# VDIFPacker — Overview

## Package Metadata

```{include} ../generated/vdif_packer/metadata.md
```

## Description

<!-- AI-GENERATED:START name="overview" -->
The VDIFPacker is an EDD pipeline that consumes SPEAD2 subband streams from the
DigitalDownConverter and packs the float-32 samples into VDIF frames for VLBI recording. It
supports writing VDIF data to disk and/or forwarding it via UDP to a recorder such as
jive5ab. Multiple input streams are interleaved across VDIF thread IDs.

The pipeline applies a spectral transform (polyphase filter bank via `nfft` and
`naccumulate` parameters) before packing and provides per-channel mean and standard
deviation sensors for monitoring signal levels.
<!-- AI-GENERATED:END -->

## Responsibilities

- Receive processed subband streams via SPEAD2 (`DigitalDownConverter:1` format)
- Pack float-32 samples into VDIF frames
- Write VDIF frames to disk and/or forward over UDP
- Control recording start/stop via a POSIX message queue (`mq_control`)
- Expose KATCP interface for remote configuration and lifecycle management
- Report per-channel statistics (`vdif-channel-mean`, `vdif-channel-stddev`)

## Operational Context

| Item | Value |
|---|---|
| Upstream | DigitalDownConverter pipeline |
| Downstream | Disk storage, jive5ab (UDP VDIF) |
| Control interface | KATCP on `--host` / `--port` |
| GPU required | No |
| Container image | `edd_dbbc` |
| Ansible role | `roles/vdif_packer/` |