Least worst drift in portable recorders?

[Mark Morreau]

I have a Zoom H4 (original version) which suffers badly from audio drift when used in conjunction with my video cameras, (Sony EX1s and Z5s), all of which keep perfect time with each other. Although I've calibrated the H4 against the cameras, and the drift is consistent, I'm getting pretty fed up with having to make this adjustment. I have a little spare cash at the moment so want to upgrade my audio recorder.
Most of my work is recording theatre shows, so I'm looking for something which will keep the best possible time with the cameras over an hour or more's recording.
These are the ones I'm considering:
Roland R-26
Olympus LS-100
Marantz PMD661
Tascam DR-40
Tascam DR-100Mk2

I realise I can't expect any of these to keep perfect time, but does anyone have any real-world experience of any of these keeping time with cameras over an hour's recording, and can tell me whether they'd recommend their recorder, or not?

Thanks

Mark

[Rick Reineke]

The tolerances of the clocks in the cheap and cameras can vary from one machine to the next, even devices of the same model. So none with keep perfect sync over an extended period of time, nor will the cameras.
You need to 'Genlock' the cameras and wordclock the recorders, preferably with a Tri-level sync system. Timecode alone will not lock a system together either.
The cheapest solution is to recalibrate sync on the timeline (in post) every ten-or-so minutes, or when out-of-sync becomes noticeable.

[Mark Morreau]

Yes, Rick, I hear what you're saying. Genlocking cameras together is not an affordable option in my situation. And since the four cameras themselves do keep perfect - and I mean perfect - time together that's not the issue.
What I'm asking for is about people's real world experience of the above recorders so I can get an idea of which is the least worst option.

Cheers

Mark

[Noa Put]

There has been a discussion about this in this forum (I couldn't find the topic back) but there the experienced audio guru's said that "cheaper" audio recorders just can't keep sync over longer periods of time.

My knowledge in audio is much more limited but I can only speak from my experience, my zoom h4 also had a bad drift in synch which I had to correct in audacity, quite easy to do but something I rather not spend time on.

But I have a Tascam dr40, a zoom h1, a Yamaha c24 and a Iriver that do keep sync on 1 hour recordings with my videocamera's. I"m not saying it's identical up to the microsecond but if I sync them all up at the beginning I cannot "hear" any audio drift after an hour so for me it works. I think that luck is an important factor :)

[Richard Crowley]

You don't mention over what time PERIOD you are seeing problems. You also don't mention WHY you think a separate audio recorder is desirable for your (undisclosed) application. Since we are shooting in the dark, it is possible that we will miss your invisible target.

Lack of sync in shots over ~10 minutes is NORMAL for low-mid end pro-sumer and low-end "pro" equipment. The fact that your cameras keep perfect sync is UNUSUAL and you should consider yourself fortunate. If they are that consistent, consider simply using one of your cameras as the primary audio recording machine. The audio system in those cameras is at least the equivalent performance of those recorders on your shopping list. If you have a good preamp/mixer feeding the camera(s) you should get equivalent performance to using one of those digital recorders.

[Seth Bloombaum]

If memory serves (I don't have one), the Tascam HD-P2 will clock to an external composite video source. Meaning, if you connect the SD composite output, or possibly HD Analog Green+Sync via a BNC cable to the deck, its clock will lock and stay locked as long as its connected.

This has nothing to do with timecode, it synchronizes its samples to the external video clock, which seems to me to be an elegant solution for long rolls.

Other decks do this trick?

[Noa Put]

Lack of sync in shots over ~10 minutes is NORMAL for low-mid end pro-sumer and low-end "pro" equipment. The fact that your cameras keep perfect sync is UNUSUAL and you should consider yourself fortunate.

I know that perfect sync is impossible on these small recorders but would you say that in a 50 minute continuous recording a drift of 1 frame is also unusual because that's what I"m getting on most of my recorders, I did a test with my Sony cx730 and my audio recorders (that all recorded in the mp3 format), made a clapping sound at the beginning and end.

I checked in Edius and there you only can zoom in on frame level but this is what I can see after 50 minutes of recording:
Iriver: 1 frame out of sync
Yamaha c24: about 75% of one frame out of sync
Zoom h1: 1 frame out of sync
Yamaha dr40: 9,5 frames out of sync

To my surprise my brandnew dr40 was most out of sync, wonder if recording a wav file (instead of a mp3) would make any difference, will test this as well in a few days)
You can see the names of each recorder on the left side (it says wav behind each recorders name but that was because I had converted to a wav file a s well to see if that made a difference but it was the same) The top wave file is from my Sony cx730.

[Noa Put]

I just used audacity to see how many milliseconds it was because there I could see more in detail:

After 49min45sec recording out of sync

Iriver: 28 milliseconds
Tascam dr40: 199 milliseconds
Yamaha c24: 19 milliseconds
Zoom h1: 25 milliseconds

Not bad for the cheap recorders, it also explains why I never heared anything out of sync as my recordings are typically about an hour, the Tascam however is new because my old zoom h4 was becoming unreliable so there I need to adjust using audacity.

