On Wed, 2010-07-28 at 17:13 -0300, Mauro Carvalho Chehab wrote: > Andy, > > Em 28-07-2010 15:18, Andy Walls escreveu: > > On Wed, 2010-07-28 at 13:35 -0400, Jon Smirl wrote: > >> On Wed, Jul 28, 2010 at 1:02 PM, Andy Walls <awalls@xxxxxxxxxxxxxxxx> wrote: > >>> On Wed, 2010-07-28 at 12:42 -0300, Mauro Carvalho Chehab wrote: > >>>> Em 28-07-2010 11:53, Jon Smirl escreveu: > >>>>> On Wed, Jul 28, 2010 at 10:38 AM, Andy Walls <awalls@xxxxxxxxxxxxxxxx> wrote: > >>>>>> On Wed, 2010-07-28 at 09:46 -0400, Jon Smirl wrote: > >>> > >>>>> I recommend that all decoders initially follow the strict protocol > >>>>> rules. That will let us find bugs like this one in the ENE driver. > >>>> > >>>> Agreed. > >>> > >>> Well... > >>> > >>> I'd possibly make an exception for the protocols that have long-mark > >>> leaders. The actual long mark measurement can be far off from the > >>> protocol's specification and needs a larger tolerance (IMO). > >>> > >>> Only allowing 0.5 to 1.0 of a protocol time unit tolerance, for a > >>> protocol element that is 8 to 16 protocol time units long, doesn't make > >>> too much sense to me. If the remote has the basic protocol time unit > >>> off from our expectation, the error will likely be amplified in a long > >>> protocol elements and very much off our expectation. > >> > >> Do you have a better way to differentiate JVC and NEC protocols? They > >> are pretty similar except for the timings. > > > > Yes: Invoke the 80/20 rule and don't try. > > At the room where my computers is located, I have two wide fluorescent lamps > each with 20W. If I don't hide the IR sensors bellow my desk, those lamps > are enough to generate random flickers at the sensors. With the more relaxed > driver we used to have at saa7134, it ended by producing random scancodes, > or, even worse, random repeat codes. So, lots of false-positive events. It is > a way worse to have false-positive than having a false-negative events. > > So, I don't think it is a good idea to use a "relaxed" mode by default. > > > > Enable NEC and disable JVC by > > default. Let the users know so as to properly manage user expectations. > > (Maxim's original question was about expectation.) > > We should discuss a little bit about RC subsystem evolution during LPC/2010, > but, from my point of view, we should soon deprecate the in-kernel keymap tables > on some new kernel version, using, instead, the ir-keycode application to > dynamically load the keycode tables via UDEV. Of course, after some time, > we may end by removing all those tables from the kernel. /me is very happy about it. The reason isn't even about size or some principle. These keymaps just increase compilation time too much... > > So, assuming that we follow this patch, what we'll have for a newer device is: > > For most devices, the keymap configuration table (rc_maps.cfg) will associate > all known devices with their corresponding keytable (we still need to generate > a default rc_maps.cfg that corresponds to the current in-kernel mapping, but > this is trivial). > > As ir-keytable disables all protocols but the one(s) needed by a given device, > in practice, if the scancode table specifies a NEC keymap table, JVC will be disabled. > If the table is for JVC, NEC will be disabled. > > So, this already happens in a practical scenario, as all decoders will be enabled > only before loading a keymap (or if the user explicitly enable the other decoders). > > So, the device will be in some sort of "training" mode, e. g. it will try every > possible decoder, and will be generating the scancodes for some userspace application > that will be learning the keycodes and creating a keymap table. > > IMO, we should have a way to tell the RC and/or the decoding subsystem to work on a > "relaxed" mode only when the user (or the userspace app) detects that there's something > wrong with that device. > > > When the user knows NEC isn't working, or he suspects JVC may work, he > > can bind that protocol to the particular IR receiver. > > > > Trying to solve the discrimination problem with blindly parallel > > decoding all the possible protocols is a big waste of effort IMO: > > > > a. Many remotes are sloppy and out of spec, and get worse with weak > > batteries. > > > > b. The IR receiver driver knows what remotes possibly came bundled with > > the hardware. (For the case of the MCE USB, it's almost always an RC-6 > > 6A remote.) > > > > c. The user can tell the kernel about his remote unambiguously. > > > > There's no burning need to wear a blindfold, AFAICT, so let's not. > > > > Why bother to solve a hard problem (discrimination of protocols from out > > of spec remotes), when it raises the error rate of solving the simple > > one (properly decoding a single protocol)? > > > > Doing many things poorly is worse than doing one thing well. > > Non-adaptive protocol discovery (i.e. blind parallel decoding) should > > not be the default if it leads to problems or inflated expectations for > > the user. > > > > > >> What happened in this case > >> was that the first signals matched the NEC protocol. Then we shifted > >> to bits that matched JVC protocol. > >> > >> The NEC bits are 9000/8400 = 7% longer. If we allow more than a 3.5% > >> error in the initial bit you can't separate the protocols. > >> > >> In general the decoders are pretty lax and the closest to the correct > >> one with decode the stream. The 50% rule only comes into play between > >> two very similar protocols. > >> > >> One solution would be to implement NEC/JVC in the same engine. Then > >> apply the NEC consistency checks. If the consistency check pass > >> present the event on the NEC interface. And then always present the > >> event on the JVC interface. > > > > It's just too simple to have the user: > > > > a. Try NEC > > b. Try JVC > > c. Make a judgment and stick with the one he perceives works. > > > > > > To have reliable discrimination in the general case between two > > protocols, given the variables out of our control (i.e. the remote > > control implementation) would require some sort of data collection and > > adaptive algorithm to go on inside the kernel. I don't think you can > > get reliable discrimination in one key press. Maybe by looking at the > > key press and the repeats together might up the probability of correct > > discrimination (that's one criterion you examined to make a > > determination in your earlier email). > > Cheers, > Mauro. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
