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Frame controls question in Compressor

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Chris Jones
Frame controls question in Compressor
on Jun 20, 2012 at 12:25:39 am

I'm asking this in the FCP forum because I thought it might be the best place (Didn't there used to be an Apple Compressor forum?)

I'm converting 23.976 video to true 24fps.

I've selected 24fps under settings in the encoder (there is no selection for 23.976 - is this a case where 24fps means 23.976?).

Under Frame Controls/Set Duration to: I'm not sure if I should select: "so source frames play at 24.00 fps. Or should I just leave it at: 100% of source?

Basically what do I set in Compressor to convert 23.976 to true 24 fps?

Thanks :)


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Rafael Amador
Re: Frame controls question in Compressor
on Jun 20, 2012 at 1:51:36 am

Click in the small triangle beside "of source" and select "23,98@24".
Then you will get "Set duration to 99,900 of source".
IMPORTANT: Keep Rate conversion "Fast (Nearest Frame)".
rafael

http://www.nagavideo.com


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Grant Strac
Re: Frame controls question in Compressor
on Jun 20, 2012 at 8:29:34 am

I hate to ask this because I hate when people don't answer my question when I post but why do you want to change from 23. 976 to 24 fps? It seems redundant to me (no disrespect in any form) to convert for that minute of a change. The 23.976 is actually the truest 24 fps. For example 29,97 frames is actually the true 30 fps because in your project over time the math evens out to 30fps. This works the same for 23.976 this mathematically will work to being 24fps but either is drop or non drop. When you are making it 24fps you are just making the file non drop. All of your editing programs will work with what you have.

Again I mean no disrespect to your workflow but I can't see any advantage to spending the time to do that. I could be wrong and you have a particular workflow that requires this but you are now using what would be considered 24fps. They are both a variation of each other. 23.976 is actually the more accurate because it does not loose that frame to make it round 24.

I would love to know more about you work flow to require you to make this modification.

I would tell you to always make it 100% of the source. Again it's redundant to make this step if you where to export the final product and bring it into other programs it would read it as 24fps and the time base calculations would correspond with both. If you calculate 23.976 over let's say 2 minutes and 24fps over that time it would value out the same product. 24 is just round so every 24frames becomes a round second and the 23.976 (I am not going to be exact on my math here this is just a example) at the first second would be 23.976 frames would make a second and by second three the frames would be a round 24 because the front two seconds that where 23.976 the difference between them would add on to the 3rd second to make it round. Just like 29.97 frames and 30fps are the same thing.


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Chris Jones
Re: Frame controls question in Compressor
on Jun 20, 2012 at 3:18:28 pm

Grant, If you have any interest in helping me understand 23.976 vs 24 fps, the help would be greatly appreciated. For some reason it's a concept I can not wrap my head around. There is something fundamental I'm not grasping.

I've spent a number of years making a feature film on 16mm film coming from a (film) photography background. So I've been thinking in terms of true 24.00 fps

To finish the movie we are adding a small amount of 23.976 footage to the 24.00fps film. The sound was also recorded at 24.00.

The film will be going to a film festival which requires 24.00

My thinking is to edit everything at 24.00 and when it's necessary do a conversion to 23.976 after the film is completed.

One thing I would really like to understand is what is exactly happening when clips are converted from 23.976 to 24.00 and visa versa. You may have answered that in your post, I'm going to have to go back and look more closely at what you said.

"They are both a variation of each other. 23.976 is actually the more accurate because it does not loose that frame to make it round 24."

From what you wrote did you mean that you drop frames when you convert to 24.00 fps? I thought it was just a speed change and the frame count didn't change

If I could really understand how the speed change is taking effect, then might understand 23.976 vs 24.00 more.

Thanks :)


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Matt Campbell
Re: Frame controls question in Compressor
on Jun 20, 2012 at 7:53:30 pm

Grant, the problem is that FCP and people use those terms very loosely. Often time when people refer to 23.976 they call it 24p. 23.976 & 29.97 refer to video frame rates. True 24p refers to film rate. Video has to do with the way the signal is carried electronically. Something to do with volts, watts, 60 hertz and all that jazz. B&W TV ran at 30 fps, when color was introduced they had to modify that to 29.97. something with drop frame vs. non-drop frame.

