Artifact-Free Automatic Loudness Control Requires
Much More Than Just “Processing for the BS.1770 Meter.”
Orban's flagship OPTIMOD TV 8685 surround/stereo television loudness controller builds on Orban's 30+ years 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 programs simultaneously. The stereo processing can operate in dual-mono mode, so it can process four subchannels in stereo or eight subchannels in mono. The OPTIMOD TV 8685 is Orban's second-generation surround/2.0 processor offers standard AES3id and SD, HD-SDI (3G) input/output and audio routing capabilities that include support for optional Dolby-E encoding and decoding. Dual redundant power supplies help ensure maximum uptime where a relay provides hard-wire safety bypass from the SDI input to the SDI output in case of hardware failure. The OPTIMOD TV 8685 is dialnorm-aware. Loudness control is excellent when measured by the ITU BS.1770 standard (as specified in ATSC A/85:2009) or by the OPTIMOD TV 8685's built-in CBS Loudness Meters. When properly installed and set up, the OPTIMOD TV 8685 will automatically make a station compliant with the CALM Act or EBU R128. In stereo mode, the four stereo processors can be made pre-emphasis aware, allowing the OPTIMOD TV 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.
Absolute Control of Loudness and Peak Modulation
The OPTIMOD TV 8685 includes third-generation CBS Loudness Controllers for DTV applications. Separate loudness controllers are available in the multichannel and 2.0 processing chains and work with the both Two-Band and Five-Band structures. The third-generation improvements reduce annoyance more than simple loud-ness control alone, doing so without audible gain pumping. Attack time is fast enough to prevent audible loudness overshoots, so the control is smooth and unobtrusive. Loudness control is excellent when measured by the OPTIMOD TV 8685's built-in ITU BS.1770 and second-generation (Jones & Torick) CBS Loudness Meters, allowing stations to comply automatically with the requirements of the CALM act. The OPTIMOD TV 8685 implements “true peak” control by oversampling the peak limiter's sidechain at 192 kHz. This allows the OPTIMOD TV 8685 to prevent clipping in a playback device's analog signal path by predicting and controlling the analog peak level following the playback device's reconstruction filter to an accuracy of better than 0.5 dB. For typical program material, accuracy is 0.2 dB. Without true peak control, analog clipping can occur even if all peak values of the digital samples are below 0 dBFS. This phenomenon has also been termed “0 dBFS+.”
Thanks to true peak control, sample rate conversion, unless it removes high frequency program energy or introduces group delay distortion, cannot cause sample peaks to increase more than 0.5 dB. For example, sample rate con-version from 48 kHz to 44.1 kHz is highly unlikely to cause sample peak clipping in the 44.1 kHz audio data. 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 OPTIMOD TV 8685 to control both short-term and long-term loudness. The only purpose of the OPTIMOD TV 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 OPTIMOD TV 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 OPTIMOD TV 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.
Orban's Optimix® Upmixer
The built-in, Orban-developed Optimix stereo to 5.0 surround upmixer provides uncolored automatic stereo-to-surround upmixing, plus phase correction that ensures that the center channel is al ways crisp and intelligible. Optimix stereo 5.0 surround upmixer is 5.1-compatible. 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 OPTIMOD TV 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 OPTIMOD TV 8685 can even improve dialog from these sources! These factors are why the OPTIMOD TV 8685's subjective audio quality wins every serious shoot-out when compared to its competition. For the surround processing, the OPTIMOD TV 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.
Adaptability through Multiple Audio Processing Structures
The OPTIMOD TV 8685 features two processing structures: Five-Band for a spectrally consistent sound and Two-Band for a more transparent sound that preserves the frequency balance of the original program material. A special Two-Band preset creates a no-compromise “Protect” function that is functionally similar to the “Protect” structures in earlier Orban digital processors.
The Five-Band and the Two-Band structures can be switched via a mute-free crossfade. Audio processing can be smoothly activated and defeated on-air, allowing programs that can benefit from full dynamic range to pass through the OPTIMOD TV 8685 without dynamics compression.
The OPTIMOD TV 8685's processing structures are all phase-linear to maximize audible transparency. OPTIMOD TV 8685's equalizers and crossovers use 48-bit arithmetic to ensure mastering quality noise and distortion performance.
