Optimod 8685 Surround ~ Overview
Artifact-Free Automatic Loudness Control Requires
Much More Than Just “Processing for the BS.1770 Meter.”
Orban's flagship Optimod 8685 surround/stereo television loudness controller builds on Orban's 30+ year experience in television audio processing to provide audibly transparent automatic loudness control and dialog intelligibility control for one surround program (up to 7.1) and four stereo (stereo) programs simultaneously. The stereo processing can operate in dual-mono mode, so it can process four subchannels in stereo or eight subchannels in mono. Put in-line and operated correctly, the 8685 will ensure that loudness meets the requirements of the CALM Act and EBU R-128.
The built-in, Orban-developed Optimix® upmixer provides automatic and completely convincing stereo-to-surround upmixing, with a solid, discrete center channel. Unlike technology derived from consumer matrix decoders, there is no program-dependent directional pumping of sound sources. Unique to this technology is extremely robust center channel phase/skew correction that never causes negative side effects. It is invaluable for older material that was originally recorded on analog tape. Optimix’s output downmixes to stereo flawlessly, and the skew correction often makes the downmix sound better than the original stereo!
There are large, important subjective differences between Optimod and competing processors. Optimod has a unique architecture that processes the center channel to correct spectral and loudness balance problems that compromise dialog intelligibility in ill-considered mixes. We have heard reports from broadcasters who have suffered increased viewer complaints about unintelligible dialog after installing the leading competitive processor. The 8685 is exactly the opposite—in addition to flawless loudness control, it also improves dialog intelligibility and maintains a full, natural sound without exaggerated “esses,” hollowed-out midrange, obtrusive pumping of ambient sound, and directional image shifts. Thanks to the Optimix upmixer, which cleanly extracts dialog from stereo sources, the 8685 can even improve dialog from these sources! These factors are why the 8685’s subjective audio quality wins every serious shoot-out when compared to its competition.
The 8685 features 3G HD-SDI and AES3id input/output, plus comprehensive handling of metadata. Dolby-E encoding/decoding and Dolby AC3 encoding are optional.
The 8685 is Dialnorm-aware and can re-author metadata as needed. Seamless switching between processing and pass-through modes (where both audio and metadata are passed through without further processing) allows the 8685 to pass pre-qualified material without modification—you can use the 8685's transparent-sounding loudness control only when needed. This makes it easy to comply with the requirements of network program providers who preprocess their audio feeds to comply with Recommendations A/85 and R-128.
For each logical processing channel (surround, stereo, or mono), the 8685 has one CBS+BS.1770 loudness controller and three loudness meters. The first meter uses second-generation CBS Technology Center loudness metering technology with an integration time of 200 ms, which is slightly faster than a standard VU meter. Two BS.1770-3 measurements are indicated: “short-term” (ungated, with a 3-second integration time), and “integrated” (gated, with a 10-second integration time). The BS.1770-3 Integrated readings can be logged for up to a week in the 8685's internal memory and for an essentially unlimited time via the included 8685 PC Remote Software for Windows®. This allows you to retain proof that your transmissions have complied with the CALM Act.
The 8685 controls loudness smoothly and unobtrusively without the unnatural-sounding gain pumping, noise breathing, harshness, stereo image shifts, and compromised dialog intelligibility that can result from naive designs whose only goal is to make a BS.1770 loudness meter look good. Only experienced human listeners can assess these artifacts; the BS.1770 meter cannot indicate them.
Since 1980, Orban has sold thousands of Optimod-TV processors and these have processed millions of hours of on-air programming. No other manufacturer can make this claim. Over the decades, we have constantly refined and polished our loudness control algorithms to provide audibly transparent loudness control that never annoys audiences. Instead of using BS.1770 as a simplistic internal model that determines how loudness is controlled, we use a much more sophisticated multiband psychoacoustic model to do this. This model is based on years of research at CBS Laboratories and CBS Technology Center and was further refined by us over a 30-year period. This model allows the 8685 to control both short-term and long-term loudness. The only purpose of the 8685's built-in BS.1770 meter is to verify that our model controls long-term loudness effectively according to the BS.1770 standard. Thousand of hours of subjective listening tests have verified that our model controls loudness without irritating audiences. The 8685 meters the processing; it doesn't process for the meter.
In our experience, the CBS Loudness Controller and Loudness Meter lock onto the program’s “anchor element” (typically speech) much more accurately than the BS.1770 meter, which also tends to over-indicate the loudness of material with low peak-to-RMS ratio (such as promos and commercials with a lot of “artistic compression) by 3 dB or more. The CBS technology is particularly effective in locking onto the anchor element even in the presence of effects and underscoring. Nevertheless, to accommodate organizations that will disqualify an automatic loudness controller if it causes a BS.1770 meter to read higher than a specified threshold, the 8685 offers a defeatable “BS.1770 safety limiter” that follows the CBS Loudness Controller in the signal path. This limiter can be set to effectively limit the indications of a BS.1770-2 gated meter with 10-second or longer integration time to a preset threshold. Because gain reduction in the BS.1770 safety limiter is usually triggered by subjective inaccuracies in the BS.1770-2 algorithm itself (particularly its over-indication of “artistically compressed” material), we prefer the sound of the processing with this limiter defeated so that all loudness control is performed by the CBS algorithm.
For the surround processing, the 8685 provides a simultaneous stereo downmix that is loudness-controlled, peak-controlled, and pre-emphasis aware, so it can drive an analog TV transmitter in countries that simulcast digital and analog signals. In stereo mode, the four stereo processors can be made pre-emphasis aware, allowing the 8685 to be purchased for immediate use with analog transmitters with the assurance that it will provide no-compromise processing for digital transmissions when the need arises. A second use for the stereo processors is processing up to four different languages in DTV program streams.
In addition to standard HD-SDI I/O and AES3id I/O, the 8685 optionally supports Dolby-E streams from and to the AES3id and SDI I/O via plug-in Dolby-manufactured modules. The 8685 can accept and emit Dolby-E metadata via RS485 serial (per SMPTE RDD 6-2008), Dolby-E-encoded streams (when the Dolby-E decoder option is fitted), and SDI [per SMPTE 2020-2-2008 (Method-A) and SMPTE 2020-3-2008 (Method-B)].
Dual redundant power supplies with independent AC line inputs help ensure maximum uptime.
The 8685 is built on Orban's flagship hardware platform. This features a GUI displayed on a quarter-VGA active matrix color LCD, making it easy to do all setup and adjustment from the 8685's front panel. To minimize latency and to achieve highest reliability, the 8685 uses a dual hardware architecture. Freescale 24-bit DSP chips do all audio processing while a separate microcontroller supports the GUI and control functions. Even if this controller malfunctions, the 8685 will continue to process audio normally. Minimum latency of the fully processed signal is 33 milliseconds, which can be padded to exactly one frame of delay for any video standard. The low latency headphone feed (containing all processing except for peak limiting) has a latency of approximately 6 milliseconds.