On Thu, Apr 21, 2011 at 1:59 PM, faginbagin <[email protected]> wrote: > I've been using the dvb-apps tools to scan for new clean QAM channels in my > area on my HVR-1600, and noticed that the frequencies listed in > /usr/share/dvb/atsc/us-Cable-Standard-center-frequencies-QAM256 only go up > to 801000000, or us-cable channel 125. I also observed that when I scan for > channels on my hdhr, using their hdhomerun_config utility, that the max > frequency it scans is 861000000, or us-cable 135. So I thought I'd try > scanning my HVR-1600 for the same frequencies that hdhomerun_config uses. > The driver rejects a couple of the frequencies with the dmesg: > > DVB: adapter 0 frontend 0 frequency 861000000 out of range > (54000000..858000000) > > So I did a little googling, trying to figure out what are valid QAM > frequencies, and came across this article: > > http://en.wikipedia.org/wiki/North_American_cable_television_frequencies > > The table for North American cable tv frequencies in that article goes up to > channel 158, QAM frequency 999.00 MHz. The article also says: > > "Many cable providers currently don't distribute any video content above > channel 139, or about 900MHz. As of 2009, it is common for TVs in North > America with built in tuners to not search analog or digital channels above > channel 139. Most TVs made before 2005 do not include a QAM tuner, and only > have an analog cable tuner which often cannot tune beyond channel 125. With > the addition of services such as premium HD content, cable providers such as > Cox Communications and Insight Communications have begun to roll out digital > cable services which use frequencies up to 1Ghz (analog channel 158), while > also dropping the analog channel formats." > > So, my questions are: > > - Shouldn't I be able to tune frequencies up to 900 MHz, cable channel 139? > > - Is the limit mentioned in the dmesg output imposed by the driver software > or by the hardware? > > - If it's driver software, should it be increased, maybe even up to 999 MHz, > channel 158? > > - I'm using Ubuntu 10.10, kernel 2.6.35-28-generic. Could it be the upper > limit has been increased in the latest v4l-dvb drivers? > > Inquiring minds want to know, > Helen
Hello Helen, These are all good questions and frankly I had never really given it much thought. I can tell you that the limit is "enforced" by the demodulator driver (assuming you have an older HVR-1600, we're talking about the s5h1409). That said, we would have to look at the datasheets for the 1409 as well as the mxl5005s to see what they can actually support in terms of frequency range. And then it's also possible that driver changes would be required beyond just increasing the maximum value. Were you able to actually find any valid signals above 125? Devin -- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
