Hi,
By default it is uridecodebin in deepstream-test3. You need to replace it with
v4l2src ! video/x-raw,format=_SOURCE_FORMAT_,width=_SOURCE_WIDTH_,height=SOURCE_HEIGHT_,framerate=_SOURCE_FRAMERATR_ ! videoconvert ! nvvideoconvert ! video/x-raw(memory:NVMM),format=NV12
You can refer to this post to set precise format,width,height,framerate.