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Old 02-23-2015, 12:27 AM   #1
CinciDVR
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Issue with TA - Bug or Feature?

Some background: I have TWC in Cincinnati. I have a basic Roamio. The Roamio has a cable card and is connected to a tuning adapter via USB. My cable signal runs into a splitter. The splitter provides a signal to the Roamio and the TA.

About a week ago, the Roamio was recording two programs on channels that do not require the TA. I tuned to the Big Ten channel, which requires the TA, on the third tuner. I was met with a "Channel not available" error. So I unplugged the power cord from the TA, counted to five, and plugged it back in. This caused a "No tuning adapter" standard def screen to appear, and the Roamio stopped recording on the two channels that don't require the TA.

So I clicked "OK" on the TA error screen and quickly switched to the first and second tuners, which had been recording, and pressed the record button to get them recording again. At the same time the green light on the TA was blinking indicating that it was rebooting. About two minutes later, the green light went solid on the TA and a standard def screen appeared say "Tuning adapter connected." At this time, the Roamio again stopped recording on the two channels that don't require the TA. WTF!

The result of all this was that I had 20 minutes of recordings before I power-cycled the Roamio. 2 minutes of recordings while the TA rebooted. And 37 minutes of recordings after the TA completed its reboot.

So why on earth would Tivo write code that quits recording channels simply because communication to the TA is lost? Surely the Tivo can tell if a video signal is still present on tuners that are recording channels that don't require the TA. The two minutes of program that was recorded while the TA rebooted, and the Roamio could not communicate with it, proves that there was signal on those channels. And more importantly, why would Tivo write code that stops recording on channels simply because communication to the TA is restored.

I can think of no reason why the Tivo should quit recording on channels that do not require the TA, so I consider this a bug. What do you think? Should I report it to Tivo as a bug?

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Old 02-23-2015, 01:37 AM   #2
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When you're using the TA, channel mappings come from the TA, for all channels. When the TA goes away, those mappings are no longer valid (even if the non TA mappings happen to be the same).

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Old 02-23-2015, 11:16 AM   #3
L David Matheny
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Originally Posted by CinciDVR View Post
So why on earth would Tivo write code that quits recording channels simply because communication to the TA is lost? Surely the Tivo can tell if a video signal is still present on tuners that are recording channels that don't require the TA. The two minutes of program that was recorded while the TA rebooted, and the Roamio could not communicate with it, proves that there was signal on those channels. And more importantly, why would Tivo write code that stops recording on channels simply because communication to the TA is restored.

I can think of no reason why the Tivo should quit recording on channels that do not require the TA, so I consider this a bug. What do you think? Should I report it to Tivo as a bug?
I agree with you. Report the problem to TiVo. If they don't agree, they may not fix it, but it certainly sounds like sloppy programming at best. Video signals don't go through the TA; it just tells the TiVo what frequency the SDV channel is on so it can set up the tuner. Once that's done, the TA shouldn't be needed again until it's time to tune another SDV channel.

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Old 02-23-2015, 04:39 PM   #4
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Pppingme gave the correct answer above. When you just have the CableCard and no tuning adapter connected, the CableCard handles all the channel mapping. As soon as you plug in the USB cable to the tuning adapter, it takes over all channel mapping (even for the non-SDV channels). And when you unplug the tuning adapter, the CableCard takes over the channel mapping function again.

I seriously doubt there is anything that TiVo could do to allow uninterrupted recording when switching between channel maps like this even if they wanted to. This is neither a bug nor a feature, it is just a limitation of CableCard/Tuning Adapter technology.


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Old 02-23-2015, 04:41 PM   #5
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Originally Posted by pppingme View Post
When you're using the TA, channel mappings come from the TA, for all channels. When the TA goes away, those mappings are no longer valid (even if the non TA mappings happen to be the same).
^^^^This is the correct answer.

When the TA is connected, the channel mapping is provided by the TA, for all channels.

When the TA is disconnected, the channel mapping switches to the CableCARD only. This causes the tuners to do a soft reboot, and download the new mapping frequencies.

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Old 02-23-2015, 05:05 PM   #6
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^^^^This is the correct answer.

When the TA is connected, the channel mapping is provided by the TA, for all channels.

When the TA is disconnected, the channel mapping switches to the CableCARD only. This causes the tuners to do a soft reboot, and download the new mapping frequencies.
That makes no sense. It should at least be able to keep recording what it is already recording blindly from the channels that it was recording from.

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Old 02-23-2015, 05:15 PM   #7
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That makes no sense. It should at least be able to keep recording what it is already recording blindly from the channels that it was recording from.
That's like saying that if I am recording a clear-QAM channel that doesn't require decryption, I should be able to just pull out the CableCard and the TiVo should be able to keep recording that channel. After all, the frequency that the channel is on didn't change when I pulled out the CableCard. But when you pull a CableCard out, the channel map from the CableCard disappears. And from the TiVo's perspective, essentially the same thing happens with the CableCard's channel map when you plug in the tuning adapter.

