How Streaming works?

Heccccc

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Hi I've got a usual home windows wi-fi network.i have shared video files across (some are shared folders others are available via a media server mediamonkey) and often I start getting a stuttering , freezing etc (in my wdtv live or Chromecast). I would like to know how the connections and streaming work. Is it all transferred through the router? Or the client and the server establish a direct connection and streaming? Another thing where is the list of PC.s and shared files stored? Is it centralised in the router or in a pc, or each time a scan is requested all nodes receive the question and answer?

Thanks a lot
 
Is it all transferred through the router?

Yes.

Or the client and the server establish a direct connection and streaming?

No - at least not in Wi-Fi terms. Of course the source and sink devices establish a connection with each other, but the actual data packets travel (for example) Source---Router---Sink.

Bear in mind that in Wi-Fi networks, "only one thing at a time can transmit" so, in the example I've cited, the Source---Router and Router---Sink transmissions cannot occur simultaneously. And that's competing with all your other Wi-Fi devices (and any neighbours on the same radio channel if they are close enough) too.

The more Wi-Fi devices you have in your locale, the more "competition" (it's anything but "fair," though the protocols try to give everything an equal chance,) there is for "air time."

Another thing where is the list of PC.s and shared files stored? Is it centralised in the router or in a pc, or each time a scan is requested all nodes receive the question and answer?

A bit of both. In a Windows network, something called a "Master Browser" is established in one of the hosts which maintains a list of all the Windows hosts connected to the network. Which host functions as the MB is determined by an "election," whenever one can't be found (for example, it's been turned off.) Over time the MB almost inevitable ends up being hosted in something that is "on" all the time such as a server. Some SOHO Routers can also function as the MB.

I don't recall whether it's mandatory for hosts to consult the MB and it's possible that later versions of Windows employ other mechanisms (I haven't "kept up" with the evolution of the technology.)

Other (non Windows) hosts might "advertise" their presence by other means - my media streamer "shouts" about itself once a second or so. IIRC Apples "Bonjour" protocol, Skype hosts, uPNP (to name just a few) do something similar.

There's nothing that catalogues the files stored within the hosts, each hosts maintains that for itself and responds whenever it's interrogated. Some OS's, especially servers, cache the indexes in RAM for faster response time.

There's no reason why client devices couldn't try to "scan" the shares and compile it's own catalogue. My NetGear media streamer can do such (not that I ever use the feature) - it scans all the shares it "knows" about (has learned or been taught) once a day. But again, such behaviour is not mandatory.
 
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Some TVs and boxes support Wi-fi direct, which does let you establish a direct connection.
 
thanks!! i have had these questions since months, looking at forums for explanations with no success, seriously... at last...thanks

now, trying to grasp some more about what is going on...

by chance are you aware if chromecast uses wifi direct?...
I remember I once read something like there was a handshake at begininng (probably in the case of using an android app as a dlna or chromecast control, between server and renderer/cc) and then the server and the renderer / cc established direct exchanges... maybe they were just omitting the (usual/obvious) router in between?, but unfortunately I could not find where I read that ...
I might guess wifi signal of android devices, pc.s is much lower than the router, so for transmission between rooms it woudln't make sense trying tu use wifi direct, or would it?

another intriguing matter to me. I am aware upnp/dlna is based on IP /http protocols (among other technologies), do you know what protocol chromecast uses? I might guess IP/ http as well?

As from what I've found, SMB is maybe the worst way of streaming and then using media server (upnp) has better performance ... but I guess the interference, noise are the remaining issues...
 
by chance are you aware if chromecast uses wifi direct?...

Not for streaming, but I believe it uses it for setting up the chromecast device (putting in your network password etc.).

I might guess wifi signal of android devices, pc.s is much lower than the router, so for transmission between rooms it woudln't make sense trying tu use wifi direct, or would it?

Quite the opposite, if you did a survey you'd almost certainly find device to chromecast distance was shorter and far more likely to be line of sight than going via a router.

The chromcast presumably connects to an existing network for ease of use. Users don't have to connect to it's network individually or switch networks every time they wish to use it.

another intriguing matter to me. I am aware upnp/dlna is based on IP /http protocols (among other technologies), do you know what protocol chromecast uses? I might guess IP/ http as well?

There are always half a dozen or more protocols involved in any transmission. From hardware to routing to data formats. So questions like 'which protocol?' and statements like 'direct exchanges' are very context sensitive. Something can be direct on the level of who is controlling the transmission and indirect on the level of where the data packets pass through.

There will be some protocols that the chromecast has to be using to talk to your network in the first place like IP, some that everything uses like DHCP, some that it's explicitly advertised as having like Wi-fi and several others besides.

If you're asking which protocols the Chromcast uses to organise the casting or stream video then I'm not sure.
 
I wouldn't worry much about streaming using SMB - plenty of us do it all the time without any problems.

The differences in performance and other matters between SMB and other protocols are so deep in the realms of nerdiness that you'd have to be a fully paid up geek that's "gone out of your way looking for it" to spot the differences. Issues with the disc systems (which are mechanical devices) and host O/S in the media server are likely to have a much greater effect. And of course...

Wi-Fi is in and of itself fundamentally unreliable - if you want fast reliable data networking, then the best solution it to use ethernet if at all possible.

I see nothing in Wiki's article on Chromecast that suggests it concerns itself with data networking below the "IP" level in the networking model, which suggest it's not worrying about the differences between ethernet & Wi-Fi and would lead me to concur with EndlessWaves that it isn't using Wi-Fi Direct.

Even with Wi-Fi Direct, there isn't a "free lunch:" Any peer-to-peer (direct router/AP avoiding) Wi-Fi transmissions still have to abide by the same "only one thing at a time can transmit" rules and "play nice" with any other Wi-Fi devices in the same locale. The more devices you have, the more data you try to move, the more competition there is for "air time" and it starts to break down.

I've worked in schools and colleges - imagine a classroom or lecture theatre full of students all armed with a laptop and a smartphone, then think about the competition for "air time" that yields. I've seen a few very "disappointed" teachers who watched their "follow along with me" lesson, which worked perfectly well when they tested it on their own, fall to bits once the class arrived!
 
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