Orban 8685 AC3 DTV Audio Processor with AC3 Option

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8685 AC3

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 8685 includes third-generation CBS Loudness Controllers™ and BS.1770 safety limiters for DTV applications.
Separate loudness controllers and safety limiters are available in the multichannel and 2.0 processing chains and work with the both the Two-Band and Five-Band structures. The third-generation improvements reduce annoyance more than simple loudness 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 ITU BS.1770 or EBU R-128 standards or by the 8685's built-in CBS Loudness Meters, allowing stations to comply effortlessly with the requirements of the CALM act. New in Version 1.1 software is a "BS.1770 Safety Limiter" which can further improve the measured performance using the BS.1770 meter and which was added for the benefit of organizations with strict objective limits on the indication of a BS.1770-2 meter regardless of the actual subjective loudness as determined by human listeners.
Using the ITU BS.1770 and CBS Loudness Meters To Measure Loudness Controller Performance

Optimix is a premium-quality, Orban-designed stereo-to-surround upmixer for the Optimod 8685 and 6585 Surround Loudness Controllers. It runs in the Optimod's internal DSP and is provided at no additional charge.

The upmix is artifact-free and sounds convincingly like true surround material. It is directionally stable with a solid center channel and excellent envelopment, and it avoids the “image steering pumping” introduced by consumer upmixers that have been repurposed for transmission.

A highly robust, Orban-proprietary algorithm eliminates the effects of phase and azimuth skew in the upmix, ensuring crisp, highly intelligible dialog and other center-channel material. Not only can it correct the effect of vertically misaligned L/R gaps in analog tape heads, but it can even correct the acoustic comb filtering that occurs when one source (like a snare drum) leaks into multiple microphones during the original recording! Hence, the stereo downmix can actually sound more present and detailed than the original stereo input while still preserving its artistic intent.

Optimix automatically determines whether the input material is two-channel stereo or surround. It does this by detecting energy in the center, left-surround, and right-surround input channels. In automatic switching mode, if it detects energy in any of these channels, Optimix will immediately bypass the upmixer. If there is no energy in any of these channels, Optimix will create a realistic-sounding surround upmix from stereo input.

All existing 8685 and 6585 users can upgrade to Optimix via a free software download.

Precise control of peak levels
The 8685 precisely controls peak levels to prevent digital clipping. The maximum level of the digital samples is controlled to better than 2%.

Pre-emphasis limiting for the two standard pre-emphasis curves of 50 µs & 75 µs
While primarily oriented toward "flat" media, the 8685's 2.0 channel processors can also provide pre-emphasis limiting for the two standard pre-emphasis curves of 50 µs and 75 µs. This allows them to protect pre-emphasized microwave links, satellite uplinks and similar channels where protection limiting or light processing is required. |Note that the 8685's 2.0 channel processing cannot provide simultaneous, independent audio processing for flat and preemphasized channels. Even though one output may be pre-emphasized while other is flat, the only difference between the outputs is that the "flat" output has de-emphasis applied to it after the processing while the preemphasized output does not.

User-Friendly Interface

Color LCD and large rotary knob
A large (quarter-VGA) color liquid crystal display (LCD) makes setup, adjustment and programming of the 8500 easy. Navigation is by a miniature joystick, two dedicated buttons, and a large rotary knob. The LCD shows all metering functions of the processing structure in use.

Navigation Joystick
Use the Locate joystick to navigate through a menu that lets you recall a preset, modify processing (at three levels of expertise), or to access the system's setup controls.

Flexible Configuration

Nine processors in one
A gain-coupled multichannel processor for up to 7.1 channels, plus four additional, independent 2.0 channel processors (whose performance is equivalent to an OPTIMOD 6300) that can be used for many tasks such as processing the audio for a second language and up to three ATSC subchannels. Because its output can be mixed into the LF and RF outputs of the multichannel processing, the primary 2.0 channel processor can also be used to process an independent feed (like the output of a sports truck, news truck, or newsroom) before it is mixed with the station's main multichannel audio path. The audio processing parameters can be set independently for the surround and 2.0 processors. (All 2.0 processors have the same processing parameters.) The 2.0 processors can be operated in dual-mono mode where each mono channel has a dedicated CBS loudness controller, BS.1770 safety limiter, CBS loudness meter, and BS.1770 loudness meter. Hence, the 8685 can simultaneously process up to eight mono audio streams for CALM Act compliance.

