Figure 1. The VPNG architecture shown here allows for live as well as store-and-forward file-based news coverage. Click here to see an enlarged diagram.
Most news producers today will tell you that the way to win the broadcast news game is to get more stories to air faster. Although this objective seems simple enough, it is often hampered by a lack of necessary equipment and resources required to make it happen. Could advanced codecs and IT-based technologies provide an answer to this quandary?
IT-based technologies can serve effectively in areas ranging from content production to editing and transmission applications. But, could these technologies also serve reliably and practically in acquiring and sharing both file-based material and live content?
The IT vision
Over the past 25 years, video news gathering has migrated from analog SNG and microwave-based ENG to digital news gathering (DNG), MPEG-2-based compressed systems and portable systems that include videophone technologies. Over the last two years, the advent of efficient, high-quality codecs such as MPEG-4 (H.264) and Windows Media-9 (WM-9/VC-9) have enabled Very Portable (laptop-based) News-Gathering (VPNG) systems. In addition, as faster, more powerful computing platforms are coupling with new IP-based transport and transmission platforms, it seems the industry is poised to take another step forward.
More than a year and a half ago, SignaSys began investigating approaches to IT-based news acquisition and sharing. One of the fruits of this investigation is the systemic architecture shown in Figure 1. This VPNG architecture allows for live and store-and-forward file-based news coverage from any reporter armed with a camera, laptop and an IP transport link. Upon investigation, additional capabilities emerged, including inter-facility content sharing through streaming live and file-based media-transfer applications — a feature valuable to station groups. This article will focus on the acquisition capabilities of such a system.
The elements
The proposed VPNG system is predicated on three major elements: the VidLink Mobile Transmit Unit (VMTU), the VidLink Mobile Receive Unit (VMRU) and the VidLink Transceiver System (VTS).
A VMTU, which addresses field acquisition, is a simple, cost-effective and portable reporter package. Based on commodity platforms, a VMTU basically consists of a DV-based camcorder, a lap-top computer, and refined but simple software compression and metadata tools. The VMTU package allows reporters in the field to acquire, prepare and transmit file-based and live content over common, low-cost IP networks. It allows them to send content not only to an associated station but to any station within their group. The same approach can be integrated into rack-mount PCs for fixed or vehicle-mounted applications, if required.
The VMTU allows direct ingest of DV-based content through an IEEE-1394/firewire interface. The DV format provides good performance, has a low component cost and is well-established in the news industry. Because non-DV based material may also need to be ingested, the system supports baseband audio and video.
Beyond ingest, the system supports light editing, metadata generation and attachment (i.e. script information, thumbnail creation, etc.), transport compression, and transmission of content to the VMRU located at the station or studio. The VMTU can use various communication modes: satellite phones, WiFi, cell phone (GSM/CDMA) IP satellite, dial-up, DSL or ISDN. The network transport interface is predicated on TCP/IP and well-developed FTP protocols, so interfacing to the various communication modes is straightforward.
Transport protocols
File Transfer Protocol (FTP) is the preferred way to transport store-and-forward video clips and associated metadata files because if the file download process is interrupted (a common occurrence on public networks), FTP permits the download to resume at the point of interruption instead of requiring the retransmission of the complete file. The Windows Media-9 (WM-9/VC-9) codec was selected as the transmission-compression algorithm for both live and file-based material. VC-9 professional provides high quality at low bit rates. It uses encoding algorithms similar to that of MPEG-4 (H.264) and provides a bit-rate savings two to three times that of MPEG-2.
In support of live applications, the system would employ VC-9 over User Datagram Protocol (UDP). In news applications, UDP is tolerant of network disruptions, degrades gracefully (dropping frames instead of experiencing system lock-ups) and requires less protocol overhead.
During system testing of live transmission, packet buffering was modified to support total system delays of less than 500ms instead of the six to 10 seconds common in VC-9 and other advanced video codecs. This allows reporters or anchors to use the system for interviews or conversations. In certain compression modes, lip-synchronization issues can be a problem The solution is to modify the audio codec to allow audio packetization and transport to take place prior to the video packetization and transport. This affords the decoder sufficient time to properly decode the audio packets and reference them to associated video frames.
File access
At the station, easy retrieval and ingest of video and audio, and metadata, is important. Efficient tools to browse forwarded field content, as well as file and metadata compatibility with existing automated news-production environments, is key to efficient workflow. As previously noted, the receiver located at the station acquires information from the field through the FTP client/server interface.
Once the system acquires the file-based content, assigned journalists can browse it and check it for integrity at their workstations, or the system can play it directly to air. If required, the associated video and audio can automatically (or manually) be translated to a file format compatible with a station's news-room production system. This includes file formats compatible with Avid (OMFI) and Pinnacle (DV-25). The baseband digital and analog outputs allow for de-compressed transfer and record as well as quality checks or real-time play-to-air. Received metadata is accessed through an SQL database query or extracted directly from the browser through standard “cut and paste” techniques.
Decoders
Live content received at the studio is handled by tightly coupled decoders integrated into the IP-addressable receivers. These VC-9 decoders are responsible for decoding incoming live streams to digital or analog baseband, allowing for interface into the plant infrastructure. The streams can then be recorded or staged for air.
Compression tools
All compression and metadata software tools for supporting both store-and-forward and live modes must be user friendly yet flexible enough to account for the varying transport link and quality requirements that may arise in the field. Thus, the system uses compression profiles to simplify operator compression settings. This allows operators to pre-set compression parameters and to select compression profiles based on familiar terms such as fast motion or taking heads. If need be, operators and individuals that are more familiar with compression technology have easy access to create or modify compression profiles.
Summary
SignaSys put together a system, performed various factory trials and deployed it for field tests. Although each trial was unique, they all demonstrated similar strengths and weaknesses. In each case, the system proved to be much quicker to deploy and get information back to the station than the standard approach. The system was fairly easy to operate, but requires some training.
Each trial has shown the system to be reliable if configured properly. Full system integration has proven to be moderately difficult and will require RF- and IT-savvy individuals to get a full system up and running. Image quality from these systems has been very good but, for live feeds, the quality is bandwidth-dependent. Overall cost-effectiveness of the system has been exceptional.
Mark Brown is the executive vice president and CTO of SignaSys.
