HM100 recorded interlaced footage when in progressive mode

[Anthony Shera]

Okay, I admit this is a WEIRD problem, but the evidence is sitting on my hard drive right now.

I was going through some previously recorded footage using the ProHD file manager (I have to use this program because I recorded in the MP4 format).

I have two shots that were filming some flowers moving in the breeze. The shots were very similar, so were ideal for the comparison I did. BOTH shots were done in 1080p25 mode, taken a minute apart. However, when playing back the second shot, I can very CLEARLY see the interlaced lines, whereas these lines are not present at all on the first shot. The difference is strikingly obvious, so I know it's not a problem relating to perception. When I hover the mouse over the clip thumbnails to check, sure enough, both shots are labelled "25p"; there is no 50i label at all.

To make sure this wasn't just a problem with the ProHD file manager program, I played both shots back in Premiere Pro at 100% scale (this is the only scale that seems to show up interlacing). And sure enough, one of the shots is interlaced; the other is not! Previewing in VLC shows exactly the same thing.

This problem also occurred on the shot taken just after the first interlaced one; but all of the shots after that, all taken within minutes of each other, are fine -- the progressive mode obviously kicked back into action (and these shots all contained sufficient movement to see if there was any interlacing).

So my question is, what on earth has triggered the JVC HM100 to revert to using the interlaced mode when I did not specify this in the menu? I know for a fact that I did not change any of these settings while recording, because the project I am doing needs to use progressive footage. And this is confirmed by the metadata which clearly says "25p".




Edit: I have just found out that while playing the footage in Premiere Pro, no matter what size I have the preview scaled to, the lines are clearly visible. This is not the case with all of the other other interlaced footage I have shot in the past with the HM100. With all other interlaced footage, the lines can only be seen at 100% scaling. The fact that I can see these lines at any scale tells me that the JVC has done something very odd -- it has recorded the interlacing as progressive footage and therefore it is as if the lines are "hard wired", and no monitor, HDTV or conversion process will be able to play back the footage so it looks acceptable!!! So along with the OIS glitch I mentioned earlier, this is ANOTHER really bad (or much worse) glitch that surfaces at random. I'm not happy right now.

Update: While I was reviewing the footage, I asked myself, "Why did I record two identical scenes with less than a minute between them?" I figured there had to be a reason for this, and the only thing I can think of is that I turned on the ND filter between both those shots. The manual says you shouldn't enable the ND filter during filming or it can cause "distortion" in the image and audio. While I already knew that and so would not have enabled it during shooting (if I did it would have shown up quite clearly), perhaps after I did enable it, I pressed the record button too quickly after that and this caused the shot to have this "distortion"? Or perhaps you shouldn't enable/disable the ND filter while the camera is on, whether shooting or not? I also just checked the audio and there is nothing out of the ordinary there. However, these theories do not explain why there was another shot after that which still shows the same "distortion" issue.

Another update: I have found this same problem again, on a totally different day. About three shots taken no more than a minute apart, in the 25p mode, have shown the interlacing issue, though after a 3-minute break, the problem goes away in the remaining shots.

[Elvis Ripley]

I have seen that before when I was capturing using the HDMI port and recording internally. If I had the camera set to progressive it was always 1080i out. Some of the 1080/24p frames from inside the camera had interlaced lines on them but I haven't ever seen this during normal shooting and I have a few hundred hours on my camera's clock. You should try changing your shooting mode to something like 720/24p and then back to 1080/25p and see if you notice it after that. I know it has to reset some stuff in the camera every time a change like that is made and I change modes all the time.

[Anthony Shera]

I know that many cameras, including the JVC HM100, only output 1080i footage via the HDMI port, even if you've shot in 1080p. However this is not my problem.

I have come to learn that the way the JVC creates 1080p footage, is by somehow time-shifting every alternate line of the interlaced signal by one frame so that you end up with a "makeshift" progressive frame. This is why I can drag a 1080p clip into a 1080i timeline in Premiere Pro, and no rendering is required, because the timeline still sees the 1080p footage as interlaced, even if that is not how it looks to the eye. (Doing the reverse -- dragging a 1080i clip into a 1080p timeline -- does require rendering, however.)

