[mythtv-users] Poor recording of races only

Sat Oct 18 01:35:42 UTC 2014

I did some testing today and yesterday.  Here's what I found......
First, watching the problem channels directly on my TV works fine.  I don't get any pauses or macroblocking.
Second, Gary asked about the frequencies on the channels in question.  Here they are:WBBM - (good channel) - 64500WMAQ - (good channel) - 54300TNT - (good channel) - 53100BBCA - (sometimes good, sometimes bad channel) - 29100
NBCSports - (bad channel) - 66300FS1 - (bad channel) - 52500FWIW.
Third, I talked to Ceton's Support.  They told me, "SNR should be 32-37 and the signal level should be between -12 and +12 with 0 dBmV ideal. So the ideal number is 37 SNR with 0 signal. Something to keep in mind, you can have low SNR (32-34) and high signal strength (+5 / +10) and be okay. You can have high SNR (36-37) and have low signal strength (-5 / -10) and be okay. You just can't have both low SNR and low signal strength at the same time, and have a good viewing experience. "
I asked about high signal and high SNR, and they said, "+12 is the upper limit, zero (0) is ideal. With SNR the higher the better, but there will always be noise, so anything above 34 will be readable. 37-39 is ideal."  So perfection would be 0dBmV and 39dB.
I finally got time to move the backend and connect it directly to the cable coming into the house from the outside box, and do some testing.  What I found was that with the backend connected directly to the incoming cable, my signal on these channels on all tuners is -4.0 to +4.6 with an average of +0.025dBmV.  SNR ranges from 31.6 to 36.6 with an average of 34.3125dB.  Based on what Ceton said, those numbers should be good.
I then connected my backend with a 1->2 splitter.  In came from the same line that comes in from outside.  Out went to the backend on one side, and was terminated on the other (though I tested it connected to my TV on the other side and the numbers didn't change significantly).  One splitter was a Radio Shack splitter rated for 5-3000Mhz.  The other I got from my cable company a long time ago (before digital switch over) and it's rated at 5-1000Mhz.  The numbers weren't significantly different with either one.  My signal strength ranged from -7.8 to -0.5dBmV with an average of -4.53dBmV.  Not nearly as good, but still within the acceptable range according to Ceton.
I then replaced the splitter with my Motorola Amplifier with the other port terminated.  My signal strength ranged from 7.7 to 13.9 with an average of 10.29dBmV.  The SNR was about the same with a range of 31.3 to 35.8 with an average of 33.08dB.  So the amp ups the signal and doesn't significantly change the SNR, as intended.  However, I wonder, based on Ceton's recommended numbers, if having a high signal might not be as good as one close to zero.  It seems weird that it wouldn't help.
Finally, decided that all of these number are wonderful, but they don't mean crap if I don't see how it looks.  I found that in all situations (direct from the drop, through a splitter, or through the amp) WBBM and WMAQ looked fine, as did BBCAmerica.  In fact, the results were the same in all tests.  When I tested directly from the outside cable on TNT, I got three "Waited xxx seconds for video buffers...." errors with a bit of stutter when I got them, then no problems.  On NBCS, I got a ton of stuttering.  While that was going on, I got some "Waited xxx seconds for video buffers" errors, then I got a bunch of Ring Buffer "Waited for data" errors.  After several seconds of this, I started getting nothing but "Decoding error.........eno:  Unknown error" with a black screen.  On FS1 I got the same stuff, in the same order, but the Ring Buffer errors said "Taking too long to be allowed to read" rather than the "waited for data" Ring Buffer errors.
So, at this point, I'm thinking that signal from cable isn't the problem.  I'm thinking those errors mean something else, though what, I have no clue.
What do you guys think?
Mike 

     On Friday, October 17, 2014 5:31 PM, Yippee Three-eight <yp_38 at yahoo.com> wrote:

 Sorry about the top post.  I'm using the Yahoo Mail interface, and, well, it kinda sucks.  I need to put this account in Thunderbird so it shows up correctly.
The shows indicate that they are recording in HD.  When I fist start the recording, the info box pops up at the bottom of the screen and shows 1080.  What I discovered though, is that - at least in the one I watched all the way through - is that only the first 5:57 of the program was recorded.  I didn't check the others, but I'm sure - based on file size - that the same was the case for all of them.
Mike 

     On Tuesday, October 14, 2014 3:39 PM, Jim <lists at morton.hrcoxmail.com> wrote:

  On 10/13/2014 8:49 PM, Yippee Three-eight wrote:

  I've finally gotten my Ceton InfiniTV 4 PCie working on Mythbuntu.  <YAY!>  Anyway, I've set up a bunch of shows to record, all of them HD.  Many of those shows record just fine.  However, I'm a racing fan, and every race I've recorded so far has been of really poor quality except one.

