Analyzing footage to do levels adjustments for conventions

[Ashyukun]

At a number of conventions in the past, including one which I am tech staff at, there has been a considerable problem upon playback of the AMV contest with the projectors not being happy with playing back certain videos (particularly really bright ones that wash out terribly). As an editor, I hate seeing this happen because it can really detract from the impact of a video when you can't see parts of it for being so washed out. For the con I work tech on, we're looking to find a way to prevent this from happening, and ideally the way to do this from my point of view as an editor is to have the editors themselves adjust the levels on their videos such that they will be within the parameters our projectors are happy with playing back, thus not requiring us to change the video in any way ourselves and potentially degrade the quality.

However, I realize that this is not a particularly simple thing for many people to understand, and that's what I'm looking for in the way of help here on. I would like to know if there are any simple programs, plugins, etc. out there that a finished video could be run-through that would analyze the levels of the entire video and determine the maximums, and ideally be able to have an input threshold that if the video exceeds it the program could either be set to output a copy of the video with the levels adjusted to where they need to be or to highlight where the problems are so the editor could make adjustments to the particular clips that exceed the set parameters individually.

Anything that you have to suggest, both in how to handle the problem and tools that could be used to fix it will be very appreciated! Thanks!

[Scintilla]

I don't know of anything like that, but recently I've been adding <b>Tweak(coring=true)</b> into my convention version AVISynth scripts,so's I know that at least the luma values will stay within the accepted range for NTSC... if that helps anyone.

[TaranT]

I almost posted this very same topic last night, although I was thinking more in terms of projectors with weak light bulbs; i.e. low light levels, lack of contrast. I'm not clear on what to do about it. Bumping the color saturation up seems to help. Also, increasing the gamma setting. However, both of these risk over-saturation if they are applied too heavily.

Sony Vegas has a Broadcast Colors effect in the Video FX set. This allows MIN, MAX and smoothness (?) settings on the luma and chroma. There are also check boxes to automatically limit colors to NTSC settings. For example, RGB values will be limited to a range of 16 to 235.

I think most footage will not have a problem since the limits will already have been applied to the DVD source. However, any manufactured still pictures need to be checked. Likewise special effects like glows and lens flares. And any scenes that are changed to black and white, or those that have a contrast/brightness effect.

[Ashyukun]

The coring=true in Tweak should be useful in general, and would make a good first-pass run-through to make sure the videos were compliant. TaranT is generally right though in that actual NTSC compliance isn't as much of a problem in most cases (though I think that making sure people know to not use full 255/255/255 white for their flashes/white fades is a good idea) because the source usually starts out NTSC compliant. The weak bulb problem is the other end of the spectrum from the problems we're encountering- ACen had a problem similar to that where their projectors in the AMV room were not really bright enough and they had to switch them to presentation mode, which nerfed the bright colors badly on a bunch of videos. And then had the opposite problem during the final awards presentations where the projectors had the same problem as the ones I'm dealing with, where they washed the brighter videos colors completely out.

In theory we could just tell everyone to add a standard Tweak() setting to their scripts (or have them run the final video through TMPGEnc via a script containing it), but the problem with doing that would be videos that are very dark overall will suffer as a result of it. Also, in a large number of cases we're probably going to have to re-encode things anyway because people won't bother with the adjustments themselves, but I want to have the option available for people to do the tweaking so they can't complain that we screwed up the quality of their video when we re-coded it.

[badmartialarts]

The only way I can see this working is if the con did it themselves. There's no way I as an editor could predict how my video will look on your equipment because (glances around room) I don't exactly have a projector system to play around with to make sure. Add in the fact that each projector is likely to have it's own issues and you see the problem. Now, if there was a quick and dirty correction to all videos that could be done without doing any recompression (say, for example, using a AVS script with ffdshow with some appropriate Tweak() settings), that would be ideal. Not sure if mpeg-1/mpeg-2 playback tools allow that kind of functionality or not....guess you could just make a .avs script for every video. Not that bringing more work down on the video staff is such a good idea......

[Ashyukun]

The idea would be that we would run some tests and figure out what levels the kind of projectors we would be using could handle reasonably, and then pass that information on in the rules of the contest. Given that not all of the editors who submit pay enough attention to be able to handle this type of correction, I'm toying with incorporating the idea one of the other video techs suggested which was having those who actually performed a color correction on their video include a few seconds of standard NTSC color-bars and assuming that anyone who does so has already made the correction to their footage. For the remaining videos, we would either have to recode them or find a way to get our playback mechanism (still being decided on, will likely be some form of MPEG2 playback- both a Netstream-equipped computer and a MPEG2 appliance are being considered) to adjust either individually for the optimum levels for each video (would be a lot of time and work on our part) or just have a blanked setting to apply to all the non-pre-adjusted ones.

The problem with using a blanket setting would be that, as I said before, some videos that are almost all dark footage (in our case, which is the projectors washing out badly) would suffer because there would be the chance of overly darkening it so that some of the scenes weren't as clear as they should be. It's going to be an interesting adventure to see how well we can pull it off.

[Kalium]

The only way to really do this that comes to mind is to have something that indicates exactly how the projector deviates from a calibrated RGB monitor... not exactly easy.

[badmartialarts]

Spiders are expensive pieces of equipment, and I know for a fact my monitor (an LCD flat panel) doesn't have the same color range as a regular CRT monitor.

[godix]

A few years ago I know there was a tmpgenc profile for conventions floating around (which I personally still have and use for my few con vids). Perhaps something along those lines could be done, either a tmpgenc profile or an avs script that the rules state MUST be used on the submitted version or the video would be disqualified. It'd also have the advantage of it'd standardize the format vids are submitted in which probably makes things simpler on you.

The disadvantage would be people running Macs or something else that doesn't allow tmpgenc or avs (perhaps not a problem, I have no idea what does and doesn't work on Macs). Plus some people would object to it just to be dicks, because they thought some other option would be better, etc.

The only other problem I can think of is you'd field 101 questions of 'I'm only used to WMM, how do I use this thingie you require?'

[Metro]

Spiders are expensive pieces of equipment, and I know for a fact my monitor (an LCD flat panel) doesn't have the same color range as a regular CRT monitor.

Adobe Photoshop ships with a utility that you can run to calibrate your monitor. (Adobe Gamma) Maybe you can use it to calibrate the projector.