NextPVR and SSD
#1
Hello.

I am using NextPVR backend on system with SSD drive. SSDs (especially those with triple level cells) dont like writing too much. For this reason I have decided to place Buffer directory on Ramdrive with small capacity (32 up to 256mb).

When i watch TV on this system with NextPVR software everything is fine, the problem starts when I try to use XBMC as frontend.

When TV is being watched the liveTV.ts file appears and grows. Once disk gets full NextPVR has no trouble to continue in displaying video. If the same happens using XBMC the player is showing short loop...

So I made the Ramdrive bigger and noticed that when file reaches about 180-200mb its liveTV-2.ts is created and streaming continues using newer file. Older file however remains present...

a) Bug or feature
b) Is it possible to forbid timeshift on backend?
c) Is it possible to define that liveTV.ts file will have specific size when it splits?
d) Is it possible to "cleanup" all *.ts files once newer is created?


Thanks.
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#2
(2014-03-21, 16:38)Offler Wrote: When i watch TV on this system with NextPVR software everything is fine, the problem starts when I try to use XBMC as frontend.

When TV is being watched the liveTV.ts file appears and grows. Once disk gets full NextPVR has no trouble to continue in displaying video. If the same happens using XBMC the player is showing short loop...
When NextPVR's own front end is watching live tv, it doesn't look at the buffer files until the user hits 'pause' or 'skip back' etc.

Quote:So I made the Ramdrive bigger and noticed that when file reaches about 180-200mb its liveTV-2.ts is created and streaming continues using newer file. Older file however remains present...

a) Bug or feature
b) Is it possible to forbid timeshift on backend?
c) Is it possible to define that liveTV.ts file will have specific size when it splits?
d) Is it possible to "cleanup" all *.ts files once newer is created?
There is usually four .ts files, created as a rolling buffer, with the oldest file getting deleted when the newest one is created. You can't disable the timeshift buffers (and still be compatible with XBMC).

Depending on the tv source (and how high it's bit rate is), the buffer can be several hundred MB, or even into the GB range. You can reduce it by setting HKEY_LOCAL_MACHINE\Software\NPVR\SlipSeconds=x (DWORD). The default value is 1200. The minimum value is 100.
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#3
Thanks for explanation. Will try.

Available TV sources are Digital Radios, SDTV and one HDTV channel (via DVBT), The last one certainly creates biggest file.

Because I am hardware limited (2gb or ram so more than 256mb of Ramdrive is not viable) it may be still troublesome.
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#4
Ok here are the results:

I set the buffer size to 100.

a) Files usually have 16-20mb, which is OK.
b) There are 4-6 files. Total buffer size for single SD channel is then 150mb.
c) Sometimes files are not cleared, even when streaming is stopped.
d) Streaming now works only locally with XBMC (127.0.0.1). Althought it can be reached from local network, it fails after 5 seconds.
(maybe related to Gotham Build but I am not sure. Maybe I just screwed some configuration).
e) When streaming same channel to two computers/devices there are created two separate sets of files which are containing exactly same data. Question is if there can be single set of buffer files, each for any channel. It would greatly reduce requirements on RAM, depending on potential clients.

To better understand the requirements - I am trying to turn Netbook into media server. Basically, it would be easier with standard HDD, but I am thinking of portable device. SSD is better power-efficient and shock proof solution, so RAMdrive is only choice.

Current potential of the hardware is to serve for up to 8 clients, but the buffer with 512mb (this is maximum I can afford to provide) and SDs channel can serve for up to for 3-4 clients. Anything that further reduces size of the buffers is good...
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#5
I think you'd be better of with a standard HDD. NextPVR's buffering scheme was just not designed to work in this minimal way from SSD.
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#6
I can add USB HDD, but performance-wise it can be troublesome in different manner. Standard disks on low RPMs (5200 for notebooks) may have trouble to read/write multiple buffers at same time.

Performance-wise is Ramdrive quite solid, but ... it simply may have trouble with more clients due capacity restrictions.
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#7
I use a 120MB SSD in my backend, it cost about $80 bucks, and I have used it 3 or more hours a day for six months or more streaming to one or 2 XBMC clients.. I backed it up to HDD and figure if/when it fails I will restore it and start again.

Martin
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#8
In this case we are talking about 1 TB SSD drive from Samsung with Triple Level Cell flash chips. 1/3 life span when compared to standard MLC flash chips, but due large capacity costed fortune... Smile

I try to find a way how to support up to 5-6 clients with larger Ramdrive, while free up as much RAM as possible.
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