CODEWITHSUNDEEP
pythonvideo-capturev4l2
Harriebo
Harriebo

Reputation: 76

Not able to generate stable video stream over v4l2loopback device with python

I am working on stream generator for my video mapping set, but I am not able to get the image steady. I open a v4l2loopback device with python-v4l2 and generate a video stream through it based on png, so can generate live video's in my vj set and still video map them and apply effects.

Test case: 1) load v4l2loopback module

2) run python:

import fcntl, numpy
from v4l2 import *
from PIL import Image
height = 600
width = 634
device = open('/dev/video4', 'wr')
print(device)
capability = v4l2_capability()
print(fcntl.ioctl(device, VIDIOC_QUERYCAP, capability))
print("v4l2 driver: " + capability.driver)
format = v4l2_format()
format.type = V4L2_BUF_TYPE_VIDEO_OUTPUT
format.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB32
format.fmt.pix.width = width
format.fmt.pix.height = height
format.fmt.pix.field = V4L2_FIELD_NONE
format.fmt.pix.bytesperline = format.fmt.pix.width * 4
format.fmt.pix.sizeimage = format.fmt.pix.width * format.fmt.pix.height * 4
format.fmt.pix.colorspace = V4L2_COLORSPACE_SRGB
print(fcntl.ioctl(device, VIDIOC_S_FMT, format))
img = Image.open('img/0.png')
img = img.convert('RGBA')
while True:
    device.write(numpy.array(img))

3) run Cheese or other v4l2 stream viewer.

The result is a proper colored and sized image, but it jumps every frame from left to right and always a little more to the left so you get a sliding and jumpy video result. What am I doing wrong?

Best regards,

Harriebo

ps: if you woul like to see the results check: link So far the LiVES, puredate, gem video mapping setup is working greath with the v4l2 streams.

Upvotes: 3

Views: 1466

Answers (1)

Harriebo
Harriebo

Reputation: 76

So I got it a sort of working, but not sure if it's the right way. What I need to do for a stable video stream:

1) don't use custom resolutions, they get messy.

2) send every frame twice. I think this has to do with interlacing / top / bottom frame.

3) for 640x480 shift all pixels 260 spaces to the left in the array, other wise the image is not straight, not for 1024x768 doh... not sure why this is.

4) play is at a slightly lower frame rate as the program can generate.

After all that it is a 99% stable every 10 sec. or so there is one buggy frame. I think it has to do that the framerate the program generates is not 100% stable.

Suggestions on why or how I can do this better are still welcome.

For updates see: https://github.com/umlaeute/v4l2loopback/issues/32

Upvotes: 1

Related Questions