Tape sync questions

[RoadrunnerOZ]

UK, Europe Australia and New Zealand all used PAL - the amazing thing is that then the images seemed clear and defined but by today’s standards they are blurry. 26” was considered massive screen size - 17”, 19” and 21” were the common sizes yet we watched them from the other side of the room - maybe being so small they didn’t appear so blurry

 

[Walrus]

A bit of history from my days at Sony Music London studios, we were having trouble getting
the assistants to stripe tape correctly, so the then tech manager (an ex video tech) wrote this.

 

[EmilFrid]

24 fps Film (F)
This frame count is the traditional count for film. It is also used for HD video formats and commonly referred to as “24 p”. However, with HD video, the actual frame rate or speed of the video sync reference is slower, 23.976 frames per second, so timecode does not reflect the actual realtime on the clock for 24p HD video.

25 fps PAL (P)
This is the broadcast video standard frame count for European (and other PAL countries) television broadcast.

30 fps non-drop SMPTE (N)
This is the frame count of NTSC broadcast video. However, the actual frame rate or speed of the video format runs at 29.97 fps. This timecode clock does not run in realtime. It is slightly slower by 0.1 %.

30  fps drop-frame SMPTE (D)
The 30 fps drop-frame count is an adaptation that allows a timecode display running at 29.97 fps to actually show the clock-on-the-wall-time of the timeline by “dropping” or skipping specific frame numbers in order to “catch the clock up” to realtime.

In simple terms the easiest way to avoid confusion and clock disparities is to use 25fps.

There should be no issue whether you slave tape to digital or digital to tape. But - the problem with slaving tape to digital is the sync-up takes longer as the tape sourced SMPTE has to be read off tape, analysed and mated to the incoming SMPTE signal from the digital source - this is done by the synchroniser which then issues servo corrections to put the tape in the right place. If the tape is in a completely different location to the DAW it has to fast forward or rewind and then chase to lock.
Digital slaving is way quicker as the tape derived SMPTE code is read by the digital slave and within a couple of frames it’s locked - no matter where the tape is, as the digital slave jumps instantly to the new SMPTE code location - it doesn’t have to wind tape.
I used this system for years without hiccups with two synched Studers, a Sony digital recorder and MIDI and audio on computer - sync source tape machine 1, track 24.

Initially, black and white video ran at 30 fps. When color video was introduced, the frame rate slowed to 29.97 fps to allow color television to run on black-and-white receivers.
Because originally television was only live and not recorded, the only way to ensure sync between studio cameras and home TV sets was to sync the signal to electrical mains. Mains were 60Hz (30fps) in the US and 50Hz (25fps) in Europe. But television was originally in black and white, so when color came along, SMPTE engineers wanted to keep the color signal backward compatible with black and white TVs. The color video signal had a tiny additional color burst signal between the existing black and white signals and so they slightly altered the frame rate from 30fps to 30/1.001 = 29.970 fps to avoid artifacts, thereby creating the NTSC color standard.

Thank you very much. You're a well of knowledge. Inspired by this thread, I went to the studio today and had Reaper read SMPTE directly instead of having it first translated into MIDI (I thought Reaper could only read MIDI) and after a few tries with settings it worked flawlessly and kept working flawlessly. Not a single hiccup. Maybe I won't have to find ways to slave the tape machine at all.

 

[RoadrunnerOZ]

Cool. I was brought up in the days of tape - the first studio I worked in we had an MCI JH24 24 track and an MCI JH500 desk with automation. SMPTE was recorded to track 24 for the auto-lock locator and desk automation was recorded to tracks 22 & 23 - this was only used at mixdown so these tracks were used up until then and made available by bouncing down tracks into stereo sub-mixes like drums, backing vocals strings etc. to leave room for multiple vocal and guitar takes or overdubs and the automation. The automation controlled the VCA faders in the desk and with each update pass the automation was bounced to an alternate track - sequence was like 23>22>23>22>23… each bounce delayed the signal by 1.2msec.
MCl's QUIOR (QUiet Initiation Of Record) circuitry eliminated punch-in and punch-out noise. These delay and ramp circuits controlled the timing of the erase and bias signals to prevent clicks and pops from being recorded onto the tape when switching into or out of record mode. Editing was done with a razor blade and a splicing block - then you had to restripe SMPTE and set a new zero start point with SMPTE offset. No copy and paste in those days.

