Examples

Continuous live preview

A common use case is generating a continuous live preview.

The general pattern looks like this:

while True:
    pending_aq = conn.wait_for_acquisition()
    aq = ctx.make_acquisition(conn=conn, pending_aq=pending_aq)
    res = ctx.run_udf(dataset=aq, udf=SumUDF())

If you take setup, cancellation, timeouts etc. into account, it could look like this:

from libertem.viz.bqp import BQLive2DPlot
from libertem_live.api import LiveContext
from libertem.udf.sum import SumUDF
from libertem.exceptions import UDFRunCancelled

ctx = LiveContext(plot_class=BQLive2DPlot)

# connect to the DECTRIS DCU, and set up a shared memory area:
with ctx.make_connection('dectris').open(
    api_host="127.0.0.1",
    api_port=DCU_API_PORT,
    data_host="127.0.0.1",
    data_port=DCU_DATA_PORT,
    buffer_size=2048,
    bytes_per_frame=64*512,
) as conn:
    while True:
        pending_aq = conn.wait_for_acquisition(timeout=10.0)
        if pending_aq is None:
            continue
        aq = ctx.make_acquisition(
            conn=conn,
            nav_shape=(128, 128),
            frames_per_partition=512,
            pending_aq=pending_aq,
        )
        try:
            res = ctx.run_udf(dataset=aq, udf=SumUDF(), plots=True)
            # do something with the result here
        except UDFRunCancelled:
            # this acquisiiton was cancelled, wait for the next one:
            continue

Example notebooks

This example is closer to a real-world application based on the Merlin simulator:

• Run UDFs on Merlin live streams
  • Usage with the simulator
  • Camera setup routines
  • Integration Hooks
  • Sample output
  • Run one scan

This example shows how to access the detector frame stream without using LiberTEM:

• Get a frame stream from a merlin detector
  • Usage with the simulator

This example shows a typical use with a DECTRIS detector, using the active API:

• Run UDFs on DECTRIS live streams