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Producer is dropping frames

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GSW videoProducer is dropping frames
by on Aug 20, 2007 at 5:55:05 pm

Hey guys,
I sent this to Media 100 last week but go no response. Figured I'd try posting it here:

I recently bought a license for Media 100 Producer v11.6.2 Intel for my university. Love it. I've been editing on Media 100i for years. It's running on a MacBook Pro 2.4 Ghz laptop. Anyway, in digitizing long clips of MiniDV footage from Canon camcorders via firewire (XL-1 & GL-1) I'm getting syncing issues after a period of time. I assume it's because maybe the cameras recorded footage at a certain frame rate (maybe 30fps) and the Media 100 is set to importing footage that's 29.97 fps. You may say I've answered my own question and I need to switch this in Media 100's import settings. Well, my problem is that I don't know what frame rate my cameras are recording at. I've looked through my camera manuals and no where is it mentioned what frame rate these Canon camcorders record at. Any of you guys run into this before? I will add that I edited a program that was about 50 minutes long & after about 20 minutes the audio and video were undeniably out of sync. I fixed that and now have a program that's OK but when trying to perform the "master to tape" function, I get an error saying "Do you really want to master this Non-Drop frame program w/ a deck set to Drop Frame?" Any advice? I'm just not sure how to check what frame rates my gear records in. I've got a:
Canon XL-1
Canon GL-1
I know better camcorders have switches on them to choose frame rates and such.
I will add that I had the Codec (SD) In & Out set to DV instead of Media100i...not sure if that has anything to do w/ it. Also, my Program Defaults is set to Drop Frame instead of Non-Drop Frame.
I'm hoping someone has some insight as to how I can proceed to making problem free programs.

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FlohRe: Producer is dropping frames
by on Aug 20, 2007 at 7:07:01 pm

You should set up your systems to work in DF mode. All DV cameras record 29.97 NTSC as far as I can say; so you also should work in 29.97 in Producer (as far as I know you cannot work in NDF anyway, but since we work in PAL all the time I am not sure about this}.
You should have a look at your drive performance; I could imagine the system dropping frames if your drives don

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David C.Re: Producer is dropping frames
by on Aug 20, 2007 at 7:18:27 pm

Couple of things. When did you purchase Producer? If you have purchased in the last 30 days you receive free support. If you are outside the free support period then we have other support options available.

You state you are dropping frames, but then state the issue is you are out of sync. Which is it? Media 100 doesn't drop frames without warning, if we do you will see a cannot play because... error. If your audio and video are out of sync while playing back, that is another issue and we will have to dig further. Right now there is no active case opened with a customer that has a audio/video playback problem.


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GSW videoRe: Producer is dropping frames
by on Aug 20, 2007 at 8:22:42 pm

Thanks for the replies Floh & Dave.
I'm honestly not sure if it's a dropping frames issue or sync issue. All I know is that I taped a 50 minute play performance that was divided into two 25 minute acts. After laying the 2 acts on my timeline and viewing them, I could clearly see an issue where the audio and video of each clip did not match. It matched at the beginning of each act but after about 15 or so minutes, you could clearly see the dialogue did not match the actors' lips. To quickly compensate for this and get the program dumped to tape, I split the clips at black curtain fades later down the timeline before the audio began to get out of sync. Then, I unsynced the audio from the video and slid the video track down the timeline about 5 frames and it then matched the audio. Lastly, to fill in the empty gap, I stretched the previous video track (before the split) 5 frames during a black curtain fade so the viewer would never see the jumpcut. It was a fairly easy fix but I'm worried that if I digitize future long clips into the editor that I'll consistently have to deal w/ audio and video matching problems. Floh, you mention this may be an issue where the hard drive isn't fast enough to play the media back properly. That could be possible. I'm using the laptops internal hard drive. I know, I'm not supposed to use the computer's boot drive but I just got the laptop and figured I'd try editing a program with it to see how it worked.

