Record webcam with only half of framerate

Hi Community,

I am testing recording the Logitech webcams (C270 and C505) with H265 encoding via v4l2loopback. The capabilities of the Webcam devices :

$ v4l2-ctl --list-formats-ext -d /dev/video3
ioctl: VIDIOC_ENUM_FMT
Type: Video Capture

[0]: 'YUYV' (YUYV 4:2:2)
	Size: Discrete 640x480
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 160x120
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 176x144
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 320x176
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 320x240
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 352x288
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 432x240
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 544x288
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 640x360
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 752x416
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 800x448
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 800x600
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 864x480
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 960x544
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 960x720
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 1024x576
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 1184x656
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 1280x720
		Interval: Discrete 0.133s (7.500 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 1280x960
		Interval: Discrete 0.133s (7.500 fps)
		Interval: Discrete 0.200s (5.000 fps)
[1]: 'MJPG' (Motion-JPEG, compressed)
	Size: Discrete 640x480
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 160x120
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 176x144
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 320x176
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 320x240
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 352x288
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 432x240
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 544x288
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 640x360
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 752x416
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 800x448
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 800x600
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 864x480
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 960x544
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 960x720
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 1024x576
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 1184x656
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 1280x720
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
	Size: Discrete 1280x960
		Interval: Discrete 0.033s (30.000 fps)
		Interval: Discrete 0.040s (25.000 fps)
		Interval: Discrete 0.050s (20.000 fps)
		Interval: Discrete 0.067s (15.000 fps)
		Interval: Discrete 0.100s (10.000 fps)
		Interval: Discrete 0.200s (5.000 fps)
  1. Clone :
gst-launch-1.0 v4l2src device=/dev/video3 ! videorate drop-only=true ! autovideoconvert ! videoconvert ! "video/x-raw,framerate=30/1,interlace-mode=progressive" ! \
        tee name=t ! queue ! v4l2sink device=/dev/video13  sync=false async=true \
        t. ! queue ! v4l2sink device=/dev/video23 sync=false async=true
  1. Verify the capabilities of the cloned devices :

$ v4l2-ctl --list-formats-ext -d /dev/video13
ioctl: VIDIOC_ENUM_FMT
Type: Video Capture

[0]: 'YUYV' (YUYV 4:2:2)
	Size: Discrete 640x480
		Interval: Discrete 0.033s (30.000 fps)

$ v4l2-ctl --list-formats-ext -d /dev/video23
ioctl: VIDIOC_ENUM_FMT
Type: Video Capture

[0]: 'YUYV' (YUYV 4:2:2)
	Size: Discrete 640x480
		Interval: Discrete 0.033s (30.000 fps)
  1. Record :
    gst-launch-1.0 -v v4l2src device=/dev/video23 ! video/x-raw ! nvvidconv ! nvv4l2h265enc control-rate=1 bitrate=4000000 ! ‘video/x-h265, stream-format=(string)byte-stream’ ! h265parse ! qtmux ! filesink location=${RECORD_PATH}/logitech_c270_$(date +“%Y_%m_%d_%H_%M_%p”).mp4 -e

However, the file is only recorded at ~15fps, half of the expected framerate:

Could you tell why I couldn’t reach the 30fps in the recorded file, please ?

Best Regads,
Khang

Best Regards,
Khang

Hi,
Please run the commands to identify where the bottleneck is:

$ gst-launch-1.0 -v v4l2src device=/dev/video23 ! "video/x-raw,format=YUY2,framerate=30/1" ! fpsdisplaysink text-overlay=0 video-sink=fakesink sync=0
$ gst-launch-1.0 -v v4l2src device=/dev/video23 ! "video/x-raw,format=YUY2,framerate=30/1" ! nvvidconv ! "video/x-raw(memory:NVMM),format=NV12" ! fpsdisplaysink text-overlay=0 video-sink=fakesink sync=0
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