What is the advantage of a 3MP OV3660 sensor on the ESP32 M5Stack camera if it can only save upto 2MP images?

Question

I am making a self-contained stills camera and the ESP32-based modules seem well-suited to my project due to the easy incorporation of a TFT viewfinder screen and TF card slot in one package. I am not interested in saving video or web streaming. I have worked with the TTGO ESP32 camera that uses the OV2640 2MP sensor and can save full 2MP UXGA (1600x1200) resolution stills (albeit with mandatory JPEG compression turned on - I have only managed to get 1.3 MP images without compression).

I see now there is a version of ESP32 camera that uses the OV3660 3MP sensor (called 'M5Stack Timer Camera'). However, the specs for that camera https://docs.m5stack.com/#/en/unit/timercam say it can save upto a maximum of UXGA - i.e. 2MP images.

So what is the advantage of having a 3MP sensor chip if you can only save 2 MP images? Or is there a way of saving the full 3MP sensor resolution (i.e. 2048 x 1536) stills from this camera?

Thanks

Answer 1

The limit isn't the camera - it's the memory.

At 3 megapixels you have 3145728 pixels. At 3 bytes per pixel (8 bits each of red green and blue) it requires 9437184 bytes to store the image. That's more than can fit into the 8MB PSRAM.

1600x1200 will probably be one of the standard resolutions that the specific camera in use can capture, and is probably the biggest size that is below 8MB in size for a single frame.

So, what advantage of having a 3 megapixel camera? Well, none to you, other than the cost. It's probably cheaper to use a newer 3 megapixel camera than an older 2 megapixel camera.

---

It is perfectly possible to run at the resolutions you desire though. This resolution is known as QXGA and is supported by the OV3660 driver in the ESP32 Camera library. There are some caveats though:

1. You must use JPEG compression. Not only is this to make the image small enough to fit into PSRAM but also to make it possible to write the whole frame into PSRAM fast enough that you don't miss bits of the data.
2. You will not be able to "do" anything with the image other than send it to somewhere else (such as an SD card or a web server). There just isn't enough room to uncompress the image.

Answer 2

I contacted the M5Stack people directly and they assured me that they made an error in their original web page specs and that the camera does indeed support full 3MP capture. So I bought one of these M5Stack Timer Cams and tested it. I can confirm that the device will save a 3 MP image at full QXGA resolution (2048 x 1536). This option was not available on with the Win10 example app they provide but it was only possible with their official Arduino 'webcam' example. This is a web server WiFi example sketch and one of the options is QXGA and this does work.

So the definitive answer to my question (based on practical experience) is that the advantage of using the OV3660 is that it can provide 3MP pictures and the original specs provided by M5Stack were misleading hence the confusion expressed in my question.

It would also be interesting to hear if anyone has managed to get OV3660 working at full 3MP on other generic ESP32 boards. So far I have seen no other example published on the web.

Answer 3

The m5stack timer camera X (OV3660) lacks support. There is nothing on how to flash and use micropython in this device. There is a cameratool you can download and take snapshots via serial port, there is the standard arduino software you can flash and that's it. I miss some guides on how to flash micropython on it and make it work with mqtt and more complex setups. I'm not an arduino person, just want to code some python on it.

I bought 2 of those cameras and those are sitting in a shelf for 6 months with 0 use. One day when someone publish a full micropython firmware for that camera, i'll give it a try.

PS: I've tried to compile a micropython firmware with OV3660 support, but no luck on make it work.