Em Wed, 12 Mar 2014 15:07:02 +0200 Antti Palosaari <crope@xxxxxx> escreveu: > On 12.03.2014 14:57, Antti Palosaari wrote: > > On 12.03.2014 14:47, Mauro Carvalho Chehab wrote: > >> Em Wed, 12 Mar 2014 14:26:35 +0200 > >> Antti Palosaari <crope@xxxxxx> escreveu: > >> > >>> On 12.03.2014 13:02, Mauro Carvalho Chehab wrote: > >>>> Em Mon, 10 Mar 2014 12:01:28 +0200 > >>>> Antti Palosaari <crope@xxxxxx> escreveu: > >>>> > >>>>> On 05.03.2014 20:49, Mauro Carvalho Chehab wrote: > >>>>>> Em Thu, 27 Feb 2014 02:22:06 +0200 > >>>>>> Antti Palosaari <crope@xxxxxx> escreveu: > >>>>>> > >>>>>>> Add documentation for RF tuner bandwidth controls. These controls > >>>>>>> are > >>>>>>> used to set filters on tuner signal path. > >>>>>>> > >>>>>>> Cc: Hans Verkuil <hverkuil@xxxxxxxxx> > >>>>>>> Signed-off-by: Antti Palosaari <crope@xxxxxx> > >>>>>>> --- > >>>>>>> Documentation/DocBook/media/v4l/controls.xml | 19 > >>>>>>> +++++++++++++++++++ > >>>>>>> 1 file changed, 19 insertions(+) > >>>>>>> > >>>>>>> diff --git a/Documentation/DocBook/media/v4l/controls.xml > >>>>>>> b/Documentation/DocBook/media/v4l/controls.xml > >>>>>>> index 6c9dbf6..5550fea 100644 > >>>>>>> --- a/Documentation/DocBook/media/v4l/controls.xml > >>>>>>> +++ b/Documentation/DocBook/media/v4l/controls.xml > >>>>>>> @@ -5007,6 +5007,25 @@ descriptor. Calling &VIDIOC-QUERYCTRL; for > >>>>>>> this control will return a > >>>>>>> description of this control class.</entry> > >>>>>>> </row> > >>>>>>> <row> > >>>>>>> + <entry > >>>>>>> spanname="id"><constant>V4L2_CID_RF_TUNER_BANDWIDTH_AUTO</constant> </entry> > >>>>>>> > >>>>>>> + <entry>boolean</entry> > >>>>>>> + </row> > >>>>>>> + <row> > >>>>>>> + <entry spanname="descr">Enables/disables tuner > >>>>>>> radio channel > >>>>>>> +bandwidth configuration. In automatic mode bandwidth > >>>>>>> configuration is performed > >>>>>>> +by the driver.</entry> > >>>>>>> + </row> > >>>>>>> + <row> > >>>>>>> + <entry > >>>>>>> spanname="id"><constant>V4L2_CID_RF_TUNER_BANDWIDTH</constant> </entry> > >>>>>>> > >>>>>>> + <entry>integer</entry> > >>>>>>> + </row> > >>>>>>> + <row> > >>>>>>> + <entry spanname="descr">Filter(s) on tuner signal > >>>>>>> path are used to > >>>>>>> +filter signal according to receiving party needs. Driver > >>>>>>> configures filters to > >>>>>>> +fulfill desired bandwidth requirement. Used when > >>>>>>> V4L2_CID_RF_TUNER_BANDWIDTH_AUTO is not > >>>>>>> +set. The range and step are driver-specific.</entry> > >>>>>> > >>>>>> Huh? If this is enable/disable, why "the range and step are > >>>>>> driver-specific"? > >>>>> > >>>>> Because there is two controls grouped. That is situation of having > >>>>> AUTO/MANUAL. > >>>>> V4L2_CID_RF_TUNER_BANDWIDTH_AUTO > >>>>> V4L2_CID_RF_TUNER_BANDWIDTH > >>>>> > >>>>> V4L2_CID_RF_TUNER_BANDWIDTH is valid only when > >>>>> V4L2_CID_RF_TUNER_BANDWIDTH_AUTO == false. > >>>>> > >>>> > >>>> Sorry, but I'm not understanding what you're arguing. > >>>> > >>>> Yeah, it is clear at the patch that there are two controls, and that > >>>> V4L2_CID_RF_TUNER_BANDWIDTH is valid only when AUTO is disabled, but > >>>> this doesn't answer my question: > >>>> > >>>> Why V4L2_CID_RF_TUNER_BANDWIDTH's range and step are driver-specific? > >>>> > >>> > >>> Hmmm. That control is used to configure RF filters. Filters set > >>> bandwidth of radio channel. There is usually quite limited set of > >>> available analog filters inside RF tuner. If you look for example > >>> FC0012/FC0013 possible filters are 6/7/8 MHz. E4000 has something 4-11 > >>> MHz. If you look those very old 1st gen silicon tuners like QT1010 / > >>> MT2060, there is no integrated filters at all - but there is external > >>> saw filter which is usually 8MHz at 36.125 MHz IF. > >>> > >>> Did you remember there is same parameter already in DVB API (struct > >>> dtv_frontend_properties bandwidth_hz)? That is control is currently used > >>> to set r820t, fc0012, fc10013 .bandwidth_hz value, e4000 implements it > >>> correctly as own control. > >>> > >>> I am quite astonished we have that big gap with our views. > >> > >> Well, on DVB, the bandwidth is specified in Hz, at DVBv5 (or via > >> an enum on DVBv3). > >> > >> Here, there's no description about the unit to be used (Hz? kHz?). > >> It just says that this is an integer, with a driver-specific > >> range and step. > >> > >> So, one driver might choose to use Hz, other kHz, and other to > >> expose some internal counter. That's bad. > >> > >> We should either use a V4L2_CTRL_TYPE_MENU type of control, where it > >> would be possible to do something similar to DVBv3 way to specify > >> the bandwidth filter, or to define that the bandwidth will be > >> in Hz, kHz or MHz. > > > > Yeah, indeed. That was my mistake. The aim was Hz yes. > > > >> > >> Probably, a menu type is better, as it allows userspace to get > >> all supported bandwidths. > > > > I though it too, but there is already a lot choices for some tuners, > > E4000 has over 30. What is maximum reasonable filter count for > > V4L2_CTRL_TYPE_MENU? I don't see any troubles on having 30 items there. Maybe Hans is aware of some troubles on having such number of items. The advantage of a menu type is that it helps userspace to select an existing range. > One fear there is also what happens when there will be some day new RF > tuner having DSP which does digital filtering ~1 Hz step? It is possible. > Mabbe the current control is enough, but probably it is place to add > comment unit is Hz (even I think people should expect it is Hz when RF > frequencies are spoken). Please remind that V4L2 API has 3 scales already for frequencies, HZ being the less obvious one, as it is the one added only for 3.14 and upper. I see two alternatives here: 1) say that this is always Hz. The problem is if some future hardware would support a bandwidth bigger than 2 GHz. That's unlikely, as using such filter would require a wide band antenna, but I won't doubt that this might happen some day; 2) say that this should follow the corresponding tuner CAPS for frequencies (V4L2_TUNER_CAP_LOW, V4L2_TUNER_CAP_NORM, V4L2_TUNER_CAP_1HZ). The advantage of (2) is that, if we latter need to support wide band filters, one would just need to use V4L2_TUNER_CAP_NORM (or a newer V4L2_TUNER_CAP_1KHZ). Regards, 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
