> > > > For bulk devices this is a maximum of 0.05 msec (32KiB/600MBps) > > I lack a bit of knowledge on how to scale this to different devices, with > different speed/framesize. My only bulk device is: > > https://inogeni.com/product/4k2usb3/ > > Which is USB 3.0, and have raw (NV12) resolution from 640x480 (max 60pfs) to 4K > (max 30fps). What would the error look like with that ? For bulk devices the maximum delay from packing multiple packets into a urb is 0.05 msec (32KiB/600MBps) Laurent's message <20231109000327.GE21616@xxxxxxxxxxxxxxxxxxxxxxxxxx> explains where those numbers come from :). Regards! > > > For 1MiB transfer isoc devices (which is the biggest we have seen), > > that is 1.8 msec. > > In both cases, this is smaller than the jitter to process the event > > itself by userspace. > > > > The time from V4L2_EVENT_FRAME_SYNC to DQBUF is around 30 msec. > > > > I do not know how much delay is considered acceptable... but if we > > take the delay argument to the extreme, we could say that > > V4L2_EVENT_FRAME_SYNC can never be implemented, because the event will > > always be delayed by something. > > We have v4l2_event.timestamp for all events, so the jitter to process the event > by userpace can be removed reliably already. > > Nicolas > > p.s. missed it earlier > > > > > > > > > -- > > > Regards, > > > > > > Laurent Pinchart > > > > > > > -- Ricardo Ribalda
