On Tue, 2009-09-22 at 08:44 -0700, Tony Sarathchandra wrote: > > Hi all, > I've been running a split FE/BE Mythtv setup with minimal > issues almost for a year now. On the BE I'm using a HVR-1600 to > receive OTA HD via the ATSC input from a roof mounted antenna. The > issue has been that on some channel, and some channels only I've been > getting what appears to be interlacing/combing effects. I have an > example of this effect from the capture here on start of 60 minutes on > CBS (4_2 KPIX-DT in the Bay Area). The effect is very pronounced > during horizontal motion involving particularly vertical features in > the picture. > > http://thinkspace.ath.cx/stuff/vlcsnap-2017280.png
I suspect you only see this on 1080i video and not 720p. Firefox says your PNG file is 1920px × 1088px, and since no one sends 1080p OTA AFAIK, you're seeing the effect with 1080i in the example. You may wish to try some deinterlace filtering to get rid of the combing. Google turned up this for MythTV: http://www.mythtv.org/wiki/Using_playback_filters I don't know if it works. > The effect is present independent of the player, whether it's on the > Mimimyth FE I normally use, XBMC or VCL on my PC in this case, hence I > put it down to a reception/BE issue regarding the OTA signal quality > reception for these stations. Hmmm. Well, this is a known effect with 1080i. You must have "young" eyes; I tend not to notice the effect that much. Well, WRT to the CX23418, the chip is pretty much a pass through of the Digital TS from OTA. But the areas to check with the HVR-1600 are: 1. use femon in another window to watch for the uncorrectable block count increasing occasionally. This would inidcate marginal reception of a locked station. 2. using the cx18 debug module option (see $ /sbin/modinfo cx18 ), turn on warnings and look for things in dmesg or /var/log/messages like: Fell behind! Ignoring stale mailbox with inconsistent data. Lost buffer for mailbox seq no ... Could not find buf ... for stream TS Possibly falling behind: CPU self-ack'ed our incoming CPU to EPU mailbox (sequence no. ...) while processing This would inidcate buffers being dropped or possibly being dropped by the driver and not being given to the application (i.e. mythbackend) due to a system level performance issue in the capturing PC. > Keep in mind it only happens only on some specific 4-6 OTA channels, > Fox (2_1 KTVU-DT) for an example using the same setup is razor sharp > with no such artifacts. Similarly the next higher channel from CBS, > 7_1 (ABC) is razor sharp, but 9_1 has the issue, 11_1 is sharp etc, it > may be alternating but I'm not exactly sure. Look for the programming being 1080i vs 720p. In my area: NBC and CBS: 1080i Fox and ABC: 720p > I initially put this issue down to a reception/signal quality problem > as my antenna was quite old and a combined VHF/UHF old style design. > So recently I decided to get serious about solving this issue and > installed a brand new DB4 UHF antenna pointed more or less in the > direction of the transmission tower. But still the problem persists. > The thing is both CBS (5_1) and NBC(11_1) are 304-321 degrees > orientation and roughly the same distance of 21-25 miles from my > place, but NBC doesn't seem to have the issue. Hence it does not seem > to be reception related. > > Following this I updated the cx18 driver to a more recent 1.2.0 > version and rescanned all the channel, but no progress. I'm kind of > stumped, anyone have any idea what may be the source of the > interlacing issue on the BE? Update things like ffmpeg and any other MPEG or HDTV decoding libraries used by your apps. Also having a lot of CPU horse power and a good graphics card might help. Other than that, look for options to turn on more sophisticated deinterlacing filters during playback. Regards, Andy > Many thanks, > > Tony _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
