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

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.

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

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 :)

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.

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?

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.

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.

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!

... 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.

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.

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.

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?

...

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 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.

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

In another thread where something similar was discussed a few other weddingvideographers claimed the same as I do, which is normal because in our business we don't use very expensive external audio recorders but preferably small and cheaper ones. I could accept having 2 recorders that are so close as luck but not 3 (taken the tascam out of consideration), especially when other colleagues come to the same conclusion.

I believe you that "on paper" it is not possible but it appears that a larger percentage of these recorders can hold sync much better then you think.

Have you actually tested several recorders I use to be certain that I and other wedding videographers all have the possibility to win the lottery :)?

We shouldn't go too far afield from the original topic, but a couple quick replies to Richard's and Steve's comments.

Certainly, temperature extremes have some effect on crystal oscillation speed, but I'm doubtful that temperature differences between devices recording the same event explain the kind of differences we're talking about in this thread.

As far as the validity of comparing the oscillators in watches and clocks vs the oscilllators in low-cost AV gear, that's an open question...unless there is specific info available to share. It could be so, but I don't see why it would be, that inexpensive camcorders and portable audio recorders use very different crystals with orders of magnitude difference in frequencies.

The experience of many of us is that the device accuracy is in the same ballpark, and there would just be no incentive for manufacturers to use more expensive parts like a 10X or 100X more accurate oscillator. Whether a $200-300 audio recorder is sourced with the exact same crystal as clocks and watch manufacturers use, I don't know...and I doubt most of those manufacturers would care to state their parts list. I suspect the circuitry that counts and processes the crystal oscillations is the biggest variable at the low-cost end, and the oscillator itself is probably a commodity part. Anyway, if there is factual information about that, it would be interesting to discuss in a thread of its own.

For my part, I've done shoots when it was in the high 90'sF (upper 30'sC), humid, and sunny. And I've done similar shoots at night when it was jacket weather. I just don't detect any difference in relative accuracy amongst the cameras and audio recorders I use.

I entered this discussion simply to say that my experience of digital audio recorder accuracy has been about what Noa's has been. And we've both taken the bother to actually measure the relative accuracies of our devices. Personally, I'd be chucking any device in the recycle bin if it put my recordings off by any more than a couple frames an hour. But, I'm fussy about such things.

It's interesting to read the kind of differences in audio 'drift' other folk are encountering. Pretty much in line, it would seem, from what you might expect from the differences in commercial grade crystals. (Only the very cheapest 'dictaphone' style audio recorders are likely to use ceramic resonators, rather than crystals, and they are likely to be much worse!).

One thing that hasn't been specifically mentioned is the fact that it is the accuracy of the camera oscillator that is the governing factor.
Say you have an audio recorder that is absolutely spot on. If it's the camera that is slightly adrift, then you have to adjust your 'perfectly timed' audio recording to fit the camera audio . That's the one in sync with the video -- so has to be the master.
Even if it's the track that's slightly wrong!

So it's not absolute accuracy that is the critical factor, but the relative accuracy of the different pieces of kit.........

Now whether cameras do generally use higher quality crystals or not?.....if not, then those that find their kit 'in sync' are indeed lucky.

It could be that the camera is adrift, and you're just lucky your recorder is adrift in the same direction -- and by the same amount!

Not to poke a hole in the boat (since we're a'drift), but you also must consider the physical distances between recording devices (most wedding venues for instance may have several hundred milliseconds of "delay" if your recorders are widely separated). If you move the recorders, that alone could account for "drift"! Under controlled conditions, you might be a little off, in "live" sound, you could be all over the place! if it's a "live" room with lots of reflected sound, even more fun!

I know that electronics now are very cheaply made, but I have trouble buying into huge inaccuracies due to electronic variables...

I typically sync multiple cameras and recorders, and have yet to see huge differences in "sync" - yes, there are likely slight ones, equivalent to short "reverb" type delays (which actually provides automatic "ambience" if mixed very carefully), but not "his lips are moving and the sound isn't the same" type stuff. I do a "fine tuning" sync off of physical motion though, rather than audio, as there can be some slight differences as noted above due to delay between audio source and recording device.

Dave, it is good to hear that your experience about drift between devices is similar to Noa's and mine.

A couple of frames variability is possible in a typical venue if you're on the move, but a couple second difference isn't unless you have a pretty massively large venue. So I don't really think that's at the root of the problem for the OP or Richard. No boats harmed in the writing of this thread!

At 30fps, audio will lag video one frame for every 37 - 38 feet of distance between source and the mic. Two seconds delay translates to about 750 yards, or 4/10 mile.

Shooting in our larger local stadiums, my high center camera's audio can lag by four frames from a mic on the field AND the video from that high center camera. That's expected since the sound has to travel an extra 150 feet past the audio recorder's mic and on to the high center camera. The light that gets recorded by the camera takes essentially no time, only nanoseconds, to travel the distance.

