Radio, television and command center link delay budget method

Low-latency link between large screen and command center: how to divide the delay budget

Published: 2025-12-24 EB-LINK Views: 1392 Low latency, uncompressed transmission, SDI, delay budget, large screen splicing

The command center requires that the picture and the voice match the mouth shape, and the radio and television director requires that switching is followed without lag. In both types of scenarios, low latency is included in the acceptance indicators. If you want to achieve the standard stably, you must first take apart the source of the delay and look at it piece by piece.

Take it apart and see the end-to-end delay

1080p50 takes about 20 ms per frame. Optical fiber propagation is only about 5 µs per kilometer, which is only 0.1 ms even across 20 km, which is almost negligible. The real big deal is coding compression, scaling, de-interleaving and splicing processing: Delays of one to several frames are common for compressed equipment, while uncompressed optical transmission is usually controlled within one frame.

Priority is given to the section from camera to matrix.1-way 3G-SDI audio and video optical transceiver, SDI itself is not compressed, and the link contribution is small.
Use this section from matrix to large screenDVI non-compressed audio and video optical transceiver, to avoid secondary compression of the picture.
When audio and video are on the same fiber, confirm whether the audio is re-quantized, and the delay of the monitoring loop must be measured separately.

How to test during acceptance

Use the signal source of time code and the shooting screen to estimate the frame difference, or use the clapping synchronization method to verify whether the mouth shape and the screen are aligned. If the difference between the two measurement points exceeds one frame, it must be checked segment by segment. Do not connect multiple scalers on the link. Zooming is a major source of invisible delay. If you can do it once in the matrix, don't do it again in the large-screen controller.

Budget is written in the design stage

It is recommended to provide an upper limit on the number of frames for the entire link, such as no more than 2 frames for the production link and no more than 4 frames for monitoring return, and list the allocation value of each segment. EB-LINK is inRadio, television and large-screen audio and video optical fiber transmission solutionsThis kind of budget table is used to organize the selection, and the indicators can be directly aligned during project review.