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A TV is for life, not just xmas!
We’ve recently been having lots of problems reported with the TBS6981 device (something I used up until very recently when TBS very kindly sent me a 6985 to allow me to do more development while keeping my TV viewing uninterrupted). Anyway there has been a lot of speculation about what exactly is the fault and where the blame lies.
Both camps (Tvheadend and TBS) have clearly got very different opinions on the matter. TBS stand by the position that since Tvheadend is the only application that appears to be affected it must be at fault. Not an entirely ridiculous statement. However the reasons for the failure are, to put it mildly, ludicrous.
The current position is that Tvheadend is sending too many requests to the driver and overloading it causing it to fail. I should at this point state that we only request the status every 1 second once locked, and during the lock period once every 50ms. This is admittedly quicker than previously (as we changed the architecture) but hardly something I would expect to strain a device of this nature. And the reason why this seems to only affect the TBS6981 (we’ve had no reports of other devices suffering such problems, including several other TBS devices), because it includes a “professional grade feature” that most other OSS drivers do not include. So the addition of such a high performance feature is the reason a simple application like Tvheadend is able to overload the device, really!
However Tvheadend have a very different view. This failure was seen previously (when we were not querying so fast) albeit it with a much lower frequency. In addition we also saw other similar failures, where for example the tuner would lock but would take an unexpected period (for no obvious reason). Unfortunately due to time constraints I was never able to get to the bottom of this problem before retiring my 6981 (I see no such problems with my 6985).
Recently a Tvheadend user also got so fed up with his tuner not working that he decided to embark on writing his own version to see if he could understand what was causing the failure and what might be done to remedy the situation. This driver has proved very successful and I would urge any 6981 users to try it, .
We now believe that we understand why the TBS driver fails so miserably. We have even managed to create a simple test application that appears to demonstrate the failure, with a simple “workaround” (hack really) to make the TBS driver appear to work (we’re pretty sure why this works). Luis’ driver has no such problems and always works, and with typical zap times that are slightly quicker than the official driver.
However TBS are sticking to there guns and are continuing to place blame on Tvheadend. To this end their driver maintainer, Konstantin Dimitrov, has created a “fixed” version of the driver that appears to work with Tvheadend 3.4. It should be noted that this version of the driver has the “professional grade” feature, as well as a whole host of other features (of varying degrees of importance) removed.
In some respects this driver does appear to “fix” the problem, indeed Tvheadend 3.4 appears to perform much more like 3.2 with this driver. However the test application we developed throws up a few more interesting results. It does appear to eventually lock, where the official driver would fail, however only at the expense of a 1-3s delay in zap time. Hardly what I’d call fixed. And although in the limited testing we’ve done so far we’ve not managed to cause this version to entirely lock up, we wouldn’t rule it out as a possibility. Though we have a suspicion as to what might have been done to stop this from happening (and also explain the delay in lock time on the second tuner).
Anyway for the sake of openness, and to keep all Tvheadend users informed, I have copied the current email thread (and will try and keep things updated).
Adam
(on behalf of the Tvheadend team)
UPDATE:
We’ve now had a couple of responses from Konstantin. One seemed slightly more positive in that he admitted not having read my test code and acknowledging he should do this. Then another saying he’d missed something he’d added to the 6984 driver, but basically still placing the blame on Tvheadend.
To be honest I’ve gotten a bit bored with this whole thing, so I’m going to send a very frank and to the point response. Including possibly a reference to a recent Linus quote (just for fun).
UPDATE:
OK, it’s now been over 2 weeks since we explicitly stated our understanding of the problems in the TBS drivers. We’ve had ZERO response from anyone inside TBS. We know that they’re now fully aware of the work Luis’ has done as its got further through the review process for acceptance into the kernel. And Konstantin has at least commented on a peripheral topic related to the submission.
I guess we can only hope that Konstantin and TBS are busy beavering away looking at Luis’ driver and discovering how to write a driver properly when it uses multiple threads accessing a shared resource!
For his part Luis’ has begun supporting other cards from TBS that use the same chipset. So far I believe this includes the TBS6980, TBS6981 and TBS6984.
