DV Artifacts/Scan Lines? (Digital8)

[BillyJeanB]

I got a Digital8 Camera to digitize a tape I have and I'm copying it directly with Firewire, but it seems like it has some odd scan line type of artifact on some parts. I only have one tape to test it with but It seems to only be on fairly bright/white parts of the screen, and It is more noticeable after adjusting the brightness/contrast.

Check the raw file, look at her face/cheek and you can just barely see it when the lights are bright. It's not interlacing, it's like a darker set of lines just there. Then when adjusting the brightness/contrast afterwards it is also more visible, and it is slightly seen on the equipment on the lower left side of the screen with the light shining on it. It doesn't go away after deinterlacing. And the lines look darker than the surrounding stuff, that's why they are noticeable. Also the S-video out and composite have the same problem when hooked to a TV, actually it is more noticeable.

Also why does the raw file look really blocky? After QTGMC it is almost entirely gone, but on the edges of everything (like her hair) in the raw file it looks very blocky, is that just part of the way it is interlaced?

I just want to make sure that this is "normal" and not something wrong with the camera I bought.. (A Sony DCR-TRV320)

[Brad]

I just want to make sure that this is "normal" and not something wrong with the camera I bought.. (A Sony DCR-TRV320)

The playback camera can't possibly be to blame, since it's a digital tape. Digital playback errors aren't subtle.

It's not interlacing, it's like a darker set of lines just there. Then when adjusting the brightness/contrast afterwards it is also more visible, and it is slightly seen on the equipment on the lower left side of the screen with the light shining on it. It doesn't go away after deinterlacing. And the lines look darker than the surrounding stuff, that's why they are noticeable.

The contrast of the very brightest part of the image alternates every half-field, for some reason.


Single field

AVISource("DV.avi",pixel_type="YUY2")
ColorYUV(off_y=-16,gain_y=-4)

SeparateFields()

Histogram()

[Attachment 51339 - Click to enlarge]

Split into two. If you open the images below in two different tabs in your browser and switch quickly between them you can see how the center of the image flickers from near-white to true white and the brightest part of the histogram jumps up to fully-clipped in the second image.

AVISource("DV.avi",pixel_type="YUY2")
ColorYUV(off_y=-16,gain_y=-4)

SeparateFields()
AssumeFrameBased().SeparateFields()

Histogram()

[Attachment 51340 - Click to enlarge]


[Attachment 51341 - Click to enlarge]

I don't know how you might fix it so both halves are exposed the same.

Also why does the raw file look really blocky? After QTGMC it is almost entirely gone, but on the edges of everything (like her hair) in the raw file it looks very blocky, is that just part of the way it is interlaced?

I'm not sure, but I think this might just be due to DV's 4:1:1 chroma subsampling and DCT compression.

[jagabo]

The interlacing comb artifacts are normal. But that's some really ratty DV video. Far worse than "normal" DV.

[BillyJeanB]

The interlacing comb artifacts are normal. But that's some really ratty DV video. Far worse than "normal" DV.

That must be because of how it was recorded right? Or somehow got worse over time? It's from 2004. I just want to be sure that there is nothing more I can do while I have the tape, because I'm sending the tape back to the person who filmed it.

After QTGMC it looks fine but could be better. I do have DV videos from MiniDV that look better as far as I can remember

[BillyJeanB]

I just want to make sure that this is "normal" and not something wrong with the camera I bought.. (A Sony DCR-TRV320)

The playback camera can't possibly be to blame, since it's a digital tape. Digital playback errors aren't subtle.

It's not interlacing, it's like a darker set of lines just there. Then when adjusting the brightness/contrast afterwards it is also more visible, and it is slightly seen on the equipment on the lower left side of the screen with the light shining on it. It doesn't go away after deinterlacing. And the lines look darker than the surrounding stuff, that's why they are noticeable.

The contrast of the very brightest part of the image alternates every half-field, for some reason.

Thanks. It doesn't bother me too much if there is nothing that can be done, it just bothers me that I could be doing something wrong or there could be something wrong with the camera. I have seen those MiniDV cameras and you're right, it's very obvious when something is wrong.

[jagabo]

The interlacing comb artifacts are normal. But that's some really ratty DV video. Far worse than "normal" DV.

That must be because of how it was recorded right?

Yes.

Or somehow got worse over time? It's from 2004.

Deterioration of the tape would look far worse.

After QTGMC it looks fine but could be better.

I did this:

LWlibavVideoSource("DV.avi", format="YUY2") 
ColorYUV(gain_y=-10, off_y=-10)
ConvertTOYV12(interlaced=true)
QTGMC()
TurnRight()
QTGMC(InputType=2)
TurnLeft()

[oln]

One thing that can make things look blocky is if the person filming was zooming in with a digital zoom. Digital8 was a sort of transitional format. High-end cameras at the time would be using miniDV (or DVCAM) instead.

[dellsam34]

That blockiness is not digital zoom if it is it would be applied to the whole frame not just the bright parts, My interpretation is that the digital camcorder's compression chip when the light level shoots up to the roof it doesn't know what to do with the clipped levels so the compression algorithm goes to low resolution mode on those bright spots to save on data bandwidth. Notice that this happens all the time with even high end camcorders when other cameras flash strikes and the bright frames look horrible. That camera shutter suppose to adjust for light level quickly but it didn't, typical problem with low end camcorders back then. But if I was there at the time of that event I would have kicked that guy with the light torch. I've seen this in night events videos all the time and I'm not talking about camera flashes, I'm talking about the idiots with a video light that they keep turning on and off to save on camcorders battery screwing other people's work.

[BillyJeanB]

That blockiness is not digital zoom if it is it would be applied to the whole frame not just the bright parts, My interpretation is that the digital camcorder's compression chip when the light level shoots up to the roof it doesn't know what to do with the clipped levels so the compression algorithm goes to low resolution mode on those bright spots to save on data bandwidth. Notice that this happens all the time with even high end camcorders when other cameras flash strikes and the bright frames look horrible. That camera shutter suppose to adjust for light level quickly but it didn't, typical problem with low end camcorders back then. But if I was there at the time of that event I would have kicked that guy with the light torch. I've seen this in night events videos all the time and I'm not talking about camera flashes, I'm talking about the idiots with a video light that they keep turning on and off to save on camcorders battery screwing other people's work.

That seems like a good explanation. Well anyway I'm glad the video isn't any worse. It's probably the only video of the event we'll ever get and it's her last ever performance so it's just very lucky to have any video of it at all.

[BillyJeanB]

I realize that having santiag in my QTGMC script is actually why it looks much better after deinterlacing, I have it in there for VHS to smooth the edges a bit bit having it totally salvages this with those blocky edges. I have it twice in the script so it does a pretty good job. It makes a big difference.