Warnings, not errors reported - but bad pixellation

Begonnen von charlesc, Mai 13, 2016, 07:41:31

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TS-Doctor 1.2.184
I've got an unexpected result in checking a file.  Perhaps you can explain if I have some setting that isn't as it should be.  Logs attached.

I'm opening a transport stream DVB-T off air recording in TS Doctor, and then manually running 'Check File'.  A lot of red and yellow errors and warnings can be seen in the green timeline, and on completion the top part of the summary graphic reports 272 Errors and 667 Warnings.  But the lower text part doesn't identify any errors with the PID MPEG2 Video stream.  And when you close that dialog box, there are no error areas identified to go to to see what they were like.
And yet the source file pixellates (screenshot from Video ReDo).

Any ideas why errors aren't identified?  This is manually run, not a batch.


>Any ideas why errors aren't identified?

I think, this happens because there is no real error correction or detection facility in the video stream.

MPEG Audio has CRC, so you can calculate that it is wrong and mark it as error.

The only thing the Doc "sees" about video streams is if there are missing packets (wrong/missing sequence number of the packet). But even with missed packets, the pic may still decode ok (for instance if the lost packet just contained "filler" data). So the Doc treats them as warnings most of the time.
Only, if there is a bunch of missed packets belonging together it will add up to the error counter because then it is very likely that something important has been lost too.


Thanks for the reply.  Interesting.

I've had a couple of recordings suddenly throw up 100's of 'errors' unexpectedly.  Ill try and track it down with further testing.

I was first surprised to see all the red and yellow peaks streaming by as it worked through the recording.  Then more surprised when it didn't flag any problem areas. 
I've seen this before with just a few errors, and thought maybe then that they weren't too important.  But with say 600+ and a huge block of red I thought something would flag.


There is another aspect you have to keep in mind.

you video is MPEG2, this is much less sophisticated than MPEG4 (used for HD) or even H265 (used for UHD).

An "Error" in MPEG2 does not really automatically create pixelation like it does in the more advanced compression methods.
There maybe just a few (your screenshot shows about 10) seconds missing but they could just look like a jump in the remaining film.
Depending on what is shown (maybe a "still shot" showing  a non moving landscape?) it may not even be noticable at all.

In MPEG4 and above even one missing packets leads to mayor pixelations instantly your large block of errors would surely be fully visible and looking ugly.

In your case it also helps that the errors are "everywhere" spanning audio and video streams equally. This gives the doc a chance to take an educated guess at which point it maybe save again to expect "good" packets again because it can follow the CRC of the audio track. To keep audio and video in sync it has to drop those video packets anyway, even if they would be correct.


I've found a few more with multiple errors, one even around 2,500.  Visible pixellation!

I know what you say about not all errors are visible.  I've seen that, invariably when TS-D has reported error(s), and shown them in the manual check window.  In double-clicking on the error number, the video playback window comes up and you get the 3 or 4 seconds around the error.  Many times you see nothing.

Unnecessary detail - removed

So doing more validation testing.  But a bit confused as to why TS-D not flagging errors.  Your explanations have helped.  Thanks.

I'm just trying to record with close to zero errors.  The signals are good, and I've a couple of sources from different transmitters.  Making sure I have the best transmitter sources.


I'm afraid, I cant help you with DVB-T issues because I never used it myself.

I once tried, but I live in an area which is almost uncovered, you need a very high outside dish to get anything and most of what you get will be errors only. This is so far away from the quality of what I can get from a dish and a DVB-S receiver that you wont spend even a thought on it. And, as I have heard, DVB-T will be turned off (and replaced by DVB-T2) from next year on already.

Also, DVB-T varies alot from country to country, so things that might be true here in germany would not be helpful in your country.

for SAT (if we ignore the T and S thing right now) I have tried USB and PCI[e] cards, none of those really worked 100% flawlessly. Some USB Controllers on the Mobos dont like the constant transmission rate, some PCI[e] busses on the Mobos get stress when bursts from other devices occupy the but too much and then they cut off the Videostream too.
The only "stable" thing for now are LAN Tuners for me (run on a seperate LAN, else you may run into the same Burst problems here too). They can provide error free reception (and recording) for ages.
They are available for -S or -C / -T / -T2, but are quite expensive ( ~400€ for a box with 4 tuners and 2 CI slots)
They "talk" the Sat-IP protocol (even if used for cable or -T reception) and run very smoothly with a software called DVBViewer (+ addon "Recording Service")). Just dont forget to use a seperate LAN card for connecting the box to the PC...

But,of course, all of this wont help if your problem originates from a simple faulty capacitor in your washing machine or other electrical device in your home or neighborhood.