Now, I imagine that this has a LOT to do with the problem I have observed. Since shooting in 720p works differently, I seriously doubt this problem would ever arise in that mode.

The question is, what has caused the camera to decide to record half of the 1080 lines one frame out-of-sync? So far I can only think of the ND filter switch somehow interfering, though that is odd since I never changed it during recording. The interlace problem seemed to go away after a few minutes of not recording anything, perhaps after I turned the camera off and turned it back on again, though I can't be sure I even turned it off during those intervening minutes.

I have also discovered that the problem can be solved by dragging the affected clip into a 1080i timeline. The interlaced lines go away after doing this. This proves that the labelled "25p" footage is in fact 50i (according to the JVC nomenclature). While it solves the problem in one sense, since an interlaced timeline with this footage would render out and play well on an HDTV, it can't ever transform the footage back into progressive unless a conversion process is used, which is undesirable.

[Leonid Yegoshin]

Anthony, Can you share the footage? Just to look into it with different means.

[Tim Dashwood]

This is a weird one. I'm going to do some tests and try to replicate.
Is there any other information you can think of that may have triggered it (besides the ND filter)?

[Anthony Shera]

Tim, I have been racking my brain to think of other possible things I could have done to trigger the problem. I have now found three instances where this problem has appeared, on three separate days. It has occurred in both the 1080p25 and 1080p30 modes. During or between the shots in which the problem exists, it is very possible I could have activated or deactivated the Telemacro mode (I have this set to the User 2 button). Other functions I may have activated or deactivated are the Zebra or the Focus Assist (assigned to User 3 and User 1). I just wish the JVC recorded this kind of metadata to each file to make diagnosis easier, but annoyingly it records very little such data. (My last standard definition camera, a Panasonic NV-GS400, recorded practically all settings used at the time, such as shutter speed, aperture, gain, white balance, and OIS etc. I'm surprised the JVC doesn't do this.)

Leonid, I will try to upload some samples soon. What's the best HD upload site? (I notice that the basic account for Vimeo only allows one HD upload per week, when I would like to upload two for comparison.)

[Leonid Yegoshin]

Anthony,

Try RapidShare: 1-CLICK Web hosting - Easy Filehosting - but it has a limit up to 200MByte.
You also can try Rapidshare.ru :: - same company but 1.5GByte limit (and faster, at least in California). I attach some brief note how to pass through Russian language menu at the end.

But first, double check - is it native MP4, I mean recorded by JVC HM100U directly to SDHC, right?

----------------
Brief instruction to upload file(s) to Rapidshare.ru :: (if you prefer it):

Go to Rapidshare.ru ::, click "browse" and select file. Mark small box in next line - ("I know the rules and will follow it" - no child porn, no copyright violation, no hate crime etc - usual stuff, you are definitely safe with your clip. You may read English version in RapidShare: 1-CLICK Web hosting - Easy Filehosting, it is the same) and press button near "Browse".

After upload, record the "URL" line - it has a direct reference to your file. During download it force you wait 60secs and suggest download after that (like RapidShare: 1-CLICK Web hosting - Easy Filehosting does).

[Anthony Shera]

Thanks for that, Leonid.

You can download an 18 MB sample of this video at

http://dl4.rapidshare.ru/1123902/29914/720p25.m2v

Please note that I downconverted the video to 720p25, but despite this, the end result is that it looks EXACTLY the same as the 1080p25 version (the lines are clearly visible). I played it using VLC. It is an MPEG-2 file.

[Doug Tessler]

This was 25 p and a still frame taken from the footage you can clearly see lines

[Leonid Yegoshin]

Originally Posted by Anthony Shera

Please note that I downconverted the video to 720p25

Anthony, is it possible to see an original clip from camcoder? The down converting process may destroy some valuable information or even add something else.

I will look your file later.

