I see a lot of color spill. Is that what you mean by 'straight line' artefacts?
Thanks for replying Harm....
No its not the spill..... the artifacts arent immediately obvious but resemble the horizontal interlacing artifacts (if that isnt confusing things!)
If you expand the image in my first post its much clearer that the embedded version.
They really start to cause problems when I key out the green which means I have to tweak lots of settings and ultimately results in loss of detail around hairlines etc.
They are also noticeable on footage that has lots of straight edges such as buildings etc.
I would reverse the process: key first in AE then import into Premiere for futher editing.
Thanks for replying Ann
I did try that approach but unfortunately I was presented with the same problem.
The lines are there in After Effects too and look even nastier when I key out the green.
Have you judge the footage in your final output (which is?)?
Final output is a TIFF sequence.....at 1920x1080
The TIFF's are for AE but then...
I would like to know the entire workflow.
Sorry I misunderstood !
I am a digital effects artist working with 3D so this is the workflow I am working with:
I shoot my plates on HD with any green screen work that might be needed.
I then get an edit that I am happy with in premiere importing the AVCHD footage as a .mts file from the camera.
I then export out a series of TIFF sequences on a per shot basis at 1920x1080. Everything is as progressive frames.
3D work is carried out in other apps and combined with the TIFF sequences in After FX.
The final comp is exported as an 'animation' codec (or similar relatively uncompressed codec) to be put back together in Premiere as a final edit complete with visual effects again at 1920x1080.
I would export from here any number of formats according to my need. eg DVD, web, etc so the codec and res would vary accordingly.
Rule of thumb is to keep it as uncompressed and as high a resolution as possible until this stage.
Just a comment about your key shooting technique based on what I see in your screen grab.
The lack of any back or rim light (and the flat lit image at the edges) makes keying more diifficult as well as creating an "unnatural look".
I can t see artifacts in your grab BTW. Artifacts are usually square or rectangular (pixel-like)
I'm importing AVCHD
You might try something not so heavily compressed.
Thanks for replying guys
I ve included a keyed version of the image to show what I mean. I think this is image is a bit clearer
To address both of your comments:
I dont have any option other than importing AVCHD unfortunately. The camera I am using saves .mts files by default and doesnt allow for saving in any other format. Therefore i can only import these .mts files.
With regards to the lighting etc on this image.....this was really just a quick crude test I made using a new HD camera.
I wanted to see how well I could key ot the green in fairly unforgiving circumstances.
However I would say that it probably isnt causing the artifacts Im talking about.
As I said, it really becomes a problem when I key out the green and tweaking theses settings to improve the matte means a trade off with detail like hair lines etc.
Ive uses HD footage with green screens before but I havent had these issues.
You said you use progressive material, but you also said:
the artifacts arent immediately obvious but resemble the horizontal interlacing artifacts (if that isnt confusing things!)
and that is what it looks like in your last screenshot. That raises the question whether the camera is truly progressive or wraps it in 60i and how does PR see the material? Does this also show on a properly calibrated external monitor? The program monitor is not the best way to judge footage.
The camera gives me a choice of shooting in 25f progressive frames or 50i although I cant be sure that it is true progressive.
In any case I always make a point of interpreting the footage on import so that it is progressive but I have to say that my knowledge of the finer technical aspects in this area is a little shaky!
With regards to my comment about the the artifacts resembling those of interlacing, I was really using this as an example of how the artifacts looked but I concede that I could be sending myself around in circles on all this!
I assume that even if the footage is interlaced by default that it can be saved out of Premiere or AFX as progressive footage/image sequences cant it?This would eliminate any interlacing issues.......I think!
Incidentally the camera I am using is a Canon HFS11. Not broadcast but it does produce a pretty good image.
You guys are clearly more clued up on all of this than I am and I welcome any other workarounds or pointers as to what I may be doing wrong.
The Canon 25pf format is actually wrapped in 50i and is not truly progressive. To test that it is properly recognized by PR, take a clip in the project window and drop it on the New Item icon. That will create a new sequence with that clip on the timeline. What are the sequence settings for that new timeline? Does it differ from your existing timeline?
The easiest way would probably be to activate your existing timeline, CTRL+A to select all and then copy/paste these in the new timeline.
I gave that a go but it doesnt seem to have made any difference
I'm a little confused I think....!
When you import interlaced material and let PR handle it as progressive, as was the case in your original sequence, you lose a lot of the horizontal resolution, (this does not apply to your new sequence!!) because PR is not very smart in deinterlacing.
Now that you have your material in the proper format, without loss to the original resolution, you have to take into consideration that you are watching interlaced material on a progressive monitor, that is not really suited to judge quality. Hence my suggestion to check the quality on a properly calibrated external monitor.
