timeshifting broken in 4.x

[bpitzel]

Hello -- anyone else think the new timeshifting behaviour in 4.x is broken? I can't reliably pause a show and expect to still watch it all, like I could with 3.7 and Tivo.

Here's what happens to me:

Case 1: Hit pause watching live TV, go make dinner or something. At some point when your buffer limit is hit, TV will start playing but it will first jump ahead XX minutes (timeslice size????), so you miss part of the show.

Case 2: Hit pause watching live TV. Pause for a while, then unpause and continue watching. Occasionally (I think when a new show starts in "realtime"), the delayed broadcast I'm watching will suddenly jump ahead. Again I've missed part of the show. It happens without warning, without touching the remote or keyboard. The buffer show on screen is empty so I can't rewind back.

Case 3: Every time I change channels, a new mpg file is created in my recordings dir. Eventually these expire but why are they there? I can't rewind or otherwise watch them through the BTV UI. Also, often when changing channels (and randomly during ff/rw) BTV will lock for 7-10 secs -- I never had this with 3.7 so I'm thinking the new timeslice code is suspect. The ff/rw hangs never happen with recorded content, only live TV.

Anyone else with me? My wife is starting to hate BTV because we often lose shows due to BTV's timeshifting weirdness. She's sticking to the Tivo for now since it's timeshifting is predictable.

--BP

[Mr.X]

Definitely sounds like a problem - have you submitted a support ticket yet?
A workaround for now would be to record shows you're watching, then just delete them when you're finished. That way you are sure to not lose them and you won't have any problems with pausing indefinitely.
Once you start watching a show, just press the REC button on the remote to make it into a recording.

[bpitzel]

Thanks -- I understand your suggestion to record every show -- and will see if it positively affects the ff/rw hang problem -- but I'm still wondering, is everyone seeing this or just me?

I've had a Tivo running for 5+ years and have become accustomed to pausing until the Tivo 30 min limit is reached. Tivo just starts playing, while BTV jumps ahead losing part of the show. I want BTV to be as good or better than TIVO in all the basic usage cases, but it isn't. And my complaints aren't about picture quality -- it took a lot of work but my BTV pq is very good. Usability is main complaint.

-- from someone who has "been there".

[StephaneM]

Originally Posted by bpitzel

Case 1: Hit pause watching live TV, go make dinner or something. At some point when your buffer limit is hit, TV will start playing but it will first jump ahead XX minutes (timeslice size????), so you miss part of the show.

This is indeed due to the new timeshift design. You'll have to tweak it a little for it to be effective.

First it depends if you want to use the "backcapture" feature or if you want to be able to pause for a long time.

Let says your are using a 6Mb/s MPEG2 quality, you'll approx. have 3GB video files for an hour of recorded content.

The way backcapture works is: the moment you press on "record", the timeshift engine will save the current slice for the current show, if the slice was not big enough to contain the very begining of the show, you'll lost it. So if you really count on backcapturing, you need to think it this way:

How many minutes is necessary for me when watching a show from the beginning to actually decide it is worth recording the whole show (there may be other usage but..). I would say that the average time is 30 min to be safe. So make you slice size : 1.5 GB

Now, the next question is: how many minutes do I need to left BTV on pause to do my things (preparing dinner etc...), I would say again that on average, you'll need 2 to 3 hours to be safe.

So the calculation is : 2.5 hours is 7.5 GB, I need 5 slices to handle it.

There is a caveat with slicing is that when you are watching 5 min shows in a series, your buffer will never reach 2.5 hours, but instead will reach 5 * 5 min: the max number of slices x the average time of the 5 previous shows.

So it depends on how often the channels you watch airs shows with a short duration in a row.

Personally my settings are : 2048 MB slice size and 6 slice count. That is to say my theorical buffer duration is 6 shows or 4 hours.

Case 2: Hit pause watching live TV. Pause for a while, then unpause and continue watching. Occasionally (I think when a new show starts in "realtime"), the delayed broadcast I'm watching will suddenly jump ahead. Again I've missed part of the show. It happens without warning, without touching the remote or keyboard. The buffer show on screen is empty so I can't rewind back.

This time, I think you are in the case where you have exceeded slice count. Unfortunately, if you are currently watching slice 5 (the oldest) and BTV needs another slice (max 5), it will need to delete the oldest, and as such will kick you out of it, and put you to slice 1 (if I remember correctly).

Case 3: Every time I change channels, a new mpg file is created in my recordings dir. Eventually these expire but why are they there?

These mpgs are the slice.

Regards,
Stéphane.

