Pre-recording for the raw_rec module?

[bouncyball]

@g3gg0:

[vstrglv]

mvl_lite.mo from magiclantern-crop3x.2017Mar21.5D3113 supports 10 and 12bit, but mvl_lite.mo from Exp. Latest Build (2017-03-27 23:39) not. Why? 5D3 1.1.3

[a1ex]

Because the 10- and 12-bit recording is not yet in mainline.

Feedback is mixed, and I don't use it in practice, so I could not judge whether it's OK to merge it or not in this state. Sorry.

[vstrglv]

Thank you alex. It's a pitty, because 10 and 12bit reduce bit rate threshold for CF card.
 If i load mvl_rec.mo and mvl_lite.mo from Exp. Latest Build (2017-03-27 23:39) and activate mvl_rec there is  sound recording now. 

[a1ex]

The two modules are not meant to be loaded together (as any symbols exported by both will conflict somehow, but the linker doesn't warn about it and I don't really know how it's handled). I should probably enforce this somehow.

The mlv_lite module from the crop_rec branch also has the H.264 proxy included, and it's faking mlv_snd status in order to show the audio meters (since you can use the H.264 stream for audio). This is the source of conflict.

The conflict with mlv_snd is an obvious one, but I bet there are more.

Not sure what's the best way to fix, as this method (exporting symbols and letting the linker figure it out) allows some communication between modules, but it has its limits.

[dfort]

I've been playing around with rec-trigger. There's a special mlv_lite module in the Experiments download page that should work on all platforms. If you configure it a certain way you can shoot single frames which is great for timelapse and animation. The way to do it is by setting the Pre-record to OFF and the Rec trigger to Half-shut:pre only.



An issue I had was that the counter shows time in minutes, seconds and tenths of seconds: MM:SS.1/10sec. so with a standard frame per second video rate you need to take a few exposures before the counter advances.



I tried changing the display so it uses a timecode like, MM:SS.FF. I thought it was pretty cool so I submitted a pull request before testing all the possible variations of the Pre-record options. a1ex found all sorts of problems with my code so I started going further and further down the rabbit hole, changing variable names and adding menu items until I got something that might be useful. It is still quite experimental so I stuck it in the Advanced menu.



As you can see I left the time display that was adapted from the ffmpeg time unit syntax as the default and added the option to display the counter in Timecode format or in Frames. This probably isn't SMPTE approved timecode because it is based on the record frame rate instead of the playback frame rate but it does advance every time a frame is saved and it displays pretty much the same minutes and seconds as the ffmpeg version.

If the camera is set for NTSC 30fps (actually 29.976 more or less) the frame counter goes from 00 to 29 then it advances the seconds counter. Likewise at 25fps it goes from 00 to 24 and at 24fps it goes from 00 to 23, just like timecode. This should help for those cases when you are shooting one-frame-at-a-time and need to be more accurate than 1/10sec.



If anyone wants to try it out I put a test build of the mlv_lite module which should work on all platforms in my bitbucket download area. Look for magiclantern-mlv_lite-rec-trigger-experiment.

Feel free to post comments on the pull request:

https://bitbucket.org/hudson/magic-lantern/pull-requests/823/display-counter-in-timecode-format-mm-ssff/diff

[DeafEyeJedi]

Thanks for this much antcipated Timecode implementation, @dfort and I guess I wasn't supposed to try this together with an Non-CPU lens info experimental build (2017-04-04) because I am getting this message below running on 5D3.123 and not sure if this is to be expected?



Perhaps I should try w Nightlies instead?

[dfort]

Interesting find @DeafEyeJedi. I only tried it with a nightly build.

Best to look at one experiment at a time.

[X-RAY]

Hey guys,
can anyone please explain how to set up the raw video for lighting photography? I played around with it and its not clear to me how especially the rec trigger setting works.
I'd like to record the last second when I hit a cable remote trigger and I thought that works when I set to "Half Shutter" but it doesn't do anything. I can only start/stop record on the back button of the 5DIII.

And is it possible to lower the fps to get more seconds pre-recorded (in the buffer)? When I use fps override it seems to alter the shutter-speed also. Can I set the fps independent to the shutter speed?

Thanks!

