Video-over-IP challenges
Oct 1, 2007 12:00 PM, BY BRAD GILMER
Transporting video over packetized networks produces high-quality results if you understand the network.
Challenges in video-over-IP transmission
As you can imagine, there are challenges in delivering streaming video over IP networks. One challenge is interoperability.
If you're designing a system that transports video over IP within a single company from one point to another, then interoperability is a nonissue. You decide on the video standards, compression standards, forward error correction (FEC) method and Internet standards.
On the other hand, if you are working with a system that transports video between different entities, or even within different branches of the same entity that use different corporate standards, then you may face some challenges. Of course, the issue of interoperability is not new for broadcast engineers, but video over IP adds a few new parameters:
- Video standards
If you are sending a type of video that is not supported by the receiving equipment, then obviously the system will not work.
- Compression standards
As with video standards, it's not a good idea to use incompatible compression standards between the sender and the receiver. Feeding MPEG4 into an MPEG-2 decoder will not achieve acceptable results. Achieving interoperability across different MPEG2 systems — while much better than in the past — may occasionally cause problems. If you are building one of these systems, be sure to test compatibility between differing encoder and decoder combinations.
- FEC standards
Recently, SMPTE produced a standard (SMPTE 2022) for the use of FEC over packetized networks. The DVB has also done some work in describing FEC methods. It is important to use standardized FEC if you want to ensure that error correction capabilities function correctly when interoperating between different equipment manufacturers.
- Internet standards
SMPTE 2022 describes a standardized way of mapping MPEG-2 transport streams onto IP. Of course, if the sender and receiver use different IP transmission schemes, then interoperability issues will result.
Overall, the good news is that standards exist to resolve these interoperability issues. Manufacturers and service providers are working together to ensure that video-over-IP installations go smoothly. Many events you watch on television today have been transported over packetized networks, so if someone approaches you about transporting video using packetized networks, you should know that it can be done with high-quality results.
Brad Gilmer is president of Gilmer & Associates, executive director of the Advanced Media Workflow Association and executive director of the Video Services Forum.
Send questions and comments to: brad.gilmer@penton.com
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