[Feature Request] 支持对话时视觉跟随 / visual gaze following during conversation #70

Background

I originally wanted StackChan to look toward the person it is interacting with during AI Agent conversation. This is related to, but not exactly the same as, traditional sound-source following. The desired behavior is visual gaze / face following during LISTENING and SPEAKING, while keeping the existing official idle behavior otherwise.

Related PR: #72

The PR has now been changed to a standalone experiment only. It no longer changes the production firmware path.

Experiment Process

1. Lightweight visual heuristic in the main firmware

The first attempt added a conversation gaze modifier to the AI Agent path and used lightweight camera heuristics based on sampled skin-color / motion cues.

Result:

• It could compile and flash, but real tracking quality was poor.
• The target estimate drifted easily.
• The head sometimes kept moving toward one side even when the face was centered.
• It did not form a reliable closed-loop tracking behavior.

2. ESP-DL / face detection evaluation

I then evaluated a more standard vision path using Espressif ESP-DL / human_face_detect.

A standalone demo was created under:

experiments/vision_tracking_demo

The demo isolates only the parts needed for the experiment:

• GC0308 DVP camera at 320x240 RGB565
• ESP-DL human_face_detect
• display debug dot for face position
• yaw / pitch serial servo output

It intentionally does not start the full AI Agent stack, Wi-Fi/MQTT, audio AFE, LVGL app flow, or normal idle animation system.

Result:

• The standalone demo can build and run the camera -> face detection -> smoothing -> servo command loop.
• With smoothing, deadband, short target hold, and servo rate limiting, the isolated demo became usable enough for basic face tracking.
• The screen dot is helpful for debugging whether the detector position and servo command agree.

3. Integration back into the full AI Agent firmware

After the standalone demo became acceptable, I tried moving the idea back into the main AI Agent firmware so that idle motion before conversation would gaze toward the face while keeping other official behavior unchanged.

Result:

• The behavior became much worse than the standalone demo.
• The device sometimes rebooted during early iterations.
• Tracking was sluggish or jittery when AI Agent, audio, network, UI, camera, and servo logic were all active.
• Serial logs showed very low internal SRAM in several runs. In the worst full-firmware tracking runs, free internal SRAM dropped to only a few KB, with observed low-water marks around hundreds of bytes to a few KB.
• I also observed AFE: Ringbuffer of AFE(FEED) is full warnings, MQTT/Wi-Fi instability, and slow response while experimenting with visual tracking in the full firmware.

Current Conclusion

The current hardware can run a minimal face tracking demo, but the full AI Agent firmware appears to be very close to the ESP32-S3 internal SRAM / real-time scheduling limit.

My current conclusion is:

• Basic visual face tracking is feasible as a standalone demo on this hardware.
• Merging it directly into the production AI Agent path is not ready yet.
• The limiting factor seems less like a single algorithm bug and more like a hardware/resource budget issue: CPU time, internal SRAM, camera quality, audio AFE, network stack, UI, and servo control are all competing at once.

Possible next directions:

• make visual tracking an optional experimental build feature only;
• use a much cheaper detector or ROI-based tracker after initial face detection;
• run vision at a very low fixed rate in a fully asynchronous pipeline;
• increase memory/partition budget if maintainers are comfortable with that;
• offload vision to stronger hardware or a dedicated vision module;
• use sound direction only as a fallback cue, not as the main first-stage solution.

Questions

1. Has anyone successfully implemented face/gaze following on StackChan or similar ESP32-S3 + GC0308 + pan/tilt servo hardware?
2. Is ESP-DL / human_face_detect considered realistic for the full StackChan AI Agent firmware, or should it stay as a standalone/optional experiment?
3. Are there recommended camera settings, model choices, or lower-cost tracking approaches for this GC0308 camera?
4. Would maintainers prefer an experimental demo PR, an optional Kconfig-based feature, or no production integration until stronger hardware is available?
5. Is there a recommended architecture for this feature so that camera sampling, screen refresh, audio AFE, and servo control do not block each other?