Damaged DVB-S2 stream

[jeroen]

Hi,

I am trying to make long high quality recordings with a TBS6991 with CI and Smartcard.
This works fine using mumudvb (based on dvblast). However, the stream has bitcorruptions 20-100 times per hour. This leads to visual artefacts in the recording during playback.
Even if I record without any processing, the visual artefacts are there when playing the stream. This is a DVB-S2 8PSK channel

Using szap-s2 we see bit error rate (BER) = 0 all the time.
It looks like there are absolutely no signal problems and we use a very large dish with good quality connectors and relatively short cables.


ffmpeg (decoding the h264) reports errors like
[h264 @ 0x464b420] cabac decode of qscale diff failed at 27 12
[h264 @ 0x464b420] error while decoding MB 27 12, bytestream (2834)
[h264 @ 0x464b420] concealing 1102 DC, 1102 AC, 1102 MV errors in B frame
frame=29605 fps= 25 q=28.0 size= 151183kB time=00:19:44.01 bitrate=1046.0kbits/s dup=39 drop=0
frame=29629 fps= 25 q=28.0 size= 151340kB time=00:19:45.02 bitrate=1046.2kbits/s dup=39 drop=0
[h264 @ 0x48e7480] left block unavailable for requested intra4x4 mode -1 at 0 28
[h264 @ 0x48e7480] error while decoding MB 0 28, bytestream (23933)
[h264 @ 0x48e7480] concealing 409 DC, 409 AC, 409 MV errors in I frame
frame=29657 fps= 25 q=28.0 size= 151465kB time=00:19:46.03 bitrate=1046.2kbits/s dup=39 drop=0
[h264 @ 0x494b240] concealing 941 DC, 941 AC, 941 MV errors in B frame
[h264 @ 0x4a76b80] error while decoding MB 36 35, bytestream (-16)
[h264 @ 0x4a76b80] concealing 58 DC, 58 AC, 58 MV errors in P frame
frame=29680 fps= 25 q=28.0 size= 151570kB time=00:19:47.01 bitrate=1046.0kbits/s dup=39 drop=0
[h264 @ 0x4c06280] left block unavailable for requested intra4x4 mode -1 at 0 6
[h264 @ 0x4c06280] error while decoding MB 0 6, bytestream (59488)
[h264 @ 0x4c06280] concealing 1399 DC, 1399 AC, 1399 MV errors in I frame
frame=29705 fps= 25 q=28.0 size= 151679kB time=00:19:48.02 bitrate=1045.9kbits/s dup=39 drop=0
frame=29728 fps= 25 q=28.0 size= 151779kB time=00:19:49.00 bitrate=1045.7kbits/s dup=39 drop=0
[h264 @ 0x4a76b80] concealing 1045 DC, 1045 AC, 1045 MV errors in P frame
[h264 @ 0x4757d80] concealing 1392 DC, 1392 AC, 1392 MV errors in P frame
frame=29753 fps= 25 q=28.0 size= 151876kB time=00:19:50.06 bitrate=1045.5kbits/s dup=39 drop=0
frame=29777 fps= 25 q=28.0 size= 151984kB time=00:19:51.07 bitrate=1045.3kbits/s dup=39 drop=0
[h264 @ 0x4757d80] left block unavailable for requested intra4x4 mode -1 at 0 15
[h264 @ 0x4757d80] error while decoding MB 0 15, bytestream (53878)
[h264 @ 0x4757d80] concealing 994 DC, 994 AC, 994 MV errors in I frame
[h264 @ 0x48e7480] concealing 430 DC, 430 AC, 430 MV errors in P frame
[mpegts @ 0x246c620] PES packet size mismatch
frame=29805 fps= 25 q=28.0 size= 152139kB time=00:19:52.08 bitrate=1045.5kbits/s dup=39 drop=0
[h264 @ 0x4757d80] concealing 946 DC, 946 AC, 946 MV errors in P frame
frame=29833 fps= 25 q=28.0 size= 152315kB time=00:19:53.08 bitrate=1045.8kbits/s dup=39 drop=0

Sometimes there are absolutely NO problems for 10 minutes. But it's not related to weather, rain, other electrical cables, we tried all that. It happens constantly, every hour, on different cards, tried different satellite dishes and tried different locations.
A regular DVB-S2 set top box has NO visual artefacts on the same coaxial cable connection.
I suspect bits get corrupted in the card or the drivers.

Please advice on how to troubleshoot this issue.

[cody]

please, provide us with full transponder parameters of the locked signal. also, Linux driver version installed. currently, my best guess is that it's related to transponder data-rate, because latest Linux drivers for 6991 have rate-limit activated by default, which can be disabled. thank you

[jeroen]

please, provide us with full transponder parameters of the locked signal. also, Linux driver version installed. currently, my best guess is that it's related to transponder data-rate, because latest Linux drivers for 6991 have rate-limit activated by default, which can be disabled. thank you

Astra 1 19.2E
12721.75Mhz
Pol:H
DVB-S2
8PSK
Symbol rate: 22000
FEC: 3/4
CANALDIGITAAL, 49.0 Mbps

Driver version: v130127
I have not had the time to test the latest drivers.
How can I deactivate rate limit ?

