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Help with mobile content standards
Brodo Faggins
Registered User regular
Registered User regular
I need to learn all the current mobile network standards and technologies for a job interview I have coming up, specifically with streaming mobile content like video to cell phones.
Can someone give me a rundown of what's available and is best for it? So far I know "3G" is the best speed available, but other terms like CDMA, EVDO, and others have me a little confused, even after I went to wikipedia. What do all the major cell service providers use?
Any info would be great.
Can someone give me a rundown of what's available and is best for it? So far I know "3G" is the best speed available, but other terms like CDMA, EVDO, and others have me a little confused, even after I went to wikipedia. What do all the major cell service providers use?
Any info would be great.
Brodo Faggins on
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Sprint = CDMA
Cingular = GSM + 3G
T-Mobile = GSM
Alltel = CDMA (I'm pretty sure)
As far as I know no mobile providers in the US support mobile to mobile video. This isn't Europe or Japan you know. ;-) (Misread your sentence on video...but it still applies)
The frequencies each company uses can be pretty easily found using the googles.
A few terms you might find to be useful to learn are GPRS, EDGE, HSDPA...if you don't know them already. EVDO is Verizons little baby. More or less 2.5G.
I know more about content related stuff and delivery over http than the actual specs for the communications protocols, so I may be slightly off on this stuff and certainly am not in much detail.
Carrier types:
GSM - Cingular/AT&T and T-Mobile are the major US GSM carriers. These are the phones that use a SIM.
CDMA - Verizon, Sprint/Nextel use CDMA. CDMA your phone is more hardwired to the network than with GSM.
Data -
GSM offers GPRS , Edge (sometimes referred to as 2.5G and sometimes considered 3G) is a faster offering and most current GSM phones support it. 3G is the latest and fastest but still somewhat limited in the US for areas that you can actually get a full speed connection with it.
CDMA networks you're looking at EVDO for data. I can't remember if there is anything else common in the US.
Content stuff:
Here's where I really know what I'm talking about and have access to more info if needed.
Audio:
You've got your monophonic, polyphonic, and truetone/realtone content.
Monophonic is pretty much not in use these days, there are 2 major formats, rtttl and imelody. There are a couple variations off of each of those that encode slightly differently/with different headers. I've worked with this stuff and so can provide specifics if you want, but it's unlikely to be needed unless you'll be working with carriers in latin america.
Polyphonic - your standard midi sounding stuff... usually midi, spmidi, or smaf. Most phones these days take these, they're nice and small, etc.
Truetones - these are actual clips of real sounds, songs, etc. Anything from regular mp3 or aac to amr, qcp, rmf, etc. There are a number of formats here both in the actual audio format and the bitrates and such they need to be recorded at. Some phones will also have size limits and whatnot.
Video - you're primarily looking at a .3gp container. 3gp is somewhat vague and can actually be a number of different video and audio formats contained in it. Usually it's an mpeg-4 video and aac audio these days although sometimes it'll be one of the amr formats for audio.
Images - could be anything... I work with phones that take gif, jpeg, and png. Some can use animated gif and some can't. There's really nothing special here, just a matter of the right dimensions for the phone's display and there's occasionally retardation with the mime-types like some carriers/phones want image/jpg and others want image/jpeg for jpg images.
DRM:
DRM will allmost certainly be involved. The major content providers like record labels tend to require it. You're primarily looking at OMAv1.0, which includes:
Forward locking - sticks a content-type header of application/vnd.oma.drm.message on the content and the device then won't allow it to be copied or sent elsewhere after it receives it. Some apps on phones ignore this.
Combined delivery - like forward locking but also includes some usage "rights" to limit number of plays or whatnot. There's a specific format for the rights. The rights and the content are delivered over http via a multi-part mime.
Separate delivery - like combined delivery except the rights are delivered separate from the content. This adds some flexibility in allowing the device to be able to send the content to another device along with the rights. In this case the content is delivered with a content-type of application/oma.vnd.drm.content.
Any phone that supports combined or separate delivery also supports straight forward locking as a requirement by OMA. There are also a couple other DRM formats... Sprint PCS has one and I forget the other. These get a gcd or cod file extension and related content-type.
Phones that support these DRM types generally support install-notify where the phone is given a url to hit after receiving the content via http post and gives a code specifying whether the content was sucessfully downloaded or not.
I dunno, I could go on and on about shit. More specifics of content types, formats, DRM. j2me related stuff that I didn't even mention, etc. Then there's brew which I know fuck all about beyond it being another application platform like j2me. There's sms and mms protocols and specs, WAP and WML and other mobile content and communications stuff like that.
So, basically, if you have a specific question or can provide more details on the job itself that may be helpful in figuring out what you might need, just ask. It's also pretty likely that the company won't expect you to know a ton about mobile content as there's no reason to know most of this stuff unless you've already worked with it.
btw, can you say who the job is with?
edit: thanks, for that info btw, it's pretty helpful. Do you know anything about various companies' subscription models?
I have to be careful about saying too much... conflict of interest and all that if someone here were to find out.
For streaming RTSP is commonly used. The problem there is that Media Player 10 Mobile, which is what Windows Mobile 5 devices such as the Samsung Blackjack, HTC-8100/8125, etc come with doesn't support RTSP.
As to how subscription models work, I know very little about that. I think usually it's $5-$10/month for X downloads... carriers usually want a chunk (I think really only a concern if you're going to be doing sms billing or some such), content owners want another good sized chunk of it, etc. I don't deal with that side of things for the most part, though,