While offering flexibility of distance and numerous other benefits, the ability to send an AV stream across a network comes with some tradeoffs.
There will always be a tradeoff in one of three areas:
- Bandwidth required
- Quality of the stream
- Latency between source and destination
Lower Latency Required
If a lower latency between the original source, across the network, and display on a monitor is required, more bandwidth will be needed.
One way to achieve this is to use a smaller GOP size or use all I-frames (see “Streaming Video & Compression” on page 11). Time is needed to process a signal using a larger GOP size and its associated P and B frames. Hence if you need the signal to be sent with less time between the original encoding and the subsequent decoding, a smaller GOP size and/or using all I-frames will help achieve your goal.
If you need lower latency to simply switch between streams faster, RGB Spectrum’s Zio® Enterprise AV-over-IP decoders can decode additional streams in the background to enable instant switching.
Higher Quality Standards
Achieving a higher-quality stream can be realized at the expense of bandwidth. By installing or upgrading network equipment to 10 Gigabit/port capacity, the frame rate, resolution and/or color subsampling of the stream can be increased. The result is a higher quality stream.
Lower Bandwidth Required
Current H.264 implementations can maintain a high quality video signal while utilizing existing Gigabit Ethernet networking equipment. In these situations, lowering the color subsampling, frame rate and resolution will help reduce the bandwidth. This bandwidth reduction means more streams can be sent across the network.
Bandwidth Requiremenets - Spatial Compression
Changing from one color subsampling ratio to another provides a signficant change to the bandwidth required for a video stream. The table below shows the bandwidth requirements for the three common color subsampling ratios at two standard video resolutions.
Bandwidth Requirements - Temporal Compression
In general, encoding a signal in H.264 format results in a compression ratio of between 20:1 and 30:1. The table below provides approximate bandwidth requirements when using H.264 compressed signals.