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fix frame timestamps to use a comparable epoch

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steady_clock's epoch is unspecified and typically counts from process start or
boot, so the published timestamp_ns could not be compared against another
node's timestamps, wall clock or a recording — and it recorded when the node
processed the frame rather than when the camera captured it.

Publish two keys on every output instead: device_timestamp_ns from
sl::Camera::getTimestamp(TIME_REFERENCE::IMAGE), and host_timestamp_ns from
system_clock. Both are Unix-epoch nanoseconds, set as dora timestamp
parameters. The SDK clock source is pinned to SYSTEM_CLOCK at construction,
since it is process-wide and decides the epoch of the device value.

Both are kept because the wall clock can step when NTP synchronises after boot
on a Jetson, while the device timestamp is what two nodes reading the same
frame can agree on.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y7g2cBJ5e3r15ZbJ9WZn8c
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cesar
2026-09-08 09:15:47 -03:00
co-authored by Claude Opus 5
parent 126dbf4f32
commit dc7f9f5501
5 changed files with 70 additions and 21 deletions
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AGENTS.md
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@@ -38,7 +38,7 @@ Camera behavior is configured entirely through environment variables (see README
- **`src/util/env.h`** — Shared inline env-variable parsing helpers (`get_env_int`, `get_env_str`, `get_env_bool`, `get_env_float`).
- **`src/zed/camera.h`** — `zed::Config`, `zed::Calibration`, and `zed::Camera` class. Camera wraps the ZED SDK lifecycle: open (with retry loop), warmup, grab (image + point cloud), calibration, and close. Exposes `handle()` for engine access.
- **`src/zed/camera.cc`** — Implementation. SDK enum parsers live in an anonymous namespace.
- **`src/main.cc`** — Dora event loop. Parses `ZED_PC_MODE` (`FULL`/`HALF`) once before the loop. On any input event (intended to be driven by a tick timer; the id is not inspected): calls `camera.grab()`, then sends `image_bgr`, `point_cloud` and `camera_info`. Point cloud output varies by mode: `FULL` sends the raw `sl::Mat` pointer (no copy); `HALF` downsamples by 2 in each dimension. Handles reconnection on grab failure.
- **`src/main.cc`** — Dora event loop. Parses `ZED_PC_MODE` (`FULL`/`HALF`) once before the loop. On any input event (intended to be driven by a tick timer; the id is not inspected): calls `camera.grab()`, then sends `image_bgr`, `point_cloud` and `camera_info`. `set_intrinsics` and `set_frame_stamps` stamp every output of a frame with the same intrinsics, `frame_id` and the two timestamps (`device_timestamp_ns`, `host_timestamp_ns`; both Unix-epoch nanoseconds). Point cloud output varies by mode: `FULL` sends the raw `sl::Mat` pointer (no copy); `HALF` downsamples by 2 in each dimension. Handles reconnection on grab failure.
- **`DoraTargets.cmake`** — Handles building or fetching dora-rs and generating the CXX bridge files. Two paths: local (`DORA_ROOT_DIR`) or git clone. Produces `dora_node_api_cxx` library and the `node_bridge.cc` glue.
- **`scripts/build.sh`** — Configure/compile/install in one shell-free-callable step. Referenced by `dataflow.yml`, the `Dockerfile` and the README.
- **`dataflow.yml`** — Example dora dataflow definition using the `git:` source format, pinned with `tag:` — dora 1.0 pins a source with the mutually exclusive `tag:`, `rev:` or `branch:`.