I loaded the bitmap images into memory beforehand and animated them on electronic paper like a frame-by-frame cartoon.
This time, I’m going to read and play back every frame from the SD card. Moreover, it also has a soundtrack.
Processing the image data
The resolution of the e-paper is 800×600, which is 60kB if we assume one bit of black and white per pixel.
Since reading data from the SD card is not very fast, I halved the data volume by reducing the resolution by half and stretching it during display.
The electronic paper is 5 inches in size, so even if the resolution is cut in half, the roughness of the image doesn’t bother me as much.
In addition, it is not a BMP file but the data to be transferred to the e-paper itself, and the processing of the display data of the e-paper from the BMP is not done, making it a little faster.
Putting audio on an image
If the image and audio files are separated, the access will be dispersed and the processing speed will be slowed down, so I decided to put the audio in the unnecessary area (black area) of the image.
The image is a dithered black and white two-tone, but it looks reasonably grayscale. The sound is processed by a separate CPU using the ESP32 multi-core, and is output from the DA output.
The original video is at “The Daily Dweebs” here.
If you watch the video of the e-paper after watching this, you’ll be like, “Oh, maybe it’s true.
Full-length videos are also available.
Unlike playing back from memory, it can store data up to the capacity limit of the SD card, since it is played back while reading from the SD card. It can store several dozen gigabytes, so it seems to be able to play fairly long videos.
However, it seems that e-paper is not suitable for video because it leaves an afterimage.