  All of those recordings show up with a yellow border.  I think that means the recording is damaged from what I've read.  When I watch the recording, every time a scene changes, the screen gets very blocky (macroblocking?) and the audio cuts out, then it will return to a beautiful recording for a moment until the camera changes, then it repeats.  It gets worse and worse as the show goes.  I haven't let it run, but I have noticed that the file size is very small.  For example, a normal TV show recorded for 1 hour at 5.xx Gb.  A formula 1 race (3 hours) recorded at 0.5 Gb. 
  I've also had some problems with BBC America.  Some recordings are great.  Some show up as yellow like the races.  Of those, some just hang the frontend.  Others come back with a message saying the file is missing.

  The one race recording I recorded without problem was a NASCAR race that was not scheduled to record, but I turned it on in Live TV.  It looked great, so I went back to the program guide and tried recording it.  It recorded fine.  As I said, these shows are all HD. 
   Initially, I was unable to record anything when I set up the box.  I was getting buffer errors.  I found that my network was running at 10Mb/s.  I fixed that so it's running at 1000MB/s, but I still have some Cat5 (not 5e) cable in the walls. 
  I looked at the channels that I've recorded on and here's what I got for signal strength and S/N ratio: TNTHD - always good:  Signal Strength - 3.8 dBmV, Signal to Noise Ratio - 32.6 dB WMAQHD - always good:  Signal Strength - 4.1 dBmV, Signal to Noise Ratio - 33.4 dB WBBMHD - always good:  Signal Strength - 5.9 dBmV, Signal to Noise Ratio - 34.6 dB
  BBCAHD - sometimes good recordings, other times not:  Signal Strength:  2.3 dBmV, Signal to Noise Ratio:  34.1 dB NBCS1HD - always bad:  Signal Strength - 3.9 dBmV, Signal to Noise Ratio - 34.8 dB FS1HD - always bad:  Signal Strength - 3.5 dBmV, Signal to Noise Ratio - 32.1 dB 
  Since it seems like a channel thing (higher channels have problems, lower channels don't), I figured I'd look at improving my signal strength.  I've had a Motorola 1-2 amplified splitter (http://www.amazon.com/Motorola-Signal-Booster-BDA-S2-Amplifier/dp/B0017I1PVC/ref=pd_sim_e_5?ie=UTF8&refRID=0REJCWJTGHQ0WF945342) on the line coming into my house for a while now.  It helped a lot as before I couldn't tune.  I've got one of those lines going to my old STB, and the other going to a 1-2 splitter.  From the splitter, one line goes to the cable modem, and the other line goes to my backend's cable tuner card.  I've always read that splitters degrade signal, so I tried disconnecting the STB and connecting one long line directly from the Motorola amplifier to my cable card.  On all channels, SS goes up by 2 - 3 and S/N goes up a bit too.  I've read that a perfect signal strength would be 0 dBmV, but I'm wondering if that's wrong. 
  Can anybody offer any suggestions on what I should look at to be able to record these shows? 
  Mike

 Mike,

 Please don't top post. 

 I don't think the races are being recorded in HD. Even bad quality HD produces large files. Can you double check things to make sure you are not recording from an SD channel or another source than you think you are?
 I'm not saying you don't have an issue with splitters and poor quality signal I just would expect to still see file sizes roughly the same as any other HD recording.

 -- 
 Jim

_______________________________________________
mythtv-users mailing list
mythtv-users at mythtv.org
http://www.mythtv.org/mailman/listinfo/mythtv-users
http://wiki.mythtv.org/Mailing_List_etiquette
MythTV Forums: https://forum.mythtv.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.mythtv.org/pipermail/mythtv-users/attachments/20141018/9b5e3d9a/attachment.html>