With Half-Sized Frame and SP/LP error, am I getting lower quality?

curt0 wrote:

The recording mode is already set to "SP".

Now, I can play and import the miniDV video on iMovie 6. However, I'm curious as to whether iMovie is inputting NTSC and saving into PAL, or vice versa. Therefore, I'm concerned about the possibility of losing quality. Would anybody know if I will be losing quality?

Was it set to "SP" at the time of the recording?

No, iMovie never lets you import PAL to an NTSC project or vice versa.

"..the last 43 minutes of clips, cannot play well on my Canon camcorder.."

Run through the tapes to see how many total minutes of material you have on these tapes. A miniDV tape records a maximum of 63 mins at Standard Play rate, and up to about 90 mins at LP (Long Play) rate.

If you have more than 63 mins of material on these tapes, then the recording was made at LP rate.

At LP rate, the tape moves at 2/3 the speed of SP, which means that the video tracks recorded on the tape are very narrow. This means that when those tapes are played in a different camcorder the heads may read the tape properly, because there's no margin for error on these very narrow tracks. When replaying an LP tape, the camcorder's heads may not properly align with the recorded track, giving the 'half frame' error you mentioned.

No camera manufacturer guarantees that any LP material will play correctly on any camcorder other than the one on which it was recorded (because of these narrow LP tracks). [Sony created the professional 'DVCAM' speed - one-and-a-half-times normal SP speed, so two-thirds the recording time - to provide -w-i-d-e-r- tracks than normal, and thus ensure that professional DV recordings can be played back and edited on equipment other than the camcorder which was used

for shooting the material.]

The only solution for LP tapes is to try importing from as many different camcorders as possible till you find one which will do the job. (I had to do exactly the same thing last week, and found that various other Sony 'consumer-grade' camcorders - the material was recorded on a Sony - couldn't 'lock onto' the LP track, but professional or 'prosumer' (more expensive) Canon (XLH1) and Sony (FX1) camcorders could play the old LP material.)

Before trying to play old tapes, whether SP or LP, always wind them fast-forward all the way to the end, then rewind them - at least once - to make sure that the tape layers don't stick together, and to ease the stresses in the tape. You should also do this once a year to every recorded tape, to avoid stresses, pinching, and 'print-through' (seepage of magnetism from one layer of tape to others).

P.S: Have you tried cleaning the 'broken' head on your old Canon? Dip a cotton bud in methylated spirits - or, better still, carbon tetrachloride 'dry cleaning' fluid - and slowly turn the head drum, and wipe up and down it, over and over again ..making sure NOT to catch cotton wool in the sharp narrow gap between each of the (two) heads, which are each halfway round the head (at 180 degrees to each other). Wipe carefully, then examine the cotton bud and see if there are any brown stains on it ..if so, you've cleaned old muck off the head. Repeat with a new cotton bud until there are no more stains on it. Leave the head drum to dry for 10 minutes, playing gentle (half) heat from a hair-dryer on it, but don't melt the plastic camcorder - so that the fluid evaporates and doesn't stick any tape to the head! - then try importing again.

P.P.S: "..It seems that iMovie 6 will not allow me to play this video.." iMovie's tolerance for damaged digital video frames is far tighter than any camcorder's: a camcorder will often replace 'damaged' frames with detail from the undamaged frame before, so doesn't give a clear idea of how damaged the video data may be. If it won't import, it's damaged, possibly through head misalignment, or through a weak or dissipated signal. (Earlier versions, such as iMovie 2.1.2, were more tolerant of 'dodgy' video, and could import material which later versions, e.g; iMHD6, won't allow accept.)

Gotta go out shortly, so this'll be a brief reply (..oh, good! says everyone!..)

The reason that it flips and "..iMovie 6 can now play and import what was the bad part of the tape, but cannot with the part of the tape that was good.." is that it's latched onto a different 'field' of the video frames (a frame is made of two 'interleaved' or interlaced half-a-picture "fields").

[You write as if you're English, but you suggest that this is American NTSC video (not English/European PAL video)].

Can't explain more now - gotta go - but "..I don't see how I can reach it through the opening for the cassette, unless I unscrew and take apart the camera.." ..yes, you might be able to unscrew two small screws which may be holding together the cover for the cassette compartment. "..Even then, I would be guessing as to which is the head drum.." ..it's the small circular shiny thing inside the cassette compartment. "..have no idea how to turn the head drum.." ..with the end of the cotton bud stick, or - gingerly - with the tip of your little finger on the upper edge of the drum. "..I don't see the heads that are 180 degrees to each other.." ..no; they're almost invisible teeny shiny bits set into the curved surface of the drum, like pairs of pinheads. "..Where do I get carbon tetrachloride?.." ..from a chemist's shop (pharmacy), or use meths (ditto).

..Gotta go-o-o-o--

EDIT: P.S; for head cleaning, see this page, although it refers to a Sony TRV900 ..but your Canon will be similar: http://www.bealecorner.com/trv900/trouble/index.html

..aaah. Back again, after a tortuous drive through the back roads of Germany.. (see you in a few days, Karsten..)

