Some Newbie "How does it work?" Questions And Problems (1 Viewer)

[Hoggle]

I am relatively new to MediaPortal, and this is my first post. I've tried MP a few times, but stability has been a serious issue. Now that the TV Server is integrated in to the release, which seems to do most of what I need, I decided to put more effort in to getting it to work:

What I am trying to do is quite complex, and is going to involve a total of eight TV tuners, spread across multiple TV Servers (two most likely). This will include three DVB-T cards/dongles, two DVB-S cards, and four analogue cards (two operating as tuners, two as capture devices). Every device will be dedicated, there will be no overlap between transponders, so all channels will always be available. The DVB-S cards are Technisat SkyStar2s, and the analogue cards will be Hauppauge PVR-150s.

At the present time I have MP set up on two systems. One TV Server, with a single SkyStar2, and one as a client. I am able to watch and record television on two channels on the same transport stream independently on each system.

What I am left wondering though is, how does it all work?

1..Without looking at it in too much detail, it appears the TV Server simply sends the required data to each client, while at the same time writing any recordings to disk. While this central storage is handy, it seem to be very expensive when it comes to IO and network usage. Is my understanding of this correct?

2..Is there any way to in the present version, or planned for MediaPortal II, to operate the TV Server in a multicast or broadcast configuration, and have client systems responsible for their own timeshifting and recording?

3..A server-side buffer would be handy to have, mixing all transport streams in to a large buffer that could be accessed later if required by specific clients (or if like me you'd like to cache all television for 24 hours), but in general live TV is only of interest when it occurs.

4..This leads on to another problem I've noticed. If I start a recording in one location, I can manage it from another. It would be handy if each client system could manage its own recordings of live TV from a remote tuner, and somehow flag them as public for access by other systems on the network. I assume this isn't presently possible?

5..A possible bug I have noticed is when a recording starts in the background, the current programme being viewed, the data in the timeshift buffer, and any already-occuring recordings, is momentarily interrupted. This is probably the biggest issue that is likely to stop me deploying MP throughout the house in the near future. Hopefully this can be fixed by something simple like changing the demuxer. Any suggestions on this issue are welcome.

6..Finally, again related to recording, it seems when I start recording, the recording starts from the live TV position, rather than the timeshift position. Is there any way to change this behaviour, so I start recording what I see, rather than what is live?

I went out and purchased a MCE remote this afternoon, and I am very impressed with the usability, even without any tweaking of the configuration. There is some unusual behaviour, but most things work as I would expect. Overall, MP is looking very good.

edit. numbered paragraphs.

 

[SciDoctor]

1...The way tv server works is the most efficient use of network bandwidth. Only required data is available in the buffer on the server to be pulled by single network clients.

2..No and not efficent, realy defeats a server configuration and centralised file/data. Also NEBULA used the method you describe with their software and it was inefficient, poorly managed,bug ridden and bandwidth hogging and as such simply wouldn't work with wifi as overheads were imense and caused havoc on every connected wired client throughout the whole network.

3..A server side buffer is in essence what tvserver uses but it strips the transport stream to specific channel+data, you can set the tvserver to buffer the whole single MUX (try a search) but this is impracticle as disk space usage is absolutly HUGE.

4..Each client is assigned its own buffer by the tvserver but buffers (of same requested channels) aren't shared at the moment, this is the only drawback and inefficiency.

5.. I don't experience this at all and is probably down to your hard drive subsystem, I have tested up to twelve concurrant recordings across six MUX and three buffered network clients.

6..This is by design and is a limitation as buffer and recording are seperate, a discussion has been requesting an EPG driven buffer which would alllow for this 'record now' function to include historical buffer data with respect to EPG data.
Maybe when feature freeze and RC status has concluded.

 

[Hoggle]

I have been attempting to resolve issue #5 without success.

So far I have tried:

Setting the TV Server to High priority, altering the drive write cache for performance over reliability, and splitting the timeshift and recording locations to two disks.

Still, within about 10 seconds of pressing the record button (often immediately), I always get a momentary pause.

I can reproduce this simply by starting a recording on the current channel, and waiting. If I rewind the live TV broadcast, I still see the pause.

I don't think disk performance is the issue. The system is a modern Core 2 Duo, with SATA drives, and I am regularly manipulating large files. I'm sure I would have noticed a performance issues. I can certainly record a full transport stream, so recording two concurrent buffers shouldn't be an issue.

