Am Freitag, den 08.05.2009, 22:01 -0400 schrieb Andy Walls: > On Fri, 2009-05-08 at 02:08 +0200, hermann pitton wrote: > > Am Mittwoch, den 06.05.2009, 23:03 -0400 schrieb Andy Walls: > > > > > For the change of UHF start I don't see any problem. > > > > > > If you're talking about the frequency for the bandswitch, I don't see a > > > problem either in general. It may cause a problem for clones of the > > > FM1216ME MK3 that don't have the same filter performance near the > > > cutover, but use the same tuner defintion as the FM1216ME MK3 in > > > tuner-types.c. > > > > > > It may be best to point any clones to a new entry that looks like the > > > current FM1216ME MK3 entry unmodified. > > > > Andy, thanks a lot for participating in such stuff and I think your > > diagnosis is right. > > > > Just a small question in between, already late here and not trying to > > cover the whole scope. > > > > What ever should be the effect of Dmitri's trick one, changing beginning > > of UHF a little. We did that for midband and there was real broadcast > > and it improved one single channel there indeed. > > > > But here, it is plain theory. I honor the lab results they have, no > > problem anyway, but to change something for not at all existing > > broadcast does exactly nothing, except for awaiting it in the future. > > > > No problem with that change, but do I miss something? > > Now that you ask, maybe. > > It first depends on whether there is a station at 441 MHz that normally > would have used the VHF-High filter and VCO, but now uses the UHF filter > and VCO. > > Channel designations I dug out of ivtv-tune: > > S38 439.250 MHz (European cable) > H18 439.250 MHz (SECAM France) > 47 440.250 MHz (PAL China) > 059 440.250 MHz (PAL Argentina) > > come close, but are unaffected by the change from 442 to 441 as the > bandswitch cutover point. These channels fall right on top of the > cutover, but are not affected by the proposed change in any meaningful > way. The VHF-High filter and VCO would still be used. Dmitri's > proposed change is a "don't care" unless the cutover point is changed to > 440 MHz. > > > Let's pretend that the proposed cutover point is 440 MHz. The high > frequencies in the channel (~ 447 MHz) may have perhaps been in the > roll-off of the VHF-High preselector filter. At the edges of filters, > amplitude ripple and especially group delay variation - two aspects of > filters that cause distortion - would have been at their worst, > affecting the high frequencies of the channel (sound and color > sub-carriers). (I assume PAL is VSB with the carrier towards the low > end, similar to NTSC.) Now instead, the low frequencies of the channel > (~ 440 MHz) may be in the roll-off of the UHF preselector filter. Thus > the vestigal sideband and carrier could be affected most by ripple and > group delay variation of the UHF filter. > > Either way, a channel at 440 MHz could face distortion by this tuner. > It really depends on the preselector filter design. > > > I also checked the MID and HIGH band oscillator spec's in the TUA6030 > datasheet. Both of them can cover 440 MHz, but it looks like the MID > band VCO may be preferred since it doesn't drift as badly as the HIGH > band VCO. Since I don't know the component values used in the loop > filters for the VCO's, I can't do any real analysis to see which VCO > would be better at handling 440 MHz. I suspect the difference may not > be significant anyway. > > > > Also, after hundreds of "new" tuners did appear, in the beginning not > > even known from where, I suggested to not allow a new tuner entry for > > all of them, only duplicate code, until they really need it and show off > > their difference. > > > > I would like to keep it especially for this one the same. ;) > > OK. > > > Such subsumed under it have done nothing for Linux so far and have to > > face their faith :) And show off, if _not_ compatible. > > > > And not the other way round. > > Wait until people complain? :) Yes, of course. They had it for free and that is the trap. Again, don't try to start it the other way round. I still wait for Dmitri, to show really off what he has. And, unfortunately, I don't have anything to test on currently :) Cheers, Hermann > > Regards, > Andy > > > Dmitri, if we are talking about the same tuner and filters, we should > > try to get Secam D/K improvements into the original tuner entry. > > > > That NTSC hack stuff might go elsewhere I guess. > > > > Cheers, > > Hermann > > -- 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