There are two distinct kinds of presets in OPTIMOD TV 8685: processing presets, which contain the settings of the 8685's audio processing controls (like compression thresholds), and setups, which contain technical setup settings (like input reference settings and channel routing). You can modify presets and setups and save them as “user presets” and “user setups.” More then 20 factory presets can be categorized into 4 groups. Digital TV, Analog TV, Digital radio and “Pass through”.
The OPTIMOD TV 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 HD-SDI I/O section supports SD-SDI (per SMPTE 259M); 1.5 Gbit/s HD-SDI (per SMPTE 292M; up to 720p and 1080i) and 3.0 Gbit/s single-wire HD-SDI (per SMPTE 424M; 1080p). The SDI I/O can de-embed up to 16 channels of audio, send them to the 8685's DSP for audio processing, and then re-embed them with video that has been delayed to maintain AV-sync. The HD-SDI module can accommodate Dolby-E® decoding and encoding via optional plug-in modules. A relay provides hard-wire safety bypass from the SDI input to the SDI output in case of hardware failure.
The OPTIMOD TV 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 OPTIMOD TV 8685 to pass pre-qualified material without modification—you can use the OPTIMOD TV 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. In addition to standard HD-SDI I/O and AES3id I/O, the OPTIMOD TV 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)].
OPTIMOD TV 8685's inputs and outputs are highly configurable via remote controllable internal routing switchers. Additionally, the outputs of the multichannel and 2.0 processing chains can be independently configured to emit the output of the AGC or the output of the multiband compressor/limiter, all configurable to use or bypass look-ahead true peak limiting.
Via the internal output routing switcher, a given output signal can be applied to more than one hardware output. This allows using the OPTIMOD TV 8685 as an AES splitter.
A stereo analog monitor output appears on XLR connectors on the rear panel. It can be configured to emit any OPTIMOD TV 8685 output signal, including a downmix of the multichannel audio. The analog outputs are transformerless, balanced, and floating (with 50Ω impedance) to ensure highest transparency and accurate pulse response. They can be used to drive a transmitter, although their normal function is monitoring. A stereo headphone jack is available on the front panel. It can be configured to emit any output signal and is independent of the stereo analog monitor output.
An audio sync input is configurable to accept AES11id or wordclock sync. You can synchronize the output sample rate of all AES3id outputs to this input. You can also synchronize the outputs to the AES3 digital input #1 or to the OPTIMOD TV 8685's internal clock. The sync source of each AES3 output is independ-ently selectable. A BNC connector can accept video sync per SMPTE 274M and SMPTE 296M, which can be used as a reference for the output audio sample rate and to correctly align Dolby-E frames with video per Dolby's requirements. The signal applied to the SDI input can also be used as a sync reference. The OPTIMOD TV 8685 contains a versatile real-time clock, which allows automation of vari-ous events (including recalling presets) at pre-programmed times. To ensure ac-curacy, the clock can be synchronized to an Internet timeserver.
Silence alarm and digital audio fault tally outputs are available.
A Bypass Test Mode can be invoked locally, by remote control (from either the OPTIMOD TV 8685's GPI port or the OPTIMOD TV 8685 PC Remote application), or by automation to permit broadcast system test and alignment or “proof of performance” tests. The OPTIMOD TV 8685 contains a built-in line-up tone generator, facilitating quick and accurate level setting in any system. Dual redundant power supplies with independent AC line inputs help ensure maximum uptime.
The OPTIMOD TV 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 OPTIMOD TV 8685's front panel. To minimize latency and to achieve highest reliability, the OPTIMOD TV 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. An API provides remote administration over TCP/IP via the RS232 serial or Ethernet ports. The OPTIMOD TV 8685 hosts a TCP/IP terminal server to allow external control of the OPTIMOD TV 8685 from either a Telnet/SSH client or a custom third party application. All commands are simple text strings. You can recall presets, operate the input and output routing switchers and more. Password security is provided. By running Orban-supplied downloadable upgrade software on a PC. The upgrade can occur remotely through the OPTIMOD TV 8685's Ethernet port or serial port (connected to an external modem), or locally (by connecting a Windows® computer to the OPTIMOD TV 8685's serial port through the supplied null modem cable).