 

[EmilFrid]

Cool. I was brought up in the days of tape - the first studio I worked in we had an MCI JH24 24 track and an MCI JH500 desk with automation. SMPTE was recorded to track 24 for the auto-lock locator and desk automation was recorded to tracks 22 & 23 - this was only used at mixdown so these tracks were used up until then and made available by bouncing down tracks into stereo sub-mixes like drums, backing vocals strings etc. to leave room for multiple vocal and guitar takes or overdubs and the automation. The automation controlled the VCA faders in the desk and with each update pass the automation was bounced to an alternate track - sequence was like 23>22>23>22>23… each bounce delayed the signal by 1.2msec.
MCl's QUIOR (QUiet Initiation Of Record) circuitry eliminated punch-in and punch-out noise. These delay and ramp circuits controlled the timing of the erase and bias signals to prevent clicks and pops from being recorded onto the tape when switching into or out of record mode. Editing was done with a razor blade and a splicing block - then you had to restripe SMPTE and set a new zero start point with SMPTE offset. No copy and paste in those days.

Very nice. Since we work solely analog (not counting digital synths and drum machines for which we need this SMPTE), I've too had to learn the art of splicing. It was very scary the first time, but you pick up all the good habits pretty quickly. I'm "only" 29 and never had that "automatic" exposure like the ones working in the 60's to 90's had, so it takes a bit of dedication. QUIOR sounds cool. IIRC a bunch of machines utilized different circuitry to combat punch noise. Perhaps MCI were first.

 

[Tubetec]

Theres an adjustment on the Studer C37 that controls the delay before the pinch roller hits the capstan after the take up reel spins up , if its mal adjusted the capstan throws out a loop of tape that the reel motor takes up with a juddering motion , it stretches the tape , which will upset timecode recorded onto it.
Ive seen it happen with other machines too .

Capstan slippage with direct drive is another thing that can hamper T/C lock as the tape effectively bounces off the heads
The MTR-90 could do this if the capstan became caked with tape residue .

As far as I remember the Studer pinch adjustment is done by eye , not instruments , to you visually inspect the tape path the moment it engages and make the adjustment for minimum tape bounce .

 

[EmilFrid]

But to get back more on topic I'd like to be of help to anyone trying to sync in the future:

1. Stripe an edge track using the free software SMPTE Tool using the same sample rate and block size as you're running Reaper. Regarding fps i used 24 this time.. The built-in timecode generator in Reaper does not work as well as the SMPTE Tool one for some reason, so do not use it.

2. Right click the play button in Reaper and turn on synchronization mode. Choose the source as "LTC: [the input of your soundcard receiving SMPTE from tape]" and the same frame rate as the one you just printed on the tape.

3. Hit play on your tape machine. Reaper should start running in playback mode now. If it's jittery or drop outy, play around with the settings in the menu that pops up when you right click play button.

4. Have fun!

I think I used 48kHz with block size 500-something during my very satisfying experiment. Reaper handles it great.

 

[Walrus]

RoadrunnerOZ, how strange! When I first started in the studio it was called CBS studios, and we had a JH400, JH500 and MCI JH24 tape machines plus a number of MCI JH110 1/2 & 1/4 2 tracks.
Our engineers got tired of only having only 21 tracks to use, so we had to connect up a Studer A810 (It had a dedicated centre timecode track and electronics) 2 track to use for bouncing the desk automation to.
This was locked to the JH24 using a Audio Kinetic Q-Lock 3.10 synchroniser. Oh the fun we had getting it to work ……

 

[RoadrunnerOZ]

The desk and tape machine made the studio (Richmond Recorders) the first fully automated (as far as automation went in those days) studio in the Southern Hemisphere at the time, closely followed by another Melbourne studio - Armstrongs (although they bought their console and tape machine first, ours was up and running before theirs). We built the place in 1977 - fully open in 1978. All the room to room wiring was done by me with individual cables - no multicore - measured, strung out on sawhorses in the car park and cable-tied together.

