Creative instruments for video synthesis and analog image processing.

Frequency Ranges

Some of the information on this page is out of date, and we are in the process of revising it. Please contact us if you have any questions.
The subject of video synchronization timing and the frequency ranges of various signals which may construct a video image can be overwhelming to a newcomer. Tackling the subject in a sequential manner is difficult, since it is challenging to promote a full understanding of one concept without assuming a passing familiarity with all of them. It is the purpose of this article to offer a brief, practical introduction to these concepts, specifically as it applies to the video artist, and the use of the modular video synthesizer as a creative instrument.

If this is foreign territory for you, we recommend you review this information several times in between exercises with your video system, or while previewing our demonstration videos. This is not an exhaustive technical guide — that information is best left for textbooks — here we attempt to simply present what you need to know in order to use a video synthesizer, and why you need to know it. We do presume a passing familiarity with synthesis concepts such as oscillators, and physics terms such as frequency and amplitude. We also presume you are familiar with some basic video concepts such as frame rate.

This article will remain a loose work in progress until designated otherwise. Please e-mail us with your questions and suggestions for improving this information.

Animation range

< 29.97 Hz, NTSC
< 25 Hz, PAL

Signals occuring at frequencies below frame rate create changes in the image over multiple video frames, such as strobing and animation. In audio synthesis, such signals would be created by Low Frequency Oscillators (LFOs), envelopes, sequencers, and so on. Sample & Hold circuits are especially useful for Animation range signals, and can be used to quantize incoming voltages to Frame rate so that they only change at the beginning of each video frame. Otherwise, hard-edged waveforms such as square waves or sequencer outputs, can create visual glitches.

Frame rate

29.97 Hz, NTSC
25 Hz, PAL
also known as
Odd / Even
“frames per second”

Interlace range

29.97 Hz – 59.94 Hz, NTSC
25 Hz – 50 Hz, PAL
Not typically a useful frequency range, signals occuring between 30 Hz and 60 Hz will cause visible modulation between Odd and Even fields.With interlaced video, every odd numbered line in the image is displayed first (the Odd field), and then every even numbered line is displayed second. When a linear signal, such as an unsynchronized video oscillator, modulates video near this frequency range, a dual image interlaced effect will result. If this is undesirable, the final output of the video synthesizer can be run through a hardware or software deinterlacer. There are many interesting techniques for purposefullly manipulating interlaced video.

Field rate

59.94 Hz, NTSC
50 Hz, PAL

also known as
Vertical Sync
V Sync

Y-axis range (or audio range)

59.94 Hz – 15.734 KHz, NTSC
50 Hz – 15.625 KHz, PAL
Known as the audio range because it roughly coincides with most of the range of human hearing, signals in this range are often oscillators (audio or video) synchronized to Field rate or left free running. Signals in this range happen across multiple lines, that is from top to bottom of the frame, modulating the Y-axis of the image in cartesian terms. Typically we are used to seeing audio waveform visualization occuring on a left-to-rightbasis, so this distinction of audio intrinsically being related to a top-to- bottom relationship with the raster image is an important one.

Horizontal
line rate

15.734 KHz, NTSC
15.625 KHz, PAL
also known as
Horizontal Sync
H Sync
total lines per frame525, NTSC
625, PAL
active lines per frame
480, NTSC
576, PAL

X-axis range (or video range)

15.734 KHz – 6.75MHz (approx), NTSC
15.625 KHz, – 6.75MHz (approx), PAL
This is the frequency range where the actual image content of a full resolution video signal takes place as it prints from left-to-right across the display (the X-axis of the image.) If a video oscillator is the image source, it is typically synchronized to Line rate. Some of the most exciting possibilities with video synthesizers lie in their ability to achieve voltage control at video rate speeds. Even though the detail in a video image occurs in this frequency range, for abstract pattern and shape synthesis techniques, it is still important to have both X-axis and Y-axis signal sources contributing to the image, which is why having at least two oscillators (one of which that can achieve video ranges) is important. The upper limit of this range is determined by many factors dependent on the system’s bandwidth and the nature of the recipient display or recording device. Typically both NTSC and PAL video are sampled at a rate of 13.5MHz, which limits the maximum bandwidth to 6.75MHz (half of 13.5MHz.)

Composite video facts

NTSC timing is also known as 480i
PAL timing is also known as 576i

Component (YPrPb) or RGsB video signals can also be in 480i/576i timing.

NTSC/PAL typically refer to 480i/576i video which has embedded color subcarrier, as opposed to Component and RGsB, which have three signals to represent each color channel.

The i in 480i/576i refers to interlaced video, which means there are two fields in each frame. Video formats with p at the end (480p, 720p, etc) are progressive, non-interlaced signals, which means there is no practical difference between Field rate and Frame rate. The video signals patched around inside your video synthesizer represent only a portion of a complete video signal (the part with the actual image), which is why you need some form of output or encoder module in order to view any of these signals on a normal television monitor. With LZX Visionary, which deals with color channels instead of a composite signal we refer to these signals as “triple colorspace signals”. These signals have more in common with the Component and RGsB videoformats than they do with NTSC/PAL. Color Video Encoder takestriple signals and encodes them into a composite signal, and also performs other functions like clipping, blanking and sync insertion in order to make the output viewable on a display as NTSC/PAL video.