Simultaneous Multiformat Encoding
Hardware or Software Encoding?
Systems that rely solely on hardware compression tend to be limited in the breadth of encoding formats they support. While most hardware-focused encoders are firmware-upgradeable to extend existing compression formats, completely new formats or significant extensions may require new hardware. As such, these encoders are not suited to evolving multi-platform, multiformat applications, but they may be appropriate for targeting a single platform such as a live satellite channel.
Systems that combine hardware and software in a common platform, on the other hand, offer greater upgradeability of supported codecs and container formats, which can be applied through software updates at any time during the lifetime of the product. Beyond the codecs and formats themselves, a hybrid hardware-software solution provides greater flexibility and robustness for automated workflows such as distribution of transcoding assets, content protection, or usage tracking through watermarking and digital rights management (DRM) capabilities enhanced by distribution partners.
What about software-only solutions? File-to-file transcoding can be achieved completely in software, as no video signal interface is required. These solutions can be particularly cost-effective for general-purpose transcoding needs, requiring little more than a computer with a robust central processing unit (CPU) and the transcoding software itself. For those transcoding large volumes of files, however, desktop-level transcoding software may offer little or no optimization for transcoding many files concurrently; even higher-end solutions vary greatly in their efficiency in creating multiple parallel outputs from large amounts of source content.
Advanced Hygiene Means Better Encodes
A key step in high-quality encoding is the work done first to the source video to make it more amenable to compression. This is called preprocessing, essentially "grooming" the source signal prior to compression.
Input signal filtering, deinterlacers, and video noise reduction are all examples of preprocessing functions that can significantly improve the bandwidth efficiency of the compressed output and, in turn, the perceived quality at a given bitrate.
This upfront preprocessing work can be accomplished in hardware, external to the CPU, building on techniques refined over many years in dedicated broadcast preprocessing hardware. Such hardware preprocessing technology is no longer only the realm of broadcast engineers, however, and is available fully integrated into PC capture boards tailored for encoding and streaming. The use of such specialized hardware enables the use of more sophisticated algorithms and greater preprocessing through put than those that rely only on software preprocessing algorithms.
As even basic software preprocessing algorithms consume processing time on the host system’s CPU, the use of hardware-based preprocessing means more CPU processing power is available for the actual compression, increasing the number of simultaneous real-time outputs that can be transcoded in a hardware-software hybrid. Optimal effectiveness in multiformat encoding, then, can be achieved through a combination of hardware and software processing.
An additional benefit of hardware preprocessing is the ability to apply settings that are common to all target outputs once (rather than performing the same operation separately for each), with preprocessing shared as input to all output compression algorithms.
Efficient multiplatform output requires encoding solutions that support multiple formats and the specific needs of each target device. No longer is it enough for an encoding system to be able to output just a full-resolution and proxy version.
Most file-to-file transcoders can create multiple output formats from a single source. All encoders supporting analog or serial digital interface (SDI) inputs can capture and encode to at least a single format from a live source or tape in real time. But the ability to do so to multiple codecs, resolutions, and bitrates concurrently is less common.
The most flexible transcoders can capture and encode to multiple formats and can output parameters at full quality simultaneously in real time. Turnaround speed is a particularly important consideration when choosing between competing options, as it directly affects the provider’s audience. Timeliness is particularly significant with news and sports content, but its significance also extends to longer-form content such as episodic series, where delay may mean losing an opportunity to engage a potential audience member.
Format-flexible encoding solutions with concurrent multiformat outputs offer numerous benefits:
• Less equipment: By eliminating the need for separate encoders for each format or target platform, multiformat systems reduce space and power requirements while lowering equipment acquisition costs.
• Reduced operational complexity: While separate encoders for each format could be deployed in parallel to achieve simultaneous deliverables, doing so adds to the complexity of the workflow. Automation requirements would increase to ensure that all encoding is perfectly synchronized for live-delivery applications, while any change to the combinations of desired deliverables may involve rerouting of signals between the encoders and reconfiguration of the settings on multiple systems.
• Faster turnaround: Systems that support multiple formats nonconcurrently can still reduce overall equipment requirements, but they require multiple passes from a repeatable source (such as tape) to achieve the desired deliverables. By performing multiformat encodes in a single real-time pass, significant time is saved.
• Less wear on supporting equipment: If the source content is tape-based, each additional ingest and encoding pass causes additional wear on the deck.
• Flexible redeployment: A content provider’s encoding needs today may be different in the future, and multiformat systems can easily be redeployed and repurposed. Significant changes in preferred deliverable formats (for example, from On2 VP6 to H.264 on a website) may also be made by offering both formats in parallel on an interim basis to reduce viewer alienation.