Vast distribution
May 1, 2009 12:00 PM, By Brian Stevenson
Use simultaneous multiformat encoding for efficient content repurposing.
While all of these benefits are advantageous operationally to the content provider performing the encoding, the speed of turnaround is particularly noteworthy, as timely availability of content is critical to audience acquisition and retention. Timeliness is particularly significant with news and sports content, but even extends to longer-form content such as episodic series.
Hardware and software
For an encoder to ingest content from a live or tape-based source, it must have at least a basic hardware component to interface to analog or SDI sources. But, precompression image processing and the actual compression itself may be performed in hardware or software.
Figure 2. Combination hardware/software encoders provide the flexibility of software enabling different formats and video processing for each of multiple concurrent real-time outputs with the quality and performance advantages of hardware for shared preprocessing.
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Systems relying solely on hardware compression tend to be limited in the breadth of supported encoding formats. Even where the hardware supports multiple formats, it may only be able to do one at any given time. Furthermore, while compression formats such as MPEG-2 are relatively mature, newer formats such as H.264 are still evolving, and new formats continue to emerge. While most hardware-centric encoders are firmware-upgradeable with certain extensions of existing formats, more dramatic extensions or completely new formats may require new hardware. As such, these hardware-centric encoders are not well-suited to multiplatform, multiformat applications, but may be appropriate for usages targeting a single platform (such as a live satellite channel).
Systems that combine hardware and software in a common computing platform offer greater flexibility in the breadth and upgradability of compression and container formats, as enhancements and extensions can be applied through software updates. Beyond the formats themselves, software-centric encoders may also provide more flexibility and robustness in the features surrounding those formats. Examples include automated distribution of the resulting deliverables (such as publishing to a Web site, or file transfer to distribution partners), branding, and content protection or usage tracking through watermarking and DRM.
Optimal effectiveness in multiformat encoding can be achieved through a combination of hardware and software processing. (See Figure 2.) A key step in high-quality encoding is preprocessing essentially grooming the source signal prior to compression. Deinterlacing, video noise reduction and filtering are all examples of preprocessing functions that can significantly improve the quality and bandwidth efficiency of the compressed output. Performing preprocessing in hardware enables the use of more sophisticated algorithms over what could be achieved in real time in software alone. Furthermore, even basic software preprocessing algorithms consume processing time on the host system's CPUs. By performing the preprocessing in hardware, more CPU processing power is left available for the actual compression, increasing the number of outputs that can be created simultaneously.
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Further contributing to efficiency in a hardware/software system, preprocessing settings common to all target outputs need only be applied once, with the preprocessing shared as input to all output compression algorithms.
Given the virtually limitless combinations of compression format, container, encoding parameters and quality settings for each deliverable, and unlimited number of deliverables, it's possible to exceed the real-time capabilities of even the most robust encoder. While systems comprised of integrated hardware and software may not have predetermined limits on the number of concurrent encodes, the CPU horsepower of the system imposes a practical limit. The number of simultaneous outputs the system can handle will vary depending on the combination of deliverables and the specifications of each. Advanced H.264 encoding, for example, is more computationally intensive than basic MPEG-2 encoding, so more outputs could be created alongside a full-resolution MPEG-2 than H.264.
When the desired combination can't be achieved in real time, workflow features of the encoder can still reduce the operational complexity and manual effort required. Automated features to ingest to an uncompressed or lossless intermediate and subsequently transcode it into the desired deliverables enable the desired results to be obtained without manual intervention. At the same time, it allows you to maintain the benefits of reduced equipment overhead, elimination of multiple playout passes and minimal operational effort.
Brian Stevenson is the director of product management for Digital Rapids.
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