fix(camera): select V4L2 for Linux device paths

[TomCC7]

Contribution path

• Small camera fix extracted from the review of feat(imitation): add profile-driven dual-arm collection #3942.
• Prerequisite for the OpenYAM learning stack.

Problem

• OpenCV can select FFmpeg for Linux camera device paths, preventing capture properties from being applied.
• Camera configuration needs to accept stable device paths as well as numeric indices.

Solution

• Accept numeric indices, numeric CLI strings, and device paths.
• Select V4L2 for Linux /dev/ paths, including /dev/v4l/by-id/.
• Keep automatic backend selection for numeric indices, network URLs, and other platforms.
• No imitation-learning, Blueprint, recorder, or dataset changes.

How to Test

uv run pytest dimos/hardware/sensors/camera/test_webcam_backend.py

• Seven cases pass, covering Linux device paths, numeric inputs, network URLs, and non-Linux behavior.
• On a machine with a webcam, the hardware API is Webcam(camera_index="/dev/video0"); call start() to open capture and stop() to release it.
• Real camera capture was not repeated during this cleanup.

AI assistance

• OpenAI Codex assisted with extraction, implementation, tests, and this description.
• Updated by OpenAI Codex (agent).

Checklist

• I have read and approved the CLA.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

@@            Coverage Diff             @@
##             main    #4159      +/-   ##
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+ Coverage   78.90%   79.43%   +0.53%     
==========================================
  Files        1469     1472       +3     
  Lines      138999   139548     +549     
  Branches    11941    12329     +388     
==========================================
+ Hits       109672   110845    +1173     
+ Misses      25930    25303     -627     
- Partials     3397     3400       +3     

Components	Coverage Δ
Tests	95.60% <100.00%> (+0.83%)	⬆️

Flag	Coverage Δ
OS-ubuntu-24.04-arm	75.11% <100.00%> (+0.26%)	⬆️
OS-ubuntu-latest	75.81% <100.00%> (+0.25%)	⬆️
Py-3.10	75.59% <100.00%> (+0.25%)	⬆️
Py-3.11	75.79% <100.00%> (+0.25%)	⬆️
Py-3.12	75.80% <100.00%> (+0.25%)	⬆️
SelfHosted-Large	30.52% <41.93%> (-0.21%)	⬇️
SelfHosted-Linux	36.65% <41.93%> (+0.37%)	⬆️
SelfHosted-macOS	36.94% <41.93%> (+1.34%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...mos/hardware/sensors/camera/test_webcam_backend.py	100.00% <100.00%> (ø)
dimos/hardware/sensors/camera/webcam.py	58.47% <100.00%> (+20.97%)	⬆️

... and 92 files with indirect coverage changes

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[greptile-apps]

Confidence Score: 4/5

Safe to merge, with a non-blocking compatibility concern affecting signed and whitespace-padded numeric camera-index configuration.

Findings

1.  Numeric indices stop parsing ▶

Summary

This change correctly selects the V4L2 backend for Linux camera device paths while retaining automatic backend selection for other sources. One non-blocking compatibility concern remains: signed or whitespace-padded numeric camera indices now reach OpenCV as strings instead of integer device indices.

_{Reviews (1) · Last reviewed commit: "fix(camera): select V4L2 for Linux devic..."}

[github-actions]

Successfully created backport PR for release/0.0.14:

• [Backport release/0.0.14] fix(camera): select V4L2 for Linux device paths #4196