Manually triggering in the UI do create those files in there. The confusion was because the lvdump over chdkptp doesn't result in any file on the SD card itself.
Right, lvdump in chdkptp streams it directly over USB, without writing to the SD card. The live view over PTP actually came first, I only realized much later that I could use the same code to record on camera for debugging. That's why the module has a dummy PTP structure.
I was indeed hoping that I could trigger the screen dump using a lua script running on the camera (of course not during video recording as you mentioned). I will look into the scrdump_schedule function.
It's a bit ugly since it's set up to run as a standalone "simple module" from the tools menu. For quick and dirty implementation, you could probably just copy most of the code (except the module / menu stuff) into luascript.c, and then add a lua function to set the parameters and kick off the task. One thing you'd want to watch out for is making sure the Lua module doesn't unload before the task exits.
Alternately, you could just grab the code to write the header (in scrdump_start) and the code to write individual frames (scrdump_frame) and have the Lua script handle scheduling. This would probably be simpler, and your Lua API could be something like
Or you could even re-use Lua io filehandles for the file, write the header using Lua, and just do scrdump_frame(filehandle, framebuffer flags)
This last option would add very little size to the module, so I might be tempted to add it to the official source. The downside is your script would be responsible for capturing each frame.
How can I easily view for example the CRW_0001.JPG resulting from a manual capture on under Linux?
You can use chdkptp, either in the gui from the live view tab, under "debug" "Play from file" or use lvdumpimg to either generate netpbm files of the frames, or pipe through imagemagic or ffmpeg to produce other formats.
Note that the lvdumpimg option requires building chdkptp from current source (I *really* need to do another release
), but the CLI is quite easy to build. GUI playback should work with the current binary builds.
Note that the current lvdump format has no time coding, so playback framerate is entirely unconnected to recording frame rate.