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Old 02-23-2015, 05:32 PM   #8
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That makes no sense. It should at least be able to keep recording what it is already recording blindly from the channels that it was recording from.
You are with Comcast and do not have a TA, Do you have any experience with using a TA? Pulling the TA USB does exactly the same thing as pulling the CableCARD temporarily, it does a soft reboot of the tuners and re-downloads the mapping info.

That is the way they work, period.

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Old 02-23-2015, 07:58 PM   #9
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Originally Posted by tarheelblue32 View Post
That's like saying that if I am recording a clear-QAM channel that doesn't require decryption, I should be able to just pull out the CableCard and the TiVo should be able to keep recording that channel. After all, the frequency that the channel is on didn't change when I pulled out the CableCard. But when you pull a CableCard out, the channel map from the CableCard disappears. And from the TiVo's perspective, essentially the same thing happens with the CableCard's channel map when you plug in the tuning adapter.
Your analogy seems correct to me, but I still don't understand why the Tivo doesn't just keep recording from the channels it last knew. Look at it this way:
  • Surely the loss of the TA (or Cable Card in your analogy) was unexpected since a recording was already underway
  • The Tivo can respond in one of two ways:
    • Keep recording from the channels it last knew in which case it might capture the program it was originally instructed to record
    • Quit recording in which case its guaranteed not to capture the program it was originally instructed to record
  • After losing communication with the TA and establishing communication with the Cable Card, the Tivo will learn one of two things:
    • The Cable Card says the channel it was recording is located on the same frequency as the TA reported, in which case it should keep recording the frequency from which it originally started to record
    • The Cable Card says the channel it was recording is located on a different frequency than the TA originally reported, in which case it should instruct the tuner being used for the recording to move to a different frequency

In no case is there any reason for the Tivo to simply give up on the recording. Depending on which scenario plays out above, the program being recorded might have a few seconds of glitch when communication with the TA was lost (caused either by the soft reset of the tuners or change of tuner frequency), but that would be much preferable to simply losing the remainder of the program being recorded. I understand that the TA and CC are low-level functions that are integral to the mappings of channels, but with just a little bit of high-level coding it seems to me that the Tivo could more deftly deal with unexpected communication issues while a recording is already underway.

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Old 02-24-2015, 06:51 PM   #10
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That's like saying that if I am recording a clear-QAM channel that doesn't require decryption, I should be able to just pull out the CableCard and the TiVo should be able to keep recording that channel. After all, the frequency that the channel is on didn't change when I pulled out the CableCard. But when you pull a CableCard out, the channel map from the CableCard disappears. And from the TiVo's perspective, essentially the same thing happens with the CableCard's channel map when you plug in the tuning adapter.
Yeah, that should be able to work too. TiVos not working with ClearQAM in the first place is pretty pathetic, although many systems don't have ClearQAM anymore, so the ship sort of sailed on that one anyway.

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You are with Comcast and do not have a TA, Do you have any experience with using a TA?
No, I don't. Luckily, Comcast hasn't (yet) resorted to the SDV kludge. I fear it's inevitable, as there's no way 200 HD's, a suite of UHD channels, and gigabit internet are going to fit on an 860mhz system without SDV, even with H.264 for the HDs and H.265 for the UHDs. They could do what TWC does (200 HDs, 300mbps) without the SDV kludge, but they would be absolutely maxed out on an 860mhz system. Hopefully, if/when they do, they implement SDV with TiVo over IP, like they do with VOD, and thus don't require TAs for TiVo.

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Old 03-02-2015, 02:54 AM   #11
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No, I don't. Luckily, Comcast hasn't (yet) resorted to the SDV kludge.
Since comcast already uses an IP backchannel to communicate with the TiVo, there's no need for an external TA. OnDemand is roughly equal to SDV in the aspect that Comcast is going to send you a signal on a random channel, and that channel is negotiated between the TiVo and comcast at the time of need.

I do suspect that comcast is doing SDV in some markets, at least on an experimental basis, and I can explain my proof later if anyone is interested, I don't know if that extends to TiVo, maybe Margret or someone could give some info on that.

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Old 03-02-2015, 05:20 PM   #12
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Since comcast already uses an IP backchannel to communicate with the TiVo, there's no need for an external TA. OnDemand is roughly equal to SDV in the aspect that Comcast is going to send you a signal on a random channel, and that channel is negotiated between the TiVo and comcast at the time of need.

I do suspect that comcast is doing SDV in some markets, at least on an experimental basis, and I can explain my proof later if anyone is interested, I don't know if that extends to TiVo, maybe Margret or someone could give some info on that.
Correct. TiVo would have to update the TiVo software to pull it off, but that's a good point. Hopefully if/when the day comes, they do it that way.

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