The No.1 Website for Pro Audio
Syncing samplitude to LTC>MTC
Old 16th November 2009
  #1
Gear Head
 

Syncing samplitude to LTC>MTC

If anyone could offer any insight to this problem it would be most appreciated.

I recently recorded a concert that was filmed and I recorded the audio separately in multitrack to my pc rig running samplitude with a rme hd9652 sound card and behringer ada800 converters. I was using an old midiman biport to convert the LTC I was receving from the dv deck that was recording the switched video to MTC.

Problem is, after mixing the audio i imported it back to final cut to line it up with the video to find that it had drifted massively over the duration of the hour of the video. Figuring that the internal bounce must have used a different clock I tried again to export the mix but this time slaving samplitude's playback back to the dv tape and recording the output live to my tascam portable recorder via spdif hoping samplitude would sync correctly.

On reimporting the mix i found again that it drifts wildly this time correlating to 90 seconds worth of drift over the duration of the hour recording (the audio finishes 90 seconds before the video does).

As far as I know i've set it up correctly. The sync setup in samp isn't very complicated, 25fps and mtc input is pretty much it. Both tape and multitrack are recorded at 48khz. Samplitude is showing the same timecode input as is being displayed on the tape but isn't really locking to it. Samplitude does take a couple of minutes to start playing once i've hit play on the dv deck but eventually samplitude does start.

Any response appreciated.

cheers
simon
Old 16th November 2009
  #2
Lives for gear
 
Geert van den Berg's Avatar
 

That kind of drift is very weird once I have tried running a recorder seperate with a consumer DV cam and even after an hour the drift is only a couple of milliseconds... nothing that actually caused it to look out of sync. The internal crystals are quite steady.

Maybe it wasn't such a good idea to sync Samplitude to the camera.
Old 16th November 2009
  #3
Lives for gear
 
minister's Avatar
LTC-->MTC will only give you POSITIONAL information. You needed a common clock to govern SPEED, like PAL BLACK on both systems.

If you assuredly have PAL BB in the studio and have double-checked it and it still is out, try digitizing the audio from the DV and sync it by hand.
Old 16th November 2009
  #4
Gear Head
 

ok, thanks for that. I wasn't sure if MTC was just positional or not. I didn't thinks it was since from my understanding it is the midi version of smpte;

MTC stands for MIDI Time Code. Its a series midi messages that tells other devices what time it is at any given moment in hours, minutes, seconds and frames. MTC is simply understood as a conversion of SMPTE timecode that goes down a MIDI cable. It is sent in quarter frame intervals as MIDI system exclusive data.

We've been stretching the mixed track in final cut and have got it to the point where it's 4 frames out at the start and 1 at the end so it is variable drift. It's a bit disturbing that the recording was so sped up, the tape analogy would be like having the recorder on varispeed. I'm not sure why this happened, i can't remember if i set the rme on master or autosync, probably the later since I would have thought the sync info was coming from the mtc hence my pc should have been the slave. Probably should have left the pc as master then.. will have to retest all this.
Old 18th November 2009
  #5
Gear Head
 

Just for future ref. if anyone in the future ends up searching this thread. I realise now that you need both MTC and Word Clock to sync the audio and video. A friend is lending me a Rosendahl Wif hopefully that will sort things out.
Old 18th November 2009
  #6
Lives for gear
 
Geert van den Berg's Avatar
 

That is what Minister already said, though it's not specifically wordclock that you need, what you need is Video sync (PAL black), which is just a pulse, all the machine need to run from in order for them to not drift. The Rosendahl will work, but you should have used that while recording, it probably won't solve your problem now.

What camera did you use? Does your camera have options to sync to external equipment? Most consumer camera's cannot sync to anything. But like I said earlier, if you make short runs, actually I tried up to an hour, with most modern stuff, if you have marked a start with a clapper they'll run quite in sync for a while if you run them free of videosync. If you can sync it to other equipment, using the Rosendahl is a good solution.
Old 18th November 2009
  #7
Gear Head
 

Thanks Geert, yes I realise that's what Minister was referring to. The reason I specified word clock is that it is the only clock or sync reference available on my audio card the rme9652.

The concert was a 5 camera scenario and it was switched live to a Sony DSR-45p (Pal-DV
). The cameras themselves where a combination of Sony 570 and 300's.

So the rosendahl is worth a try. I'm hoping i can get the computer to slave to the speed of the playback from the DSR-45p. Otherwise it will be manual adjustment.
Old 18th November 2009
  #8
Gear Head
 

Just to clarify. Is Video Sync or Pal Black equivalent to the term black and burst?
Old 19th November 2009
  #9
Lives for gear
 

Quote:
Originally Posted by url View Post
Just to clarify. Is Video Sync or Pal Black equivalent to the term black and burst?
Video Sync, REF, Blackburst all refer to the same thing.
📝 Reply
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
🖨️ Show Printable Version
✉️ Email this Page
🔍 Search thread
🎙️ View mentioned gear