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Juanjo MoraRe: Producer is dropping frames
by on Aug 20, 2007 at 8:54:00 pm

Hi Guys!

GSW, I don't really know what is causing your audio out of sync issues, but just as a hunch I'd check the sample rates of your cameras, most DV cameras have two sample rates for recording audio: 48KHz in "SP" mode (this is the highest quality setting and records two channels of audio to the tape) and 32KHz in "LP" mode (this is the low quality setting, the tape lasts longer and 4 channels of audio are recorded, it's useful if you're doing audio overdubs or narration in-camera).
This could cause the sync issues you're seeing but it's a remote possibilty: when digitizing through FireWire, Producer detects the sample rate automatically and changes the Hardware Input Setting acordingly.

As for your second problem the "do you really want to master this non-drop frame program with a deck set to drop-frame"...

This is typical of Time Code issues in NTSC world and our European friends are free from it... as you may know, due to not being running exactly at 30fps, NTSC Time Code accumulates over the lenght of a program a difference or discrepancy with the "Real World Time"; this causes problems for Broadcasters that have to measure and plan their programing schedule accordingly to this "Real World Time"...

So, to have Time Code and lenght match the "Real World Time" clock Drop-Frame Time Code was introduced, as its name says it "drops" frames to match "Real World Time", only IT DOES NOT DROP FRAMES (confusing, uh?) what it drops is the Time Code Frame Number every once in a while to compensate for the discrepancies with the "Real World Time" clock.

So, your system is not droping frames, it's just asking what kind of Time Code flavor do you want written to tape.

As you have stated, you do have your Program Default set to Drop-Frame, but I suggest you do a double-check and confirm that the timeline of the program you're trying to get to tape is really set to Drop-Frame....with the timeline active go to Progam and search for a command that says "Show in Drop-Frame"if your program is in Non Drop-Frame and viceversa... other way to check is to look in the Time Code window in the timeline: if the character between each pair of time code numbers is a ":" then your program is in Non Drop-Frame, if it is a ";" then your program is in Drop-Frame mode.

Well once you're certain that your program is in Drop-Frame mode (if that is what you wish... usually if your program is for broadcasting it HAS to be in Drop-Frame, and most DV decks -don't know about the JVC- are set by default to Drop-Frame Mode, if you're going to postproduce or do DVD authoring it's better to use Non Drop-Frame mode), you can output to tape, if it gives you the error again, get out of master to tape mode and turn your DV deck off, wait 10 secs and then on. That's it.

Sorry for the long and convoluted post, but I'm writing this as it comes to my head (and english is not my first language)... hope it

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GSW VideoRe: Producer is dropping frames
by on Aug 21, 2007 at 3:30:31 am

Thanks for the post. I will add that I recorded my audio in 12-bit 4 channel mode on a Canon XL-1 because I was using a feed from the audio board on ST-2 (channels 3 & 4) and some wireless mics at the front of the stage on ST-1 (channels 1 & 2.) Maybe the camera detected 12-bit mode and changed something when digitizing via firewire. ????

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HolyCowSeattleRe: Producer is dropping frames
by on Aug 25, 2007 at 5:43:55 pm

Just a quick thought.....

Is the 12-bit audio on this particular camera UNLOCKED?

Remember there are twop types of audio with DV LOCKED and UNLOCKED.

LOCKED: Good for everything.
UNLOCKED: Not so good for long form projects.

This alone could be causing the problem.


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GSW VideoRe: Producer is dropping frames
by on Aug 25, 2007 at 6:02:49 pm

Not sure. I've never heard of locked and unlocked DV audio. It was recorded on a Canon XL-1 and I don't recall seeing an option like that when choosing in 12 bit.