Inputs & Outputs
The 8685 provides 3G HD-SDI I/O, one (+ loop) video sync reference input, four AES3id inputs, and three AESid outputs. All AES3id inputs and outputs are transformer-coupled, appear on BNC connectors, and have 75 Ω impedance. Audio I/O from both the HD-SDI and AES3id ports includes sample rate converters and can operate at 32, 44.1, 48, 88.2 and 96 kHz sample rates.

Configurations via remote-controllable internal routing switchers
OPTIMOD 8685's inputs and outputs are highly configurable via remote-controllable internal routing switchers with scene memory, allowing various configurations to be recalled easily via GPI, clock-based automation, 8685 PC remote software, Ethernet or serial ASCII commands, and the 8685's front panel. 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 limiting.

Use 8685 as an AES splitter
Via the internal output routing switcher, a given output signal can be applied to more than one hardware output. This allows using the 8685 as an AES splitter.

Stereo analog monitor output
For both the base I/O configuration and the HD-SDI module, a stereo analog monitor output appears on XLR connectors on the rear panel. It can be configured to emit any 8685 output signal, including a downmix of the multichannel audio. The analog outputs are transformerless, balanced, and floating (with 50 Ω impedance) to ensure highest transparency and accurate pulse response. They can be used to drive a transmitter, although their normal function is monitoring.

Stereo headphone jack
A stereo headphone jack is available on the front panel. It can be configured to emit any 8685 output signal and is independent of the stereo analog monitor output.

BS.1770 loudness meter logging
The 8685 comes with an application for Windows PCs that writes the indications of the 8685's built-in BS 1770 loudness meters to local or network storage. This password-protected application can log the indications whenever the PC is connected to the 8685 via a TCP/IP network. The user can select a logging interval and all readings are time-stamped. The logging application can be configured to automatically send a notification e-mail to a selected address when logging starts or stops.

Dolby Digital Metadata I/O
Two RS485 serial ports allow the 8685 to accept and emit Dolby Digital metadata. Metadata can also be de-embedded and re-embedded in the HD-SDI V-AUX area and, if the Dolby E modules are installed, de-embedded from and re-embedded into Dolby E data that is conveyed either through the HD-SDI connection or the AES3id connections.

Dual-mono mode
The 8685's 2.0 processing offers a dual-mono mode that allows two entirely separate mono programs to be processed, facilitating multiple-language operation.

In this mode, both processing channels operate using the same processing parameters (like release time); you cannot adjust the two channels to provide different processing textures.

Sync Input
An audio sync input is configurable to accept AES11id or wordclock sync. You can synchronize the output samplerate of all AES3id outputs to this input. You can also synchronize the outputs to the AES3 digital input #1 or to the 8685's internal clock.

The sync source of each AES3 output is independently selectable.

Dual power
Dual power supplies with independent AC line inputs provide redundant operation.

All connections are rigorously RFI-suppressed
All input, output, and power connections are rigorously RFI-suppressed to Orban's traditional exacting standards, ensuring trouble-free installation.

The 8685 is designed and certified to meet all applicable international safety and emissions standards.

Adaptability through Multiple Audio Processing Structures

Complete audio processing system
A processing structure is a program that operates as a complete audio processing system. Only one processing structure can be on-air at a time. OPTIMOD 8685 realizes its processing structures as a series of high-speed mathematical computations made by Digital Signal Processing (DSP) chips.

Two processing structures
The 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.

"Protect" function
A special Two-Band preset creates a no-compromise "Protect" function that is functionally similar to the "Protect" structures in earlier Orban digital processors.

Rides gain over an adjustable range of up to 25 dB
The 8685's AGC rides gain over an adjustable range of up to 25dB, compressing dynamic range and compensating for both operator gain-riding errors and gain inconsistencies in automated systems.

The AGC output is available to drive STLs, so the 8685 can be used as a studio AGC.

Switching between processing structures and Pass-through mode
Switching between the Five-Band and the Two-Band audio processing structures occurs via a mute-free crossfade. Additionally, a Pass-through mode can be smoothly invoked without switching artifacts. Pass-through mode passes audio, metadata, and video through without alteration. Delay does not change between Pass-through and active processing modes, thereby maintaining AV-sync.