The last wedding I did, (several years ago) was an outdoor event. The three cameras were at least 50 feet away. The groom wore an omni directional lav connected to a Sony Minidisc walkman in his pocket. Each camera had scratch audio.
In post all four audio sources were flawless after 35 minutes. All that was needed to do was adjust for delay, but the MD was rock solid with the video.
I'm considering a multi channel Tascam perhaps the DP24, with a number of wirelesses.
What I've heard many times over is that SD cards easily slow down as they fill up (usually after 50%). Could this be a cause for drift?

Thank you, everybody, for your contribution to this thread. It seems that real-world experience suggests that these recorders might be more accurate than the theory suggests.
Particular thanks to Noa whose real-world testing of his devices has influenced my buying decision.

Remember that my findings are not to be considered as standard deviation for such devices, from what I hear from other users (that are doing weddings) they all say their recording device is also pretty close, not always dead one but I guess like in my case several milliseconds off per hour. In my case that means moving it one frame per hour in general to maintain sync. Can we know what you decided to buy?

To the OP, I've shot a lot of video of live performances, over many hours in the last few years. I'll post a few examples at the end of this post. I've never had enough drift, if any, to worry about. I thought about jam syncing and get professional gear to really sync right, but have found I've never needed it. I use a Canon XF305, XF105 and sometimes a 7D or 5D Mkiii. I have used in the last two years, in order, a Zoom H4n (it died on me prematurely and was the least professional of the units I have used), the Tascam HDP2, a great recorder but somewhat dated, but if I was doing theatrical off camera Indie productions I likely would have kept it). My buddy who is a professional audio engineer up here claims the Tascam is the best cheaper unit he has used, and that it's pre-amps were the cleanest he has heard, and it does jam sync. The videos of the Brothers Four and Mark Pearson on my web site below were all recorded on the Tascam. I also borrowed a friends' non TC Edirol (the hard drive based one) and my current unit, a Marantz PMD 661. My earlier videos of the Brazilian Choro were all onto Edirol and were continuous have concerts, no stopping the camera, so like one hour of music. The concerts from the last six months are all PMD 661 recordings.

If I was still shooting tape, then it could be a problem of the tape transport, and that, yes, might cause you enough grief to look at jam syncing or actually running TC from a pro unit for doing so.

As I said, I've always synced up after the fact, and even stopped using Plural Eyes because it seemed easier to just find the sync point visually in my NLE's (I've gone through FCP, Vegas and now on Adobe Premiere/Audition).

I would say that if you are having drift problems, it's likely your recorder, and buying a new one, of the caliber of the ones I mention above, will likely solve your problem. As I mentioned, the Zoom H4N seemed to be the least capable of the ones I've owned/used. I think that out of them, if I bought one today, I would be likely to either get the Edirol R-44 (for four solid XLR inputs if you need them) or the PMD661, which I have liked the best of all of them. A great professional level tool. (used by radio field reporters around the world as I understand it). Certainly not a Sound Devices but we aren't talking about you spending that kind of money. If I was doing truly remote professional level work with a crew, I'd just save up and buy the SD. They are top quality.

To be clear, I am not a professional audio engineer. Just a videographer who cares about getting my sound as good as I can.

My videos are at
https://vimeo.com/mountainstone/videos

They aren't "perfect", some were shot with single camera, some multi and a mix of a lot of varied cameras that sometimes didn't match quality, but all the concerts you see often ran hours in length, and I would shoot continuous takes until the breaks between bands. I've shot nonstop for a half a show without experiencing any noticeable drift.

Could I through in another ball. Could the drift have anything to do with CBR or VBR? Shoot me down if you want. I know nothing.

Could I through in another ball. Could the drift have anything to do with CBR or VBR? Shoot me down if you want. I know nothing.

No. There are at least three COMPLETELY DIFFERENT AND INDEPENDENT kinds of "compression".

1) TIME compression is where you take a recording and make it shorter. Modern digital techniques allow us to do this without changing the pitch. And conversely you can STRETCH a recording to make it longer.

2) AMPLITUDE (or LEVEL) COMPRESSION (aka LIMITING) is the process of reducing the amplitude (or level or loudness) of the audio signal so that it fits within the maximum value of the digital sample. Allowing the audio signal to go over FULL SCALE in a digtal recording will CLIP the audio. This is typically a rather bad thing to be avoided (unless you are doing fuzz e-guitar). Of course, there are corrolaries in video as well, where you can :"blow out" the whites by opening your lens too wide. In video-land "blow-out" means "clipping"

3) DATA COMPRESSION is where you take the resulting stream of data values (whether audio or video) and reduce how much storage space (and/or transmission time) they take up. There are both "lossless" and "lossy" methods of doing this data reduction. CBR and VBR are two generic descriptions of the results of this data compression. Note that data compression DOES NOT CHANGE the sample rate, so it doesn't change the length of the clip. Well-known examples of data compression include MP3 for audio and MPEG for video. Both MP3 and MPEG (and most other compression schemes) have both lossless and lossy variations, as well as CBR (constant bit rate) and VBR (variable bit rate).

