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Summary of Contents for Dolby Laboratories DP561
- Page 1 Model DP561 Dolby Digital (AC-3) Real-Time Encoding System Users' Manual Issue 4 Part No. 91396...
- Page 2 Dolby Laboratories be liable for incidental, special, direct, indirect or consequential damages (including but not limited to damage to software or recorded audio or visual material), or loss of use, revenue or profit even if Dolby Laboratories or its agents have been advised, orally or in writing, of the possibility of such damages.
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Page 3: Table Of Contents
TABLE OF CONTENTS 1.1 Introduction ..................1-1 1.2 Features..................... 1-2 1.3 Dolby AC-3 ..................1-2 1.4 Regulatory Notices ................1-3 2.1 Overview ..................2-1 2.2 Host Computer ................. 2-2 2.3 DSP Cards ..................2-2 2.4 Digital Audio Input................2-2 2.5 Dolby AC-3 Output Data..............2-2 2.6 SMPTE Time Code ................ - Page 4 Digital Input/Output Settings .......... 6-5 6.1.3 Bit Stream Information............6-5 Example................6-5 Center Downmix Level ........... 6-5 Surround Downmix Level ..........6-6 Dolby Surround Mode............. 6-6 Dialog Normalization............6-7 Language Code..............6-7 Audio Production Info Exists.......... 6-7 Mixing Level ..............6-7 Room Type ..............
- Page 5 Input/Output Page............8-5 Time Code Page .............. 8-7 8.2.4 State Control..............8-7 State Control Buttons ............8-7 The Status Bar ..............8-8 8.2.5 Menu Commands .............. 8-8 File Menu Commands ............. 8-8 Help Menu Commands............ 8-9 8.3 Remote Control Configuration Files ..........8-9 8.3.1 Converting Local Mode Configuration Files.....
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Page 6: Introduction
Dolby Laboratories will supply users with an upgrade diskette. The purpose of this manual is to describe operational aspects of the Model DP561 encoder, including the hardware architecture, input/output connections, and user- The format is described in documentation entitled "Annex B, AC-3 Data Stream in IEC 958 Interface";... -
Page 7: Features
DVD video discs in NTSC countries (optional elsewhere), and DVD-ROMs. In both multichannel and two-channel formats it is also specified for ASTC digital television broadcasting. Please contact Dolby Laboratories for available technical papers on Dolby AC-3. -
Page 8: Regulatory Notices
Regulatory Notices Troubleshooting must be performed by trained technicians. Do not attempt to service this equipment unless you are qualified to do so. Exposed portions of the power supply that are electrically "hot" may exist when the cover is removed. In order to reduce the risk of electrical shock, the power cord MUST be disconnected when the cover of this equipment is removed. - Page 9 IMPORTANT SAFETY NOTICE This unit complies with the safety standard IEC65. To ensure safe operation and to guard against potential shock hazard or risk of fire, the following must be observed: If the unit has a voltage selector, ensure that it is set to the correct mains voltage for your supply. If there is no voltage selector, ensure that your supply is in the correct range for the input requirement of the unit Ensure fuses fitted are the correct rating and type as marked on the unit.
