Endless continuous/burst mode via remote - how many FPS? (no video) - Creative Uses of CHDK

Kozuch

5

Endless continuous/burst mode via remote - how many FPS? (no video)

« on: 14 / August / 2014, 02:54:08 »

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Hello,

I am new to CHDK an I am looking for a solution for a computer vision project. I need to remotely trigger stereo camera. I need at least 1 FPS (more is better of course) for endless continuous shooting. I want to record for several minutes (maybe 15) like this.

The trigger is an important part of the setup because of stereo frame synchronization. I can not use video because I need to sync frames with other sensor data (GPS etc.) - I plan to trigger (via custom controller) each individual frame in my series. So I need a deterministic system to know exactly when a photo was taken. I can have fixed focus and only need auto exposure.

Can someone recommend any camera HW that is capable of at least the 1 FPS? Can you tell me what models (in what price ranges) can do certain FPS? I guess I will get more FPS with DSLRs, especially the high-end ones.

I am asking here and not at StereoData Maker (SDM) project since SDM seems to have very limited HW support - I know it can be probably easily ported when CHDK is supported on given model, but still its extra work to do. Also, they do synchro up to 1/16,000th of second and I will be happy with a 1/1000 or even 1/100 sync accuracy. I am also not sure on the continuous requirement but they could probably do it.

My maximal expense can be about $1500 for both cameras, but I am interested in theoretically learning about even more expensive solutions. Of course, low-cost is always a plus.

Thanks for your help!

« Last Edit: 14 / August / 2014, 03:24:58 by Kozuch »

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waterwingz

12140

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #1 on: 14 / August / 2014, 08:56:31 »

1 fps will be a stretch with any Canon P&S unless you shoot in continuous mode. But continuous mode locks both focus and exposure, and does not give precise control of picture taking time, which is not what you need?

« Last Edit: 14 / August / 2014, 08:59:30 by waterwingz »

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Ported : A1200 SD940 G10 Powershot N G16

Kozuch

5

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #2 on: 14 / August / 2014, 09:44:37 »

I dont mind locked focus but locked exposure would be a problem probably (outdoor environment). Anyways I talked to SDM guys after posting this and it seems I may be use their videosync solution.

However, what I described above would be an ideal solution for me though. But I understand there are technological restraints - like the ones you talk about. Regarding time control - I will be probably better off with SDM synced video than with P&S continuous mode. Also, I need to go up to 5-10 FPS, which rules P&S out completely probably.

Could the continuous mode go on forever? No buffer or writing to sd problems?

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waterwingz

12140

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #3 on: 14 / August / 2014, 10:10:24 »

Quote from: Kozuch on 14 / August / 2014, 09:44:37

I dont mind locked focus but locked exposure would be a problem probably (outdoor environment).

Some of the stuff lapser did last year will let you adjust exposure "on fly" in continuous mode and IIRC correctly get you into the 1fps range. Some of his customizations have since been added to CHDK and reyalp is apparently working on others.

Quote

Anyways I talked to SDM guys after posting this and it seems I may be use their videosync solution.

However, what I described above would be an ideal solution for me though. But I understand there are technological restraints - like the ones you talk about. Regarding time control - I will be probably better off with SDM synced video than with P&S continuous mode. Also, I need to go up to 5-10 FPS, which rules P&S out completely probably.

It would be interesting to hear what the SDM "guys" proposed to do for you. You could certainly make the same mods to CHDK and stay with a GPL compliment open source solution if that is important to you?

Quote

Could the continuous mode go on forever? No buffer or writing to sd problems?

Depends on camera and to some extent on SD card class but 1 fps should be no problem. Modern cameras like the SX50 tend to slow down around 5fps but image size and compression tend to play a role there too.

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Ported : A1200 SD940 G10 Powershot N G16

reyalp

14110

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #4 on: 14 / August / 2014, 17:26:59 »

Quote from: waterwingz on 14 / August / 2014, 10:10:24

Some of the stuff lapser did last year will let you adjust exposure "on fly" in continuous mode and IIRC correctly get you into the 1fps range. Some of his customizations have since been added to CHDK and reyalp is apparently working on others.

The exposure can be adjusted on the fly, the hard part is knowing what it should be.

Using the the current CHDK 1.3 trunk, you can get reasonable exposure using the existing shot_histogram function in conjunction with shooting hooks. This can be done either in continuous mode or using the "hold half press, click full press" approach of the "fast hdr script" mentioned in this thread http://chdk.setepontos.com/index.php?topic=11527.0

If Kozuch is analyzing the images externally after each shot, that could also be used to decide the next exposure.

It's also worth noting that many cameras have a reduced resolution "low light" or similar mode which is substantially faster than normal shooting. These will probably get a fair bit over 1 FPS on most cameras, but because these modes don't use a standard raw buffer, shot histogram will not work correctly.

Quote from: Kozuch on 14 / August / 2014, 09:44:37

Could the continuous mode go on forever? No buffer or writing to sd problems?

