Why do Logic display frames this way? [SOLVED]

I am having problems making Logic display frames (in the big SMPTE display) the way Final Cut does; simply 00 to 24.

Logic shows 01, 02, 02,79, 3,79, 5 etc..

Why?

 

I am working with a movie-file in HDV 1080p25 (PAL)

 

k

Edited October 6, 2010 by wip

In Logic's Display/General preferences, change Display SMPTE to "Without Bits".

 

J.

Thanks Jordito!

 

k

You're welcome!

 

J.

There's only one problem with this...

 

I'll wait for someone to ask "what?" and then I'll tell ya.

 

You'll probably want to know.

 

Yup, you probably do.

yes please, ski. tell, tell!

don't wanna get annoying suprises later...

OK then!

 

What we see in this picture is the Giant SMPTE Display overlaying a frame of a QT movie opened in Logic. Look at the timecode burn in the movie itself. It's showing 01:21:29:18. Let's just refer to that as "frame 18".

 

http://www.score2picture.com/L9pix/bitz.jpg

 

In Logic's SMPTE counter, we see the same t/c number, but it ends with ".79" which means 79 bits. In Logic, each frame gets subdivided into 80 bits, numbered from 0 to 79. WIth that in mind, let's see how this relates to film frames...

 

Each frame of film or video lasts for a specific amount of time. How long each frame lasts depends on the frame rate. For example, one frame at 25 fps lasts 40 milliseconds. Logic divides each frame by 80, so at 25 fps, each bit represents .5 millisecond of time.

 

Now let's look at Logic's SMPTE counter in the picture. As we can see, it includes bits. In the counter we see the same timecode number as in the film, plus 79 bits. As stated previously, a frame is divided into 80 bits, numbered 0 - 79. So consider this: if Logic's playhead (or an event or marker) were positioned just .5 milliseconds later in time (one bit more) we'd be at frame 19 of the film, not frame 18! So for all intents and purposes, Logic's playhead is not positioned at frame 18. It's at frame 19!

 

So let's say you needed to pop your file at the top of frame 18 (meaning, add a 2-pop at the beginning of your cue's audio file to give the editor a sync point). If you aligned the pop where we see picture's frame 18, you're going to be almost exactly one frame off! And if Logic's SMPTE counter were not showing bits, you'd introduce the same error.

 

Pops, hit point markers, anything that requires syncing to frames needs to be done on the "leading edge of the frame", not somewhere in the middle, not somewhere towards the end (as we see here). This means that your pop really needs to be placed at frame 18, zero bits.

 

So when you set Logic to display SMPTE without bits, you run the risk of introducing as much as a 1-frame error in all of your hit placements, pop placements, marker points, and so on. So unless you view SMPTE with bits, you will have no idea how far into that frame you are.

 

And it's not like displaying SMPTE without bits causes Logic to make the movie file "snap" to the leading edge of a frame. No, no, no. When you locate the playhead to a particular position, all Logic does is send a timecode number to QT and the movie file jumps to that position, regardless of Logic's bit count. There is no "hard sync" of picture between Logic and the QT movie. And since Logic's playhead can be positioned anywhere within that frame, the only way to ensure that pops, markers, events, etc. are positioned on the leading edge is to view the bits value and get it as close to zero as possible when setting markers, popping files, figuring out hit points, etc.

 

Yes, "as close to zero as possible". I say this because sometimes it's not possible to get the bits value to be exactly at zero. But if you can manage to get it to [timecode].01 or [timecode].02 then you'll be fine.

Edited October 7, 2010 by ski

Just a lil' follow-up...

 

I would urge you and any film composer to experiment with the above situation so that you can discover the ins and outs of this behavior for yourself. Suggestion: keep the display preferences pane open and off to the side. Turn off the display of bits. WIth a movie loaded up and Logic set to the correct frame rate for that movie, move the playhead to any position in the film. Turn the display of bits on and see where the bits counter is. Turn it off again and set the playhead to another position. Turn the bits display on. I think it'll be an enlightening exercise.

thanks for the heads up, ski!

 

k

You're welcome!

Good point ski, and thanks for the explanation!

 

The way I've avoided losing my place in relation to the video's frames, is by using the "Rewind one Frame" and "Forward one Frame" commands. This way I know the playhead matches the top of the frame and I don't have to worry about the bits.

 

J.

Hi Jordito,

 

I just tried this out hoping for the best, but unfortunately that doesn't seem to work. Seems as though Logic constantly introduces rounding errors even into even-numbered frame rates (I'll get to what I mean by that in a minute).

 

I just did a test using an animation (true 24 fps). At the very top of the film (bar 1 1 1 1) Logic's SMPTE counter and picture's t/c burn are perfect, just as you'd expect:

 

http://www.score2picture.com/L9pix/frame0.jpg

 

But FF'ing just 1 frame in, we see this: Logic's SMPTE counter is nearly one whole frame ahead of the leading edge of the frame! And the picture hasn't moved either!! And that's because FF'ing by one frame hasn't advanced Logic's playhead exactly one frame -- it's only FF'd by 79 bits, not 80.

