The device disappear after calling close() for a few seconds.

[hanyazou]

While investigating #517, I've noticed that it takes a few seconds to restart the Kinect device after calling close(). And the USB deice disappear for a second. This means that you must wait for a while before you call enumerateDevices() and openDevice() after calling close(). This issue might depend Mac OS X.

You can reproduce this issue with stock Protonect.

case 1 (hungup)

$ ./bin/Protonect; sleep 0; ./bin/Protonect

1. Stop with ESC key after the first Protonect shows the image.
2. Second Protonect does not show any images.

[Info] [Freenect2DeviceImpl] enabling usb transfer submission...
[Info] [Freenect2DeviceImpl] submitting usb transfers...
[Info] [Freenect2DeviceImpl] started
device serial: 005697142447
device firmware: 4.0.3912.0
[Debug] [DepthPacketStreamParser] not all subsequences received 1022
// no messages. it seems that no data come from the device.

In this case Ctrl-C and ESC can not stop the second Protonect. It requires kill -KILL.

case 2 (error)

$ ./bin/Protonect; sleep 1; ./bin/Protonect

1. Stop with ESC key after the first Protonect shows the image.
2. Second Protonect can't detect the device.

[Info] [Freenect2Impl] enumerating devices...
[Info] [Freenect2Impl] 12 usb devices connected
[Info] [Freenect2Impl] found 0 devices
no device connected!

case 3 (this works fine)

$ ./bin/Protonect; sleep 3; ./bin/Protonect

1. Stop with ESC key after the first Protonect shows the image.
2. Second Protonect shows the image also.

[xlz]

The device disappear after calling close() for a few seconds.

What is wrong with this?

[hanyazou]

@xlz Please refer case 1 and case 2. It fails randomly depending on the timing. This type of behavior debase stability of system which uses this library.

For example, this test script fails randomly because of this issue.

#!/bin/bash
test()
{
$* &
pid=$!
sleep 5
kill $pid || exit
sleep 1 # longer wait required
}
test UserViewer
test Protonect
test NiViewer

[xlz]

The Kinect reboots and it takes 3 seconds. What can you do about it?

Case 1 fails because you try to use the Kinect when it is shutting down. Case 2 fails because the Kinect is still booting.

How to not shut down the Kinect when the program exits?

[hanyazou]

Thank you for the information. I understand that two fixes are required.

fix-1. wait until the shutdown sequence starts and the device disappears in close().
If only close() knows the device will reboot, Close() should take care of this.

fix-2a. wait until the device comes back in close().
same reason as 1. but this looks too much.

fix-2b. wait (retry) in enumeration if enumeration detects adaptor only like 71519cf
While the reboot sequence takes 3 seconds, it takes only 1~1.5 seconds until the USB device entry comes back. So this takes less than 2 seconds in worst case.

[hanyazou]

Or libfreenect2 records in some persistent storage that the device is in reboot sequence.

[xlz]

I don't want to force artificial wait in libfreenect2. Maybe the user will stop using Kinect altogether. The user can wait externally if they want to restart the Kinect.

sleep 1 # longer wait required

As is said, what's wrong with sleep 3?

The question is still here: How to not shut down the Kinect when the program exits? You proposed several ways to wait for the shutdown, not what I'm looking for.

[xlz]

I think the thing you are actually proposing is USB hotplug.

[hanyazou]

The user can wait externally if they want to restart the Kinect.

In this way, libfreenect2 library or manual should provide information how long the user must wait before enumeration and open. We can describe 'wait 3 seconds before reuse' in document. But shorter wait is better. To make the wait time shorter, we need more information from the device at runtime.

The question is still here: How to not shut down the Kinect when the program exits?

The stop() and close() kick shutdown sequence. There is no problem if the program exits suddenly with exit() or uncaught signal or exception.

This script runs without random errors. Because the device does not shutdown, Protonect shows the image window quickly.

#!/bin/bash
test()
{
$* &
pid=$!
sleep 5
kill -KILL $pid || exit
}
test Protonect
test Protonect
test Protonect

[xlz]

There may be an easy fix. Can you try commenting out this line in src/libfreenect.cpp?

  command_tx_.execute(ShutdownCommand(nextCommandSeq()), result);

[xlz]

I have good results with the above fix on Linux and Windows. How does the above fix work on Mac?

[hanyazou]

@xlz I'm very sorry to find that your fix does not work on my Mac.

And I found that

There is no problem if the program exits suddenly with exit() or uncaught signal or exception.

was not true.
If the Protonect call exit(1) in the sigint_hanlder() the device may reboot with probability 1/10 or so. I can't address the condition and timing in which the device reboot for now.

[xlz]

ok, then what is the deterministically reproducible method to not shut down Kinect on Mac? (It must not remove a majority of stop() and close() code.)