Hi Adrian, I read the ticket, but I never used MythTV so far, anyway, I think you are facing "normal" problems: 1) IMHO Myth should not rely on the signal-strength and signal-to-noise-ratio. The different hardware which is in use in the different devices are producing different results (because of calculation problems (not floats in kernel-space) and differences). For DVB/ATSC devices MythTV should rather monitor the LOCK-status, BER and UNC to form an opinion about the signal-quality. (For the nova-t-usb2 there is additionally a bug/mistake in pseudo-signal-calculation, which leads to a signal-strength of zero when the signal is actually _very_ good.) 2) USB1.1 devices (and USB2 devices running on a USB1.1 hub) that are using BULK transfers for MPEG2-TS transfer are facing a problem. The bandwidth of USB1.1 is not enough for receiving the complete transport stream of a DVB-T channel (which is about 12 to 16 MBit/s). That's why all DVB devices on USB1.1 using a PID filter in hardware to just get the packets with the requested PIDs. Problem: If only a PAT is requested it will take a quite long time to fill the BULK-transfer buffer. The BULK-URB won't return to the driver (and thus to the demux/section-filter) unless it is full. (That's why Malc has to use -5 as a parameter of dvbscan to get something (because the PID 0x10 (NIT: network information) is only repeated with a larger interval and it is small too)). Unfortunately I had problems by reducing the buffer-size of URBs (so that it won't take too long to get the URBs back)... which would be a solution. This problem does not exist for USB1.1 device using isochronous transfers for MPEG2-TS delivery. Patrick. -- Mail: patrick.boettcher@xxxxxxx WWW: http://www.wi-bw.tfh-wildau.de/~pboettch/ On Thu, 29 Sep 2005, Adrian Wilkins wrote: > A number of us are having problems with MythTV and DVB-T, mostly with > USB tuners, it seems. > > The longest thread on their bugtracker regarding this is > http://svn.mythtv.org/trac/ticket/343 > > In particular, it's puzzling me that both my USB tuners, a Nova-T and > a DEC2000t, will record fine at the command line (using tzap), but > refuse to work with MythTV (they have previously worked just fine, it > seems to be the new signal monitoring code that Myth has introduced). > > The output from tzap looks weird though, esp. the Nova-T, which > reports zero signal as soon as it gets a proper lock (meh?). This is a > card that will stream a playable (mplayer) TS to disk with no trouble, > but Myth refuses to watch that channel. > > The problem would may be that Myth is waiting for PAT/PMT to appear > and considers it to be absent. The developers speculate that this may > be a driver problem. > > One assertation by a developer was that Myth probably gives the API a > bigger workout than your applications and that he might be able to > provide code that would break things ; I'm sure that would prove a > tasty challenge. > > I'm happy to perform whatever contortions necessary to aid resolving > this, as my wife is upset because House, MD hasn't recorded for four > consecutive weeks now and she's getting withdrawal symptoms ;-)
