Multipurposed proxies for content management
Aug 17, 2007 3:47 PM
Content management in a tapeless production and distribution environment has changed how broadcasters store and locate programming. Proxies can help asset management applications identify content and also be used for other purposes.
Let’s first examine how content will be located in the enterprise-wide storage infrastructure. The media asset management (MAM) application must span a storage configuration where mixed storage technologies are used depending on workflow requirements. PC-based desktop search and accessmust be supported so any authorized person in the organization can browse content.
Proxy images can help MAM applications identify content. Through careful analysis of production workflows and distribution formats, proxies can also be used for editing, Web and mobile applications.
Search and access
Inventorying A/V content presents many classification problems. Because a visual representation (a proxy) can aid in identifying content, proxy creation and display has become an integral part of most MAM applications.
Visual identification is particularly relevant to graphics. For example, a station logo may exist in many forms. The station may use any combination of call letters, channel number and network affiliation as graphic elements. Just these three attributes lead to multiple possible combinations. A visual means to quickly identify the desired logo can improve workflow efficiency.
Proxies to the rescue
Content management in a tapeless environment has changed greatly. Storingprogramming on a physical tape has evolved to digital files on disks. Accordingly, locating content has evolved from tracking down the tape to the use of software. By displaying a small thumbnail proxy, content identification is simplified.
When generating proxies, there is an issue as to which frame should be used to identify the content. Consider a segment that opens on a stadium crowd scene. The proxy alone is not enough to identify the material.
Metadata attached to the proxies at ingest solves this problem. This requires, however, the assignment of descriptive text upon content ingest. An elegant content identification solution may use some form of textual description that could be used as a PSIP event information table (EIT) or extended text table (ETT). This will eliminate steps in repurposing content later in the broadcast chain.
Common proxy formats include MPEG, AVC and VC-1. Still frames at a 1Mb/s data rate are automatically generated during ingest and can be viewed on a PC using widely installed media players. This enables networked users to run the MAM applicationand view the proxies.
Multipurpose proxies
With careful planning and creative system and workflow design, there exists an opportunity to exploit proxies for other purposes. For example, besides using still proxies in MAM applications, proxy editing systems are possible.
The technique uses MPEG, AVC or VC-1 compression to transfer or stream video frames in real time to a client machine. The media network generally consists of a centralized SAN that stores the uncompressed video. The video proxy frames are linked (or point) to the full-resolution frames stored in the SAN. An editor can produce the story, complete with transitions, using low-resolution proxies. The resulting EDL guides the rendering of a completed segment. The rendering can be performed as the content goes to air and is stored on a server or tape. This can reduce media network traffic.
Because proxies are being streamed in real time through the internal infrastructure, they also can be used for Internet distribution.
Proxies generated for low-resolution editing could also be used as video for mobile DTV applications and cell phone delivery. Using AVC or another compression algorithm, content can be reduced to data rates of about 768kb/s retaining acceptable video and audio quality. Prototype mobile DTV systems, vying for ATSC standardization, can multiplex processed proxies in the standard 19.29Mb/s MPEG-2 transport stream along with normal OTA programming.
Intelligent design
Storage capacity and network traffic can become issues when putting proxies to multiple uses. If large amounts of content are ingested on a daily basis, even when it is moved offline to less expensive storage, proxies must be kept in high accessibility, high-cost storage. And if hundreds of users are going to be searching for content and streaming proxies across broadcast and corporate networks, the possibility exists for sluggish MAM application performance.
With intelligent infrastructure design, proxies can be used for at least four purposes: asset management, proxy editing and for Internet and mobile delivery. Storage and network requirements must be carefully considered, however, and integrated with workflows that support production and distribution that is heavily dependent on proxies. There are benefits to leveraging proxies for multiple uses, but the network performance and storage requirements exponentially increase system complexity.
The next Transition to Digital will examine storage technology implementation for parallel production.
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