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matlabbe
5062bf0614
* rtabmap_sync tests and doc * Added some diagrams * cleanup some diagrams * fixing running tests in parallels
113 lines
4.7 KiB
Markdown
113 lines
4.7 KiB
Markdown
# rgbd_relay
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Republishes an [`rtabmap_msgs/msg/RGBDImage`](https://docs.ros.org/en/jazzy/p/rtabmap_msgs/msg/RGBDImage.html), optionally compressing or decompressing it on the way through.
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An `RGBDImage` can carry its images raw or compressed. This node converts between the two so that the expensive form crosses the network only where it has to: compress before a wifi link, decompress on the other side.
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With both `compress` and `uncompress` left false the message is forwarded untouched, which makes the node a plain relay — useful to give a topic a second name, or to bridge two incompatible QoS profiles with `qos_sub` and `qos_pub`. See [Bridging QoS profiles](#bridging-qos-profiles).
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## Usage
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Compress before sending over a slow link:
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```bash
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ros2 run rtabmap_util rgbd_relay --ros-args \
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-r rgbd_image:=/camera/rgbd_image \
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-p compress:=true
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```
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```python
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ComposableNode(
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package='rtabmap_util',
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plugin='rtabmap_util::RGBDRelay',
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name='rgbd_relay',
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parameters=[{'compress': True}],
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remappings=[('rgbd_image', '/camera/rgbd_image')])
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```
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A relay at each end of the link, so only the compressed form crosses it. Once it is raw again it feeds the SLAM node directly, and [rgbd_split](rgbd_split.md) unpacks it into the plain `Image` topics RViz can display:
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```mermaid
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flowchart LR
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subgraph ROBOT["robot"]
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CAM["camera driver"]
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SYNC["rgbd_sync"]
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RELAY1["rgbd_relay<br>compress: true"]
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end
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subgraph REMOTE["remote computer"]
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RELAY2["rgbd_relay<br>uncompress: true"]
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RAW(["rgbd_image_relay"])
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MAP["rtabmap"]
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SPLIT["rgbd_split"]
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RVIZ["RViz"]
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end
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CAM -->|"rgb, depth,<br>camera_info"| SYNC
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SYNC -->|rgbd_image| RELAY1
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RELAY1 -->|compressed| RELAY2
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RELAY2 --> RAW
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RAW --> MAP
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RAW --> SPLIT
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SPLIT -->|rgb, depth| RVIZ
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```
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## Subscribed Topics
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| Topic | Type | Description |
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| `rgbd_image` | [`rtabmap_msgs/msg/RGBDImage`](https://docs.ros.org/en/jazzy/p/rtabmap_msgs/msg/RGBDImage.html) | Queue depth `queue_sub`, 5 by default. |
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## Published Topics
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| Topic | Type | Description |
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| `rgbd_image_relay` | [`rtabmap_msgs/msg/RGBDImage`](https://docs.ros.org/en/jazzy/p/rtabmap_msgs/msg/RGBDImage.html) | Queue depth `queue_pub`, 1 by default. Published only when someone is subscribed. |
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## Parameters
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| Parameter | Type | Default | Description |
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| `compress` | `bool` | `false` | Fill the compressed fields of the output. Color becomes JPEG; depth becomes PNG, or JPEG when the message carries a stereo pair rather than depth. Fields already compressed on input are passed through as-is. |
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| `uncompress` | `bool` | `false` | Fill the raw fields of the output by decoding the compressed ones. Fields already raw on input are passed through as-is. |
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| `qos` | `int` | `0` | Reliability of both sides: `0` system default, `1` reliable, `2` best effort. |
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| `qos_sub` | `int` | value of `qos` | Reliability of the `rgbd_image` subscription alone. |
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| `qos_pub` | `int` | value of `qos` | Reliability of the `rgbd_image_relay` publisher alone. |
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| `queue_sub` | `int` | `5` | Queue depth of the `rgbd_image` subscription. Must be at least 1. |
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| `queue_pub` | `int` | `1` | Queue depth of the `rgbd_image_relay` publisher. Must be at least 1. |
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## Bridging QoS profiles
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A subscriber that asks for **reliable** will not connect to a publisher offering **best effort** — the request cannot be satisfied, so the two silently never match. A best-effort subscriber, on the other hand, connects to either.
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That is a real problem when a camera driver publishes best effort and the consumer insists on reliable. Set the two sides of the relay separately and it forwards across the gap:
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```bash
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ros2 run rtabmap_util rgbd_relay --ros-args \
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-r rgbd_image:=/camera/rgbd_image \
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-p qos_sub:=2 \
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-p qos_pub:=1
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```
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```mermaid
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flowchart LR
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CAM["camera driver<br>publishes best effort"]
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SYNC["rgbd_sync"]
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RELAY["rgbd_relay<br>qos_sub: 2, qos_pub: 1"]
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MAP["rtabmap<br>needs reliable"]
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CAM -->|"rgb, depth,<br>camera_info"| SYNC
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SYNC -->|rgbd_image| RELAY
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RELAY -->|rgbd_image_relay| MAP
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```
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Both parameters default to `qos`, so setting `qos` alone configures both sides at once.
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Reliability is all that is bridged — durability is left at the default, so a transient-local publisher is not converted. The queue depths are separate too, through `queue_sub` and `queue_pub`.
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## Notes
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Setting neither `compress` nor `uncompress` forwards the message unchanged and skips all image handling — the cheapest path by a wide margin.
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Setting both is allowed and produces a message carrying each image twice, raw and compressed. That is rarely what you want.
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Depth is compressed as **PNG**, a stereo right image as **JPEG**.
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