[bpitzel]

Thanks --- technically it makes sense, but it doesn't make sense from a user experience perspective.

Why would it be designed this way? I don't want Snapstream's under-the-cover architecture answer, I'd love to see Snapstream's "it's an improved customer experience because of..." answer, or "yes this is a bug and we'll fix it" answer. Timeshifting is a core feature of the PVR experience, so it should work flawlessly for the user.

I miss the old 3.x circular buffer, because I didn't have to think about it. If I paused too long, BTV would start playing but I wouldn't lose part of the show. This seems to be standard behaviour for PVRs except BTV 4.x

--BP

[StephaneM]

Originally Posted by bpitzel

Why would it be designed this way?

Because SnapStream choosed this implementation.

I don't want Snapstream's under-the-cover architecture answer

I don't work for SnapStream, this is my answer in order to help you. If you actually think about my advice, you should achieve the effect you are searching. It's up to you to welcome my suggestion or not.

I'd love to see Snapstream's "it's an improved customer experience because of..." answer, or "yes this is a bug and we'll fix it" answer.

This is a user forum, don't come here in the hope to complain and wait for an official answer from SnapStream. For this you'll have to contact technical support.

Timeshifting is a core feature of the PVR experience, so it should work flawlessly for the user.

It works flawlessly, given it's current design. There is some limitations, I explained those limitations (as well as I exposed them, like other users to SnapStream).

This seems to be standard behaviour for PVRs except BTV 4.x

As far as I know, other PVR softwares are all using (with one exception), the implementation of Microsoft, that is are using the Stream Buffer Engine (found in MCE, that comes with DVR-MS mandatory file format). On the other hand SnapStream made his own engine, this is a proof of their good work and no doubt it will improve with time (this is also why the SnapStream engine works with many non hardware encoding tuners or software encoding tuners that don't come with an MCE MPEG2 encoding software).

Now you are free to revert to BTV 3.x or use the other PVR softwares.

Regards,
Stéphane.

[bpitzel]

Hey relax -- my complaint is to Snapstream, not you. I read a separate post from Snapstream explaining the tech behind the new timeslice setup (after another user complained), how it's important from an architectural perspective, but no explanation for why the customer experience was changed as well.

They took a feature that worked fine in 3.x and in my opinion, broke the user experience in 4.x. Others may disagree, and if so I've love to hear why.

Yes, this has been reported separately to snapstream, but I'm curious to see if others agree the experience was degraded from 3.x to 4.x.

It's required quite a bit of time -- more than I thought when I dove into this -- to get a decent htpc setup. Over the course of many months I've worked through countless picture quality issues (it's now top notch), took care of heat/stability problems, remote control probs, etc. With those out of the way BTV functionality is still preventing this setup from replacing my TIVO.

-BP

[StephaneM]

Originally Posted by bpitzel

Others may disagree, and if so I've love to hear why.

I neither agree or disagree, because I tweaked the settings so as the behavior is the same as with the previous buffer engine. And it offer you the ability to "backcapture" the show you are viewing : that is saving what you already watched from the begining of the show, this was not possible with the previous buffer engine.

So if you take the time to follow my suggestion, you'll still have the ability to pause a show for a long time as you were used to.

There is still some inconveniences, but they will surely be adressed in the future.

I don't see why this behavior can prevent you from using BTV as a Tivo replacement: you have the ability to tweak the settings to achieve the same results, with the added benefit if you really wannabe assured not to miss your show to press "record", then "pause" before preparing dinner... I guess it's a matter of viewing experience. I used to watch Live TV when I first used BTV, then I quickly switched to record the most important shows and reserving Live TV for casual viewing.

In fact our TV experience is better now in our house because we "plan" what we are watching a week before and enjoy viewing when it's time to: that is after preparing dinner, eating (without TV on) and drinking a little italian expresso...

Regards,
Stéphane.

Note: I'm relax, i'm just explaining to you that I don't work for SS and that these forums are a place for helping each other not a place to complain and wait for SS to respond.

[bpitzel]

Thanks for your feedback and info!

The fact you can adjust the buffer size is a big plus over Tivo -- but my wife has had BTV drop the slice she was watching enough times she stays away from it and sticks to the Tivo (circular buffer with backcapture ability). Having BTV picture quality and sound quality (SPDIF) much better than Tivo won't budge her.

On the plus side, that means the BTV drive, 3x the Tivo drive, gets filled with my shows only

All said, it seems snapstream could add a rule to never delete a timeslice file if it's being watched (or paused on). I've got plenty of free space on the drives, so BTV wasn't deleting my "currently being watched" slice as a last ditch effort.

