Digi AnywhereUSB Plus — Isochronous devices Bandwidth & Port Placement.

High‑resolution, high‑frame‑rate cameras can exceed the bandwidth of a single USB Host Controller when connected together. To avoid bandwidth exhaustion, place cameras across different Host Controllers or reduce camera stream requirements.

AnywhereUSB Plus hubs expose multiple USB Host Controllers (HCs) behind their front-panel ports. Each Host Controller has a finite isochronous bandwidth budget (used by video/audio streams). If the combined camera streams on one Host Controller exceed its capacity, the USB stack will fail allocations and you will see:

Error: USBD_STATUS_NO_BANDWIDTH
Cause: Combined isochronous (and other) transfers exceed the Host Controller’s available bandwidth.

Host Controller Port Mapping

AW08 (AnywhereUSB Plus 08)

• One Host Controller per pair of front-panel ports
• Mapping:
  • HC-A: Ports 1 & 2
  • HC-B: Ports 3 & 4
  • HC-C: Ports 5 & 6
  • HC-D: Ports 7 & 8

Rule of thumb (recommended):
Place one high‑resolution camera per Host Controller.
Examples:

• Put one camera on port 1 or 2 (same HC), another on port 3 or 4, another on port 5 or 6, etc.

AW24 (AnywhereUSB Plus 24) — Reference

• One Host Controller per group of 4 ports
• Mapping pattern (example):
  • HC-A: Ports 1–4
  • HC-B: Ports 5–8
  • HC-C: Ports 9–12
  • HC-D: Ports 13–16
  • HC-E: Ports 17–20
  • HC-F: Ports 21–24

Rule of thumb (recommended):
Place one high‑resolution camera in each 4‑port group (e.g., one in 1–4, one in 5–8, etc.).

Bandwidth Limits (Theoretical)

• USB 3.x cameras: up to ~393 MB/s per Host Controller (theory)
  Note: Real usable is less because the USB stack reserves bandwidth for control & other transfers.
• USB 2.x cameras: up to ~24 MB/s per Host Controller (theory)

Important: Practical throughput is lower than the theoretical maximum. Always account for:

• Isochronous overhead
• Control transfers
• Concurrent audio streams
• Host CPU/driver behavior

Placement & Configuration Scenarios

Scenario A — Highest Reliability (default recommendation)

• AW08: Place one camera per Host Controller:
  • Camera 1 → Port 1 (or 2)
  • Camera 2 → Port 3 (or 4)
  • Camera 3 → Port 5 (or 6)
  • Camera 4 → Port 7 (or 8)
• Rationale: Avoids bandwidth contention and USBD_STATUS_NO_BANDWIDTH.

Scenario B — Two cameras on the same HC (if you must)

• Condition: Only if combined resolution + frame rate + audio stay below the isochronous budget for that HC.
• Example approach:
  • Reduce resolution (e.g., from 4K to 1080p).
  • Reduce frame rate (e.g., from 60 fps to 30 or 15 fps).
  • Disable or lower audio sampling rate if possible.
• AW08 Example: Two cameras on ports 1 and 2 can sometimes work if their combined isoch load is within limits.

Troubleshooting Guide

1. Symptom: Camera fails to start or drops stream; logs show USBD_STATUS_NO_BANDWIDTH.
   • Action: Move the camera to a different Host Controller (e.g., from port 2 to port 3).
2. Symptom: Intermittent frame drops or audio glitches.
   • Action: Reduce resolution and/or frame rate; consider disabling or reducing audio bandwidth.
3. Symptom: Multiple cameras on one HC work sporadically.
   • Action: Separate cameras across different HCs per the mapping above; verify each camera alone is stable.
4. Validation Steps:
   • Confirm camera USB speed (2.0 vs 3.x).
   • Ensure latest drivers/firmware for cameras and AnywhereUSB.
   • Check host utilization and network stability (for network‑attached AnywhereUSB deployments).

Best Practices

• Plan capacity: Assume one high‑resolution camera per HC unless testing proves otherwise.
• Start conservative: Begin with lower resolution/frame rate, then increase until stable.
• Account for audio: Microphone streams add bandwidth—disable or reduce if unnecessary.
• Document mapping: Keep a simple port → HC chart in deployment notes for quick moves.
• Monitor logs: Watch for bandwidth allocation errors after changes.

Summary: High‑resolution, high‑frame‑rate cameras can exceed the bandwidth of a single USB Host Controller when connected together. To avoid bandwidth exhaustion, place cameras across different Host Controllers or reduce camera stream requirements.