"..does this mean that the video that iMovie 6 imports, will contain half the data, and hence half the quality?.." Not usually; normally it imports ALL the data, and ALL the quality. It's just that in THIS case it doesn't seem to be able to latch onto all the data - i.e; both fields of each frame. The reason appears to be that there's a lack of head alignment, or the tapes were recorded with dirty heads, or the tapes - even though no longer than 63 mins - may possibly have been recorded at LP rate, therefore can't be accurately played back by another device.

"..That's interesting that you think I write as if I'm English. What made you think that? I'm Canadian. Cameras were bought in Canada.." ..Ahh: Canadian ..I knew that you weren't American! ..I forgot about Canada - sorry! There you are; you write in the Queen's English, not in American.

"..isn't it possible that I end up with a Canon camera that plays like my brother's Sony camera?.." ..It's possible, yes.

"..The Sony camera can already play all parts of the tape, but iMovie detects the bad parts.." ..and doesn't import them properly. (It's also possible, but not likely, that your brother's camera may have mis-aligned tape-heads, hence the bad tracking.)

I'm desperately trying to think of some way to force better reading of the original tapes. If there is NO other way to do it, then instead of a digital (FireWire) import, you could connect an analogue lead (..with yellow 'composite' video, and red and white stereo audio..) to the A/V out socket of one or other of the camcorders, and then feed that analogue (non-digital) output through a digitiser, which could be a standalone digitiser box (..the things which are sold for copying old tapes..) or could be another camcorder which has 'analogue pass-through' ..which, in effect, accepts an analogue input and passes that out as a digital signal via FireWire. That would convert the reasonable-quality (all the data) analogue output into a freshly-digitised format which would be acceptable to iMovie.

At the back of my mind there's some other message, or reason, why you're getting only 'half-frames', and a half-forgotten remedy for this. I'll have a think overnight (..bed time for me, after the "tortuous drive" ..see above) but now it's past my bedtime, so maybe Lennart has a better idea than my... z-z-z-ZZZZZ.. g'nite! ..Or, as you're in Canada, I'll say "Bonsoir"!

I..I hope this appears in the right place..)

After a good night's sleep - and lunch at the Anna-Sophia - it suddenly came to me:

(..I was going to ask for further help in the Final Cut Pro forum..)

I remembered where I'd seen this message about half-frames before: I don't know if this applies, as you say that these tapes are about 7 years old, but if the material was recorded in progressive mode (..were there Progressive camcorders 7 years ago?..) then those 'Progressive' frames aren't made of two different fields adding together to make single frames; they're made of repeated single frames at twice the rate of ordinary whole frames ..in other words, full 'frames' of information pretending to be half-frame 'fields'.

(Ignore the terminology if it's incomprehensible!) What this means is that iMovie 6 has to throw away half the information, because there's too much: it's been doubled. Nevertheless, discarding half a 'Progressive' frame doesn't lose information, as all the info is there in each of the 'doubled' frames.

Ordinary, 'interleaved', [i] video is like this:

½

½

and it takes two half-frames ('fields'), one after the other, to make a single frame.

'Progressive' [p] video is like this:

1

1

with each of those 'half-frames' actually being a complete frame (but they're interpreted as being there twice by iMovie 6).

So losing one of those complete frames won't diminish the quality when iMovie treats them as a pair of 'fields'. (Later versions of iMovie, such as the current version, often do, in any case, throw away half that info, creating [p] frames which consist of the same info displayed twice.)

Anyway ..what I'm saying is that it's just possible - you'd need to check the specs of your original Canon camera - is that you recorded your movie(s) in 'progressive' format (..it was an option which many people didn't understand when camcorder makers raced to offer this 'novel' form of recording to display on new, progressive-capable TVs..) and that may also be a reason why you're getting the "half-sized frames" error message from iMovie.

Did that help..? ..Or was it just confusing? ..I can post a message in the Final Cut forums to ask for further help there, if you like..

(..Please scroll up to the third post in this topic, just under your second post ..that's where my latest reply landed, as all of these replies were getting narrower and narrower..! - the one with the lightbulb image..)

Unless the cameras shoot 50fps or 59.94fps they aren't shooting true progressive frames. They shoot what's called progressive segmented frames (PsF). PsF video is made up of two fields. The two fields are identical, but each field is only half the resolution, just as each field in an interlaced format is half the resolution.

(..very quick reply; am going out again tonight..)

Thanks for the link to the instruction manual - this camera is NOT a 'progressive' camera.

"..Do you agree with user OvERaCiD23?.." ..Yes, Doctor, I concur.

"..The third post, after my second post, is a post from Lennart Thelander. Your first post appears after my reply to Lennart.." ..I dunno; I can only speak for my display. Yours may be different.

"..If I do not lose quality, then I'm okay and I will simply do this for the bad parts of tape:

- Disconnect the camera from the Mac.

- Start up iMovie 6.

- Start playing my miniDV tape (on the Sony camera)

- Connected the firewire from the camera to the Mac

If I don't have progressive, but have half frames, do you think that I will or will not lose quality?.."

Try it and see! ..You may spend 10 minutes in experimenting, but it'll be 10 mins of experience gained.

G'nite - or whatever the Canadian was for "good night"! I'll read your reply in my morning..

(P.S: On my display, Lennart's reply is beneath this reply of mine to you! But let's not go into that..!)

The material is not progressive. If you can capture it there will be no quality loss. (Actually there isn't any quality loss in the captured DV media in any version of iMovie, but that's a different story.)