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Page 10: Overview
SECTION 2 HARDWARE ARCHITECTURE Overview Note The exact hardware configuration may change as hardware availability and improvements dictate. Your unit may vary slightly from the description below. The Dolby AC-3 encoder specifications, however, remain unchanged. The physical encoder consists of a number of printed circuit cards plugged into an ISA (Industry Standard Architecture) bus computer. -
Page 11: Host Computer
The host computer includes the CPU itself, disc controllers, keyboard, serial, and parallel ports, and RAM. On the model DP561, these functions are located on a ISA bus plug-in PC card. On the DP561B, the functions are located on the motherboard. -
Page 12: Smpte Time Code
DP561. SMPTE Time Code In addition to the audio inputs, the Model DP561 can accept a SMPTE time code signal by means of a reader card installed on the ISA bus. The time code signal may be used to accurately control the start or stop time of the encoder. -
Page 13: System Synchronization
In this case, all AES/EBU input signals from the digital audio source(s) must be synchronous with each other. At this time, the DP561 encoder will support input digital audio sampling frequencies of 48 kHz and 44.1 kHz. The encoder will be automatically sense the input sampling frequency and set all internal encoder parameters based on this value. -
Page 14: Unpacking
SECTION 4 PRE-INSTALLATION Unpacking Before unpacking the DP561, inspect the outer carton for shipping damage. If there has been any penetration to the carton, be sure to inspect the unit for any physical damage in those areas. Several accessories have been included in the packaging. Please compare them... -
Page 15: Claims For Shipping Damage
The DP561 has numerous jumpers and switches, both inside the unit and on the rear panel. These should not be disturbed, as results may be unpredictable. Dolby does not support the use of the DP561's PC platform for applications that are not described in this manual. -
Page 16: Mounting
DP561B - Refer to Figure 5.1 for rear panel connector locations. See Figure 5.2 for connections to the earlier version of the DP561B. DP561 - Because of its weight, devise a method of supporting the unit at its rear by means of accessories that may be available for your specific rack. Mounting slides are another suitable alternative. -
Page 17: Digital Audio Output
SMPTE Time Code Connections In addition to the audio inputs, the DP561 accepts SMPTE time code, which can be used to accurately control the start and stop times for the encoder. In addition, the time code may be embedded in the output data stream with its associated audio data. -
Page 18: Remote Interface Connections
COM1 or COM2 of the external PC using the supplied serial cable (or any serial cable with all 9 pins wired straight through). Note: Dolby Laboratories does not supply or recommend specific brands or models of external PC equipment. The system requirements for the external PC are: â... - Page 19 SWITCHED AC OUT SWITCHED AC OUT CARD KEYBOARD IN KEYBOARD IN NOT USED Figure 5.3 Model DP561 Rear Panel Connectors VGA MONITOR OUT VGA MONITOR OUT COM 1 COM 1 TIME CODE LOOP THRU TIME CODE LOOP THRU TIME CODE IN...
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Page 20: Dolby Ac-3 Parameter Control
AC-3 code, and will subsequently invoke the DP561 control program in local control mode. This program is named "ac3ctrl". In local control mode, the DP561 will only respond to commands entered from the DP561 keyboard. For information on using the remote control features of the DP561, please see Section 6.4. -
Page 21: Audio Service Configuration
character must be typed in the same case as shown on screen. The meaning of each menu item is described below. 6.1.1 Audio Service Configuration Data Rate Data rates that are supported by the Dolby AC-3 real-time encoder depend on the selected Audio Coding Mode parameter. In general, audio coding modes that include fewer channels in the bit stream have lower data rate limits. -
Page 22: Low Frequency Effects Channel On/Off
channels. Table 6.3 lists all eight modes and defines which input channel is used for encoding based on the selected mode. If the mode is set to 1+1, then two completely independent program channels (dual mono) are encoded into the bit stream, and are referenced as Ch1 and Ch2. -
Page 23: Output Format
Note AES/EBU 1 is the master input, and must always be present in order for the encoder to lock to the input signals. When the Audio Coding Mode is set to 1/0, the center channel (C) is encoded. For this configuration, it may be convenient to choose Input Channel Assignment mode 6, because the center channel is mapped to Channel A of AES/EBU 1. -
Page 24: Surround Input 3 Db Attenuation
This menu item activates a sub-menu which supplies the user with information about the state of the digital audio input signals which are applied to the Model DP561. The sub-menu also allows the user to change certain bits in the AES/EBU or S/PDIF channel status of the DP561 digital output signal containing the AC-3 bit stream. -
