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07-26-2014, 01:44 PM   #1
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4K timelapse "bug"

Just played around with the 4K timelapse functionality and writing this just in the hope that someone else might find it useful
Basically the 4K timelapse (that you can activate in movie mode by pressing the "Up" 4-way controller and selecting "Interval Movie Record") records it's output in an AVI file with MJPG (Motion-JPEG) compression. I did a 15 min recording with picture taken after every 2 seconds.
That should give me 15min * 60 (sec/min) / 2 = 450 frame video.
What I actually got was a 1353 frame video that was at 24fps and about 56 seconds long.
Since this was somewhat unexpected I investigated a bit and I can clearly see that each and every frame was in the output file 3 times.
There is no difference whatsoever between those frames.
MJPG is not like MP4 or other common compression methods that compare frames to the previous one and can compress identical frames a lot so sadly this means the file is actually 3x larger than it has to be. In reality the output is a 8fps video with frames duplicated twice to look like 24fps but it gives absolutely no advantage.
It's fairly easy to get rid of those duplicate frames completely (and without any loss of quality) by using for example VirtualDub and setting "Direct Stream Copy" and "Process every 3rd frame".
Pity though that such a waste of time, card space etc. was deemed necessary by someone.

My personal guess why it was done like that:
Likely 24fps was chosen for the timelapse as the lowest commonly used standard framerate (lowest is better as we all want our pretty timelapses to last a long time) - and then likely someone higher up the corporate ladder complained that their resulting timelapse was too short I know it sounds stupid but it's such a stupid "feature" - ok, bug as I wrote in the title already - that I just can't think of a better reason.

Hope it might be helpful for someone else who uses this feature.
And I know that "pros" just shoot pictures and convert them to video on the computer, not in-camera because that gives more creative freedom etc.

07-26-2014, 02:03 PM   #2
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darwinfish105 is one of the best at time lapse and here is one of his 4K K-3 time lapse :
High-Def(????): PENTAX K-3??????????


07-26-2014, 03:40 PM   #3
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QuoteOriginally posted by procyon Quote
activate in movie mode by pressing the "Up" 4-way controller and selecting "Interval Movie Record") records it's output in an AVI file with MJPG (Motion-JPEG) compression. I did a 15 min recording with picture taken after every 2 seconds. That should give me 15min * 60 (sec/min) / 2 = 450 frame video. What I actually got was a 1353 frame video that was at 24fps and about 56 seconds long. Since this was somewhat unexpected I investigated a bit and I can clearly see that each and every frame was in the output file 3 times
I'm not interested in 4K myself, but perhaps it's a limitation imposed by the processing speed. What happens when you take a picture every 6+ secs?

Dan.
07-26-2014, 03:43 PM   #4
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In K-01 the timelapse was (or still is, didn't recently) to put the files also in threefold in the movieclip, 5 frames and playing 15 fps. So they have done it before.

07-26-2014, 04:11 PM   #5
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QuoteOriginally posted by dosdan Quote
I'm not interested in 4K myself, but perhaps it's a limitation imposed by the processing speed. What happens when you take a picture every 6+ secs?

Dan.
The issue is not that it takes less pictures than expected - it takes the correct amount of pictures - but then duplicates them twice to make an impression of more frames. It would be faster to just not duplicate and write one frame per one "click" of shutter

---------- Post added 27-07-14 at 02:13 ----------

QuoteOriginally posted by RonHendriks1966 Quote
In K-01 the timelapse was (or still is, didn't recently) to put the files also in threefold in the movieclip, 5 frames and playing 15 fps. So they have done it before.
Ok, sad to hear that - guess it's here to stay then. Oh well - time to invest in even bigger SD-cards then I guess
07-26-2014, 04:58 PM   #6
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QuoteOriginally posted by procyon Quote
time to invest in even bigger SD-cards then I guess
What if you set your JPG quality to just 1 or 2 stars? Does that make any difference to file size?
07-26-2014, 05:33 PM   #7
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Why not just use the intervalometer and make the AVI yourself using the free and excellent MakeAVI??
I found the Pentax TL Movie result to be rubbish actually.
07-27-2014, 02:02 AM   #8
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QuoteOriginally posted by Steve.Ledger Quote
Why not just use the intervalometer and make the AVI yourself using the free and excellent MakeAVI??
I found the Pentax TL Movie result to be rubbish actually.
That does deliver much better IQ.

07-27-2014, 09:01 AM   #9
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I know that there are better solutions and I have used them - it doesn't change the fact that this particular implementation is severely braindead.
Also I don't get why I would want to change the JPG quality level? Even if that makes the file smaller it would lower the quality which is not something I would want.

Regarding the comments about quality - what kind of issues did you notice? Is the downsampling to 4K bad (i.e. aliasing, artefacts) or the JPG compression in the MJPG too strong (I saw frames of about 2MB inside the AVI)?
07-27-2014, 11:18 AM   #10
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QuoteOriginally posted by procyon Quote
I know that there are better solutions and I have used them - it doesn't change the fact that this particular implementation is severely braindead.
And so, you use a better method because there's nothing you can do about the brain dead one, right?
07-27-2014, 02:46 PM   #11
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QuoteOriginally posted by Steve.Ledger Quote
And so, you use a better method because there's nothing you can do about the brain dead one, right?
Exactly - but to be honest I can do one thing - write about it somewhere where people who might use that themselves will see it and hopefully find out about it's shortcomings beforehand
Which is what I kind of said twice in my first post
07-27-2014, 05:07 PM   #12
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Fair enough. Clearly I wasn't thinking.
07-28-2014, 04:04 AM   #13
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timelapse bug indeed

Both Pentax Q and K-3 which I own has similar behaviour. The Q actually replicates every frame 5 times, while the K-3 does 3. Pentax should modify the firmware so that the user could select the number of replication with the possibility to completely disable it. Yes, you can removed them in VirtualDub, but that is extra work. Smooth timelapse can only be achieved with no replicated frames. The user should also be able to select the resulting fps in my opinion, since this is only a matter of a single parameter value in the AVI file container.
07-28-2014, 12:14 PM   #14
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QuoteOriginally posted by norArn Quote
Both Pentax Q and K-3 which I own has similar behaviour. The Q actually replicates every frame 5 times, while the K-3 does 3. Pentax should modify the firmware so that the user could select the number of replication with the possibility to completely disable it. Yes, you can removed them in VirtualDub, but that is extra work. Smooth timelapse can only be achieved with no replicated frames. The user should also be able to select the resulting fps in my opinion, since this is only a matter of a single parameter value in the AVI file container.
Good that you mentioned that - I have been puzzled by the Q-10's timelapse video which gives a video which shows up as 24fps in the file info but looks more like 5fps. I only used it a couple of times and gave up, but I was more thinking that it was something I was doing wrong.
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