how many different MD streams from a core?

[thedaver]

Another semi-basic question, but it's not obvious from the FAQ.

If I build a core with 2 analog cable sources, 1 satellite source, I have a DVD in the core's drive and a media (dvd video) library attached to the core, then (in my way of thinking) the core has 5 possible video output streams that MDs in the house could draw from.  Can those be streaming concurrently?

Or, asked another way, if my representation of 5 possible streams from the core (above) is appropriate AND if I have 5 MDs in the house, can all 5 streams be running concurrently - one each to a different MD?   If not, what limitations must be considered.

Thanks so much for your answers and wisdom!
Dave.

[seth]

 
Here is a real world example for you. My core has 3 PVR150 cards in it. 2 of them go to satellite receivers, one of them goes to a Roku Netflix Player box. I also have media stored on the various hard drives attached to the core, as well as a DVD drive.

In this scenario, I was using 4 MD's and the core hybrid MD.

Core/Hybrid was watching a satellite feed from MythTV.
MD 1 was watching a DVD placed in the Core/Hybrids DVD drive
MD 2 was watching the Netflix Player Feed
MD 3 was watching a video playlist stored on the Core/Hybrid
MD 4 was watching a recording in progress from tuner 2 on the satellite box

My network is Gigabit, with a Gigabit feed from the core. MD 1 was also connected Gigabit, MD 2, 3 and 4 are connected 100Mbit.

It can be done, Using the media map, I could have easily taken the DVD stream, or the Video stream, or the Netflix stream, and sent it to all or 1 or 2....

So the answer is Yes it can be done.

Isn't this the most powerful media platform ever?? 

Regards,

Seth

[thedaver]

That absolutely friggin rocks!  Thanks Seth!

[krys]

not to overlook the obvious, but I have streamed 5 different video files from the HD to 5 different MD's at once before. I really dont understand how this works but it does.

[colinjones]

Krys makes an important point that is easy to overlook. You are envisaging streams (for that is what LMCE calls them) as necessarily being different from each other. Clearly "sources" are likely to be a single stream, although you can effectively get more by adding multiple cards (like seth) or using cards with multiple tuners (like me). But the fundamental difference with your media libraries is that every file is effectively a potential, parallel stream. So you can stream 5, say, different files at one, or in combination with any of the "real" sources like tuners. Moreover, because of the clever way LMCE handles "streams" you can bifurcate a stream and send it to multiple MDs simultaneously! Move them from MD to MD in real time, use Follow Me (which is functionally similar), split streams mid-movie, stop the splits or even control things like volume simultaneously across all sync'd MDs using the same split stream... it goes on and on!

[krys]

while on the topic, when I tested and streamed 5 files to 5 diff MD's at once I was only using 1HD, so how the hell does one HD send out data for 5 files all at once? that head must be screaming across the disk

[colinjones]

HDD's do that all the time! The data rate that your drive can achieve is far greater than that required for 5 video streams. Any sequential file reading and the drive will usually read-ahead for the next chunk of data and store it in cache (Operating Systems do this as well at a higher layer with larger caches) so that when the request comes to read the next part of the file, it is accessed instantly from cache (either the HDD cache or the OS cache) requiring no mechanical head movement. Inherently, a video stream isn't read at the full rate the HDD is capable of because the stream isn't running that fast either. So the requests for the next block of data are not continuous, they are bursty/periodic/on-demand. So even without this caching a HDD would still be able to stream many files "simultaneously" just with more head movement - but the head is capable of moving in milliseconds, many times per second, pretty much continuously for years cos this is the type of activity you would expect to see on a busy server anyway, just accessing normal files, when under load.

Now apply this logic to video files.... see?

[thedaver]

Man, you gurus should be writing a book!   It would be a great read. 

[patmankn]

Hmm.. does anyone have some experiences with multiple streams using data stored on a NAS?
i guess the HDD performance on a NAS should be plenty ;O) but... what's the best pratice setup to get the best performance? Multiple Gbit NICs? iSCSI ? I pretty much like the idea, to store my stuff in a NAS (upcoming project: buildung a multi TB ZFS NAS) as i don't have to take care of my data, if i want to test a new LMCE version ...
so how are your results with so many streams... anyone?

Pat

[colinjones]

makes no difference, you will have plenty of bandwidth for multiple streams on pretty much any current HDD technology whether it is based in a PC or a NAS. Gbit is fine, you can even get away with 100M in most cases for a small number of streams. Particularly if we are talking about the average downloaded media file which are typically only a handful of Mb/s at most. SDTV and HD generally is more challenging of course, but even SD TV across 100M should allow several streams (you can rely on getting at least 70M through FastEthernet, often as high as 95M) an SDTV stream is usually around 6M (even lower in some countries and on cable services) so as long as your switch is decent, away you go.