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Today, most video post production for standard-definition content has moved onto disk-based, non-linear editing (NLE) systems. These systems offer improved flexibility over linear, tape-based systems by allowing a workstation fast access to any part of the digital media file. The advent of NLE systems that manage media content as digital files also allows content to be managed over its lifecycle as an integrated process using data networking infrastructure. Content can be digitized, edited, enhanced with graphics and effects, broadcast, archived, and reused for new programming as digital files, greatly improving the work process.
Advances in shared storage infrastructure using shared storage area networks (SANs) have further improved the post-production work process. Shared SANs allow content to be digitized centrally, eliminate the need to move very large video files among workstations, reduce the time to get programming on the air by allowing multiple editors to work on a project simultaneously, and simplify versioning control. Several vendors have provided proprietary shared SAN solutions, which have become widely used for standard-definition video production.
The value of integrated workgroup NLE systems has not yet been realized for high definition (HD) content because of limitations of existing storage solutions. This is a primary bottleneck to expanding HD content available for broadcast. 1080i video (one standard for broadcast video) requires a minimum of 165 MB/Sec to each workstation. The requirements for 2K film-quality digital video approach 400 MB/Sec. As uncompressed 1080i HD video has eight or more times the bandwidth requirement of standard definition video, most existing shared SAN systems are unable to support the throughput requirements. Hence, most HD editing systems used today have single-station direct attached storage, or editing is done in compressed format, each of which has substantial cost, time, and or quality limitations.
CHALLENGE
In the absence of a shared SAN that allows multiple workstations concurrent access to large content files, the post-production process is a sequential process (Figure 1). The major disadvantages of the solution are:
- File copy to local disks for each workstation may use network, tape, or physical transfer of disks - A two-hour content file may take more than four hours to transfer using a Gigabit Ethernet network
Figure 1. HD Video Workflow Steps without Shared SAN
Each process step?digital capture, editing, adding e ffects and graphics, and rendering finished video?ha s to wait for the previous step to complete, and for the file to be transferred to local disks of the next workstation. As two hours of uncompressed 1080i video is well over a terabyte of data, this can be an extremely time consuming process, even with a Gigabit Ethernet network infrastructure. Many facilities output the intermediate project steps to tape, and then re-ingest the tape at the next workstation. In either case, the time of video, audio, and effects editors is poorly utilized, and the time to get content on air can be lengthened considerably.
One of the challenges in integrating this process into a workgroup SAN environment with concurrent shared access to storage is that the performance requirements vary greatly by process step:
- Capture needs fairly low CPU power, but is very high in I/O requirements. - Editing requires very high I/O bandwidths.
- Rendering requires very high CPU power and relatively lower I/O bandwidth. Processing is typically distributed across large numbers of inexpensive blade servers.
- Broadcast requires very high I/O bandwidth.
A workgroup shared SAN that streamlines the post production process for HD video and film has to address both technical and economic requirements. High I/O process steps need to be provided with guaranteed 165 MB/Sec per-station file access (or more for film projects). Yet it may be uneconomic to connect large numbers of inexpensive rendering servers to the SAN using the high-performance Fibre Channel networking required by ingest, editing, and broadcast stations.
SOLUTION
Sanbolic Inc. and Cisco Systems solution for the NLE systems consolidates the post production process for uncompressed HD video onto a shared workgroup SAN that greatly improves the cost and time efficiency of the process (Figure 2). This solution is integrated using Cisco MDS 9000 Family multiprotocol switches and LaScala and Melio storage management software from Sanbolic Inc, in conjunction with standard high-performance storage arrays.
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