AD3100 Digital/Analog Stereo Audio Delay/Synchronizer

The AD3100 Digital Stereo Audio Processor is a flexible, multi-function device that is ideally suited to applications in both audio, and video/audio production and post-production. With both analog and digital inputs and outputs, the AD3100 is at home in analog, digital and hybrid installations. The AD3100 can be used as: a variable audio delay for automatic lip sync correction; a variable pitch corrector; a fixed audio delay of up to 6.144 seconds (adjustable in 1 mS increments) for obscenity screening, or other audio delay requirements; a sample rate converter between professional and consumer digital audio formats; a "bridge" between analog and digital audio systems.

The pitch shifting feature of the AD3100 corrects audio pitch errors of up to ± 25%. A typical source of these errors is off-speed playback from a telecine for film/PAL video conversion, VTR, or other audio sources. The amount of pitch shift applied to the input can be set in increments of 0.1%.

When used for lip sync correction, the pitch shift feature allows the AD3100 to rapidly track a video delay change (such as the 1 or 2 frame shift that occurs with pointer crossover in a video frame synchronizer). The pitch shifter is enabled automatically to add a shift that is equal and opposite to the shift caused by the changing delay. Conventional correctors typically restrict the rate of delay change under these conditions which can leave the audio out of sync for many seconds, or even minutes after the video delay change has occurred.

Lip sync correction is completely automatic when the delay of the AD3100 is controlled with a control pulse from compatible video frame synchronizers, such as the Pixel Instruments DS4200, VS5200, or VS2100. If your video processor does not provide a delay control pulse, the Pixel Instruments DD2100 or DD3100 Video Delay Detector can be used to measure the actual video delay and "steer" the AD3100.

The AD3100 has AES/EBU, SMPTE and S/PDIF (consumer) digital audio inputs and outputs. The input and output sample rate can be chosen from 32 kHz, 44.056 kHz, 44.1 kHz or 48 kHz. The output sample rate can be the same as the input (automatic mode), or can be independent of the input for inter-format applications. For video installations, where it is important that the audio and video sample rates be synchronized to a common reference, the AD3100's output sample rate can also be frequency locked to an internal crystal or to an NTSC or PAL video reference.

In an obscenity screening application, pressing the "Dump" button on the front panel, or a remote "Dump" button causes an instant zero delay, censoring the unwanted audio in memory. After the button is released, the delay is increased at a controlled rate, quickly restoring the original setting. During delay changes, the pitch shifter minimizes pitch modification of the audio.

The front panel of the AD3100 includes an LCD mode/status display, dual bargraph audio level display and gain trim controls for the analog input and output. Performance specifications are exceptional for both the analog and digital paths. For analog input/output, 20 bit linear PCM with 64x oversampling results in a flat frequency response and wide dynamic range. Digital input/output is essentially transparent, within the limitations of the format selected.

Features

• Automatic lip sync correction
• Pitch correction up to ± 25%
• Delay range of 6.144 seconds for obscenity screening
• Analog inputs and outputs
• AES/EBU, SMPTE and S/PDIF digital inputs and outputs
• Sample rate conversion between digital formats

Pixel Instruments Corporation, 110 Knowles Drive, Los Gatos, CA 95032. Tel: 408-871-1975; Fax: 408-871-1976.