Phase-linear processing structures
The 8685's processing structures are all phase-linear to maximize audible transparency.

Mastering-quality noise and distortion performance
The 8685's equalizers and crossovers use 48-bit arithmetic to ensure mastering-quality noise and distortion performance.

Orban's PreCode™ technology
Orban's PreCode™ technology manipulates several aspects of the audio to minimize artifacts caused by low bitrate codecs, ensuring consistent loudness and texture from one source to the next. It is particularly useful when processing for netcasts or mastering for any low bitrate channel.

PreCode includes special audio band detection algorithms that are energy and spectrum aware. This can improve codec performance on some codecs by reducing audio processing induced codec artifacts, even with program material that has been preprocessed or mastered by processing other than OPTIMOD. There are several factory presets tuned specifically for low bitrate codecs.


Eight programmable, optically isolated GPI ports
The 8685 can be remote-controlled by 5-12 V pulses applied to eight programmable, optically isolated "general-purpose interface" (GPI) ports.

8685 PC Remote software
8685 PC Remote software is a smooth, responsive graphical application that runs under Windows XP, Vista and 7. It communicates with a given 8685 via TCP/IP over modem, direct serial and Ethernet connections. You can configure PC Remote to switch between many 8685s via a convenient organizer that supports giving any 8685 an alias and supports grouping multiple 8685s into folders. Clicking an 8685's icon causes PC Remote to connect to that 8685 through an Ethernet network or initiates a Windows Dial-Up or Direct Cable Connection if appropriate. The PC Remote software allows the user to access all 8685 features and allows the user to archive and restore presets, automation lists, and system setups (containing I/O levels, digital word lengths, GPI functional assignments, etc.).

Remote administration over TCP/IP
An API provides remote administration over TCP/IP via the RS232 serial or Ethernet ports. The 8685 hosts a TCP/IP terminal server to allow external control of the 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.

Versatile real-time clock
The 8685 contains a versatile real-time clock, which allows automation of various events (including recalling presets) at pre-programmed times. To ensure accuracy, the clock can be synchronized to an Internet timeserver.

Silence Alarm & Tally Outputs
Silence alarm and digital audio fault tally outputs are available.

Bypass Test Mode
A Bypass Test Mode can be invoked locally, by remote control (from either the 8685's GPI port or the 8685 PC Remote application), or by automation to permit broadcast system test and alignment or "proof of performance" tests.

Built-in line-up tone generator
The 8685 contains a built-in line-up tone generator, facilitating quick and accurate level setting in any system.

Software Upgrade
The 8685's software can be upgraded by running Orban-supplied downloadable upgrade software on a PC. The upgrade can occur remotely through the 8685's Ethernet port or serial port (connected to an external modem) or locally (by connecting a Windows® computer to the 8685's serial port through the supplied null modem cable).