I assume MediaPortal is only manipulating the transport stream, and not waiting on the TV card in any way, but I was wondering if signal quality could be responsible for my problem?

I currently have my dish connected via a flat coax cable through a window. Signal quality is reported as about 20%, even though there are no visible or audible errors in the stream. This is a test setup, so this afternoon I will try connecting directly to another dish, and will see if that makes any difference.

Thanks.

Technisat SkyStar2 (x2)
MediaPortal 1.0 RC2
Vista Ultimate x86_64
Western Digital WD2500JS (x2) / E6600 / ICH8

 

[SciDoctor]

Post some clean logs in debug mode .

We can see what tswriter is doing during this period of viewed pause/stutter.

I would guess some system action is causing continuity error in the stream.

Signal strength etc is only a very rough guide as there isn't a standard that all drivers adhere to and canonly be used to compare against same tuner on your system.

 

[Hoggle]

Thanks for your assistance. I have attached clean logs as requested.

I simply did the following...

Start MediaPortal
Access My TV
Go to full screen mode
Start recording, selecting the option to record the current programme.

Within 1-2 seconds of starting recording, the pause occurs.

Thanks.

 

[SciDoctor]

Your tswriter log shows you do have continuity errors on your streams, why I don't know, but these can show perceived stutter .

The other thing I noticed is your EPG grabbing is quite agressive, looks like you have both idle and timeshift EPG grab enabled and time between grabs is very low.

Do you need to do a full grab every couple of minutes, this could possibly cause some stutter just becaus of sytem i/o; as a test try changing the time to every hour.


Also only grab from channels that carry EPG data, it used to be that the EPG grab would continuously repeat grab if it was expecting data but none was there, I can't test this as all UK DVB-t channels carry all the same EPG data

 

[Hoggle]

I've set the EPG check to 240 minutes, and turned off the gap filling options. I have a quick related question on this. Am I correct in assuming that if a card is associated with specific channels, that card will never attempt to get EPG data for other channels?

The problem is still present after making this configuration change, but starting recording on the 'My TV' page instead of full screen, I noticed a pattern. The problem occurs around the time the red recording icon appears in the GUI. It may be that this is just when recording actually starts, possibly delayed a little when using the current programme option.

Problems of this kind are not apparent at any other time, only when recording starts, and I've been watching most of my television through MediaPortal since the weekend.

Please let me know if you would like any other logs. By the end of next week I should have some PVR-150s to test with as analogue capture devices, so that might help isolate the cause of the issue.

Thanks.

 

[Hoggle]

I now have a PVR-150 installed to capture analogue TV, and the same issue with corruption is occuring when recording starts.

The analogue card has also introduced some new problems, which I assume are known issues. Specifically, I am unable to watch the stream on two clients, and if the front end crashes, I am unable to watch. I get "No card available", despite the card being dedicated to a single purpose.

 

[RickDeckard]

[...]

5..A possible bug I have noticed is when a recording starts in the background, the current programme being viewed, the data in the timeshift buffer, and any already-occuring recordings, is momentarily interrupted. This is probably the biggest issue that is likely to stop me deploying MP throughout the house in the near future. Hopefully this can be fixed by something simple like changing the demuxer. Any suggestions on this issue are welcome.

[...]

what cpu do you have in your tv server? I had the same issue with a single core Athlon 3700+.
Since I swapped out that CPU for a lowly Pentium Dual Core E2160 the problem disappeared, so I assume the extra core helped a lot.

Before that, I added extra hard drives and experimented with differtent timeshifting and recording folders on different drives, but that never helped.

 

[Hoggle]

Thanks for your suggestion, but no luck with a solution so far.

The CPU I have on my desktop is an Intel E6600. I set up a new TV Server, using an Intel E2200 CPU, Windows XP SP3, and Hauppauge PVR-150s, installing the required decoder software for MediaPortal as documened on the site.

I am still seeing momentary corruption when recording starts, even when the source is the PVR-150, which has an on-board MPEG2 encoder. It appears the corruption is occuring either in MediaPortal, or one of the filters on which MediaPortal depends, rather than a signal quality issue, since the PVR-150 should be outputting a clean MPEG2 data stream.