Wrong incoming frame length

[niXman]

hi,

I'm using ubuntu-20.04 with v4l2loopback-0.12.3.

I have two v4l2 loopback devices with the following characteristics:

ffprobe /dev/video0

Input #0, video4linux2,v4l2, from '/dev/video0':
Duration: N/A, start: 17479.219834, bitrate: 331776 kb/s
Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1280x720, 331776 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc

ffprobe /dev/video1

Input #0, video4linux2,v4l2, from '/dev/video1':
Duration: N/A, start: 17481.786751, bitrate: 117964 kb/s
Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x512, 117964 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc

but I ran into a problem with the frame size in webrtc source code: https://webrtc.googlesource.com/src/+/refs/heads/main/modules/video_capture/video_capture_impl.cc#132

YUV420 frame size in bytes should be 1280×720+640×360×2 == 1382400 but was read 1384448...

IncomingFrame() called from here: https://webrtc.googlesource.com/src/+/refs/heads/main/modules/video_capture/linux/video_capture_linux.cc#411

struct v4l2_buffer filled here: https://webrtc.googlesource.com/src/+/refs/heads/main/modules/video_capture/linux/video_capture_linux.cc#398

but pay attention, webrtc works great for my second video stream! (/dev/video1: yuv420p, 640x512)
so I think the problem is not in the webrtc code.

any ideas?

best!

[niXman]

looks like the problem is in gstreamer's v4l2sink plugin...

[mariannasb]

can you comment on what you found on v4l2sink?

[umlaeute]

Here's the relevant bugreport for the v4l2sink: https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/2532