Next, I need to figure out why I get frequent 7-10 sec hangs during live tv ff/rw and channel changing (new to 4.x). And why does putting 2 video folders on 2 drives cause BTV 4.x to not notice the main drive is full, therefore populating it with 0mb attempted recordings (3.7, 4.x)? There's also how exclusive fullscreen video sometimes pops into windowed mode in the middle of watching a show. Or why every 2nd or 3rd remote control button press is lost with BTV (but not with Tivo using same harmony 659 remote). I won't push those issues here further until I've spent more time eliminating suspect causes.

-BP

[StephaneM]

Originally Posted by bpitzel

I need to figure out why I get frequent 7-10 sec hangs during live tv ff/rw and channel changing (new to 4.x).

I never use FF/RW (only skip forward / backward), but you can try to adjust the "Reaction Delay Compensation" this may be the cause of the 7 seconds pause (as by default this delay is seven seconds).

Though it has nothing to do with channel changing, for this one you can try other MPEG2 decoders or you may be short on available RAM (I noticed on my work PC that when there is low memory condition, your PC will be mostly fine except when dealing with large files, I guess this is one of the weakness of Windows, mainly because of the way the page file is handled).

And why does putting 2 video folders on 2 drives cause BTV 4.x to not notice the main drive is full, therefore populating it with 0mb attempted recordings (3.7, 4.x)?

I don't use BTV disk managment mainly because I don't trust anything that could delete things automatically and never encountered a low space condition on my drive, but it seems that BTV will attempt to record even when there is no space left on your drive.

If you want something that will automatically put your recordings on your second drive, you can always use my Web Guide (if you are running either Windows XP Pro or Media Center) : each time a recording is about to begin, it will check if there is enough space on the target drive, and if not will make the recording happen on the next drive with maximum space on it (you just have to enable the feature -some configuration are needed prior to this for the Web Guide to query for available disk space - and set the low space condition and select the drives you do not want any recordings be done).

There's also how exclusive fullscreen video sometimes pops into windowed mode in the middle of watching a show.

This is not surpizing me, BTV by default does not run in this mode just to avoid this. Whe you have a DirectX application in Exclusive Fullscreen mode and another application take the focus (or something like this), the DX application is forced to exit Exclusive FS, there is no way for BTV to prevent this. So either you don't run BTV in Exclusive FS, or find the cluprit that make it go out for FS.

Or why every 2nd or 3rd remote control button press is lost with BTV (but not with Tivo using same harmony 659 remote).

You cannot compare using the Harmony with BTV and Tivo : the Harmony emulate the Tivo remote when using Tivo, and emulate your PC remote when using BTV. So this is not because the Harmony works with the Tivo that it has to work with BTV.

It is the original remote control software you'll have to investigate. The majority of remote control software is issuing keystrokes to the active Window. With what you said about Exclusive FS, it is obvious that something is sometimes stealing the focus, and as a consequence the remote keypress will be passed to that theft instead of BTV (just a theory). Depending on your remote software, you can tweak it a little (it's easy with an Hauppauge remote), for instance : put the remote in "BTV exclusive mode", and when in this mode it will force the remote software to find and activate the BTV window before sending the keystroke, when quitting BTV, put the remote in "General" mode (so as it can work for other application).

It is also possible that BTV is busy when you are sending the keystroke and does not respond to the command. But generally there is a buffer so it will still carry on the command; for instance when you are navigating in the guide, BTV will suddenly stop moving, but will resume one seconde after it pause.

Regards,
Stéphane.

[gmanning]

Originally Posted by StephaneM

This is indeed due to the new timeshift design. You'll have to tweak it a little for it to be effective.

Personally my settings are : 2048 MB slice size and 6 slice count. That is to say my theorical buffer duration is 6 shows or 4 hours.

This time, I think you are in the case where you have exceeded slice count. Unfortunately, if you are currently watching slice 5 (the oldest) and BTV needs another slice (max 5), it will need to delete the oldest, and as such will kick you out of it, and put you to slice 1 (if I remember correctly).

I am wondering if I am not having a similar problem. I am running 4.2 trial and noticed that LiveTV will pause or hang while tuned to a digital HD channel for some time (don't know how long, was away from the TV at the time). It also happened during playback of an HD recording at 49 minutes, but I don't know if the two are related. I have not noticed this happening on an analog SD channel.

Does this sound like it could be something happening with the timeslices? Perhaps the higher data rate of the HD channels requires some changes to the buffer settings? If so, should I just set them about 3x the values mentioned above?

I too am trying to retire my aging Series 1 Tivo.

Gary