---
orphan: true
---

# xengine_metadata_v1.yml

```yaml
# THIS IS THE OLD (V1) METADATA FORMAT, NOT THE CURRENT FORMAT
#
# The purpose of this "X-engine metadata" file is to document the file format.
# It will be used in two contexts:
#
#  1. Every X-engine node sends this file to every FRB node, at the beginning
#    of the TCP stream.
#
#  2. As a configuration file for the "fake correlator" used for testing.
#
# This is a minimal "version 0", and will be extended later.

version: 1

# Frequency channels. The observed frequency band is divided into "zones".
# Within each zone, all frequency channels have the same width, but the
# channel width may differ between zones.
#   zone_nfreq: number of frequency channels in each zone.
#   zone_freq_edges: frequency band edges in MHz.
# For example:
#   zone_nfreq: [N]      zone_freq_edges: [400,800]      one zone, channel width (400/N) MHz
#   zone_nfreq: [2*N,N]  zone_freq_edges: [400,600,800]  width (100/N), (200/N) MHz in lower/upper band
#
# In this config, we have:
#  Total frequency channels: 28160
#  Channel widths (MHz): [ 0.00610352, 0.012207, 0.0244141, 0.0976562, 0.195312 ]

zone_nfreq: [8192, 8192, 6144, 2048, 3584]
zone_freq_edges: [300, 350, 450, 600, 800, 1500]


# Optional: which frequency channels are present?
# A list of distinct integers 0 <= (channel_id) < (total frequency channels).
# Only makes sense in "context 1" (see above), to indicate which frequency channels
# are sent by a particular X-engine node.

freq_channels: [ 0, 10000, 20000, 28159 ]

# Number of beams, and their "beam ids" (opaque integer identifiers).
# If beam_ids is absent, it defaults to [ 0, 1, ..., (nbeams-1) ].
# Future versions of this file format will include more beam info (e.g. sky coordinates).
# I didn't specify anything concrete, since I didn't know what would be the best match
# for existing X-engine code.

nbeams: 3
beam_ids: [ 100, 200, 300 ]

# When an X-engine node sends metadata to an FRB search node, it indicates the starting time
# of the data stream that will follow. Currently, we represent the starting time by a sample
# count, which must be a multiple of 256. Future versions of this file format may use something
# different (FPGA count?) and provide more time-related metadata. I didn't specify anything
# concrete, since I didn't know what would be the best match for existing X-engine code.

initial_time_sample: 0
```