Compression artifacts and shutter speeds

[Jeffrey Butler]

Well, I must say that I wound up with the worst footage I've shot so far! But I don't think it has much at all to do with some of the settings pulled from Tim's stuff. I adjusted the knee, the DNR, black stretch..."color stuff", really.

I got sooo much compression artifacting! I was shooting 60p, but really needed a faster shutter. The 1/60 has produced great slo-mo, but lousy (blurry) freeze frames. Anyway, there is no higher multiple of 60 for shutter speed, so I shot 500. 7.5/15/30/60/100/250/500/1000/2000 I think are the options - the only multiple(s) of 60 are 30/60?? Is that intentional? Doesn't it seem odd that you have an entire "camera mode" that can only shoot one shutter speed? And that mode is great for sports? The freeze frames were more crisp with 500, and I did turn off DNR, but honestly, this stuff was horrible.

How many settings can you store on the supplied memory stick? It should be dozens... I can see loading up a "sports" setting and "concert" setting and a this and that...I keep seeing the overwrite pop up, and it would seem, even though I rename the stuff, that it's only storing one...

[Tim Dashwood]

Originally Posted by Jeffrey Butler

The 1/60 has produced great slo-mo, but lousy (blurry) freeze frames. Anyway, there is no higher multiple of 60 for shutter speed, so I shot 500. 7.5/15/30/60/100/250/500/1000/2000 I think are the options - the only multiple(s) of 60 are 30/60?? Is that intentional?

1/60th of a second isn't really fast enough for freeze frames. Just imagine shoot 1/60th on a still camera. If you want ideal freeze frames for sports you are looking at 1/500th at least.

Were you shooting in 720P60 mode? If you are shooting in that mode with the intent to slow the footage down to 30fps or 24fps then don't use 1/60th shutter. It will look blurry. Double it (which you pointed out is technically impossible) or use 1/100 for authentic 'film' style shutter without the obvious stroby look.

As for your comment on compression: what type of compression artifacting were you seeing? Blocks, mosquito noise, 8-bit gradiant compression?
I'm curious because I've shot alot of 60P the past couple of months and even though I would say that not every shot is always perfect, I've had very good luck - especially considering I always slow that footage down to 24P.

[Jeffrey Butler]

Originally Posted by Tim Dashwood

Were you shooting in 720P60 mode? *snip...Double it (which you pointed out is technically impossible) or use 1/100 for authentic 'film' style shutter without the obvious stroby look.

As for your comment on compression: what type of compression artifacting were you seeing? Blocks, mosquito noise, 8-bit gradiant compression? I'm curious because I've shot alot of 60P the past couple of months and even though I would say that not every shot is always perfect, I've had very good luck - especially considering I always slow that footage down to 24P.

Soccer_042807 14&15 show a previous game w/ DNR ON. That's the only setting that I can think of that would have such a dramatic difference - but what changed btwn. the two games was DNR on to off; shutter from 1/60 to 1/500 and black stretch on from normal.

The mode was 720/60p for both shoots. The key jpeg to look at is 050507 #9 - that one has horrible all over it. The 8 & 10 are on either side of it - a total of 3 frames - one before, one during, and one after to show the places without motion.

The other two shots 042807 14 & 15 are two shots with a similar amount of motion, if not more, than the "horrible one" - and while the compression is there (all clips are Apple Intermediate Codec)(and images are jpegs highest quality) it's masked - and perhaps that's what the DNR is doing...

Here's the link to the video segment that is represented by 050507 8,9,10 Though the still frames really do tell most of the story, I posted an .mp4 at 8000 kbps - however, it does smooth out most of the noise. I'll upload the "raw AIC" stream if there's any interest...

A few notes about the shoot - it was a gray day, ND2 was on, the shutter was 1/500 the mode was 720/60p the capture method was Final Cut Pro, firewire, Apple Intermediate Codec. I have real issues capturing straight to the HDV 720p codec Apple supplies. It's takes the first few seconds of each shot to determine that a new clip is being made, and essentially nips every shot by 3 or 4 seconds - useless...so I have to use AIC until I can figure out what's up with FCP's native 720/60p mode....

Ya know, after looking at all this footage and trying to compare, I think ALL of it has more compression in it than I originally thought. I think it's time to make Apple's native 720p support/capture work. I wonder just how much is really getting added by AIC. Oh, and I'm using the 17x upgraded lens...maybe HDV just sucks in certain situations, and I need to get a CineAlta (haha).

[Jeffrey Butler]

Originally Posted by Sean Adair

Jeffrey: only 4 slots on a SD card, no matter what size, also 4 user slots in the camera itself.

