All generally available Media Players does not support RAW format (8 or 10 or 12 bit). You need some custom application to do this job.
If your firmware is correct except the RAW 8, you would have seen some color in the media players. Please state that what is the error that the media players showing.
Can you please confirm whether the data flow is fine with your firmware? Which device you are using here FX3 or CX3?
I am using uvc example from AN75779
I am using FX3S kit
[video4linux2,v4l2 @ 0x7fa1b8009280] Cannot find a proper format for codec 'none' (id 0), pixel format 'none' (id -1)
Assertion *codec_id != AV_CODEC_ID_NONE failed at libavdevice/v4l2.c:821
Please see this thread. May be it will help you to understand the issue:
Try to re-install the "v4l2" and then try again. Also list down the devices as mentioned in the above thread and look for the FX3 in the list.
Thanks & Regards