers. Increasingly, this content is compressed and sent to digital set-top boxes (STBs) in homes.

These systems require broadcasters to use digital turnaround solutions, which remove a digital program from a national source and add it to a multichannel, digital multiplexed stream — digital in to digital out. Digital turnaround-based systems can benefit from using digital program insertion (DPI).

Ad insertion techniques

Ad insertion products are comprehensive systems that integrate several different components including storage devices, a compression system, scheduling programs, distribution networks and a switcher/splicer. (See Figure 1.)

Storage is the central component in an ad insertion system. Ads are stored in videotape banks in analog format or in video servers in digital form after being compressed using, for example, the MPEG standard. The server receives new programming and advertising content from such sources as tapes, encoders, compressed files on DVDs, or from the distribution network.

The digital compression system consists of encoders that compress the ads to high-quality constant bit rate (CBR) MPEG files for storage and playback. Scheduling systems create the time controls for the ad or clip database, arrange the ads on the server, build ad packages, and remap the outputs from the video server. Billing and management functions may also be included with scheduling. Contribution is performed through the master headend by file transfer over an existing network. This process is necessary for distributing the compressed ads or programs to several sites.

When both the original program and stored ads are in analog TV format, a standard switch can function as the splicer. Selecting between the incoming program and the stored ads is predetermined. The switch becomes a multiplexing unit with splicing capabilities for digital TV services. The splicing of MPEG streams allows local ads to be inserted into digital programming seamlessly and assures smooth and uninterrupted delivery of the content.

Analog ad insertion

Original ad insertion systems operated solely on analog programs and ads. National feeds would sometimes include gaps into which local ads were to be dubbed. The splicer would switch, at predetermined times, from the national content to local ads or programming. Automated analog playout systems included cue tones in the original content, such as a movie, to indicate the points of insertion for ads. These audio cue tones were used to trigger insertion into the network feed with a video switch.

When television networks and service providers started transmitting digital compressed programming, local content insertion still used analog methods. In the analog workflow, incoming MPEG-2 content is decoded back to analog formats (NTSC, PAL).

The local content, if stored digitally, is also converted to analog and inserted into the output stream. Systems that transmit digital content to the user's home would require that the modified program be encoded again to MPEG. Most ad insertion solutions available today use analog insertion techniques. (See Figure 2.)

Though this process is effective for local content replacement, it is problematic. The process of two encoding/decoding passes can degrade overall video quality.

MPEG is a lossy compression system that deletes unnecessary information the human eye does not see. Multiple encoding and decoding may remove too much information, causing visual artifacts.

A more important issue to the provider is that analog insertion in a digital system is a very expensive process. Multiple decoders and an encoder may be required to create the system, which thus requires increased time and labor for system configuration and management.

Digital program insertion

DPI is a completely digital version of local content insertion. DPI requires that original content include ad insertion markers in the MPEG-2 transport stream as part of the service information tables and according to the SCTE 35 standard.

Special encoders enable creation of the program insertion markers in the transport stream during the contribution process. These digital markers are similar to the cue tones used in analog ad insertion. At the local station or headend, the splicer detects insertion markers in the transport stream. The insertion markers trigger the video server to insert the relevant ads automatically. Communication between the splicer and the video server is based on the SCTE 30 protocol.

The benefits of DPI

Programming remains in MPEG form throughout the process, so multiple encoding and decoding is not required, and image quality is preserved. The the content's quality is based solely on original encoding parameters, which the broadcaster controls.

DPI equipment costs less than analog insertion. It does not need decoders to convert the original content and local ads to analog formats. Likewise, no encoder is required to recompress the modified content back to digital format. The equipment cost savings is multiplied by the number of digital channels the local service provider offers on its system.

Bit-rate issues

One issue that must be considered with DPI systems is dealing with the different bit rates of the original and local content. Due to system bandwidth limitations and the fact that ads are stored in constant-bit-rate format, the DPI system must be able to adjust the bit rate of the local content to match the original program. This process is known as transrating and is performed in the digital domain.

Transrating may also be required on the modified content to be combined properly into a multichannel multiplex that has a limited aggregate bit rate. A single device may now perform both the transrating and splicing functions.

The Scopus solution

Scopus Video Networks offers a comprehensive ad insertion solution for distributors, direct broadcast satellite and cable TV operators. The solution is based on the company's IVG-7500 Intelligent Video Splicer, part of the IVG-7000 Intelligent Gateway series, and its real-time encoders and receivers, which feature advanced DPI capabilities. (See Figure 3.)

The video gateway enables service providers to offer targeted services to their subscribers. It is a powerful and scalable DSP-based headend in a box, housed in a 1RU chassis.

At the distribution or contribution site, Scopus encoders allow injection of the SCTE 35 ad insertion marker. The IVG-7500 accomplishes powerful digital processing, statistical multiplexing, bit-rate reduction, flexible grooming and extensive stream monitoring. Conditional-access control is also monitored through the system.

It simplifies the DPI system at the local station or headend. Original content is received and decrypted using IRDs. The DPI system then allows service providers to combine the functions of splicing, scheduling, transrating and multiplexing into one device. It coordinates the video server via SCTE 30-defined interface. The system can handle ad insertion for multiple programs simultaneously. Therefore, it also reduces the need for individual splicing functions per program.

Along with flexible ad insertion, the splicer offers PSI/SI and PSIP processing, electronic program guide insertion, conditional-access integration, complete network management and personalized services, such as pay-per-view. It reduces the amount of hardware required to accomplish local content insertion, while increasing the system flexibility for a service provider.

The splicer provides ad insertion, rate shaping and grooming capabilities for digital simulcast network architectures. The system features superior-quality, seamless SD and HD splicing, and standards-based DPI implementation (SCTE 30 and SCTE 35) for compatibility with major ad servers and, in turn, an integrated ad insertion solution within a distributed or centralized all-digital architecture. This capability gives cable operators the valuable option of inserting local ads and program content, such as off-air or PEG channels, into premium HDTV content.

In addition to its DPI capabilities, the new system offers an advanced joint transrating statistical multiplexing mechanism, as well as powerful and flexible grooming features and high-quality rate shaping. Advanced management and redundancy solutions built into the IVG-7500 help users maximize uptime.

Taking targeted ads further

Continually evolving technologies for targeted content insertion hold the promise of reaching consumers on an individual basis. The increasing adoption of digital STBs by consumers and the wholesale migration of the broadcast industry to digital operations, in conjunction with advances in the leveraging of purchasing and marketing data, mean that DPI has the potential to bring tailored advertising to specific household viewers. Robust encoding and multiplexing solutions allow broadcasters to maximize local ad dollars for a valuable bottom-line boost.


Michael Acer is a manager of customer engineering for Scopus Video Networks.

References

  • ANSI/SCTE 35 2004 Digital Program Insertion Cueing Message for Cable
  • ANSI/SCTE 30 2006 Digital Program Insertion Splicing API


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