You CAN get shutter at 1/120 by going into variable shutter mode in the switch menu. It sure takes a while to wind into it, but it will stay there until you change the custom shutter setting to something else (you can turn the shutter off). I don't think it will make that much difference from 1/100 though.

Ok. I noticed the shutter in 24p has a 24/48 and in 60p has 30/60, so the camera is doing a little bit to help. I wouldn't expect the shutter to affect much more than light, but perhaps it was just a double whammy to turn DNR off, shoot in medium gray light with a fast shutter - whereas a 1/60 under similar conditions would actually blur the noise a bit already (+ DNR) in a fast pan...still - this can hardly be the sports shooters format of choice...there's something going on here! Maybe 720/60p is, but perhaps not using HDV.

So there's room for only 4 scene files on these cards, then? Hmm....that's not very impressive. Maybe I should just be happy for the ability to load the same config on multiple cameras and move along...but I can't help but want the ability to load files for all these settings specific conditions. I mean, it's like a filter set in post! But being able to actually apply them in time sensitive situations (like a wedding, or just going indoor/outdoor) kinda sucks. I'm going to have a print a hard copy out out and keep it with me - as opposed to being able to load and go...it'll kinda work, but...

[Sean Adair]

wow, that is some blocky image (#9).
Some of it probably comes from stacked consecutive different systems of compression, but I trust you in describing the footage. I've had some very poor results at times, and great results other times.
Paolo mentioned that one of the triggers for noise (which translates to compression artifact) is large areas of uniform color.
http://www.dvinfo.net/conf/showpost....26&postcount=4
I wonder if the grass is giving you this effect here?
I've also had very complex busy scenes that compressed very well, which seems counter-intuitive.

[Sean Adair]

and re those SD cards, it would be nice if large cards could take more files, but hey, there are better things to complain about. The 4 spaces in the camera make 8 user files on demand, and smaller SD cards are only about $15 now, so you could get a wallet full if you want.

[Jeffrey Butler]

Originally Posted by Sean Adair

wow, that is some blocky image (#9).

Yeah, I wouldn't mind if it came from a Sony HC-3 or Canon DV20...but what are those other two chips for!? LOL. I'm starting to want Sony's new (mini) XDCAM w/ manual lens (read - other format)....

I absolutely love this 17x lens...and...I'm willing to really learn this camera. So that being said, I will continue to press into figuring it out, but man...I could actually see this happening in the Viewfinder...that's how serious it was...so there's not much of it getting added in post.

[Jeffrey Butler]

Originally Posted by Sean Adair

The 4 spaces in the camera make 8 user files on demand, and smaller SD cards are only about $15 now, so you could get a wallet full if you want.

That's not a bad idea. I need to look into the user spaces in the camera...I haven't found those yet. In fact, I just today found that the shoulder grip actually slides back and forth. If only the viewfinder could move forward a bit - then that earpiece may actually be useful...

[Stephan Ahonen]

What is wrong with shutter speeds that aren't exactly multiples of 1/60?

[Jeffrey Butler]

Well, that's a good question. I think I have an answer, but outdoors, it's a moot point.

Frame rate it typically an offshoot of the power cycle of the country you're in - for instance, if you were to shoot in an NTSC country, your power is going to be be 60Hz - power that drives all the lights in the country. So if you shoot at a multiple of 60, you won't ever see flicker. What's flicker? Well, if you take your camera over to another country that has power at 50Hz and you shoot a shutter multiple of 60, lights in the scene will actually flicker. Especially fluorescent lights.

I shot in Vietnam and was kind of aware of this, but when I checked my dailies I realized that I had neglected to set my shutter at 1/100 - and boy did those fluorescent lights go crazy! And of course, you could really see this on an interlaced monitor. But at 1/100 everything was cool - and that all because of the 50Hz power cycle. SO, any multiple of 50 was in the clear for light flicker. And in NTSC countries it's 60.

It's kinda like shooting a television set. You have to match the refresh rate of the screen or you'll get that black bar....

But we're talking about shutter rates and compression, so it beats me - I guess that's the question.

So why is a higher frame rate out of doors bad? Well, I dunno - does it have anything to do with the HDV 720/60p? I was asking the question in the context of 60p (or 50p). Does this progressive frame capture at 60 frames per second act in anyway like the power hz does? I'm not sure. The shutter affects a lot of things, but compression? Perhaps if it doesn't allow enough light in....

Though forget compression - is it necessary to match the shutter to the capture rate?