DD2100 Video Delay Detector
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Features

Measures video delays up to 8.99 fields in 525 or 625 line systems
Works with any video synchronizer or video processing device
PAL and NTSC compatible



Description

The Pixel Instruments DD2100 Video Delay Detector is used to measure the delay of video signals which are passed through video processing instruments.

In today's television systems, it is quite common for the video signal to undergo several substantial delays such as those caused by video synchronizers, noise reducers and color correctors. Each processing step can add several fields of delay to the video, which causes the corresponding audio to be advanced with respect to the video. Such audio to video synchrony errors can cause visible "lip sync" problems, which may be consciously perceived by the viewer. The DD2100 measures the actual video delay and controls Pixel Instruments AD2100 or AD3100 Audio Synchronizer for automatic lip sync correction.

The DD2100 operates by comparing frames of video which are input to a video device with frames of video which come out of a device. A given input video frame is stored in memory and all the output frames are compared to the stored frame until an output frame which matches the stored input frame is found. By counting the number of frames which are output until the matching frame is detected, a coarse measurement of delay is obtained.

The phase of the input and output vertical syncs are compared to determine the fine delay, which is added to the coarse delay to generate a very accurate delay measurement.

The delay can even be measured with static images (e.g. captions) because the highly refined digital signal processing circuitry in the DD2100 can lock to the random noise which is present on video signals to determine delay on otherwise identical frames. In addition, the DD2100 can recognize and accommodate static changes in the video signal such as luma gain and setup, or chroma gain and phase differences. Because of the immunity to static changes, the DD2100 can be used with color correctors, noise reducers and frame synchronizers which provide operator or automatic adjustments of the video processing parameters.

It has been demonstrated in psychological tests at Stanford University that viewers who watch television commercials having a five field audio advance perceive the commercials more negatively (e.g. less interesting, more unpleasant, less influential, more aggravating, less successful) than the same commercials which are played with the audio in sync with the video. It was also found that several test subjects were unable to detect the delay consciously and thus were completely unaware that there was an audio to video synchronization problem.

In addition to any visible "lip sync" problems, the mistiming of audio and video will cause a subconscious reduction of the program's entertainment quality to the viewer. The cause of this effect is believed to be the unnatural advanced sound relationship. In our natural environment we are used to hearing audio slightly delayed with respect to images due to the slower speed of sound waves as compared to light. Advanced audio is unnatural and therefore believed to cause subconscious stress to the viewer which creates a loss of enjoyment of the program.

Specifications

8.99 Fields (switch selectable .99-8.99 fields)
Minimum Time to Field Acquisition
12 seconds (with suitable scene change)
Nominal Internal Measurement Resolution: 102.4 uS

Inputs

Non-delayed Video (high impedance loop-through)
1 Volt p-p +/-10 %
Delayed Video (high impedance loop-through)
1 Volt p-p +/-10 %

Outputs

TTL Pulse, Positive Going Matching Delay Serial Data, Communicates with AD2100 or AD3100 Audio Delay

Power

115/220 VAC, 50/60 Hz
30 Watts Max.

Mechanical

Width 19.0" (48.3 cm)
Depth 18.5" (47.5 cm)
Height 1.75" (4.5 cm)
Weight 6.5 lb. (2.5kg)

Front Panel Display

Type Alphanumeric, 2 line x 20 character
Delay Display Format Internal Measurement converted to nearest .1mS, updated twice per second
Display Indicators
Field Correlation Update
Time Since Last Correlation
Alarm: Undelayed Video Error*
Alarm: Delayed Video Error*

*An alarm indication indicates a sync phase lock error and/or loss of sync.

Patents
Pat. 5,751,368, 5,530,483



Pixel Instruments continuing product development programs may result in changes to specifications and features without notice.