[Keith Moreau]

I just had the same thing happen to me the other night. It was a band performance in a bar and I thought it might have something to do the shutter interaction with the neon light that was in the window and sending some light to the scene, although it didn't make too much sense.

Unique camera parameters about this shoot:

The lighting there was abysmal, so I had the camcorder on high gain (9 or 18 db) , and in 1080 30P aperture wide open with a 1/30th shutter speed. I usually tape in 1/60 second shutter speed or faster. On other thing unique about this shoot is that I had the camcorder plugged into the AC/DC power supply, so I wouldn't have to worry about changing batteries during the 3.5 hour shoot.

This glitch remained on about 3 hours of HM100 video I shot that night over the span of about 15 files, it didn't come and go as others have mentioned. (used file/card spanning, I turned off record only a few times during breaks. The spanning didn't work quite as reliably as expected, maybe I'll address that into a different forum post.

The recording was not critical, or I would have cared a bit more and tried to correct the problem in post, but as it was it was just for feedback for the band and for a SD DVD to give the band.

Looking at this forum thread it makes sense that there is some bug that is causing this. I did a more important shoot the following morning and it seems everything was recorded normally (I had it mostly in "Auto").

Does it have to do with gain, shutter speed, AC power, or is it some random thing? Also the problem is you really can't tell anything is wrong with the LCD. I looked at the original clips directly from the HM100 through an HDMI port and I can't see interlacing like I can when playing the files via FCP or Quicktime. Maybe the problem a glitch in the file information that the HM100 writes and that QT uses, I don't know. All I know is that playing clips that appear to be recording in the same format, on my Mac with 10.5.7 this particular night's 1080 30P files had this problem.

I tried seeing if putting the clip into a XDCAM EX 60i timeline to see if I could fix it, and it didn't for me. It looks like the interlacing is embedded into progressive video, there's no way to 'deinterlace it.' so the footage is junk. It seems that the problem is not just that you have interlaced instead of progressive, it's that you have interlaced footage put into progressive frames. You can't fix it in post. If you had an important shoot with a lot of movement, you'd be screwed.

I'm just hoping this is an isolated incident. I haven't closely looked at all the previous footage I've shot with the HM100. I think most of it is OK though, but I'm not certain.

Attached is a screen capture of an area of an arm moving which clearly shows the interlacing (this was from my FCP canvas window, and not the whole frame)

So Tim, JVC or others, if you are listening, please, please investigate. If you want I can upload some files to one of your FTP sites so you can investigate further.

[Leonid Yegoshin]

Keith,

Is it MOV?

Can you share the original clip if it is not MOV file? (I can't work with .MOV files, all my stuff is for MPEG/MP4).

P.S. As for now I see the common - low light (ND filter in Anthony case). It seems that under shutter speed 1/30 there is some jadder...

[Keith Moreau]

Leonid, it is a .MOV, I shoot in that mode because I use a Mac. I do remember that when I first turned the HM100 on I believe I had the ND on. I don't think I had it recording right at that point, but I did turn the ND off while it was still powered on. This shouldn't be an issue though, I do it all the time.

Probably we need to do more tests to see if we can repro it. Problem it is doesn't seem to show up easily unless you copy over the MOV /.MP4 files.

[Andy Urtusuastegui]

I want to try some tests. But first, I need to understand a few things.

1. Are we testing for 24p, 25p, and 30p in 1080 mode?

2. Does the HM100 capture 24p natively (24 frames, not 24p over 60i)

3. Does the HM100 capture 30p natively (30 frames, not 30p over 60i)

I can not get a clear answer from the documentation on how the HM100 handles these.

Thanks.

[Elvis Ripley]

1. Are we testing for 24p, 25p, and 30p in 1080 mode?
It seems like his were 25p I have seen my own under 24 but I shoot a lot under that and only noticed it when and HDMI cable was also plugged in. I am talking about the 24p the camera recorded, not what came out of the cable.

2. Does the HM100 capture 24p natively (24 frames, not 24p over 60i)
Native
3. Does the HM100 capture 30p natively (30 frames, not 30p over 60i)
Native