Feature films also have an audience in Europe, and HDTV @ 24fps can easily service this market.
Our episode clients were early adopters of the new high-definition television standard. They quickly realized the future popularity of HDTV, and though there is presently limited HDTV original broadcasting in North America, they wanted to ensure future compatibility in their current productions. Feature films also have an audience in Europe, and HDTV at 24fps can easily service this market. However, they did not want to make significant changes to their method of operations. They had every right to assume the telecine transfer and post-production facility would make the necessary preparations to provide them with U-Matic and VHS offline editing cassettes, even though the frame rates (and timecode) of the HDTV film transfers may not be the same as the offline cassettes.
This presented Toybox with a challenge. How could we simultaneously color correct and transfer their materials in any one of the HDTV formats and provide them with the usual complement of vertical interval editing codes on a standard-definition offline videocassette? Additionally there had to be a solid lock between the EDL our clients returned to us and the codes on the Master HDTV, to provide for the possibility of searching for scenes on the original film should re-transfers be required. There might also be a requirement to cut the negative and create a new finished film using laser recorder technology.
Searching for a solution led me to Evertz Microsystems. The Evertz HD9025TR, HD9150 and KeyLog Tracker conversion package promised to maintain all the traditional codes within an HDTV pipeline.
Toybox also wanted to have the film numbers recorded in the correction list of our color corrector to enable us to search the film via the edgecode using the transport controls of our color corrector in case there was a need to re-transfer scenes from the original film. To this end, Evertz produced code that would pass the relevant information through an auxiliary communication port on the tracking computer for input to our Pandora color corrector.
So how is this information gathered, transmitted, stored and displayed? The HD9025TR can be thought of as a code formatter rather than simply as a timecode generator for multiple frame rates. All configuring on the HD9025TR encoder must be done via the companion Keylog Tracker software system.
Upgrading an SDTV suite that already has a 5500 Film Decoder requires an upgrade to a 5550. The film decoder converts the number information from the edge of the film into a serial datastream and transmits this to the encoder via RS-232, where it is combined with audio source timecode (30fps) if sync sound is desired. From the telecine the encoder receives bi-phase clock pulses and frame ID pulses that inform it of the position and cadence of the film during the transfer to tape. This information, and the generated master timecode, is then encoded into a bitstream and inserted into the Vertical Ancillary Data Area (VANC) of the HDTV bitstream. The resulting HDTV SDI bitstream is then recorded onto the original transfer tape. Simultaneously, the transfer materials, codes and comments are logged on the tracking computer and then saved on removable media for export to other systems.
Another piece of equipment in an HDTV setup is the HD9150, an HDTV-to-SDTV converter with character keying capabilities as well as a VANC data reader. (It is worth noting the SDTV output of the HD9150 was not designed nor intended for broadcast. Its primary function is monitoring and the making of offline cassettes.) The converter has two SDTV output formats, analog and 601. Because the converter can read the metadata generated by the HD9025TR, all codes recorded in the VANC of the master HDTV deck are maintained in the downconversion. This is no mean task when converting between 24psf HD masters and 30i SDTV offline cassette. Consider what must be done. Obviously the SDTV will require the insertion of a 3:2 cadence because we are going from 24fps to 30fps. The cadence must be predictable and replicable. The timecode on the original transfer tape is also turning over at 24fps, so the downconverter must generate 30fps timecode.
The system has provided us with a solution for our episode clients, although we had to work out a few bugs as our units were early release versions. One was in the communications modules of the tracker computer, which intermittently and erroneously displayed communications errors during the configuration procedure of the HD9025TR. Another caused an internal buffer in the encoder to overflow, resulting in an interruption of the VANC metadata. Both were quickly isolated and resolved. Also, the HD9150 had a color-space conversion problem that resulted in standard-definition conversions of a green hue. Evertz has solved this problem as well.
For more information on the Evertz HD9025TR, HD9150 and KeyLog Tracker, circle (452) on Free Info Card.
Bill Varley is chief engineer at the Toronto Toybox division of The Command Post & Transfer Corp.
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