Tvheadend

Do you have some data errors for the DVR entries or continuity errors in the logs?

Yes, but varying - from 0 errors to 20, one of the "odd" recording had none, the other one only two. THe USB tuners also report roughly the same continuity errors without the effects mentioned above, these are strictly limited to the Fritz!Box DVB-C streams.

However, I do get some odd messages in the logfile:

rep "Tuner" tvheadend.log | grep -i input
Jan 15 11:23:16 zuul tvheadend¹⁴²⁶⁸: satip: SAT>IP DVB-C Tuner #2 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 15 11:33:22 zuul tvheadend¹⁴²⁶⁸: satip: SAT>IP DVB-C Tuner #2 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 15 11:43:39 zuul tvheadend¹⁴²⁶⁸: satip: SAT>IP DVB-C Tuner #2 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 15 11:54:15 zuul tvheadend¹⁴²⁶⁸: satip: SAT>IP DVB-C Tuner #2 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 15 12:04:20 zuul tvheadend¹⁴²⁶⁸: satip: SAT>IP DVB-C Tuner #2 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 15 12:14:56 zuul tvheadend¹⁴²⁶⁸: satip: SAT>IP DVB-C Tuner #2 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 15 22:09:00 zuul tvheadend⁶³⁴⁹: satip: SAT>IP DVB-C Tuner #1 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 15 22:14:00 zuul tvheadend⁶³⁴⁹: satip: SAT>IP DVB-C Tuner #2 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 16 05:39:02 zuul tvheadend⁶³⁴⁹: satip: SAT>IP DVB-C Tuner #1 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]

and

Jan 15 22:09:00 zuul tvheadend⁶³⁴⁹: satip: SAT>IP DVB-C Tuner #1 (192.168.178.1) - RTSP error -5 (Input/output error) [9874-200]
Jan 15 22:09:02 zuul tvheadend⁶³⁴⁹: subscription: 00C3: service instance is bad, reason: Tuning failed

Does the 6490 have firmware 7.01? Did you assign different ip adresses for each tuner? I also use 6490 and have no problems with recording on a E2 Box (TVH running on Pi2)

Oh, and you should change the payload to 32712

@Stephan Gradl Mees: Nope, 06.87 (this is a Vodafone/KD Box). About the different addresses: I tried it out (DVB-4, using a different address). If worked at first.. however, when I tested the setup by recording 4 different channels (on 4 diffeent muxes), suddenly all 4 tuners where having serious data errors, so I switched it back to the default setup - 2 tunes, one IP.

Where do you set up this payload? Haven't found a setting in the DVB-C-tuners..

The issue with 4 Tuners at the same time having issues is known by AVM and has been fixed in 7.0 (I was the one who was constantly bothering them for one year straight until they finally fixed it), it is due to the completely weird way the cableinfo daemon which sends the data behaves. You can not watch more than 2 HD channels at the same time (or more specific, if you exceed 25Mbit/s you will experience packet loss). In 7.0 this issue has been completely resolved and 4HD Channels work perfectly fine.

Oh I forgot: You can not have multiple tuners on one IP, that will not work with the box. Use 2 tuners on 2 IPs, that should work.

You find payload under
General/Sat>IP Server/RTP over TCP Payload
With the default value 7896 i also had several stream abortions.

Oh I forgot: You can not have multiple tuners on one IP, that will not work with the box. Use 2 tuners on 2 IPs, that should work.

Not exactly. This is true if you manually select "DVB-C 4", but if you revert/leave it the way it was ("Auto"), both tuners work fine using one IP (apart from the problems I mentioned, but these also occured in DVB-4 mode)

The "problems" involve that the second stream drops and only one of them is sending data, this is not what I would call "2 streams working". If the channels are on the same frequency it will work, but that is not a second stream so that doesn't really count.