This is from the 1996 (Lucasfilm) THX site.
The Making of a THX Laser Disc
The THX Laser Disc Program began in 1993 to improve the quality and consistency of laser discs. The motivating force behind the program was the fact that on a properly calibrated Home THX Audio System a tremendous amount of variation in the quality of laser discs was noticed.
Tom Holman, along with Principal Video Engineer Dave Schnuelle, began investigating all of the many steps in the laser disc mastering and manufacturing process. They developed monitoring techniques and quality assurance principles to solve the many problems they found along the way. One technology that was developed was the THX Video Test Signal. The patented THX Video Test Signal is inserted into a video signal's vertical interval (the space leftover between each video field). This allows a computer to continuously monitor the black level, white level, chroma level, chroma noise, phase, frequency response, etc. of the video signal. This ensures that no video signal degradation occurs during duplication.
Here is a brief description of all of the steps that go into making a THX laser disc. Remember that a THX Laser Disc does not use any special surround sound format. THX Laser Discs have soundtracks recorded in Mono, Stereo, Dolby Surround, and/or Dolby Digital.
The first step is to calibrate the video monitor and the audio playback system. THX engineers use a Photo Research Spectra-Radiometer to carefully calibrate the black level, white level, greyscale, and color balance of the video monitor being used in the transfer. The Spectra-Radiometer measures the wavelengths of the light coming from the video screen and can display the actual spectrum on a computer. This gives the engineer valuable information on color and greyscale as well as on the actual purity of the phosphors being used in the monitor. The purpose of this calibration is to ensure that decisions made by the filmmaker on the color of the transfer are done under correct and repeatable conditions. The Photo Research device is calibrated regularly to National Bureau of Standards specifications.
The second step is to calibrate the dubbing machines. The frequency response, phase, azimuth, and level of each channel (2 channels for Dolby Stereo transfers, 6 channels for Dolby Digital) are checked to ensure accurate playback of the soundtrack master tape.
Once the system is calibrated, THX engineers monitor the transfer and answer any technical questions that arise. The transfer of picture and sound are done at the same time to ensure correct synchronization. All decisions about content, colorimetry, etc. are made by the film company, and many times the director, producer, or cinematographer is present. THX engineers are present in an advisory capacity only. Much of the look of a movie transfer is the responsibility of the telecine artist and the studio advisor.
Upon completion of the transfer (usually to a D-1 digital video tape), THX Laser Disc engineers step in to begin supervising the duplication process. The D-1 master tape is digitally transferred to a digital D-2 video tape. At this stage, the patented THX Laser Disc test signal is inserted into the video vertical interval.
On a parallel path to the video transfer, the 2 channel analog print master is transferred to digital audio. If the laser disc contains a Dolby Digital soundtrack, Dolby engineers work along with THX engineers to transfer the 6 track print master and convert it into the 5.1 channel Dolby Digital serial bitstream. One more Digital D-2 video copy is made and it is at this stage the soundtrack is married to the video print. The FM analog tracks are copied, the digital 2 track Dolby Stereo soundtrack is copied, and (if used) the Dolby Digital bitstream is transferred as well.
It is from this final digital D-2 master tape that the laser disc master is made. Since a laser disc contains an analog video signal, the digital video of the D-2 master tape must be converted to analog at this point. Once the laser disc master is made, THX engineers inspect a sample from each stamper to ensure that the quality of the original transfer is maintained. A test disc must go through a computerized test process using the patented THX Video Test Signal. It must also go through a review by a THX Laser Disc QC technician. To ensure the highest quality possible, every transfer and sample disc is looked at and listened to. THX Laser Disc QC technicians have the power to reject entire pressings of laser discs, and they have used that power on occasion.
The goal of the THX Laser Disc Program is to ensure that the look and sound of a movie is preserved through the complicated picture and sound transfer processes. You may notice some picture and sound differences between THX Laser Disc titles, but those differences were decided upon by the movie makers themselves.
The technologies developed by the THX Laser Disc Program become increasingly important when you look at the future of home video. THX engineers are currently working with many digital video formats, including DVD, to ensure that the filmmaker's intentions are preserved for the future.
Although there's no mention of DVNR, it is my impression that the DVNR took place during the Telecine and it was controlled by Telecine artist (or colourist). The DVNR was probably used like any other adjustment i.e. like the settings for colour or black level. I believe the DVNR was an 'automatic' process that had only one setting for Luma and one for Chroma with a scale 0-10, and I would suspect it was set to handle the worst parts of the print and then probably not changed during the transfer, and that's why some (many) parts were clearly over-filtered.
Anyway IMO also the D1 Telecine master would be DVNR filtered and after the D1 there were no more video tweaks applied.
The printing master would be the final D2 tape. The lack of dotcrawl in the GOUT suggest a non-composite source like D1.
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