XL1S imaging problem/question

[AlexOsadzinski]

Oh, one last thing that I mentioned before: a tape recorded on my Sony TRV10 plays back perfectly on the XL1S, i.e. no black line. All this data seems to narrow the problem down, although I don't have a block diagram of the XL1S to figure it out myself:

- the lens mount and/or CCD are not misaligned (evidence: 16:9 captures have the black line)
- the physical tape recorder isn't the problem (evidence: direct captures with no tape inserted show the problem)
- the Firewire interface isn't the problem (evidence: tapes recorded on a different camcorder model play back with all 720x480 pixels showing up)

This suggests that there's some alignment/firmware/adjustment problem with how the output of the CCD is converted to a 720x480 image.

[Bill Ravens]

Alex....

As it was explained to me, there is no onboard codec involved in DV to avi capture. There is a codec inside the camera that does the initial compression/encoding. During a capture, the digital data is essentially copied across the firewire bus to the hard drive. When that data is view, of course, it runs thru a decompression codec. When it is manipulated in an NLE and re-rendered, it is run thru a compression codec. These are the only times the codec is used....not during capture.

[AlexOsadzinski]

I guess that makes sense. So, when capturing directly from a DV camera over Firewire into, say, Windows Movie Maker, choosing the DV codec means that no compression or transcoding takes place?

I wonder if the XL1S problem is with its onboard codec, then?

[Rob Lohman]

Capture is actually a bad term with our digital cameras. What
we actually do is a real-time copy. We copy the digital bit stream
DIRECTLY (and 100% the same) off the DV codec inside the
camera or off the tape (on playback). Your computer does not
touch this signal as long as you are storing it as a DV stream
(that is. And the program doesn't do anything stupid).

If you capture directly to mpeg or another AVI codec (like Divx)
you will re-encode. If you save to AVI type 1 or 2 or a native
.DV file (or on the Mac to Quicktime DV) you are NOT altering
the video and audio information and compression in any way.
I especially say video and audio and not stream because it
is possible that the software mixes these two together
differently (Type 1 vs. type 2 AVI files for example). The digital
data will not alter though!

So capture should actually be cald real-time copy or something.

[Rob Lohman]

I think the camera's diagram goes something like this
(recording, not playback):

1. lens
2. CCD chips
3. electronics to gather the streams and alter them
(combine colors, frame mode, gain, auto modes etc.)
4. encode the signal to a DV stream
5. output to tape/fireware/viewfinder


Presumably it goes wrong in either step 3 (probably the
most likely part!) or 4.

[Justin Chin]

I believe the encoding and compression is done separately from the viewfinder/output. Am I correct on this? Most DV cameras do it that way, so checking your image on tape is critical.

I'm sure someone smarter than me has some input.

[Steve Siegel]

I hope this doesn't sound like I'm trying to take advantage of other people's troubles (well, I guess I am!), but this thread is really scary.
I just sold my XL-1 and will be buying an XL-1s next week. Is this a problem in just new units, or has the XL-1s always had a black line at the bottom?
Would it be worth trying to find one manufactured a while back?

Thanks for your indulgence. I guess I'll be joining in you soon.

Steve Siegel
oporornis@yahoo.com

[Rob Lohman]

Steve,

They all seem to have this. It depends on your output if you
are going to have troubles with this. Ofcourse it is worying
non-the-less.

Justin... I doubt they will compress the signal and decompress
it again for viewing.. so I think the signal for the viewfinder
and other outputs gets out before the comrpession. This
might be an interesting way to see if the problem is before
or after the DV compression.

Tape does not need to be checked, someone else did already.
I'll hook my XL1S up to an old analog capture board to see
what kind of signal comes of the SVHS and composites ports.
I'll let you all know.

[Justin Chin]

Rob, I meant that the video signal is split, one to the viewfinder/output the other to compression and then tape. By checking our tape, I mean looking at it after you've shot scenes to make sure that you've got the color density you're looking for. Basically checking to see what the compression does at the tape level since you don't see it "live" in the viewfinder or field monitor.

[Rob Lohman]

Justin,

I doubt you will see compression in the viewfinder. You might
in the monitor, but I still doubt it.

I checked with my analogue capture card and found there is
at least some distortion. I'm going to check it tomorrow with
moving footage (had no time today). I still think the error is
not in the DV compression but in the previous (electronic?) stage.

[Ron Stoole]

This is BAD news for me! After reading through this thread with alarm, I immediately checked my camera and saw the black and white line everyone is talking about.

I am a multimedia developer and have just bought the XL1S specifically for full motion video used in interactive CDROM presentations. I edit the video on Premier and compress it down to an mpeg.

So the fact that you don't see the line on a TV does not apply to me...in my work you see the whole image including the overscan. Also, we have just completed a presentation in which the video was shot with an XL1 and it does not appear there.

This is just not good enough. The XL1S is an expensive piece of equipment and I expect better from Canon. I am going to take this up with them, and I sincerely hope they come up with a fix soon.

I'm really pissed off, because I balanced the purchase of this camera very carefully with the Sony PD150, and decided to go with the XL1S because of the ability to add features.... and I'm beginning to regret my decision.

Ron

[Dan C.]

If I put footage shot with the XL1s on DVD, and then watched it on a standard TV, would these underscan lines be visible (Im guessing not)?

[Rob Lohman]

Dan,

They wouldn't be. They would probably if those people are
watching the DVD on a beamer or projector for example. Best
thing to probably do is just "overwrite" these couple of
lines with black to be sure in any case. This shouldn't be
to hard todo. Ofcourse the whole movie needs to be
re-rendered (in my case this always happens due to color
correction etc.).

Canon should still fix this problem ofcourse.

[Dan C.]

Incidentally, why do TVs not show these underscan lines?

I have been thinking that it was so that any defects or irregularities at the edge of the picture were not visible.

[Ozzie Alfonso]

You really don't want a regular TV set to underscan unless you want to see all the creeping, crawling lines and dots that broadcasters place in the horizontal bar. You'd see them along the top of your frame.

Canon has to fix the problem but I'm not certain Canon is the only company manufacturing prosumer cameras that's guilty of poor tech QC. I believe I've seen the same problem in some Sony camcorders. The problem might even vary from camera to camera.

By the way - the "problem" is only a problem when we see the full frame as in QuickTime movies and other computer based playback software.