For Chris, and I what I needed months back, was true 24p output for a DPX to film out. Film runs at 24p while video on HDTV's can run at 23.976 and or broadcast 29.97 (or 59.94i).

Chris, I would use rafael's method. That dude knows what he's talking about. he's helped me loads of times.

But to answer your question, in Compressor, Encoder tab, Video settings, I set the frame rate to 24 and in the frame controls tab, followed Rafaels method. This is essentially what Cinema Tools does as well. It will conform your 23.98 to 24p. And, from your other post to me, if you don't need audio, no worries. Cinema Tools will do this almost instantly and give you a true 24p file. But, make sure you save a copy first and use that copied file to conform with because Cinema Tools will write over the existing file. Again, this happens instantly so you don't have to wait for saving or exporting.

this is essentially speeding up your footage 0.1% to fill the gap. Such a small increment won't be noticable. So once you conform, edit that into your new 24p sequence with your other 16mm footage and you're good to go.

OS 10.6.7, Mac Pro 2 x 3 ghz quad-core intel xenon, 4 gb ram and AJA IoHD


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Matt Campbell
Re: Frame controls question in Compressor
on Jun 20, 2012 at 8:07:19 pm

Chris, here is the link to the thread i posted about 24p to 23.98 conversion you wanted to see mentioned. this is the opposite of what we're talking about but the prodecure are about the same. And where we netted out was to have our dub facility here in NYC do the standards conversion on their hardware converter, like an Alchemist.

http://forums.creativecow.net/thread/8/1160456

OS 10.6.7, Mac Pro 2 x 3 ghz quad-core intel xenon, 4 gb ram and AJA IoHD


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Andrew Kimery
Re: Frame controls question in Compressor
on Jun 20, 2012 at 8:20:38 pm

I have to disagree with you Grant. It sounds like you are treating timecode and frame rate interchangeably even though they are two separate things. Frame rate is how quickly frames are captured or played back where as timecode is just a labeling system to give each frame a unique number.

It's like pages in a book and page numbers. Lets say I have a 100 page book and, in normal fashion, each page gets a number starting at 1 and ending at 100. If I decide to only number every other page then my last page number will be 50 but I will still have 100 pages in the book. Like wise, I could 'drop' a few page numbers along the way, but still number each page, so my last page number is 110 but I will still only have 100 pages in my book.

The 29.97 frame rate is not the same thing as 30.00, 23.976 (sometimes called 23.98) is not the same thing as 24.00 and 59.94 is not the same as 60.00.

For example:
A 60min clip of 30.00 fps footage will contain 108,000 frames
A 60min clip of 29.97 fps footage will contain about 108,107 frames

If we label frame 1 as 00:00:00:00 and count up one number per frame we will obviously get two different final numbers that represent the same duration of time. This is where drop frame timecode comes into the picture. Drop frame timecode will systemically skip (or 'drop') timecode numbers so that the timecode read out of the 29.97 footage will stay the same as the timecode readout of the 30.00 footage (which is the same as real time). It will not drop frames of video (even though the name implies that).

The FCP 7 manual actually has a pretty good write up about frame rates and timecode.
http://documentation.apple.com/en/finalcutpro/usermanual/index.html#chapter...


-Andrew




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Chris Jones
Re: Frame controls question in Compressor
on Jun 21, 2012 at 5:24:43 am

Thanks everyone for all the help! I feel a lot more comfortable with the ole' "23.976 or 24.00?" question.

I'll use Rafael's method. At first when I used Frame controls I was getting jagged edges along straight lines, but maybe I had a setting wrong. It's working great now.

I did have another mystery. A couple times about 10 seconds into a clip I would get 1 and double frame. I tried conforming it a number of different ways and kept getting the same thing. I checked the source footage and it was not there.

I just did a convert using Rafael's way and it went away.... but I'm pretty sure I tried it that way before and got it... but maybe not. I noticed it on another clip too. I'm not sure if it's a glitch from the advanced pull down removal or not. It's not the end of the world, since I can always remove 1 frame.

