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Rocksteady latency, can it be improved? If so, here's a suggestion.
232 9 5-17 23:21
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David_Harry
First Officer
United Kingdom
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Hi.

With Rocksteady activated there is a very noticeable delay, or latency, between the Action's procesessor doing its work to sample the incoming image from the sensor then calculate and process the stabilisation before writing the file.

The delay is caused because the image you see on the Pocket's screen is the post buffer version. This latency is the difference in time between the photons hitting the photosites of the sensor, the sensor data being fed into a temporary video buffer, the data being manipulated for EIS in the video buffer and then finally exiting the video buffer with a delay/latency and being written to a file. Obviously this is a very oversimplified explanation of the process, there are many other things going on such as muxing, image processing etc. and stuff I don't understand but this is basically how it works.

So, my question. Before the video buffer and stabilisation processing, is the picture data viewable as a coherent picture? If so, would it be possible to send the pre-buffer image data, unprocessed and without stabilisation, to the screen. While this won't show a stabilised image it would however give a realtime, no latency or a latency shorter than a frame, picture on the screen.

If this is possible, there could be a mode switch and indicator telling the operator that the mode is switched on, this would let the operator know that they're sacrificing monitoring a stabilised image with latency for the convenience of a realtime image that doesn't show the processed Rocksteady version.

I'd imagine such a function would be very useful, if possible, for anyone shooting time and sync critical footage, which I'd imagine would be nearly all action shooting and most drama shooting.

Cheers,
Dave.
5-17 23:21
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Oh-no
Second Officer
Hong Kong
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Hi Dave, there are test in Hongkong, at 4K 60fps with RS, the latency is almost half a second. Youtube video at 2:13

5-17 23:27
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Oh-no
Second Officer
Hong Kong
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A Youtube video by Kinotika, at 5:10, they demo the latency


5-18 00:46
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DJI Stephen
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Hello and good day Dave. Thank you for reaching out and for the information you have given us today. Let me please forward this thread/information to the designated DJI department. In addition after the evaluation of the engineers, significant suggestions or requests will be implemented via the firmware update, app update, etc. For any updates, please stay tuned to the latest news in our DJI official website at www.dji.com or by checking the Release Notes specific for your product. Thank you for your valued support.
5-18 11:03
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David_Harry
First Officer
United Kingdom
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Audio/Video synchronisation issue since v01.07.00.20???

Hi.

Since v01.07.00.20 I seem to be having synchronisation issues that I'd not noticed as being so obvious with previous software versions. The audio is quite late.

Every camera that I've ever used will always be about 1 or 2 frames out, something not usually noticable, but my Pocket now feels later.

Has anyone else noticed this?

I'll do a clapper test and if it's not user error, me, I'll post a quick example.

Cheers,
Dave.
5-18 15:35
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Ray-CubeAce
First Officer

United Kingdom
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There was a much earlier thread about this not originally posted by me, Dave. I discussed and verified that the audio is five or four frames out of sync to the video dependant on the frame rate chosen. It was constant and didn't vary within a given take. I think that was two updates ago.  I haven't checked the latest update for this. In fact, I haven't used my Pocket since the update.
I will look for the thread.
5-18 16:59
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Ray-CubeAce
First Officer

United Kingdom
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Found the thread here.

https://forum.dji.com/forum.php? ... p;page=1#pid1744304
5-18 17:04
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David_Harry
First Officer
United Kingdom
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Hi Ray.

Thanks for that. Yes, the exact same problem but on the latest update for me. While it was slightly there in the previous update it wasn't very noticeable unless you looked for it. Without measuring it, I'd say that it's now about 5 or 6 frames at 25FPS.

I'll do a clapper test with all the frame rates to see how it is across them all, although I only ever shoot 25 and the high frame rates I only use for optical slow motion, so sync wouldn't be a problem for that stuff for me personally.

I've also noticed something else but it may be me screwing it up. When in that new hyperlapse mode and switching to it from a PAL frame rate, it came back as NTSC 29.97. This shows itself as frame interpolation when in a PAL timeline. Strange thing is that my NLE can be forced to read out media at a predetermined frame rate other than the files actual frame rate.

As a for instance. If I add 29.97 footage to a 25 timeline this would usually interpolate to keep the same time. But I can force the 29.97 to be read at 25, which gives a picture without interpolation but which is slowed down. Which is fine for optical slow motion. If I do it with the hyperlapse files, force 29.97 to 25 the resulting playout is interpolated. This can sometimes be got around by also forcing nearest neighbour but that process can repeat frames which looks like a frame hold or jump effect.

Like I said it may be user error on my part although when I toggle back and forth it does go back to 25 as it should. But it is odd that I can't force the 29.97 media file to read as 25 with a slow down.

Cheers,
Dave.



5-18 17:52
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Ray-CubeAce
First Officer

United Kingdom
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David_Harry Posted at 5-18 17:52
Hi Ray.

Thanks for that. Yes, the exact same problem but on the latest update for me. While it was slightly there in the previous update it wasn't very noticeable unless you looked for it. Without measuring it, I'd say that it's now about 5 or 6 frames at 25FPS.

Hi Dave,
I haven't had a chance to go out yet and try anything since the update.  I'm typing here to give my eyes a break from the backlog of still images I'm currently trying to process from my last two assignments.  
I will be out Thursday evening and will try to get some footage to look at and get info from.  Unfortunately, it will be mainly a photo shoot again as its mainly a preview evening for an exhibition for children and I'll be spending more time getting model release forms signed than anything else.

How do you get your video file information?
I have to use MediaInfo as my video editing software is limited in that department.
5-19 05:29
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David_Harry
First Officer
United Kingdom
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Ray-CubeAce Posted at 5-19 05:29
Hi Dave,
I haven't had a chance to go out yet and try anything since the update.  I'm typing here to give my eyes a break from the backlog of still images I'm currently trying to process from my last two assignments.  
I will be out Thursday evening and will try to get some footage to look at and get info from.  Unfortunately, it will be mainly a photo shoot again as its mainly a preview evening for an exhibition for children and I'll be spending more time getting model release forms signed than anything else.

Hi Ray.

I use my NLE or one of my encoders for info. If they have problems with certain codecs or containers/wrappers I'll use MediaInfo or something inside AVIsynth or FFmpeg with a GUI (I'm no good with CLI).

Cheers,
Dave.
5-19 06:08
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