syncing DA 88s and HD tapes

[eastwestaudio]

forgive me if this has been discussed - i've tried searching thru older posts, and didn't come across anything...

when dealing with an HD project for TV with a time code rate of 23.976, how should one make a da 88 to properly be sync-able to a hdcam tape?

one method i've heard is to playback PT and lock the da88 deck at 24fps. therefore, if a future user needed to sync up that da 88 tape to the hdcam master, they can just select a .1% speed difference on the da 88 deck and the two tapes (time codes) should play in sync.

this seems to make sense to me - i just wanted to hear from a second source that this would work. is this a good method? is this a standard at all?

(the fact is, in the delivery requirements from the network, they don't specify a time code rate for the da 88)

thanks

-greg-

[Richard Fairbanks]

Even though that will work if you are using analog audio in/out, the DA88 deck will be running at 47.952kHz, requiring sample rate conversion to transfer digitally. I would try to clarify the specs before assuming that option!

(For those who don't understand the problem, DA88 decks don't know what 23.976 timecode is. Their hardware is designed to lock at 24fps only. They don't take tri-level sync either, so for HD work they must be locked to timecode or wordclock...which should be 48kHz. Forcing them to lock to 24 frame code running at 23.976 also forces them to run their hardware innards slower, throwing the sample rate down to 47.952kHz. So, the choice is to run them at the correct sample rate, which prevents simple timecode chase-lock at 23.976, or run them off speed, which requires digital sample rate conversion. Personally, I think it is better to run the decks at the correct sample rate. Anyone who works with a standard def downconversion, such as foreign language distributors for the next several years, can take a DA88 tape, set the deck for 29.97 code, and lock up. They could NOT do that if the DA88 tape is meant to be played .1% slow. In short, the network should clarify their spec.)

[Matt Chan]

we used the downconvert from an F500 deck to sync up 29.97 pro tools sessions to 23.98 hdcam tapes for screenings. could the same method not be used for a da88? we would take the downconvert vitc (29.97) from the composite output of the f500 into our sync io, send ltc (29.97) from the sync io to the da88, and genlock to the composite video signal at the same time.

[minister]

hey, that's clever Matt!

[Richard Fairbanks]

Sure! That does the trick. I'm pretty sure a Soundmaster could do it also. One way or another, if you want the DA88 to run correctly with 48kHz sample rate you have to convert 23.976 code count into 29.97 non-drop, with matching HH:MM:SS.

[Matt Chan]

yeah i can't remember who told us about it but it works like a charm.