Overall though it seems to have a working workflow and a greater understanding of what I'm doing :) Thanks again all for the help :)


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Matt Campbell
Re: Frame controls question in Compressor
on Jun 21, 2012 at 1:32:00 pm

Chris, it could just be a glitch, but it sounds to me like frame doubling. This will often happen when working with 23.98 footage in a 29.97 sequence. FCP doesn't add in the proper pulldown with 1080 material (only with 720p material), so it will add in 4:2 pulldown, versus 3:2. You'll see 4 clean, different frames and 1 duplicate frame, repeated for the length of that clip.For web stuff, I usually don't care much, but that prob won't fly for broadcast.

But that's only a guess. Without seeing the footage I can't really say.

Anyway, sounds like you've found a workflow that works for you. Compressor is great for a lot of things. For me, I rely on Cineman Tools for a lot things like this. Both work.

OS 10.6.7, Mac Pro 2 x 3 ghz quad-core intel xenon, 4 gb ram and AJA IoHD


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Matt Campbell
Re: Frame controls question in Compressor
on Jun 21, 2012 at 1:26:10 pm

Excellent summary Andrew. Couldn't have said it better myself.

OS 10.6.7, Mac Pro 2 x 3 ghz quad-core intel xenon, 4 gb ram and AJA IoHD


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Chris Jones
Re: Frame controls question in Compressor
on Jun 21, 2012 at 4:53:51 pm

"You'll see 4 clean, different frames and 1 duplicate frame"

That is what is so strange. There is no pattern to it. Just on some clips, several seconds in... 1 duplicate frame, then no more.

Maybe it was because I had the settings wrong and it was trying to preserve length of the clip after it adjusted the speed. But even so, the clip I found it on was only about 30 seconds in total length and the double frame was only about 10 seconds in...so I wouldn't think it would need to do it.

But as long as it's a double frame and not a missing frame, I'm okay. I plane on converting the edited scenes to DPX in the end, so I can just remove the one DPX frame.

I've really come to love working with still image sequence files.. :)


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Skip Cercelletta
Re: Frame controls question in Compressor
on May 31, 2014 at 12:26:20 pm
Last Edited By Skip Cercelletta on May 31, 2014 at 12:33:02 pm

thank god someone gets it. there is simply no reason today that we need to keep dragging this antiquated system along any longer for this very reason.. confusion! just simply use 24p like they did in the 1930's and call it a day. it's not extremely difficult to understand one number 24, not 23.976, not 23.98 which no one is too sure if it's the same or not. in reality it's not, a simple math class would confirm this. why must we habitually drag this nonsense along. the english never put themselves through this painful experience 25 in 25 out, done! from this point forward i'm using straight 24p timebase, audio and timeline and finally be known for something in hollywood besides a janitor!!!
ps: i've listened to thousands of explanations as to the reasons for this madness from vacuum tubes to boulders but after listening to the reasons i now know why we are still stuck with insane system. philo farnsworth, the "real" father of television, ... ripped off, poor man, started with 24 frames, made sense to him because film was 24. unfortunately it worked but didn't work. the phosphor in those days wouldn't stay excited in-between frames and would pulse driving people nuts, not to mention epileptics, so he went to 30 of no other reason than to see if that frame rate would cause less of an issue and it did but not enough to solve the problem. long story short fields came into play and that now brings us to the dewey decimal system we labor under today. after the war, that would be the second out of many, muntz sold millions of black and white sets to returning soldiers at about the time color was about to come out. the powers that be at the last moment figured out that the old b&w sets couldn't understand the color signal and basically saw nothing; sort of like the trillion dollar hubble telecope with a lens they tested in space and not on the ground. any school boy thats ever gone fishing could have understood refraction, apparently not. on with our nightmare. to solve their problem they came up with the idea to clip 3k worth of a frame to trick the black and white tv's into thinking they were receiving a b&w signal and it worked. fast forward 45 years after we walked on the moon 6 times and drove cars around, we are still stuck with this fairy tail that americans can't view hd without a couple thousands of a frame takin' out... sweet jesus help us all.



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