Optimod 8585 ~ Penteo® Surround Synthesis from Stereo
When the 8585 was first introduced, we chose not to include 2.0 to 5.1 surround synthesis. There were several technical reasons (including stereo and mono downmix compatibility), but our dominant concern was the subjective quality of the algorithms, none of which sounded fully convincing and some of which sounded downright ridiculous.
Since then, we have evaluated and licensed the Penteo® Surround "panorama slicing"™ algorithm (http://www.penteosurround.com/). For the first time, we heard an upmix that sounds like discrete five-channel while preserving the balance of the stereo source without coloration. We were particularly impressed by Penteo's ability to place dialog firmly in the center channel even when the mix includes other elements placed around the stereo soundstage. Moreover, Penteo surround material downmixes back to the original stereo, absolutely respecting the vision of the original mixing engineers.
"The Penteo system is based on entirely new stereo analysis," says John Wheeler, Penteo, LLC founder and inventor of the new technology. "We believe it's the first truly significant breakthrough in the art of converting stereo into 5.1 surround sound in the last 15 years."
Orban's Penteo upmixer for the 8585 resides in a stand-alone 1 rack unit chassis that is controlled by the 8585 via an Ethernet connection The Penteo unit will only upmix if it detects a controlling 8585 on the same subnet; otherwise it will remain in "pass-through" mode.
The Penteo upmixer has three AES3 inputs and three AES3 outputs. In an 8585 without the optional HD-SDI I/O card, the Penteo upmixer is placed immediately before the 8585's inputs in the signal chain. In 8585s with the HD-SDI card, the card's three AES3 inputs and outputs allow the Penteo upmixer's I/O to be wired in a loopthrough configuration that allows audio originally embedded in the HD-SDI bitstream to be sent to the Penteo upmixer and then to the 8585 for loudness processing.
The Penteo upmixer expects stereo material to be applied to its Lf/Rf input. Program-adaptive automatic mode switching is available, where the Penteo detects whether its input is receiving stereo or 5.1 material and automatically activates upmixing if it detects stereo. If 5.1 material is detected, it is passed through to the Penteo's output with the same delay as the upmixed material, preserving lip-sync. One can also control the Penteo's modes from the 8585 by using its GPI, clock-based automation, terminal mode via RS232 or Ethernet, or PC Remote via RS232 or Ethernet.
The combined delay of the Penteo and 8585 processing is a minimum of about 166 ms and can be padded to exactly 5 frames of 30 or 25 fps video. The 8585's optional HD-SDI card automatically delays the video to maintain lip-sync. In installations without the HD-SDI card, the video delay must be implemented elsewhere.