I do not know enough about the Canon pf format to explain why you still see interlacing artifacts, when in the ideal situation you would see two identical fields. What you can do to get to the bottom of this is to go to your playback settings, and check what happens if you choose Display first Field, then change it to Display Second Filed, then Display Both Fields. If my assumption is correct using the first or second field will remove the interlacing artifacts and when using both fields, you will see it again.
Hope this helps.
I suspect this is related to canons pf format.
I have played around with some settings to no avail.
Interestingly I exported a single frame and loaded it into Photoshop. I then ran the de interlace filter on it which removed the artifacts.
Interesting...... (and annoying that there isnt a similar filter in AFX or Prem!!)
I've been looking into some of these issues as I'm working on a project in which I used a Canon HDV camcorder that recorded using the 24pf format; I'm using 24p instead of 25p, but I think the same principles should apply.
Based on the reading I've done, the reason you're seeing those artifacts is that, well, 24/25pf was never actually meant to be interpreted and viewed as progressive footage. The simple explanation is that it's a rather haphazard way of packaging a progressive "look" into an interlaced stream, without actually generating progressive footage. Yes, we can interpret the footage through a few different workarounds, but due to HDV's and AVCHD's 4:2:0 chroma sampling and their interframe nature, you'll almost always see those artifacts because we're essentially putting the fields together in an order in which they don't belong! This will be especially noticeably in any portion of the video where you have lateral movement, as the field-based long GOP recording isn't recording discrete images for each and every frame. This is an issue with MPEG encoding/decoding, especially where you have strongly saturated colors, such as the hard line between your actor's arm and the green screen. This page is about DVDs, but the concepts apply to MPEG-4/AVCHD as well: http://www.hometheaterhifi.com/volume_8_2/dvd-benchmark-special-report-chroma-bug-4-2001.h tml
This currently-open thread over at VideoHelp might offer some insight, even if the camera isn't the same. There are numerous issues to deal with when recording to such a compressed format. You might consider getting an add-on card for your computer that would let you record uncompressed from your camera through its HDMI output. In that case, you can eliminate the 4:2:0 chroma subsampling issue, and might even be able to circumvent the frame rate nonsense, as well.
Thanks so much for taking the time to post that info.
Interesting......progressive doesnt mean progressive in this instance. I guess ultimately its a consumer level camera I am using that doesnt quite cater for some of the things Im expecting it to do, although when one reads that a camera records progressive frames it doesnt seem unreasonable to assume that it does exactly that.
Ill take a look at the links you posted and educate myself a little further on all of this.
many thanks again.
Matt, you are not alone in this. The Marketing departments do a great job in veiling the true capabilities of a camera in fantastic (hollow) phrases that lead many people to believe the claims, including the sales people, who most of the time have no idea what they are talking about and/or are heavily influenced by their bonus opportunities and lose objectivity.
This may sound arrogant, but I think I have some basic understanding about video, editing and computers, that in some cases may surpass the average Joe, and I have seldom met a sales person able to answer my questions, including Japanese reps from Sony at the IBC, where you would think they have their best people around. Last year it took three of them to give me a definite answer to a question, at least I still hope it was the definite answer. This happens repeatedly, so the conclusion is that either I ask very dumb and unintelligible questions, or they don't know all the answers. I prefer to think the latter is the case.
On that assumption, it is no wonder that a lot of people are given incorrect or incomplete info when they need to make a decision and it is pretty difficult to make a well founded decision on partial or incorrect information. It ends up like a poker game.
CS5 ( and previous versions) appears to have a bug in the way it decodes AVCHD - I'm sure that is part of your problem. There is recent discussion on other forums about this - to avoid posting links you could perhaps google the following: avchd premiere cs5 chroma
Try decoding your AVCHD footage to Cineform avi using their free 14-day trial version (HDLink is their transcoding tool) and see if that helps.
A second part to your problem may be related Canon's PF format, which even HDLink seems to mis-recognise. Decoding using libavcodec with ffdshow (both freeware) gives a proper decode of PF footage. But I realize this may be sounding like Greek by this point ... sorry. Again some googling may help.
Thanks Harm...glad Im not the only one!
Not good is it......
Well Im starting to get some interesting info on all this now. The latest is that the artifacts could also be partly caused by a bug in the AVCHD import.
and as I type this another post has just confirmed it!!
Those horizontal lines on the left hand image are exactly what I am getting on my footage. True it can only be seen close up but as someone points out its a real pain when it comes to green screen!
Interestingly a PDF doc suggests that Canon cameras (including my one ) are specifically supported by Premiere.
If I dont have any joy I may well start asking about IVTC and pulldowns to get around the problem........my head hurts now
Well if we are posting links, then Matt you should have a read of this thread, starting with post #56. which specifically discusses proper decoding of AVCHD from Canon HF-series PF footage:
Looks like a decode before import is in order
Ill have a good read of the link....
The camera I am using saves .mts files by default and doesnt allow for saving in any other format.
That's true of most cameras. The suggestion was ultimately to use different cameras.