mrousavy
commented
2 weeks ago I'm experiencing camera lag
What does that mean? What is camera lag? Is the FPS slow? Is it completely freezing after 6 images? Is it stuttering behind? Is it sometimes smooth sometimes stuttering? Post a video so I can see what you are talking about.
STRATEGY_BLOCK_PRODUCER is used intentionally, this is the behaviour a Frame Processor should have. This is the same strategy that is also used on iOS.
It's what I'm trying to explain in the Frame Processor documentation page - frames stream in as often as they can (with fps={30}, 30 times a second, or every 33ms), and if your Frame Processor is not fast enough to finish executing before a new frame arrives, it might drop a new Frame.
STRATEGY_BLOCK_PRODUCER basically means that we push Frames into a queue, and if the queue is full we drop all Frames until a slot is free in the queue.
So if your queue is too slow, you need to do one of two things;
- Optimize your Frame Processor to make sure it finishes within 33ms (make
scanOCRfaster) - Use
runAsyncto run something that takes longer asynchronously. If your FP is called 30 times a second and you userunAsyncwhich takes longer than 33ms to execute, it will skip running that runAsync code until the Async Context is free again, which is exactly the same behaviour as usingSTRATEGY_KEEP_ONLY_LATEST. That's what theenableFpsGraph={true}should help you with. If you easily hit 30 or 60 there, you're good.
With the introduction of runAsync we have the power of using STRATEGY_BLOCK_PRODUCER by default, and STRATEGY_KEEP_ONLY_LATEST being opt in (aka using runAsync).
What STRATEGY_KEEP_ONLY_LATEST does is essentially just not calling the ImageAnalysis function if it is still busy. There is no magic behind it - it's simply dropping Frames and allowing the Preview to run freely, we can do the same thing with runAsync.
So I'm not sure if I understood your issue correctly, so curious to hear your thoughts on this after the above explanation as to why I think STRATEGY_KEEP_ONLY_LATEST is a bad idea. :)
ismaelsousa
What's happening?
With the back pressure strategy set to
STRATEGY_BLOCK_PRODUCERinstead ofSTRATEGY_KEEP_ONLY_LATESTI'm experiencing camera lag while processing OCR unless I userunAsync(). I've confirmed that changing the strategy resolves the issue andrunAsync()isn't required.https://github.com/mrousavy/react-native-vision-camera/blob/main/package/android/src/main/java/com/mrousavy/camera/core/CameraSession.kt#L348
I previously opened issues in these two OCR repos prior to learning with Ismael on Discord that the issue was indeed the back pressure strategy:
Reproduceable Code
Relevant log output
Camera Device
Device
Samsung Galaxy 24 Ultra
VisionCamera Version
4.0.1
Can you reproduce this issue in the VisionCamera Example app?
Yes, I can reproduce the same issue in the Example app here
Additional information