 

[RoadrunnerOZ]

RoadrunnerOZ, how strange! When I first started in the studio it was called CBS studios, and we had a JH400, JH500 and MCI JH24 tape machines plus a number of MCI JH110 1/2 & 1/4 2 tracks.
Our engineers got tired of only having only 21 tracks to use, so we had to connect up a Studer A810 (It had a dedicated centre timecode track and electronics) 2 track to use for bouncing the desk automation to.
This was locked to the JH24 using an Audio Kinetic Q-Lock 3.10 synchroniser. Oh the fun we had getting it to work ……

The Q-Lock had machine specific cards and separate controller and control box with the cards mounted inside if I recall. Never had the opportunity to use the Q-Lock.
I modified a Tascam ES50/51 synchroniser to work two Studer A820 tape machines. This had its own SMPTE TC generator to stripe to tape. The lockup was incredibly quick as they had the ability to set chase, lock and braking parameters for the slave as well as tune the master machine locate functions - this was great to be able to sync machines with the same or different reel sizes - the big 14” reels were much heavier so we needed different presets for different combinations like small+small, small+large,
large+small, large+large - we used two different reel sizes. I set them up fine tuned so the two machines would land, start and sync locking in less than a second (or two with the big reels) so we only needed to set a couple of seconds preroll.

 

[Walrus]

Yes, The Q-Lock used machine specific EPROMS, but we only had 2 cards to start with, so we changed the EPROMS when we used a different machine.
The 3.10 was a horrible device, I think it used serial processing so you put the cards in the order of priority. It could sometimes take an hour to get it going!
The later 4.10 used parallel processing (I think, it was a long time ago!), and worked much better. We then changed to Lynxs and never looked back.

 

[Gold]

I think it was said earlier in the thread but it is generally preferable to have the tape machine chase the DAW and not the other way around. The reason is that the DAW has to do real time sample rate conversion to alter the speed as it chases. SRC these days is much better than it used to be but this operation is not easy for SRC. There is no degradation when dynamically changing the speed of the tape machine.

 

[RoadrunnerOZ]

Yeah - some DAWs are better equipped for this than others - varispeed capable DAWs should chase fine. A lot of them were designed around videotape lock and so this is an inherent part of the architecture but with the advent of digital video with stable frame rates some DAWs may have problems.

 

[pvision]

SMPTE is interesting stuff. I discovered that when you turn the tape over, to record backwards echo, if you repatched the SMPTE from 24 to 1, the SMPTE reader worked perfectly, but obviously counted backwards. So - obviously - each SMPTE frame contains hours, minutes, seconds & frames

Also, when editing multitracks, it doesn't worry SMPTE at all. It reads OK, it just jumps

I used to use an SRC 2 to sync a DAW to tape (Voyetra Sequencer Plus on a Compaq Portable) and it would maintain sync even over an edit, so I suspected the sync pulse was derived from frame edges rather than values. Thinking back this was syncing new production to existing tape, so I didn't edit tape after sequencing

Lots of this will mean nothing to post-tape people, I realise! But so much recording was done with synced machines, and with SMPTE readers like the SRC and SBX-80, it was everyday stuff and it worked very well

 

[aurt]

The ideal way to lock the DAW and an analog machine together, or at least the only absolutely rock solid way I've ever seen, involves resolving both machines to video black burst, so the timing reference is the same, and the code is for position. This allows each machine to have the same reference for how long a frame is, and never worry about jumping a frame in the middle of things. I've had sessions running three rooms, each with two 2" decks, a DASH machine, and at least one Pro Tools rig locked and transferring for months, and the only problem I encountered was when some idiot (me) mounted the black burst box in the same rack as the Fairchild. Somewhat outside of its temperature spec.

My process from back in the day:

Stripe time code (29.97 to be able to lock to video. I suppose you'd have 25 frame black burst gens across the pond) on the analog machine using the internal speed reference, and synchronizer disabled. Then enable the sync box (I used Adams Smith Zetas or MicroLynxes mostly), external speed ref, and set it to resolve the code to the video reference. On playback, now the analog deck will hit the start of each frame in a very predictable way. Otherwise, the little variations of the deck can confuse the DAW, which is expecting X number of samples per frame, and if it doesn't get them can just jump a frame here and there to keep up. You then need the proper hardware for the DAW to receive video ref, and set the timing reference to use that, and use SMPTE for positional reference. Now everyone is on the same page, and will merrily chase for as long as you have tape, or video.

I can't imagine synchronizers costing much these days. A Microlynx with the AGC card would, I think, translate video ref to wordclock to let you resolve the DAW, as I don't know if there's a hardware piece akin to a Sync I/O for Reaper. You might even be able to do with Reaper what Pro Tools used to be able to do, and have the MicroLynx see and drive the DAW as the TC gen. It's nice to be able to have everything locked with one box. The remote even has transport control for whichever is master.