[Walter Schulz]

Some options are available for some cams only. See https://builds.magiclantern.fm/features.html
The option you are looking for is "MOVIE_REC_KEY" in Movie tab and 5D3 is the only cam *not* supported. If there is a "REC key" item in your Movie tab I want to call it a bug.
However there is an item "Sticky HalfShutter" in Prefs tab -> Misc key settings and that's a different ball park.

Have you tried using IR remote control to stop video recording?

[X-RAY]

Hey there, didn't know that the 5DIII doesn't support the option.
You mentioned the "Sticky HalfShutter" but how does that help in my case?!

And does anybody know how to set a small framerate like 10fps and shoot with a separate shutterspeed like 1/50?

[Walter Schulz]

I don't own a 5D3 and cannot test it.
But - as said above - 5D3 is the only cam not supporting "Half-Shutter" for movie start/stop and therefore I have serious doubts about this option inside this module working at all (on 5D3).

"Sticky Half-Shutter" does indeed not help for your problem.

Have you tried IR remote trigger in movie mode?

[a1ex]

Hey guys,
can anyone please explain how to set up the raw video for lighting photography? I played around with it and its not clear to me how especially the rec trigger setting works.
I'd like to record the last second when I hit a cable remote trigger and I thought that works when I set to "Half Shutter" but it doesn't do anything. I can only start/stop record on the back button of the 5DIII.

I've only tested it using the half-shutter button from the camera (not with a cable remote). Should work out of the box - can you show your raw video settings?

With the rec trigger enabled, the LiveView button (labeled as start/stop on 5D3) would only prepare and end the recording session; to record any frames, you would have to press half-shutter.

The "Sticky HalfShutter" Walter is talking about, does not apply here; this is a special build of mlv_lite that has a half-shutter trigger for recording (e.g. record one frame, pre-record 1 second before the trigger and so on). It's also available in the crop_rec_4k builds. It's not yet in unified because... I didn't use it for more than a few very short test clips before committing the code, so right now I have little or no idea how it performs.

[X-RAY]

Have you tried IR remote trigger in movie mode?

Sorry, but I dont have one to try out.

I've only tested it using the half-shutter button from the camera (not with a cable remote). Should work out of the box - can you show your raw video settings?

With the rec trigger enabled, the LiveView button (labeled as start/stop on 5D3) would only prepare and end the recording session; to record any frames, you would have to press half-shutter.

The "Sticky HalfShutter" Walter is talking about, does not apply here; this is a special build of mlv_lite that has a half-shutter trigger for recording (e.g. record one frame, pre-record 1 second before the trigger and so on). It's also available in the crop_rec_4k builds. It's not yet in unified because... I didn't use it for more than a few very short test clips before committing the code, so right now I have little or no idea how it performs.

Ohh, now that you told me and as I tested the options again I understand it. The start/stop just like starts the container ... after that I can start recording with the half shutter. Right, that works fine. :-) And now I also understand the prerecording especially the option with 1-frame / pre only. So thats the setting I need to choose when shooting lightnings. So that I can record the maximum amount of frame buffer BEFORE pressing the Half Shutter button.

So now my only question remaining is how to get the fps down independent to the shutter speed. Alex, do you have a tip on that? :-)

[a1ex]

For FPS, the low light mode will scale the shutter speed, while the other modes will not.

Unfortunately, only low light is compatible with high-res modes on 5D3 (at least for now). You should, however, be able to adjust the shutter speed after dialing the FPS.

[X-RAY]

For FPS, the low light mode will scale the shutter speed, while the other modes will not.

Unfortunately, only low light is compatible with high-res modes on 5D3 (at least for now). You should, however, be able to adjust the shutter speed after dialing the FPS.

Great ... you know your code! :-D I set exact fps and after that the shutter speed can be set separate without a problem. Now I can set it up exactly as I want. thx

[Francois_lune]

Hi there,

I am using the Pre-recording (half-shutter) function to digitalize Super 8 films. A projector is sending a signal to the camera for each frame allowing me to record Raw videos fully synchronized.

However I am asking myself how this function works exactly.

The projector is running at 8 fps. The timing of the capture start to be accurate when the fps of the camera is a least double. Around 18fps is fine. Under this value, the timing is bad.

I don't really understand why. Does it mean that the function only "check" if the half-shutter is pressed at the frequency of the fps set on the camera?

In my case I though that the fps would not play any role as the actual recording speed is set by the projector.