Page 25: Center Downmix Level
Center Downmix Level Mix Level 1 (default) 0.707 (-3.0 dB) 0.596 (-4.5 dB) 0.500 (-6.0 dB) Table 6.5 Center Downmix Level Values Surround Downmix Level This parameter indicates the nominal downmix level of the surround channel(s) with respect to the left and right channels (consistent with the ITU BR specification). -
Page 26: Dialog Normalization
Dialog Normalization This parameter indicates how far the average dialog level of the encoded program is below digital 100%. Valid values are 1 to 31, which are interpreted as -1 dB to -31 dB with respect to digital 100%. The value of Dialog Normalization affects the sound reproduction level. -
Page 27: Room Type
A second value for this parameter type will become active when the Audio Coding Mode is 1+1 and the Audio Production Info Exists parameter for Ch2 is set to "yes." This second item applies to the second independent channel (Ch2) residing within the bit stream. Room Type This parameter appears in the bit stream and the menu item is active only when the Audio Production Info Exists parameter is set to "yes."... -
Page 28: Encoder Status
6.1.4 Encoder Status The fields listed under Encoder Status supply the user with information about the current status of the Model DP561 encoder. The meaning of each field is described below. Dolby AC-3 Encoder Version This field displays the AC-3 software version running on the DSPs. -
Page 29: Current Audio Bandwidth
This field indicates the time code at which the DP561 will automatically stop encoding (assuming it was previously running). For more information on using SMPTE time code to control the DP561, please see Section 6.2. 6.1.6 Saving the Parameter State It is not mandatory that the user quit the control program, "ac3ctrl", before... -
Page 30: Time Code Operation
Then, when you quit the new software for the first time, the DP561 will attempt to save the state in the new format to the same file. As a result, you will be asked if you want to overwrite the old configuration file. -
Page 31: Command-Line Control
6-12 time, the encoder will start coding the incoming audio data. Note that the user may manually start or stop the encoder at any time using the "enter" key. There is an additional parameter appended to the displayed start and stop times; it is delineated by a colon following the frame number. -
Page 32: Configuration Files
Running the control program with command-line arguments makes use of configuration files, which are binary (non-readable/editable) files which may be used to set the mode of operation and parameters for the DP561 encoder. The configuration file specifies all encoding parameters including Audio Service Configuration, Input/Output Control, Bit Stream Information, and also time code start/stop times and the encoder state. -
Page 33: Command-Line Usage
If the state configuration file does not exist, the control program will set the encoder into the default state as defined in Section 6.1 above. Finally, as described in Section 6.1.6, the current DP561 software uses a different file format for its configuration files than was used by the original software release. - Page 34 6-15 Notes Do not put a space between the "x" and the time code value. Always include two digits for the HH, MM, SS, FF fields, e.g., "0" should be specified as "00," and "1" should be "01." The SAMPLE field may range from one to four digits (with a value of 0 to 1535). -y = Time Code Stop Time This parameter is used to specify the encoder stop time code value.
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Page 35: Example 1
6-16 Example 1 Consider an audio program which is to be encoded into 4 segments: A, B, C, and D. The time code start and stop times for each segment are given as: Segment Time Code Start Time Code Stop 00:00:01:00 00:14:24:00 00:14:24:00... -
Page 36: Remote Control Mode
DP561 monitor, but cannot be changed using the DP561 keyboard. The remote control software is described in detail in Chapter 8. The DP561 starts up in the local control mode by default. To switch to the remote control mode, simply choose C –... -
Page 37: Remote Parameter State Control
"ac3state.cfg" described in Section 6.1.6 is essentially ignored in remote control mode. Thus, it is not necessary to quit the ac3ctrl program before powering down the DP561. In fact, it is not even necessary to connect a keyboard or monitor to the DP561 at all! -
Page 38: Software Updates
A power-on, reset, or warm boot (ctrl-alt-del) will work. The autoexec.bat file on the floppy diskette will copy the new C4x executable code to the DP561 hard drive. The machine will beep three times to indicate completion of the update. -
Page 39: Software Installation
Once started, the remote control program tries to stay in constant communication with the DP561. For this reason, it is important that you not disconnect the serial link or shut down the Model DP561 while the remote control program is running - doing so will result in an error message on the Windows PC. For more information about remote control error messages, see Section 8.4. -