[Steve House]

Generally the maximum misalignment tolerances for a clip to be considered to be in proper sync are: 0.00 frames audio leads video (audio file faster/shorter than video file), 0.25 frames audio trails video (audio file slower/longer than video file).

Noa, I want you to pick 7 numbers between 01 and 49 - I'm going to buy some Lotto tickets this week and you must be the luckiest fellow on the planet!

[Richard Crowley]

Originally Posted by Noa Put

... would you say that in a 50 minute continuous recording a drift of 1 frame is also unusual because that's what I"m getting on most of my recorders,.

Yes, I would say that is HIGHLY unusual. It is much more common for a 50 minute shot to be out of sync by several SECONDS. Your unusual fortune has given you a very unrealistic expectation for that grade of equipment.

I'm with Mr. House. Buy a lottery ticket and you can buy full genlock/timecode equipment with the millions of €€€ you will win.

[Pete Bauer]

Richard and Steve, I don't think several seconds worth of drift within an hour is either usual or acceptable. Something's wrong there.

The amount of drift that Noa is describing is more what I'd expect with devices that are freewheeling (not continuously jamming or gen locked). I recently bought a Tascam HD-P2 for the TC jamming capability, to replace a little M-Audio MicroTrack II, so I tested it's TC accuracy against my three XF105's.

With pull-down OFF, the Tascam was 2.50 frames/hr too fast compared to the XFs, whereas setting pull-down to "29.97 Down" it was only 1.58 frames/hr too fast (38 min/frame). That was the closest match I could get. I never tested the MicroTrack, but from having used it many times in dual recording with those same cameras, I'm sure it isn't more than a frame or two slow per hour.

I believe that most of these less expensive audio devices use crystals that are similar to those that go into digital wristwatches. Not dead-on, but the drift is generally a second or so a day.

Interestingly, though, two of the three XFs were dead-on at 24 hours and the third was approximately a half-frame fast. I was surprised enough at that accuracy that I let the whole setup run another 24 hours. The Two XFs were still frame-accurate and the third was a mere 1 frame fast. I was quite amazed. Don't know if that is lottery-lucky or if they really put more expensive and accurate timing systems in the XFs. Maybe the latter; Sound Devices are on the much pricier end of field audio gear and claim drift of just 0.2 part per million, which translates to about 0.5 frames in a day. So near-zero drift CAN be done...for a price.

BTW, I am having some recording issues with my Tascam, so if I can figure out what's going on, I'll post separately on that at a later time.

[Richard Crowley]

I don't think it is acceptable, either. But I don't see that it is unusual. Consider that even high-end professional equipment uses internal quartz crystal oscillators for clocks which cost maybe 1-2 euro/dollar/pound, at most. These mass-production devices have pretty good accuracy (especially compared to older mechanical gear), but nobody expects that any two pieces of gear can maintain decent sync for a whole hour without some sort of interconnection to synchronize the clocks.

People who are getting extraordinarily good sync from non-locked equipment should consider themselves fortunate, but others should not expect that kind of performance from any two random pieces of gear, especially gear from different manufacturers.

IMHO, it is not valid to compare the clocks in A/V equipment to the oscillators used in timepieces (such as wristwatches). Note that the clock frequency is several orders of magnitude lower, and furthermore, they are individually tweaked on the assembly line to provide the kind of accuracy expected from timepieces. The clocks in electronic equipment (including camcorders and digital audio recorders, etc) are typically not adjustable.

[Seth Bloombaum]

Pete B., see my post #6 above. Have you continuously clocked your HD-P2 to the composite/sync output of your camcorder, does it lock like it seems it should? I expect this would be a good method for tethered operation, is it?

[Steve House]

Originally Posted by Richard Crowley

...

IMHO, it is not valid to compare the clocks in A/V equipment to the oscillators used in timepieces (such as wristwatches). Note that the clock frequency is several orders of magnitude lower, and furthermore, they are individually tweaked on the assembly line to provide the kind of accuracy expected from timepieces. The clocks in electronic equipment (including camcorders and digital audio recorders, etc) are typically not adjustable.

Maintaining a constant temp is part of the way long-term accuracy is achieved and wristwatches are worn in contact with a very stable temperature regulator, the human body.

[Pete Bauer]

Originally Posted by Seth Bloombaum

Pete B., see my post #6 above. Have you continuously clocked your HD-P2 to the composite/sync output of your camcorder, does it lock like it seems it should? I expect this would be a good method for tethered operation, is it?

In the type of multi-cam event shooting that I've been doing recently, it is not practical to stay tethered. I jam LTC and then untether. That requires a male BNC to male XLR cable (probably hard to find locally but easily had from B&H or other big e-tail sponsors for $10-20 depending on brand and length) to send out the LTC from the camera to the Tascam.