Connecting RPi cam v1 with CM4 using waveshare Nano baseboard (CM4-NANO-A)

I am trying to connect my Pi cam (ov5647) with CM4 and waveshare nano baseboard. I updated the config file by adding following lines in the end:

dtoverlay=ov5647,cam0
gpu_mem=128
start_x=1

Libcamera commands are working perfectly but the ffmpeg commands are giving errors. I listed my camera devices and /dev/video0 is listed under unicam. Here it is:

bcm2835-codec-decode (platform:bcm2835-codec):
        /dev/video10
        /dev/video11
        /dev/video12
        /dev/video18
        /dev/video31
        /dev/media3

bcm2835-isp (platform:bcm2835-isp):
        /dev/video13
        /dev/video14
        /dev/video15
        /dev/video16
        /dev/video20
        /dev/video21
        /dev/video22
        /dev/video23
        /dev/media1
        /dev/media2

unicam (platform:fe800000.csi):
        /dev/video0
        /dev/media4

rpivid (platform:rpivid):
        /dev/video19
        /dev/media0

Here is the ffmpeg error:

[video4linux2,v4l2 @ 0x558c9e5490] ioctl(VIDIOC_G_PARM): Inappropriate ioctl for device
[video4linux2,v4l2 @ 0x558c9e5490] Time per frame unknown
[video4linux2,v4l2 @ 0x558c9e5490] ioctl(VIDIOC_STREAMON): Invalid argument
/dev/video0: Invalid argument

Basically, I am trying to use the legacy camera stack to use ffmpeg instead of libcamera but no matter what I do, ffmpeg is giving invalid argument but libcamera is working fine. Ps: I am really a newbie with RPi so really sorry for any mistakes and kindly let me know if any other config details are needed to debug my error.