  • Frequency Response (Bypass Mode)
    • Surround Processing: ±0.10 dB, 20 Hz-20 kHz for 44.1 kHz or higher input/output sample rates. At 32 kHz input and/or output sample rate, the passband is reduced to approximately 14.7 kHz.
    • 2.0 Processing: Depending on settings, is flat or follows standard 50 µs or 75 µs pre-emphasis curve ±0.10 dB, 20 Hz-20 kHz (except at 32 kHz; see above). Output can be user-configured to be flat or pre-emphasized.
    • (Pre-emphasis limiting allows any of the 8685's 2.0 processors to drive an analog television transmitter that uses an preemphasized FM aural carrier. This function is particularly useful when used with 2.0 processor #4, which can emit a loudness-controlled and peak-limited downmix of the surround audio. Preemphasis limiting is also useful for certain older analog studio/transmitter links.)
  • Noise: Output noise floor will depend upon how much gain the processor is set for (Limit Drive, AGC Drive, Two-Band Drive, and/or Multiband Drive), gating level, equalization, noise reduction, etc. The dynamic range of the A/D Converter, which has a specified overload-to-noise ratio of 110 dB, primarily governs it. The dynamic range of the digital signal processing is 144 dB.
  • Polarity (Bypass Mode; Operate Mode when processing chain is configured for linear phase): Absolute polarity maintained. Positive-going signal on input will result in positive-going signal on output.
  • Internal Processing Sample Rate: 48 kHz. We believe this provides maximum audible transparency by minimizing numerical “noise” in the equalizers and filters while still preserving a pure, transparent sound. The double-precision equalizers and crossover filters used throughout the 8685 produce at least 6 dB lower noise and nonlinear distortion than they would at 96 kHz.
  • Processing Resolution: Internal processing has 24 bit (fixed point) or higher resolution; uses nine Freescale (formerly Motorola) 250 MHz DSPB56724 dual-core 24-bit fixed-point DSP chips.
  • Delay: The minimum available input/output delay is approximately 33 ms with look-ahead limiting active and 6 ms with look-ahead limiting bypassed. This can be padded to exactly one or two frames of 24, 25, 29.97, 30, 50, 59.94, or 60 frames/second video up to a maximum delay of 60 ms. (Two frames are required for 59.94/60 fps progressively scanned video.) The HD-SDI connection provides video delay of up to 11 frames to compensate for the delay of the 8685’s loudness processing (approximately one frame), Optimix® upmixer (approximately five frames) and optional Dolby-E® decoder and encoders (one frame apiece).
  • Surround Processing Stereo Coupling: All channels of the AGC and compressors are coupled using RMS summation. The user can select whether or not the LFE channel contributes to the RMS sum in the AGC and compressor control sidechains. Peak limiters in the multiband compressor limiter and look-ahead limiters all operate uncoupled to prevent transients in a given channel from causing audible loudness modulation in other channels. In additional, the compressors acting on the center channel can be uncoupled from the remaining channels within a user-selectable window, allowing the processing to correct the balance between dialog and remaining program elements automatically.
  • 2.0 Processing Stereo Coupling: Stereo or dual-mono. In dual-mono mode, both processing channels have the same subjective adjustments (as determined by the active preset) but are otherwise independent, making this mode appropriate for dual-language transmissions. In stereo mode, the user can set the maximum permitted gain difference between the channels in each band of the multiband compressor/limiter. 2.0 Stereo/Dual-Mono operating mode can be set via GPI, Ethernet and serial connections, internal clock-based automation, and AES3 Status Bits.
  • Loudness Level Meters (x5 or x9): One set of meters for the surround processor and one set of meters for each of the 2.0 processors. In dual-mono mode, each mono channel has one set of meters. Meters can be displayed on the 8685's front-panel screen and on PC Remote software. A set of loudness meters includes a BS.1770-2 meter and a CBS meter, which are displayed side-by-side. The ITU BS.1770 meter displays Short-term and Integrated Loudness simultaneously on the same scale. The integrated loudness measurement shows the loudness of the previous 10 seconds of program material with equal time-weighting and gating per BS.1770-2. The CBS meter’s display time constants are matched to the loudness integration time of the human ear, reaching steady-state level in approximately 200 ms and having a decay time constant of approximately 300 ms. The short-term meter uses the Jones & Torick algorithm developed at CBS Technology Center. (B. L. Jones & E. L. Torick: "A New Loudness Indicator for Use in Broadcasting," J. SMPTE, September 1981, pp 772-777.)
  • Peak Control: As recommended in ITU-R BS.1770-3, the peak limiter is oversampled at 192 kHz, yielding a worst-case overshoot of 0.5 dB at the analog output and for all output sample rates. (To achieve this performance at 32 kHz output sample rate, it is necessary to set the 8685’s lowpass filter cutoff frequency to 15 kHz.)