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HolyCowSeattleRe: Producer is dropping frames
by on Aug 27, 2007 at 5:35:22 pm

In spite of what this article states, we have experienced problems in the past using 12-bit unlocked audio. (Drift and pitch shifting in older versions of Premiere and Avid.) We compensated by using ADAT's in the field for multitrack audio, and our current cameras all record 4 channel audio (16-bit/48khz) in we dont mess with this anymore.

Quick explanation borrowed from another website....

From the website:

What's the difference between locked and unlocked audio?

Locked audio is "audio done right": the audio sample clock (the digital time reference used in the sampling process) is precisely locked to the video sample clock such that there is exactly the same number of audio samples recorded per "audio frame" of video (not all TV formats and sound sample rates have a neat integer relationship between audio samples and frames, so an "audio frame" is my term [similar to a "color frame"] for the number of video frames it takes for audio and video to match up in the same phase relationship).

For PAL, 625/50 video, locked audio provides exactly the same number of samples per video frame with either 32 or 48kHz audio, but for NTSC, 525/59.94 video, the 48kHz "audio frame" is 5 video frames: locked audio will provide exactly the same number of audio samples for every five video frames, though not every frame within that 5-frame sequence has an equal number of audio samples. 32kHz locked "audio frames" cover a whopping 15 video frames!.

[There is such a thing as an AES/EBU audio frame, but I'm not sure it that's the same thing I'm referring to. Comments/clarifications welcomed!]

Unlocked audio: theory:

Unfortunately, such precisely-locked audio clocks are expensive. Since DV was designed as a consumer format, unlocked audio was allowed as a cost-saving measure. In unlocked audio, the audio clock is allowed some imprecision, such that there can be a variation from the locked spec of up to +/- 25 audio samples written to tape for every frame, instead of a precise and exact number.

This economy measure is simply one of allowing the audio clock to "hunt" a bit around the desired frequency; the phase-locked loop (or other slaving method) used to keep the audio sampling in sync with the video sampling can have a bit more slop in its lock-up, with the audio sampling sometimes running a bit slower, sometimes a bit faster, but always staying in sync over the long run. The total amount of sync slippage allowed in unlocked audio is +/- 1/3 frame -- not enough to really worry about.

It's the difference between walking a dog on a short leather leash, always forcing the dog to stay right by your side (locked audio), and using a long, elastic leash or one of those "retractable clothesline" leashes that allows the dog to run ahead a bit or lag behind (unlocked audio). In either case both you and the dog will get where you're going at the same time, but along the way the "unlocked" dog has a bit more freedom to deviate from your exact walking pace.

Unlocked audio should not cause audio sync to drift away from video over a long period of time. The audio clock is still linked to the video clock; it's just allowed a bit more oscillation about the desired frequency (more wow & flutter if you will) as it's trying to track the video clock. Like the dog on the springy leash, it can run a bit ahead or a bit behind the video clock momentarily (up to 1/3 frame ahead or behind), but in the long run it'll still be pacing the video clock and on average will be right there in sync with it. I have shot one-hour continuous takes of talking heads with a consumer DV camcorder (DCR-VX1000) and experienced no drift at all between audio and video.

DV cameras and VTRs generate unlocked audio, both in 32 kHz 12 bit and in 48 kHz 16 bit recordings. DVCAM and DVCPRO cameras and VTRs generate locked audio in 48/16 audio format, and DVCAM can also generated locked 32/12 audio.. 44.1kHz, discussed below, is never locked; it has no neat integer relationship with either 625/50 or 525/59.54 frame rates.

Some non-linear DV/1394 editors generate locked audio, some output unlocked, and some allow the choice. DV gear is happy to record locked audio via 1394, as is the DVCAM DSR-20 VTR. The DVCAM DSR-30 VTR can also be made to record unlocked audio with a bit of coaxing (see Tidbits).

Also, many non-linear editors output 16 bit 44.1 kHz audio (at least on PC platforms), which both DV and DVCAM 1394-equipped decks record without any problems. 44.1 kHz is part of the Blue Book spec, so this is not too surprising.

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