—
Email Thread (I have temporarily removed Rob’s comments, this is simply because I didn’t ask his permission, and having now done so I will remove the comments until I’ve heard back from him)
TBS6981: Issue when using both frontends simultaneously in Tvheadend |
Rob Hunter | 10 June 2013 13:02 | |
To: euro_support@tbsdtv.com
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Adam Sutton | 10 June 2013 15:12 | |
To: Rob Hunter
Cc: euro_support@tbsdtv.com
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Konstantin Dimitrov | 11 June 2013 08:40 | |
To: Adam Sutton
Cc: Rob Hunter, support <support@tbsdtv.com>
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Adam Sutton | 11 June 2013 09:29 | |
To: Konstantin Dimitrov
Cc: Rob Hunter, support <support@tbsdtv.com>
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Konstantin Dimitrov | 11 June 2013 11:05 | |
To: Adam Sutton
Cc: Rob Hunter, support <support@tbsdtv.com>
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Adam Sutton | 11 June 2013 11:30 | |
To: Konstantin Dimitrov
Cc: Rob Hunter, support <support@tbsdtv.com>
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Rob Hunter | 16 June 2013 15:21 | |
To: Adam Sutton
Cc: Konstantin Dimitrov, support <support@tbsdtv.com>
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Konstantin Dimitrov | 21 June 2013 19:10 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov | 21 June 2013 19:44 | |
To: Adam Sutton
Cc: Rob Hunter, support <support@tbsdtv.com>
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Adam Sutton | 21 June 2013 20:08 | |
To: Konstantin Dimitrov
Cc: Rob Hunter, support <support@tbsdtv.com>
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Rob Hunter | 21 June 2013 21:07 | |
To: Adam Sutton
Cc: Konstantin Dimitrov, support <support@tbsdtv.com>
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Rob Hunter | 21 June 2013 23:04 | |
To: Adam Sutton
Cc: Konstantin Dimitrov, support <support@tbsdtv.com>
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Adam Sutton | 22 June 2013 09:12 | |
To: Rob Hunter
Cc: Konstantin Dimitrov, support <support@tbsdtv.com>
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Rob Hunter | 22 June 2013 17:33 | |
To: Adam Sutton
Cc: Konstantin Dimitrov, support <support@tbsdtv.com>
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Konstantin Dimitrov | 1 July 2013 16:26 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov | 1 July 2013 16:37 | |
To: Adam Sutton
Cc: Rob Hunter, support <support@tbsdtv.com>
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Rob Hunter | 1 July 2013 16:46 | |
To: Konstantin Dimitrov
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov | 1 July 2013 17:02 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Rob Hunter | 1 July 2013 17:08 | |
To: Konstantin Dimitrov
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov | 1 July 2013 17:24 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Rob Hunter | 2 July 2013 11:26 | |
To: Konstantin Dimitrov
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov | 10 July 2013 19:47 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Adam Sutton | 10 July 2013 20:16 | |
To: Konstantin Dimitrov
Cc: Rob Hunter, support <support@tbsdtv.com>, Luis Alves
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Konstantin Dimitrov | 10 July 2013 21:26 | |
To: Adam Sutton
Cc: Rob Hunter, support <support@tbsdtv.com>, Luis Alves
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Konstantin Dimitrov | 10 July 2013 21:52 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Rob Hunter | 10 July 2013 22:03 | |
To: Konstantin Dimitrov
Cc: Adam Sutton, support <support@tbsdtv.com>
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Rob Hunter | 10 July 2013 22:03 | |
To: Konstantin Dimitrov
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov | 10 July 2013 22:15 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Rob Hunter | 10 July 2013 22:56 | |
To: Konstantin Dimitrov
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov | 10 July 2013 23:36 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Rob Hunter | 11 July 2013 09:33 | |
To: Konstantin Dimitrov
Cc: Adam Sutton, support <support@tbsdtv.com>
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Adam Sutton | 11 July 2013 21:34 | |
To: Konstantin Dimitrov
Cc: James Liu@tbs, bob@tbs, support <support@tbsdtv.com>, Rob Hunter
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Konstantin Dimitrov | 11 July 2013 22:04 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov | 11 July 2013 23:09 | |
To: Adam Sutton
Cc: James Liu@tbs, bob@tbs, support <support@tbsdtv.com>, Rob Hunter
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Adam Sutton | 12 July 2013 10:44 | |
To: Konstantin Dimitrov
Cc: James Liu@TBS, bob@TBS, support <support@tbsdtv.com>, Rob Hunter, Luis Alves
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Konstantin Dimitrov | 15 July 2013 19:48 | |
To: Adam Sutton
Cc: James Liu, bob, support <support@tbsdtv.com>, Rob Hunter, Luis Alves
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Konstantin Dimitrov | 18 July 2013 19:06 | |
To: Rob Hunter
Cc: Adam Sutton, support <support@tbsdtv.com>
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Konstantin Dimitrov <cody@turbosight.com> | 18 July 2013 19:23 | |
To: Adam Sutton
Cc: James Liu, bob, support <support@tbsdtv.com>, Rob Hunter, Luis Alves
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Adam Sutton | 18 July 2013 21:25 | |
To: Konstantin Dimitrov
Cc: James Liu, bob , support <support@tbsdtv.com>, Rob Hunter , Luis Alves
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Rob Hunter | 18 July 2013 22:40 | |
To: Konstantin Dimitrov
Cc: Adam Sutton, support <support@tbsdtv.com>
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