Page 40: Audio Level Meters
Also, the meter channels reflect the channel assignments, which may be different than the channel ordering on the DP561’s AES/EBU inputs. That is, the meter labelled "L" corresponds to the left coded channel, regardless of which AES/EBU input the left channel happens to be assigned to. -
Page 41: Bitstream Info Page
Bitstream Info Page This page, shown in Figure 8.2, contains fields for parameters that provide additional information about the coded bitstream, including: Center Mix Level Surround Mix Level Dolby Surround Mode Copyright Bit Original Bitstream Audio Production Info Exists Mix Level Room Type Figure 8.2 The Bitstream Info Page Preprocessing Page... -
Page 42: Dual Mono Page
Note The Digital Deemphasis, Bandwidth Lowpass Filter, and RF Overmodulation Protection features are not available on the Model DP561. These controls have been disabled, and the Digital Deemphasis status will always indicate "Off". The compression input level meter displays the "overall" level of all coded channels, which is used by the dynamic range compressor to determine the appropriate amount of boost or cut. -
Page 43: Input/Output Page
Audio Production Info Exists Mix Level Room Type Compression Input Level Meter Compression Line Mode Meter Compression RF Mode Meter Figure 8.4 The Dual Mono Page Note In dual mono mode, the two channels have independent dynamic range compression behavior, including independent dialog normalization settings, and independent compression input level and line mode/RF mode meters. - Page 44 If they do not match, the fault is generally in the device that is feeding the DP561. Note that the DP561 uses the measured sample rate to determine the sample rate used for the encoding process – which is displayed in the Audio Service Configuration section.
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Page 45: Time Code Page
The DP561 has two primary operating states: "encoding" and "stopped". Two other states, "prerolling" and "clearing", occur during transitions between the encoding and stopped states. The DP561 state may change based on start/stop time codes, or by manual command from the user. -
Page 46: The Status Bar
"LED"-style lights that indicate the current state of the DP561. If the start button is lit, then the DP561 is in the "encoding" state. A third button indicating time code control (stopwatch) is always lit. This serves as a reminder that the DP561 is always "on-line" with respect to time code –... -
Page 47: Help Menu Commands
Figure 8.8 The About Box Remote Control Configuration Files The Model DP561 Remote Control software is able to save all DP561 encoding parameters to a configuration file on the external PC’s hard disk. In fact, whenever you quit the remote control program, it saves the current parameters to a file named "ac3state.cfg. -
Page 48: Converting Local Mode Configuration Files
The configuration files used by the remote control program are not the same format as those used by the "ac3ctrl" program in the local control mode of the DP561. If you have created your own configuration files using the local mode user interface, you will need to convert them into the remote program format in order to use them with the remote control program. -
Page 49: Remote Control Error Messages
8-11 Remote Control Error Messages If the Model DP561 Remote Control program is unable to connect to the DP561, or if the connection is unreliable, you may see an error message on the external Windows PC. This section lists some of the error messages that you might encounter, along with possible causes of the underlying problem. - Page 50 8-12 Busy poll status timeout This message occurs if the DP561 takes too long in responding to a message from the remote control program. This generally means that the DP561 microprocessor is not operating fast enough to keep up with all of the requirements of the DP561 system.
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Page 51: Interface Description
In some applications, it is necessary to capture Dolby Digital bitstreams as hard disk files for subsequent mastering. This section outlines one method of recording the output bitstream of a Model DP561 to disk, using a Unix workstation and a IEC-958 SCSI capture device. -
Page 52: Encoder Output Format
AC-3 packets. The minimum time code packet length is 0x0060, (96 bits, or 3 IEC 958 frames), as defined in Annex B. The DP561 includes 32 bits of additional information in the time code packet which may be useful for disc mastering applications, and so the time code packet length is 0x0080, or 128 bits. - Page 53 The program reads AC-3 disc files, and formats the data into the same type of IEC 958 output as described above for the DP561. In this case, the output stream will come from the DAT-Link+'s output connectors. This may be useful as a monitoring tool for the recorded AC-3 disc files.