 

http://www.score2picture.com/L9pix/frame1.jpg

 

If I manually increase the bits value by one, so that we wrap to the next frame, NOW we're at frame 00:

 

http://www.score2picture.com/L9pix/frame2.jpg

 

Note that I couldn't get the bits value to be exactly at zero. By incrementing it up just one (which should have been "bit 00") Logic changed it to "bit 01" on its own. For me that's close enough, but still, there's a decided lack of precision here.

 

At 24 fps, the 1-bit-shy business is consistent over the course of the film. So on one hand, your idea of jockeying the current position of the playhead using RW or FF one frame is great, but Logic's t/c counter is, for all intents and purposes, showing you that the playhead position is one frame LATER but picture is still going to be one frame SHY. So that's at 24 fps and a tempo of 120 BPM.

 

The situation gets really ugly when you're working with an "unevenly numbered" frame rate such as 23.976 or 29.97. The rounding errors that occur as you hit FF or RW by 1 frame to navigate the playhead can be easily seen (when bits are displayed, natch). Depending on where you are in the film you could be no bits off, 20 bits off, 40 bits off, etc.

 

So unfortunately -- at least on my system -- the RW and FF by frame functions won't resolve the situation. I'd like to ask if you could check this phenomenon for yourself and see if you get the same behavior.

Edited October 7, 2010 by ski

Above post updated with 3rd image and add'l information.

Thanks ski, but what I meant was using the commands while looking at the t/c burn, not Logic's SMPTE display.

 

J.

Right. That's going to appear to work. But when it comes to the placement of markers, pops, anything where you're looking to place them on the leading edge of a frame, you can't judge this by picture alone -- and as explained, that's because the playhead can be positioned inbetween the leading edge and trailing edge of each frame.

Right. That's going to appear to work. But when it comes to the placement of markers, pops, anything where you're looking to place them on the leading edge of a frame, you can't judge this by picture alone -- and as explained, that's because the playhead can be positioned inbetween the leading edge and trailing edge of each frame.

 

Damn...well, thank you ski, I'll keep that in mind if I ever get another scoring or post project (I'm no expert). Last project I did was audio post for a documentary and I relied on those commands to navigate the project (25fps). I guess any errors were minimal (or not important due to the nature of the project) as the video editor never said anything about the audio being off...

 

Any suggestions on how to navigate accurately by frames in logic...if any?

 

J.

Any suggestions on how to navigate accurately by frames in logic...if any?

 

...Or do we have to rely on manually compensating when we want to place the playhead right at the leading edge of a frame?

 

Another question: Why does Logic subdivide the frame in 80 bits specifically?

I ask because I find FCP can deal with audio at the subframe level, but it subdivides the frame in 100 bits (or something else?):

 

WorkingwithAudioattheSubframeLevel

While the smallest unit of video is a single frame, the smallest adjustable unit of audio in Final Cut Pro is 1/100 of a frame. Audio level and pan keyframes, as well as the sync between the video and audio tracks of a clip, can be set with an accuracy of 1/100 of a frame.

 

Just curious, if you know something about this, please tell

 

J.

Why does Logic subdivide the frame in 80 bits specifically?

Because that's how the time code format is defined by the Society of Motion Picture and Television Engineers. 0-23 Hours : 00-59 Minutes : 00-59 Seconds : 00-any-arbitrary-number-anyone-can-come-up-with-in-an-attempt-to-just-make-our-lives-harder Frames : 00-79 Subframes (also referred to as SMPTE bits)

FCP subdivides the frame in 100 bits

Because this avoids the question ""Why is that 80 Subframes ?" Nowhere in your quote does it say "Subframe" or "SMPTE bit", though. There are 80 Subframes in a SMPTE Frame. 1/100 of a Frame is not related to Subframes in any way.

 

Christian

FCP subdivides the frame in 100 bits

FCP allows subframe keyframing to a resolution of 100 per frame, but that's not related to the actual timecode format.

Thanks fuzz and fader,

 

Before I let this go for good (I hate being a pest), what about the other question, the one about accurately navigating frame by frame in Logic? Do we always need to compensate manually to land the playhead at the beginning of a frame? And how do we actually know we're at the beginning of a frame if we cannot trust Logic's smpte display or the rewind and forward one frame commands in relation to the burnt-in timecode?

 

J.

Do we always need to compensate manually to land the playhead at the beginning of a frame?

I've not had any problems using the RW/FWD one frame command. It's one of the very few ways to get the playhead to be "frame friendly". That always lands my playhead at the head of the frame, but sometimes at the tail of the previous. Not that it matters much. But to further illustrate the need to show bits, the pic shows both locations as frame 15, but the second one is obviously frame 16.

