NDI Genlock refers to a function that allows an NDI device to synchronize its timing with another NDI source on the network. Essentially, it's about ensuring consistent timing for video frames being sent.
Understanding NDI Genlock
At its core, NDI genlock leverages the timing information from an existing NDI stream to regulate the output of another NDI device. The primary goal is to achieve precise synchronization, which is crucial in professional video production environments where multiple sources need to be perfectly aligned.
According to the provided reference:
"The NDI genlock instance can connect to any NDI sender visible on the network and uses the timing from this NDI sender to correctly time and pace the sending of video frames, insuring both the overall framerate and the individual frame start times remain consistent with the selected NDI source."
This means that instead of sending video frames based on its own internal clock, an NDI source configured for genlock will look to a designated 'master' NDI source for its timing cues.
Why is NDI Genlock Important?
Timing and synchronization are critical in video workflows, especially when mixing or switching between multiple cameras, graphics, or other video sources. Without proper synchronization, you can encounter issues like:
- Frame tearing: Parts of different frames appearing simultaneously.
- Stuttering or jitter: Irregular motion due to inconsistent frame delivery.
- Lip sync issues: Audio not matching the video.
- Switching artifacts: Glitches or delays when cutting between sources.
NDI genlock helps mitigate these problems by making sure that the frames from different sources are presented or delivered at exactly the right moment relative to each other, based on a common timing reference (the selected NDI sender).
How NDI Genlock Works
The process involves the NDI genlock device (the 'slave') connecting to a chosen NDI sender (the 'master'). The slave device then constantly monitors the timing of the frames being sent by the master. It uses this timing information to adjust when it sends its own video frames.
Key aspects include:
- Connecting to a reference: The genlock device establishes a link to a specific NDI source on the network.
- Timing extraction: It extracts the frame timing and pacing information from the reference source.
- Pacing adjustment: It adjusts its own frame sending rate and individual frame start times to match the reference.
- Consistency: This ensures its overall framerate and the precise timing of each frame align with the master NDI source.
Think of it like musicians playing in an orchestra. Without a conductor (the master timing source), each musician might play slightly out of sync. With a conductor, everyone follows the same tempo and cues, resulting in a harmonious performance. NDI genlock acts as that conductor for multiple NDI video streams.
Practical Applications
NDI genlock is particularly useful in setups involving:
- Multi-camera live productions: Ensuring all camera feeds are perfectly synchronized for clean switching.
- Integration of graphics and playback systems: Aligning graphics or pre-recorded clips with live camera feeds.
- Distributed production workflows: Synchronizing NDI sources coming from different locations or devices on the network.
By implementing NDI genlock, production teams can achieve cleaner switches, smoother playback, and a more professional overall result.