- Page 54 -r = Single pack output data into right channel. Default = double pack into both channels. Either the l or r option may be used to specify that the AC-3 and time code packet data occupy only one of the IEC 958 channels. Left and right correspond to A frame and B frame, respectively.
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Page 55: Disc File Formats
AC-3 Disc File Formats Introduction This document contains specifications of four different AC-3 file formats which are currently in use, and partial specifications for some other formats. This specification considers the AC-3 files to be a sequence of dataframes. Each dataframe consists an AC-3 syncframe and may include a header containing a time stamp or other information. - Page 56 Dataframe_type_0x0B The AC-3 syncframe is defined as a sequence of bits of data. The length of a syncframe is always an integer multiple of 16. The first 16 bits of the syncframe is the AC-3 syncword. This syncword has a value of ‘0000 1011 0111 0111’ (0x0B77), where the left (or most significant) bit is transmitted first.
- Page 57 Dataframe_type_0x00 The AC-3 file type 0x00 includes a 16-byte header at the beginning of each dataframe. The balance of the data frame is the AC-3 syncframe with sequential byte ordering. Syntax Field Bytes Value Comments dataframe_type_0x00() file_type_code ; 0x00 Indicates frame type 0x00 smpte_hours ;...
- Page 58 Syntax Field Bytes Value Comments dataframe_type_0x01() file_type_code ; 0x01 Indicates frame type 0x01 hdr_len ; 0x10 Header length, 16 bytes smpte_ts_word[0] ; See Annex A smpte_ts_word[1] ; See Annex A smpte_ts_word[2] ; See Annex A smpte_ts_word[3] ; See Annex A smpte_ts_word[4] ;...
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Page 59: The Smpte Time Stamp
The SMPTE Time Stamp An excerpt from Annex B of ATSC Document A/52 (“Digital Audio Compression Standard (AC-3)”) is reproduced below. The information in Section 4.8.2 (“Time Stamp Payload”) shows the contents of the smpte_ts_word[n] (where n = 0 to 5) which are included in some of the AC-3 file formats. - Page 60 A-10 Audio Signals to be encoded IEC 958 signal Digital Audio Encoder Coded audio + time code S M P T E T i m e C o d e Figure 1. Encoding audio with time code. Preamble values Time stamps are conveyed by data bursts with a value of 0x2.
- Page 61 A-11 upper bits of payload words 0-3. If flag bit f1 is set to a ‘0’, this information has not been provided, and the upper bits of payload words marked [ ] are all set to ‘0’. The sample number in word 4 is an unsigned integer which indicates the sample number (Sn in Figure 2) to which the time code value applies.
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Page 62: Operation With A Dat-Link
NOT interrupt recac3, and load the second DA-88 tape. Locate the second tape to a few seconds prior to the stop time of the first tape. Next, type "r" on the DP561 keyboard; this will copy the stop time as the new start... - Page 63 When the new stop time is reached and the DP561 has stopped encoding, stop the recac3 program by typing "ctrl-c." The program will display the number of time code and Dolby AC-3 packets written to disc.
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Page 64: System Specifications
APPENDIX B SPECIFICATIONS System Specifications Audio Coding Method Dolby Digital (AC-3) Data Rates and Channel Modes Total Data Channel Modes Rate (kbps) 1+1, 1/0, 2/0 1+1, 1/0, 2/0 128,160 1+1, 1/0, 2/0, 3/0, 2/1 1+1, 1/0, 2/0, 3/0, 2/1, 3/1, 2/2 224,256,320,384, 1+1, 1/0, 2/0, 3/0, 2/1, 3/1, 2/2, 3/2 448,512,576,640... -
Page 65: Hardware
BNC connector, 75 ohms, can be adapted to AES/EBU or SMPTE 276M. Remote Serial Interface RS-232, 38400 baud. The DP561 COM1 port is normally configured as a DTE device; using the null modem adapter switches this to a DCE device.
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