 

But for "spotting" audio to a frame head, it's much better to not use the playhead but reference from the region itself. Regions will follow the snap settings, unlike the playhead which likes ticks. So Snap to Frame, Snap to Absolute Value, and the region anchor lands at the head of the frame, every time. Then adjust the anchor location in the sample editor to fine tune exactly what event happens at the frame head.

 

Make sure "Lock Arrange Position When Moving Anchor" is unchecked.

Do we always need to compensate manually to land the playhead at the beginning of a frame?

I've not had any problems using the RW/FWD one frame command. It's one of the very few ways to get the playhead to be "frame friendly". That always lands my playhead at the head of the frame, but sometimes at the tail of the previous.

 

Thanks, fader8. I was beginning to think that maybe those commands were worthless. Like I said before, last project I did with video was audio post for a documentary (a year ago). I remember using those commands (and also markers) for navigating the project. I can't remember the bit about landing at the tail of a frame, but most likely I did. However, I didn't have to spot anything as my job was to get rid of wind rumble and other noise, setting levels, EQing, etc. Basically cleaning the audio up and making things sound as coherent as possible.

 

But for "spotting" audio to a frame head, it's much better to not use the playhead but reference from the region itself. Regions will follow the snap settings, unlike the playhead which likes ticks. So Snap to Frame, Snap to Absolute Value, and the region anchor lands at the head of the frame, every time. Then adjust the anchor location in the sample editor to fine tune exactly what event happens at the frame head.

 

Make sure "Lock Arrange Position When Moving Anchor" is unchecked.

 

I'll keep that in mind....and the bits....in my SMPTE display.

 

Thanks again fader, fuzz, and ski.

 

J.

You're welcome!

 

Yes, you can trust Logic to get you to the leading edge of the frame. However, the only way to do this is to manually scroll the bits value to get you there. In my experience you cannot trust Logic's FF/RW-by-frame commands to ever accurately get you there.

 

I don't look at this as a matter of compensating for anything other than the shortcomings of Logic to be able to accurately calculate the width of a frame at any given frame rate. It's not like once you arrive at the leading edge that Logic (or QT) are lying to you. And I'm confident that as picture plays you're seeing an accurate and repeatable representation of how your music (or foley or whatever) sync to picture. What I'm going on about at length here is the ability to spot a frame at the leading edge. And no, you just can't use FF/RW to get you there accurately.

In my experience you cannot trust Logic's FF/RW-by-frame commands to ever accurately get you there.

How far off are you seeing it? I can't make it land anywhere except subframe 0 of the desired frame, or subframe 79 of the previous frame when using that command. I do notice that the actual frame (picture) head can occur at 79, 00, 01 or 02. It's not exactly precise, but I haven't noticed it worse than that.

Hola Señor Ocho,

 

I too get consistent results using 30, 25, and 24. But try it with 29.97 or 23.976 and I think you'll see what I'm seeing. And if you're not then... it'll be fodder for further discussion!

I have a very novice question about seeing frames in Logic 9.

I am using Motion Assist to create a video.

Both it and Logic 9 are set to 25 frames fps.

In Motion Assist the Intro ends at 191 frames. But I don't see this read out any where on the transport bar in Logic 9.

Is there a way to see this?

Thanks

191 frames at is 7.64 seconds of footage. So at the end of the intro the SMPTE readout in Logic will likely show something like 00:00:07:12. That's 0 hours, 0 minutes, 7 seconds, 12 frames. [EDIT: confirmed now that I see there's a screenshot attached to your post. See below for why it reads out 8 seconds instead of what I said above].

 

BTW, why are you working at 25 fps? Unless you're creating this for Europe or Australia (where 25 fps is the normal frame rate for film) then I'd suggest using 29.97 for video or perhaps 23.976 (otherwise known as 23.98, which is not the same as 24).

Edited July 24, 2014 by ski

Ah, now your image has shown up.

 

The reason Logic is rounding up to 8 frames is because you have the Display preferences set to not show bits. So change that to display SMPTE with bits. Then the timecode readout will be more accurate.

One more thing... Logic doesn't (and can't) show frame numbers in the way you're seeing them in your other program. I'd suggest seeing if there's an option in Motion to display frames as SMPTE (timecode).

 

Otherwise, you'll have to do the math.

 

Traditionally, when it comes to audio post production, composers, editors, mixers, use timecode for spotting frames, not the kind of frame number you're seeing in Motion.

One more thing... Logic doesn't (and can't) show frame numbers in the way you're seeing them in your other program. I'd suggest seeing if there's an option in Motion to display frames as SMPTE (timecode).

 

Otherwise, you'll have to do the math.

 

Traditionally, when it comes to audio post production, composers, editors, mixers, use timecode for spotting frames, not the kind of frame number you're seeing in Motion.

Thank you Thank you, Motion Artist did have that option. This will work just fine and I thank you.