Thank you for the support!

[cody]

current rate-limit is 65 Mbps. so, it can't be that. next idea i have is:

create text configuration file "/etc/modprobe.d/tbs.conf" with line inside:

options saa716x_tbs-dvb ci_spd=1

then you need to reboot to activate it.

that will reduce the CI access speed in case your CAM doesn't like the higher speed.

[jeroen]

current rate-limit is 65 Mbps. so, it can't be that. next idea i have is:

create text configuration file "/etc/modprobe.d/tbs.conf" with line inside:

options saa716x_tbs-dvb ci_spd=1

then you need to reboot to activate it.

that will reduce the CI access speed in case your CAM doesn't like the higher speed.

Unfortunately it makes no difference.
I had some IRQ problems getting this board to work in de server (A HP Proliant DL360p Gen8 1U server)
Initially the card was not detected, until we enabled PCI-e legacy mode. The server has a SandyBridge chipset
I see there is also an int_type parameter. Perhaps I can try playing with that one ?

[jeroen]

I have tried different interrupt settings, no improvement.

I also tried
options dvb-core dvb_demux_speedcheck=1

syslog shows me

[ 6298.841141] TS speed 61867 Kbits/sec
[ 6299.427149] TS speed 61867 Kbits/sec
[ 6300.021251] TS speed 62287 Kbits/sec
[ 6300.607240] TS speed 62287 Kbits/sec
[ 6301.209517] TS speed 61659 Kbits/sec
[ 6301.795535] TS speed 61659 Kbits/sec
[ 6302.397781] TS speed 61659 Kbits/sec
[ 6302.983875] TS speed 61867 Kbits/sec
[ 6303.577831] TS speed 62287 Kbits/sec
[ 6304.163960] TS speed 62076 Kbits/sec

values are quite close to 65Mbit, how can I disable this rate limit ?

[cody]

I have tried different interrupt settings, no improvement.

I also tried
options dvb-core dvb_demux_speedcheck=1

syslog shows me

[ 6298.841141] TS speed 61867 Kbits/sec
[ 6299.427149] TS speed 61867 Kbits/sec
[ 6300.021251] TS speed 62287 Kbits/sec
[ 6300.607240] TS speed 62287 Kbits/sec
[ 6301.209517] TS speed 61659 Kbits/sec
[ 6301.795535] TS speed 61659 Kbits/sec
[ 6302.397781] TS speed 61659 Kbits/sec
[ 6302.983875] TS speed 61867 Kbits/sec
[ 6303.577831] TS speed 62287 Kbits/sec
[ 6304.163960] TS speed 62076 Kbits/sec

values are quite close to 65Mbit, how can I disable this rate limit ?

8PSK, 22000kSps, 3/4 is about 49 Mbps and your assumption what the above shows is completely wrong - the above doesn't show the steam is 62Mbps, but the active rate-limit. you can convince yourself in that in one very easy way - even if you unplug the cable from LNB input and run 'dvbtraffic' you should get the same output, i.e. showing you the rate-limit in place.

so, considering what you have already tried and that you're testing signal with just 49 Mbps rate, i believe your CAM is causing the data corruption. that's why my suggestions is to unplug the CAM and test if there is data corruption in such case - after all it's not necessary to decrypt the date in order to tell if TS data are corrupted or no.

[jeroen]

Can you give me a pointer on how to analyze a TS stream without decrypting it ?
I can record encrypted ts packets with szap-s2 -r and then dd from /dev/dvb/adapter0 but how to figure out they are corrupted?

[jeroen]

Okay update.
I managed to get a working configuration using sasc-ng and a smartcard reader. I can watch encrypted channels without the CAM.
The corruption is still there.

using scan-s2 I see ber almost always zero and when it goes higher (values around 100) , the unc (uncorrected blocks) is still 0. That means there shouldn't be any transmission errors, correct?

I am still using mumudvb (this time on adapter 2 = virtual adapter via dvbloopback from sasc-ng).

Other ideas ?

[cody]

what you've done with sasc-ng doesn't answer anything, because it could be your smart-card reader is not set properly, i.e. it causes delay/lag in the keys, which leads immediately to picture (and sound) corruption. also, that doesn't rule out problem with what displays that video/audio data like codecs. the easiest way to analyze the pure TS data without decrypting them is to use DVBlast - it's debug output, which is active by default, shows messages in case there is TS data corruption. so, you can just set streaming with DVBlast and monitor the debug messages (if any, because if everything is fine, there will be none). i still believe there is communication problem between your CAM and CI interface on TBS card, which is the most common source of TS corruption, because FTA channels are fine for you. so, another good idea is to try different TBS card (if you have such available) or different CAM.