Optimix™ Upmixer

  • Location: Built into the Optimod.
  • Processing Delay: 146 ms
  • Upmix: 2.0 to 5.0; 5.1-compatible.
  • Auto-detection: Defeatable auto-detection can detect stereo and surround inputs automatically and switch upmixing on when stereo material is detected.
  • Bass Management: Bass energy below 80 Hz is not upmixed. Any energy below 80 Hz in the left/right inputs is routed to left front/right front outputs respectively so that home receivers can perform appropriate bass management for a given setup.
  • Downmix Compatibility: If Delay Correction is OFF, Optimix reads the Optimod’s downmix parameters (Center and Surround downmix coefficients) from the Optimod and automatically chooses gains for the five upmixed channels that make the downmixed signals identical to Optimix's stereo inputs, assuming a Dolby Lo/Ro downmix. Optimix takes into account the settings of its Front/Rear Balance and Center Width controls.
    It is the user's responsibility to make sure that the Optimod's downmix level controls agree with the Center Downmix Level and Surround Downmix Level in the AC3 metadata that is being transmitted to consumers. (Per Dolby, the default value of both is -3 dB.)
    When Delay Correction is ON, the stereo downmix includes the effect of the center channel delay corrector, which can make the stereo downmix crisper and more intelligible than Optimix’s stereo inputs.
  • User Controls:
    • Center Width determines whether extracted center-channel information will be routed solely to the center output, or if some amount of the center energy is blended into the Left Front and Right Front outputs. While setting this control to “0” maximizes the “discreteness” of the upmix, some operators prefer to mix a certain amount of center energy into Lf and Rf to ensure that dialog is not lost completely if the center channel is not correctly set up at the consumer’s receiver.
    • Front/Rear Balance controls the ratio between the Lf/Rf and Ls/Rs levels above 80 Hz, which determines the amount of envelopment in the upmix.
    • Delay Correction automatically corrects time skew or phase shift between the left and right input channels. It prevents comb filtering in the derived center channel. This maximizes mono compatibility and maintains the best possible crispness and intelligibility in the center channel, which usually contains dialog or vocals.
    • Mode sets Optimix to BYPASS, UPMIX, or AUTO modes.


