WTMJ-DT and Statistical Multiplexing

[techboy]

Does anyone in this group use a PC card made by MIT (Macro Image Technology)for HD reception?  Models MDP100, 110, 120, or 130?  Since WTMJ-DT has switched to Statistcal Multiplex stream configeration, my PC tuner card will not receive the main program without blocking, lock-up or pixelation.  ( The sub channel is OK, but I'm not that interested in the weather ).  I'm working with the manufacturer on the problem, but as statistical multiplex is a new tecnique to OTA and only in use by a few stations, they aren't particularly concerned yet.  I am also asking if anyone else has obsevered pixelation / blocking that can't be explained by loss of signal, low RF, or multipath?   Perhaps other receivers are not compatible with statistical multiplexing.   Thanks:    Tod

[Doug Mohr]

Does anyone in this group use a PC card made by MIT (Macro Image Technology)for HD reception?  Models MDP100, 110, 120, or 130?  Since WTMJ-DT has switched to Statistcal Multiplex stream configeration, my PC tuner card will not receive the main program without blocking, lock-up or pixelation.  ( The sub channel is OK, but I'm not that interested in the weather ).  I'm working with the manufacturer on the problem, but as statistical multiplex is a new tecnique to OTA and only in use by a few stations, they aren't particularly concerned yet.  I am also asking if anyone else has obsevered pixelation / blocking that can't be explained by loss of signal, low RF, or multipath?   Perhaps other receivers are not compatible with statistical multiplexing.   Thanks:    Tod

I saw your posting on the AVSforums about this. I have 3 MyHD MDP-120s in the house all running OTA. I can honestly say that I have not watched TMJ in well over a month, if not two. I do know that when I reformatted one of the machines, auto-scan didn't find TMJ. I had to manually add it.

I will make a point to watch some repeats tonight. Probably Earl and Office and let you know what happens.

Is it only on HD programming or on all formats? I'll try getting home in time to watch the news as well.

Doug

[jimbop99]

I have a DVICO fusion lite running BeyondTV 4.3. I have noticed a lot more problems with channel 4 lately. Mostly jerky picture. I don't know if its related.

[bubbaridesfast]

About 2 months ago I started having pixelation problems on 4-1 OTA. In fact I also asked about it on here and some one noted interference from another out-of state station if I remember right.
It really bothers my wife, she always switched to the SD signal for 4 on D* but Friday I upgraded my D* and get the locals in HD  and she is happy with that (except rainfade is still a problem but that's because of all my trees).

I'm not familiar with Statistical Multiplexing, maybe that's the cause of what I have been experiencing. We had no problems with 4-1 for the previous 2 years we've received it OTA.

[techboy]

Bubbar:  My I please ask on what equipment you experienced the pixelation?  I only have the problem on my PC tuner card.  Thanks

Tod

[bubbaridesfast]

Bubbar:  My I please ask on what equipment you experienced the pixelation?  I only have the problem on my PC tuner card.  Thanks

Tod

Please, just call me bubba or on-time for dinner...
I had this problem OTA on my LG LSS-3200A receiver - not with a pc tuner card. On Friday I upgraded to a D* H20 and haven't watched enough 4-1 to notice if I still have this problem with this OTA tuner.

[Doug Mohr]

I've made a point of watching TMJ the last few evenings and I am experiencing the same issues. Sound stays steady but picture seems to get out of sync, then pixelate and catch up about once a minute. Very annoying.

I'm on a PC tuner, MyHD MDP-120

[RJRobb]

Experiencing drop outs on channel 4.1 with my Dish 811 receiver.  Signal strength use to be in the low to mid 90s.  Now it's only in the mid 80s.  
My HP2600N has problems with their 5.1 audio.  It breaks up, is lost, then resets in a matter of a few seconds.  Signal strength meter doesn't drop when this occurs.  Generally happens after prime time, i.e. during Leno - Tonight Show.  Anyone else notice this?

[techboy]

The Statistical Multiplex problem caused by the OTA encoder should not manifest itself on a satellite service feed.   The satellite guys get a fiber feed before local encoding.

I've talked with many guys who are not seeing an OTA  problem and a few who are.  No real pattern emergies here.   The guys at MIT ( MyHd PC tuner card ) analyzed a stream I recorded and FTP'd them and they don't see any unusual patterns or instability in the PES, PMT's or PID's and the data is clean, i.e., no multipath issues or RF trouble.  I don't see break-up any less in the 4x3 shows than the 16x9 shows.  4x3 uses less bandwidth, so one would think it would not suffer as much from compression artifacts if SM really works as it should.   Anyhow, for now, I've given up trying to watch WTMJ-DT OTA on my PC.  If I come up with some real information later, I'll start another thread.  I'd still like to hear experiences from anyone else using a MIT or Fuson video card.  Tod

[bubbaridesfast]

So far with the tuner in my new D* H20 STB I no longer seem to experience the signal problems that I did with my LG box (fingers crossed).

[John Brundage]

I'm also having problems with 4.1.  I get pixelization and dropouts once every 3-4 seconds.  I have a Toshiba DirectTV receiver.

[techboy]

I continue to have a problem with ch 28 WTMJ-DT at my location in Glendale / Whitefish Bay.  On my PC tuner card the video pixels and locks frequently.  On my Sony reciever, the piture either locks or goes black.  On either device, the audio continues normally.  I've changed antennas with no improvement.   This problem may or may not be related to the SM encoding.   It's just that I first noticed it about the same time WTMJ added the sub channel.   I really can't see any correlation between the picture content and the break-up.  That is, it doesn't seem to matter if there is rapid motion or no motion, wide screen or 4x3.  So, I have concluded that I most likely have a reception problem related to my location.  Perhaps a multipath issue or local RF interference.  I have NO issues with any other channel.  

I'd surely appreciate hearing from any other forum members who are experiencing the same issue on WTMJ-DT.  Please include where you are located.

Tod

[StarvingForHDTV]

4-1 occasionally pixelates for me, but does not lock up.  OTA with Samsung set top box.

[bimmer_immer]

I have a MyHD MDP-130. I also have the periodic macroblocks you describe.
This is new behavior. The same card did not do this before.

Interestingly, the captured stream plays fine on Videolan client. So it must be some sensitivity in the MyHD playback.I have not tried other MPEG decoders yet, but I will.

I did run a snippet of the combined multiplex through an offline  transport stream analyzer. It found a couple of PCR interval errors. These should be reasonably benign.

I also tried running the stream through T-STD analysis. On program 1 (4.1) this produced 1000's of buffer overflows in video buffer and a lesser number in the audio buffer in a 40 seconds snippet. Program 2 (4.2) also had overflows but not as many.

Buffer overflows mean that data is going into the decode buffer faster than it is being removed.  I also observed what seems like a long interval between the picture's arrival time and the PTS (over 800msec) -- which would correlate with a rather large amount of data in the decode buffer.

It is important to state that this could be an analyzer giving a "false positive".  It does point to a potential problem. In the past  I have seen a high correlation between these types of errors and visible artifacts.

TMJ engineering reading this?

-Brian

[tencom]

I too, experienced a macroblock break-up problem, with channel 28, as did others and traced the problem to the video accelerator IDCT function .
I have a FUSION HDTV PCI tuner and the problem,  is with the relationship between the CPU and the computers video accclerator board, where the macroblocks are assembled for display. by disabling the DXVA or hardware accleration feature of the video board, through the FUSION software and let the CPU do all the processing I was able  to eliminate the macroblock break-up problem, this increased the CPU usage rate but solved the problem.