HDMI video input to OpenGL texture PI 4

[jimknopf2]

I want to use OpenGL ES vertex and fragment shader to work on HDMI video data received by a TC358743. Which interface or API shall I use to have the fastest transfer of video data to OpenGL ES texture. It runs on a PI 4.

# /boot/config.txt
dtoverlay=vc4-fkms-v3d
dtoverlay=tc358743

# Video source
/dev/video0

# texture initialize
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 1920, 1080, 0, GL_RGB, GL_UNSIGNED_BYTE, nullptr);

# texture update
unsigned char data[1920*1080*3];
read(FileDesc, data, 1920*1080* 3);
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 1920, 1080, GL_RGB, GL_UNSIGNED_BYTE, data);

The current problem is the slow transfer of each frame to GPU memory with glTexSubImage2D which takes about ~50ms. Can someone please help? Thank you.

[6by9]

You want to use dmabufs for zero copy between kernel subsystems.
V4L2 has an ioctl VIDIOC_EXPBUF to export the buffer as a dmabuf fd.
eglCreateImageKHR has a way to pass all the dmabuf parameters into EGL, as used in https://github.com/6by9/drm_mmal/blob/x ... mal.c#L476

I suspect that V3D won't import UYVY, but I'd hope it supports BGR3 if you pass DRM_FORMAT_RGB888 via EGL_LINUX_DRM_FOURCC_EXT, but if not then you can pass it through the ISP (either using MMAL or V4L2 M2M on /dev/video12, both of which can support dmabufs) to convert to an acceptable format.