Note specifically VBR (variable bit rate) does not imply that the sound (or video) speeds up or slows down depending on the bit rate. It just means that the amount of (compressed) data may be higher at times, and lower at other times (typically depending on the complexity of the signal/data). For example you can compress the snot out of silence or black without losing anything.

These all border on gross oversimplification. Each of these qualify to be the focus of a graduate-level course or a stack of textbooks.

Am just bumping this up to share the results of a couple of sync tests I've done with my recently purchased Roland R-26.

In two separate one hour sync tests, running the R-26 recording WAV at 48Khz alongside my Sony EX1, I could not see any drift at all. AFAICT the R-26 kept perfect sync with the camera.

I was surprised, but very pleased.

I'll be using the R-26 in real life situations on a number of shoots this week, and I'm curious to see if I continue to get such good sync.

Am just bumping this up to share the results of a couple of sync tests I've done with my recently purchased Roland R-26.

In two separate one hour sync tests, running the R-26 recording WAV at 48Khz alongside my Sony EX1, I could not see any drift at all. AFAICT the R-26 kept perfect sync with the camera.

I was surprised, but very pleased.

I'll be using the R-26 in real life situations on a number of shoots this week, and I'm curious to see if I continue to get such good sync.How are you testing the sync?

How are you testing the sync?

Got my metronome out, set it to 60bpm

Pressed "Record" on EX1 and R26 at about same time.
Used clapperboard to mark audio and video start.
Let it all run for just over an hour.
Used clapperboard again to mark audio and video end.
Brought files from EX1 and R26 into Premiere and put both on timeline.
Zoomed into timeline at frame level.
Lined up starting clapperboard marks on both audio tracks.
Went to end of timeline.
Looked at end clapperboard marks.
At frame accuracy they were in the same place.

Then panned the EX1 audio track left and the R26 Audio track right and listened to playback to see if I could hear metronome clicks out of sync. Couldn't.

Then repeated the whole thing. Same result.

See any flaws in my methodology? Please say if you do.

I could compare them in Audition too, to get down to sample rather than frame accuracy, but that can wait: right now 1/25 second good enough for me.

Mark...that is a pretty slick little audio test. Simple & elegant. Bravo, dude.

Cheers,

J.

You would have enjoyed using a clockwork Bolex, carefully adjusted to a 50i TV screen whilst pulling junk film, working with a Sony TCD10 Pro II and holding sync for about 20 seconds.

The Nagra IV.2 and CP16R were good for one frame or less in 8 minutes.

If you haven't had to pull in a 1 in 44 frame sound stretch which occurred with an old UHER1000 Report Pilot after a shakeup on a rough road had reset the speed, you have not lived.

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.
Mark

Mark, can the H4 record 48Khz wav? Were you recording wav or mp3? I'm asking because I have the Sony Ex1 and H4n, and when I set the H4n to wav at 48Khz, drift is less than 1 frame over a period of 1 hour. I'm editing on Edius 6. I never record mp3, it'll always go out of sync. The holy grail, then, is to record .wav at 48Khz.

Back when I worked at Grass Valley Group in the late 80s and early 90s, we made a Reference Master Sync Pulse Generator with a temperature-controlled crystal oscillator. This was intended as a master clock in a studio or broadcast head end. You would then send color black from it to slave SPGs distributed throughout the building.

The oscillator was about the size of a tennis ball, but in the shape of a cube. It had a thermostat and an oven in a sealed metal case. And, no, it wasn't cheap!

And if you had two stations, each with it's own reference SPG, the two buildings would still drift and need a frame synchronizer for live feeds.

It would be nice to have genlock or equivalent on budget AV production gear. It beats carrying around a couple of oven-encased crystals!

One concern with any sync test is that they can vary unit to unit and in different temperature and humidity situations. Not to dis the test though. It's about as good as we can do without calibrated clocks or genlock.

Mark, can the H4 record 48Khz wav? Were you recording wav or mp3? I'm asking because I have the Sony Ex1 and H4n, and when I set the H4n to wav at 48Khz, drift is less than 1 frame over a period of 1 hour. I'm editing on Edius 6. I never record mp3, it'll always go out of sync. The holy grail, then, is to record .wav at 48Khz.

Yes, the H4 can, and I did, record at 48Khz .wav. Glad to hear the H4n is better at keeping sync. Personally, I didn't want to get another Zoom product.
Compared to the Roland R-26 the H4 now feels like a plasticy complicated POS, destined for eBay.

But to be less snarky, it's great that the current generation of these pocket recorders seem very good at keeping strict time. That'll be modern microelectronics for ya.