Unable to get two cameras to asynchronously read frames

[y2k0999]

Describe the Issue
When I run the tutorial code in two instances concurrently, each connecting to a separate camera, the recording is not done asynchronously, ie one camera finishing recording before the other starts.

To Reproduce
Steps to reproduce the behavior:

1. Connect two genicam cameras via a switch to an Nvidia Jetson.
2. Run the tutorial code in two different tty's at the same time, each connecting to a unique camera.
3. Print out the filename of the frame when saving it
4. See that the print order is synchronous

Sample Code
I mostly just used the tutorial code for this.

• [] Yes
• No

Sample output:

connected to cam 1
connected to cam 2
saving image: cam1/0.png
saving image: cam1/1.png
...
saving image: cam1/10.png
saving image: cam2/0.png
...
exiting cam1
saving image: cam2/10.pong
exiting cam2

Expected Behavior
I expected the frames to be taken asynchronously, ie the print out would look as follows:

connected to cam 1
connected to cam 2
saving image: cam1/0.png
saving image: cam2/0.png
saving image: cam1/1.png
saving image: cam2/1.png
...
exiting cam1
exiting cam2

Configuration

• OS: Jetson Linux 36 (same behavior on Ubuntu 22.04)
• Python: 3.10
• Harvester: 1.4.3
• GenTL Producer: Matrix Vision
• Camera: 1x hikrobot (20482448@24fps) && 1x teledyne dalsa nano (30084112@10fps)
• Other hardware: Jetson AGX Orin (same behavior on x86 intel machine)

Reproducibility

This phenomenon can be stably reproduced:

• Yes
• No.

This happens every time.

Actions You Have Taken

• I've read the Harvester FAQ page.
• I've tried using Python's multiprocessing and multithreading libraries to efficiently split the execution.
• I've tried using different sessions so the processes have no common ancestor

[y2k0999]

Sorry about the code formatting issue. I don't know what the problem causing it is.

I found this issue and copy pasted his code with threading and multiprocessing, both of which presented different issues. Threading still is reading the frames sequentially, multiprocessing hangs on the call to ia.start() for the second camera.

`

def camera_stream(camera_name):
print(camera_name, 'entered fork')
camera_name.start()
print(camera_name, 'started_cam')
for frame in range(20):
time.sleep(1)
print('iterating over frame', frame)
buffer = camera_name.fetch()
print(camera_name, datetime.now())
component = buffer.payload.components[0]
w, h = component.width, component.height
buffer.queue()
if name == "main":
h = Harvester()
h.add_file('/opt/ImpactAcquire/lib/arm64/mvGenTLProducer.cti')
h.update()
device_found = h.device_info_list
ia = h.create(0)
ib = h.create(1)
device_found = [ia, ib]
procs = []
for name in device_found:
print('about to fork')
#proc = Process(target=camera_stream, args=(name,))
proc = threading.Thread(target=camera_stream, args=(name,))
print('finished forking')
procs.append(proc)
proc.start()
print('procs started')
for proc in procs:
proc.join()
print('finished join')

ia.stop()
ia.destroy()
ib.stop()
ib.destroy()
h.reset()

`
jet@ubuntu:~/harv_test$ python3 italian_main.py
about to fork
finished forking
<harvesters.core.ImageAcquirer object at 0xffff61ca1900>procs started
entered forkabout to fork

finished forking
<harvesters.core.ImageAcquirer object at 0xffff61ca1900><harvesters.core.ImageAcquirer object at 0xffff61ca2920> started_camprocs started

entered fork
<harvesters.core.ImageAcquirer object at 0xffff61ca2920> started_cam
iterating over frame 0
<harvesters.core.ImageAcquirer object at 0xffff61ca1900> 2024-06-28 17:02:51.845528
iterating over frame 0
iterating over frame 1
<harvesters.core.ImageAcquirer object at 0xffff61ca1900> 2024-06-28 17:02:52.875362
iterating over frame 2
<harvesters.core.ImageAcquirer object at 0xffff61ca1900> 2024-06-28 17:02:53.916362
iterating over frame 3
<harvesters.core.ImageAcquirer object at 0xffff61ca1900> 2024-06-28 17:02:54.940115
iterating over frame 4
<harvesters.core.ImageAcquirer object at 0xffff61ca1900> 2024-06-28 17:02:55.992438