A lively meeting was held on Thursday 6th January at Twickenham Film Studios. The topic under discussion was digital-to-analogue sound transfer and its attendant problems. The consensus was that the committee should concentrate on defining a line-up standard for digital (in particular DAT) to analogue transfer. Problem areas were defined as follows:
Click on the picture for full size image.
The general feeling was that to keep matters simple, what was required was a line-up procedure that could be related to standard Nagra line-up, a level which has been around for many years and everyone seems to understand. A line-up standard of -18 (digital metering) has been adopted by the European Broadcasting Union and this is as good a starting point as any. It is, however, worth noting that across the Atlantic, the SMPTE has adopted a line-up standard of -20. Provided that floor mixers/sound recordists regard this -18 line-up in the same way as the Nagra -8 line-up that we all know and love, and modulate the track accordingly and providing the transfer bay then re-records this track in a similar way to a Nagra transfer, all should be well. However it is apparent from a graph produced at the meeting (see above) that the -18 digital line-up tone (on a Fostex DAT machine anyway) is 4 dB higher than the standard Nagra line-up tone. This would seems to suggest that an accurately modulated DAT track would have to be lowered by 4 dB relative to Nagra Line-up in the transfer bay to achieve a nicely modded lump of mag. A complication arises here in that flux density relative to output level differs from studio to studio - peak recording levels are therefore bound to be different. In other words a re-recording made in one studio may, in absolute terms, playback higher or lower in another studios. Worse, a track successfully transferred in one studio at a given level may end up as an under or over modulated track if transferred elsewhere.
The decision was taken to do a bit of consumer research amongst prominent sound post production facilities including Pinewood, Twickenham, Delta, De Lane Lea, Cine Lingual, Magmasters, Anvil, Video London, Interact, Mobitrack, BBC, Granada, Central, Yorkshire and Meridian. A questionnaire listing queries on peak flux level, Dolby level, type of metering used, Nagra line-up relative to that meter, DAT line-up relative to that meter, is to be devised and sent, along with a DAT tape and a 1/4 inch tape to the above facilities with the request that the DAT and the 1/4 inch be transferred to 16mm centre track and 35 mm track 1 at 25 fps with no Dolby as if the said DAT and 1/4 inch were actual rushes. The results would, of course, be kept confidential and plotted on a graph. The decision was taken to ask Gerry Humphreys to 'acquire' some sample DATs from a friendly manufacturer, and that Rob James should 'front' the letter to the various heads of sound. As yet no date has been set for a further meeting of the committee.