In general, most powershots will shoot continuously at about the same rate until the card files up. A few have special burst modes that behave differently.

Are you planning to do your computer vision stuff on the camera itself, or on some external device connected to the cameras USB?

Doing any significant processing on the camera itself will be problematic, because the CPU is quite slow.

If you are using a separate system to analyze the images, you can use PTP remote shoot to save the data directly over USB. However, the camera still allocates some resources for each shot so you can't shoot "forever" without rebooting. Also note that some ports have problems with remote shoot http://chdk.wikia.com/wiki/User:Nafraf/RemoteShootIssues and some do not have remote shoot fully implemented.

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Kozuch

5

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #5 on: 14 / August / 2014, 18:32:29 »

The application of the whole setup should be "stereo mobile mapping system" (simply a road/terrain 3D scanner) mounted on a passenger car. I only need to capture all the data when mapping - take stereo images and geospatial data (GPS/IMU) - I will do all other things (stereo depth estimation, visual odometry) in post processing.

However the tricky part is sensor fusion - I need to sync image (or video) and GPS/IMU. That is why I would like external trigger, because I could control the trigger and save current GPS data along in sync.

I am not sure if you are (or I am) not confusing continuous shooting mode with external trigger at certain FPS. What I need is the external triger at given FPS. The FPS would ideally be around 10. However, I could start at 1 FPS (is better than nothing).

This should be the result of (part of) my project:
https://www.youtube.com/watch?v=NiMlVgEu7mg

« Last Edit: 14 / August / 2014, 18:36:53 by Kozuch »

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reyalp

14110

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #6 on: 14 / August / 2014, 21:34:11 »

Quote from: Kozuch on 14 / August / 2014, 18:32:29

The application of the whole setup should be "stereo mobile mapping system" (simply a road/terrain 3D scanner) mounted on a passenger car. I only need to capture all the data when mapping - take stereo images and geospatial data (GPS/IMU) - I will do all other things (stereo depth estimation, visual odometry) in post processing.

OK, that clears things up. When you said "computer vision project" I jumped to the conclusion that it mean doing something in real time with the images.

Quote

However the tricky part is sensor fusion - I need to sync image (or video) and GPS/IMU. That is why I would like external trigger, because I could control the trigger and save current GPS data along in sync.

How exact does this need to be? tenths of a second? Milliseconds? Microseconds?

Quote

I am not sure if you are (or I am) not confusing continuous shooting mode with external trigger at certain FPS. What I need is the external triger at given FPS. The FPS would ideally be around 10. However, I could start at 1 FPS (is better than nothing).

It is possible to have the camera in continuous mode but control the actual timing start of each shot, by stopping the firmware right before the shutter opens. That can be done using the "shoot hooks" in 1.3.

It is also possible to get speed similar to continuous mode using scripted key presses to simulate holding down the half press and clicking the the full press.

You can use either of these methods with PTP USB control (http://chdk.wikia.com/wiki/PTP_Extension), but that has uncertainty of several tens of milliseconds at best.

Using the USB remote (http://chdk.wikia.com/wiki/USB_Shutter_Remote) you can potentially get sub-millisecond precision, although there is some variation between models. I'm not sure if the current code will let you directly use either of the methods described above to shoot quickly with precision sync, but if not it should possibly to implement fairly easily.

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waterwingz

12140

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #7 on: 14 / August / 2014, 21:57:42 »

Quote from: reyalp on 14 / August / 2014, 21:34:11

I'm not sure if the current code will let you directly use either of the methods described above to shoot quickly with precision sync, but if not it should possibly to implement fairly easily.

The precision sync function is just a pause in the shooting sequence right before the shutter opens that waits for the USB 5V signal to go away. I guess the trick is to also halt the next shot until the 5V asserts again ?

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Ported : A1200 SD940 G10 Powershot N G16

reyalp

14110

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #8 on: 14 / August / 2014, 22:13:17 »

Quote from: waterwingz on 14 / August / 2014, 21:57:42

The precision sync function is just a pause in the shooting sequence right before the shutter opens that waits for the USB 5V signal to go away. I guess the trick is to also halt the next shot until the 5V asserts again ?

So if you put it in continuous mode and held down shoot in script, just pulsing the 5v off at a rate slightly slower than the max continuous rate might do it.

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waterwingz

12140

Re: Endless continuous/burst mode via remote - how many FPS? (no video)

« Reply #9 on: 14 / August / 2014, 22:21:26 »

Quote from: reyalp on 14 / August / 2014, 22:13:17

Quote from: waterwingz on 14 / August / 2014, 21:57:42
The precision sync function is just a pause in the shooting sequence right before the shutter opens that waits for the USB 5V signal to go away. I guess the trick is to also halt the next shot until the 5V asserts again ?
So if you put it in continuous mode and held down shoot in script, just pulsing the 5v off at a rate slightly slower than the max continuous rate might do it.

Not clear to me that would work. Can you hang things in one of the shooting hooks waiting for the 5V to assert (or return immediately if it has) ?

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Ported : A1200 SD940 G10 Powershot N G16