# SDK 1.6.4 on a Stinger X8: lepton0_encoded never publishes H265 frames

Source: https://forum.modalai.com/topic/5432/sdk-1.6.4-on-a-stinger-x8-lepton0_encoded-never-publishes-h265-frames
Category: Development Drones (https://forum.modalai.com/category/44/development-drones)
Posted: 2026-09-23 02:24:53 UTC by Alex Z 1
Replies: 0 · Views: 2

## Alex Z 1 · 2026-09-23 02:24:53 UTC

**Hardware:** VOXL 2 Mini (M0104) on a Stinger. SKU `/data/modalai/sku.txt`: `MRB-D0013-6-V1-C33-T8-M26-X8` (X8 = Lepton). ADB serial `6299769b`. USB VTX dongle Realtek `0bda:8812`, product string "VTX Gen 1.5". Paired ModalAI VRX (same `vtx.key`, 5825 MHz).

**Software version:** Full flash today of `voxl2-mini_SDK_1.6.4.tar.gz` (MD5 `12c726bed8e72d68ec489533e15ba9ef`), `/data` preserved, SKU reconfigured as above. Last confirmed after flash (bird is offline now, so this is not a fresh `voxl-version` paste):

- System image `1.8.08-M0104-14.1a-perf`
- `voxl-suite` **1.6.4** (was 1.5.0)
- `voxl-lepton-server` **1.4.0** (was 1.3.3)
- `voxl-vtx` **2.2.27** (was 1.4.7)

**Configuration / services:** SoftAP off. `voxl-vtx` and `voxl-lepton-server` enabled and active. VTX RF: 5825 MHz, bandwidth 20, FEC on, STBC 0, `/data/modalai/vtx.key` present. Active VTX source was switched between `hires_low_latency_misp_encoded` and `lepton0_encoded`. Lepton config is stock SPI bus 0, `en_rotate: true`, `shutter_mode: manual`. 

**What I am trying to do:**

Send the downward Lepton to the VRX using the stock SDK 1.6 path: `voxl-lepton-server` publishes `/run/mpa/lepton0_encoded` (H265), and `voxl-vtx` uses that pipe as its profile `source`. RGB already works on the same radio and VRX.

**What actually happens:**

`lepton0_raw` and `lepton0_color` publish live frames (RAW8 / RGB, 160×120, ~8.8 fps). `/run/mpa/lepton0_encoded/info` exists and reports `string_format: H265`, 160×120, 9 fps, server `voxl-lepton-server`. `voxl-inspect-cam lepton0_encoded` stays at "Waiting for Server" indefinitely. No encoded frames, with or without `voxl-vtx` subscribed.

`voxl-lepton-server` log:

```
WARNING: OMX SetTargetBitrate: H265 CBR requires bps >= 3.0Mbit (1000000 bps provided). Using FPS hack. scale = 3.000000
H265 encoder initialized (160x120 @ 9 fps)
WARNING: ion buffer pool exhausted — reusing idx N (age=~455ms, gen=…)
```

The ION warning repeats on every frame from first boot. Verbose run also prints "Received a complete frame, publishing" for the raw path, then the same ION exhaustion, and the encoded client still never receives a frame.

Pointing VTX at `lepton0_encoded` makes the VRX drop to signal lost. Pointing it back at `hires_low_latency_misp_encoded` restores video immediately (same frequency, same key). So the RF link, key, and VRX are fine. The encoded Lepton pipe is empty.

**Steps to reproduce:**

1. Flash VOXL 2 Mini SDK 1.6.4, preserve `/data`, configure SKU `MRB-D0013-6-V1-C33-T8-M26-X8`.
2. Confirm `voxl-lepton-server` is running and `voxl-inspect-cam lepton0_raw` shows ~9 fps.
3. `voxl-inspect-cam lepton0_encoded` — stays "Waiting for Server".
4. With SoftAP off and VTX on a channel the VRX already locks (here 5825), `voxl-configure-vtx -s hires_low_latency_misp_encoded` — VRX shows video.
5. `voxl-configure-vtx -s lepton0_encoded` and restart `voxl-vtx` — VRX loses signal. `lepton0_encoded/info` is present; `voxl-inspect-cam` still waits.

**Question:** On SDK 1.6.4 / `voxl-lepton-server` 1.4.0, is `lepton0_encoded` supposed to emit H265 for a 160×120 Lepton, or is the encoder known not to produce frames (ION pool exhausted, OMX 1 Mbit vs 3 Mbit CBR warning)? Release notes for 1.6.6 only say lepton-server 1.4.1 is a rebuild against `libvoxl-codec` 0.1.1 ("OMX parity with camera-server"). Is that the fix for this, and can you provide `voxl2-mini_SDK_1.6.6.tar.gz` (MD5 `5e412872759cca0c5252aa02c29b31ef`)? 1.6.6 is not on the public download page.