  • HD-SDI Input/Output 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). Input and output are on BNC connectors. A bypass relay is provided.
    Unless the bypass relay is directly connecting the HD-SDI input to the HD-SDI output (which is true when no AC power is applied to the 8685 and when it is booting up), the HD-SDI input is internally terminated with 75Ω.
  • Audio Channel Support: Supports only SDI audio channels 1 through 8.
  • Dolby-E® Support: Sockets exist to accept Dolby-E encoder/decoder modules; unit is field-upgradeable to support Dolby-E.
  • Delay for A/V Sync: Includes up to 11 frames of video and metadata delay to preserve AV-sync. Core 8685 loudness control processing requires one frame of delay; the built-in Optimix® upmixer requires an additional five frame delay; Dolby-E requires one frame for decoding and one frame for encoding.
  • Dolby E Metadata Support: Supports Dolby-E metadata received through HD-SDI and RS485 interfaces per SMPTE RDD 06-2008. The metadata in the HD-SD stream must be embedded the HD-SDI VANC data per SMPTE 2020-2-2008 (Method-A) or SMPTE 2020-3-2008 (Method-B). Digital Audio Inputs (x4)
  • Configuration: Each of four hardware inputs accepts two audio channels per AES3id standard, 24 bit resolution. Internal programmable routing switcher allows any of the 10 physical input channels to be routed to the LF, RF, C, LB1, RB1, LFE, LB2, RB2, STEREO L, or STEREO R inputs of the audio processing. For the 2.0 processing, unit can detect Stereo or Two-Channel status bits appearing at Input #1 and switch the 2.0 processor between stereo and dual-mono modes. Input #4 can also be used as a sync input, accepting wordclock or AES11id sync.
  • User Bits: Unit can pass AES3id User Bits from Input #1 to Output #1.
  • Sampling Rate: 32, 44.1, 48, 88.2, or 96 kHz, automatically selected.
  • Connector: BNC, female, shell bypassed to chassis via 1000 pF capacitor, EMI-suppressed. 75Ω impedance, terminated.
  • Input Reference Level: Variable from -30 dBFS to -10 dBFS.
  • Filtering: RFI filtered.
  • Bypass Relay: When the Optimod is powered down or booting up, each AES3id input is hard-wire bypassed to the corresponding AES3id output via a relay.
    Digital Audio Outputs (x3)
  • Configuration: AESid. Internal, remote-controllable routing switcher allows sending LF, RF, C, LB1, RB1, LFE, LB2, RB2, STEREO L, STEREO R, DOWNMIX L, and DOWNMIX R to any hardware output channel.
  • Sample Rate: Internal free running at 32, 44.1, 48, 88.1 or 96 kHz, selected in software. Can also be synced to the AES3id Input #1,or to the sync input (which supports AES11id and wordclock) at 32, 44.1, 48, 88.1 or 96 kHz, as configured in software. (Passband is limited to approximately 14.7 kHz when using 32 kHz input and/or output sample rate.)
  • Word Length: Software selected for 24, 20, 18, or 16-bit resolution. First-order highpass noise-shaped dither can be optionally added, Dither level is automatically adjusted to complement the word length.
  • Connector: BNC, female, shell bypassed to chassis via 1000 pF capacitor, EMI-suppressed. 75Ω impedance, terminated.
  • Output Level (100% peak modulation): -20.0 to 0.0 dBFS software controlled.
  • Filtering: RFI filtered.
  • Audio Reference Input
    • Configuration: Can accept wordclock or AES11id (75Ω) sync, automatically detected.
    • Connector: Female BNC.
    • Termination: Internally terminated with 75Ω
  • Analog Audio Outputs
    • Configuration: One pair of outputs, which can be configured in software to emit LF, RF, C, LB1, RB1, LFE, LB2, RB2, STEREO L, STEREO R, DOWNMIX L, DOWNMIX R, LF/RF, C, LB1/RB1, LB2/RB2, STEREO L/R, and DOWNMIX L/R signals.
    • Source Impedance: 50Ω, electronically balanced and floating.
    • Load Impedance: 600W or greater, balanced or unbalanced. Termination not required or recommended.
    • Output Level (100% peak modulation): Adjustable from -6 dBu to +24 dBu peak, into 600Ω or greater load, software-adjustable.
    • Signal-to-Noise: ≥ 100 dB unweighted (Bypass mode, 20 Hz–20 kHz bandwidth, referenced to 100% modulation).
    • Distortion: ≤ 0.01% THD (Bypass mode, de-emphasized) 20 Hz–20 kHz bandwidth.
    • Connectors: Two XLR-type, male, EMI-suppressed. Pin 1 chassis ground, Pins 2 (+) and 3 electronically balanced, floating and symmetrical.
    • D/A Conversion: 24 bit 128x oversampled.
    • Filtering: RFI filtered.
  • Audio Sync Input
    • Configuration: Can accept wordclock or AES11id (75Ω) sync, automatically selected.
    • Connector: Female BNC, shell grounded to chassis.
    • Termination: Internally terminated with 75Ω.
  • Video Sync Input
    • Video Sync input (per SMPTE 274M and SMPTE 296M) 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 (SMPTE RDD 6-2008 and Dolby Labs published specifications) in cases where HD-SDI is not in use. When HD-SDI is in use, frame sync is obtained from the HD-SDI input stream provided that the HD-SDI input complies strictly with SMPTE 299M 5.2.1 (CLK [audio clock phase data]).
      The video reference input is on a female BNC connector and is internally terminated with 75Ω.
  • Remote Computer Interface
    • Configuration: TCP/IP protocol via direct cable connect, modem, or Ethernet interface. Modem is not supplied.
    • Serial Port: 115 kbps RS-232 port DB-9 male, EMI-suppressed.
    • Ethernet Port: 100 Mbit/sec on RJ45 female connector.
      RS-485 Serial Interface (x2)
    • Hardware: 115 kbps RS–485 port DB–9 male, EMI-suppressed.
    • Compatibility: Designed to be hardware-compatible with Dolby Digital® hardware that sends and receives Dolby Digital metadata.
  • Conveying and Re-authoring Dolby Metadata
    • The 8685 can, via an SMPTE RDD 06-2008-compliant RS-485 serial connection, via an HD-SDI connection, or via embedded Dolby-E metadata (when the optional Dolby-E modules are installed in the HD-SDI module), automatically convey its active surround metadata value to a downstream Dolby Digital encoder like the Dolby DP-569, which must be set up according to its operating instructions to receive and act upon this input. This greatly reduces the possibility that operator error will cause the wrong value of surround metadata to be transmitted to consumers.
    • To emit an RDD 06-2008-compliant signal, the 8685 must be receiving a valid input stream that is compliant with RDD 06-2008—this is necessary to synchronize the output metadata to video frame boundaries per the Dolby specification. When a valid input stream in present, the 8685 passes this stream unchanged to its output except for the following modifications:
      • The ac3_dialnorm word in the output metadata stream is reauthored so it is the same as the 8685's active Dialnorm value.
      • The ac3_dynrnge word in the output stream is set to 0, indicating that the downstream AC3 encoder must reauthor the line-mode DRC