Checking sync, you can bounce a track over to the DAW, a drum overhead say, then, while chasing, bring the two versions up on the desk with one flipped in phase. You should hear low level, and very thin sound, generally swishing around a bit.

 

[RoadrunnerOZ]

Never had issues using 25fps - drop frame causes sync issues however.
With using a DAW if you do cut and splice edits on tape you have to restripe the SMPT back to tape as you can’t set multiple offset points in most DAWs except for a global offset which is what you use for the restripe.

SMPTE is interesting stuff. I discovered that when you turn the tape over, to record backwards echo, if you repatched the SMPTE from 24 to 1, the SMPTE reader worked perfectly, but obviously counted backwards. So - obviously - each SMPTE frame contains hours, minutes, seconds & frames

I think somehow the synchronisers for tape machines are able to read code both ways to allow for rewind read on slowdown to chase. The synchroniser controls everything including the tape lifters - it crosses into code read mode when the servo motor read gets close to target position IIRC.

Also, when editing multitracks, it doesn't worry SMPTE at all. It reads OK, it just jumps

Yeah but the jump is what you don’t want in a DAW or you’re in a world of hurt.
Essentially the code is a string of pulses or bits, containing information pertaining to the hour, minute, second and frame, the type of time code (nondrop or drop frame) etc. So it refers to an absolute position for each LTC block of data - hr/min/sec/frame. Offsets can also allow for subframe as well in some software.

 

[porkyc]

Yes, The Q-Lock used machine specific EPROMS, but we only had 2 cards to start with, so we changed the EPROMS when we used a different machine.
The 3.10 was a horrible device, I think it used serial processing so you put the cards in the order of priority. It could sometimes take an hour to get it going!
The later 4.10 used parallel processing (I think, it was a long time ago!), and worked much better. We then changed to Lynxs and never looked back.

I worked at Whitfield St as well.
I never saw a AK310 work ever at any studio I went to.
For me, best synchroniser.....Lynx Timeline. Had the best chase routines.
Redbus we used BTX, but I fitted both Adams-Smith and Fostex 4030 units successfully to JH24s
PC

 

[aurt]

Never had issues using 25fps - drop frame causes sync issues however.

Wouldn’t expect SMPTE to be the choice anywhere but the US.
Wouldn’t expect drop frame to be the choice anywhere but NTSC countries.

I worked at Whitfield St as well.
I never saw a AK310 work ever at any studio I went to.
For me, best synchroniser.....Lynx Timeline. Had the best chase routines.
Redbus we used BTX, but I fitted both Adams-Smith and Fostex 4030 units successfully to JH24s
PC

I worked at one place that had recently retired their Q-Locks, thank goodness, and heard the stories. The AS Zetas worked well for me. You could get in and adjust the constants to make individual machines behave better. Of course, that means you have to get in and adjust the constants. I got to be a big fan of the MicroLynx.

 

[guy_4]

Hello EmilFrid,

To get a 100% reliable synchronization system, there is only one word : RESOLVE.

That's what " aurt " is saying in his previous post, and he clearly explains the process.

ALL machines ( whether tape recorder, video player, DAW, TC generator ) must have their clock / capstan / slaved and locked to a common reference for SPEED, often a Black Burst Sync pulse generator.

When you'll press "PLAY " on the keyboard of your MicroLynx :
1/ the Tascam will start playing at nominal speed, and its Capstan Speed will be controlled continuously by the REF speed,
2/ TC from the Tascam tape track will be read by the MicroLync and it will give the Address where the DAW must go. Also a fresh TC from the Lynx TC generator ( in Jam Sync mode) will be sent to the DAW, and the WC from the AGC card will phase lock your DAW to the REF.

Then both your Tascam and your DAW will play in a perfectly stable and reliable way...every time !

Many moons ago TimeLine had published a booklet titled " SMPTE made simple " .
I heavily suggest you to find a copy, it explains a lot on synchronisation systems.

Good luck !

Best,
Guy

 

[RoadrunnerOZ]

Wouldn’t expect SMPTE to be the choice anywhere but the US.

SMPTE was the standard tool for most recording studios - MTC (MIDI Time Code) was a secondary choice but had its problems and you couldn’t put it directly on tape. There was a small lag in the SMPTE to MTC conversion in some synchronisers and also present in the MIDI transmission/reception circuitry - small but there. Also you couldn’t run really long distance with MIDI or you’d get dropouts.