MHP to laptop interface possibility

MHP to laptop interface possibility

Introduction

The DVB-MHP system (Digital Video Broadcasting - Multimedia Home Platform) system for which there is the http://www.mhp.org webspace is a major international initiative in the development of interactive television.

The system works by the unidirectional cyclic broadcasting of software which is selectively used by Java-based computer systems which are either built-in to a domestic television set or are contained in what is termed a "set-top box".

No telephone line connection is needed in order for local interactivity to be produced. This is what MHP parlance terms the "enhanced profile" as in the phrase "enhanced television".

The MHP system also has provision for a telephone line to be connected to the television and the television to make telephone calls. This is termed in MHP parlance "interactive profile", though the telephone call need not be made to the central broadcasting computer; it could be made to somewhere else, such as a mail-order company.

This page is to investigate whether the MHP system could use that telephone link to get information out of the television and into a laptop, even though the laptop is just a few feet away. If that is possible, a standard MHP television which uses technology intended to send information by telephone messages to places many miles away would be used to send information to a destination just a few feet away.

The software system of the MHP television is Java, though for this MHP to laptop interface system it would be necessary for the MHP system to handle laptop software as data and pass it through as data and then the laptop sytem can use it as software.

An analogy which has helped me in thinking about this system is as if a main-line railway system is being used to deliver raw material (say, grain) to a factory (say, a breakfast cereal factory) where the factory has its own internal railway system. As long as the railway hardware is compatible, then railway wagons containing the grain can get to the factory by means of an "exchange siding". This is a section of track where the main-line railway locomotive can push the trucks onto, without the locomotive going very far into the siding itself, and from where a factory locomotive can pull the trucks, without going very far into the siding itself. The locomotives may be very different in size and power and in the way that they work, yet as long as certain basics such as track gauge are the same then a workable system can be achieved.

I am thinking that a sort of exchange siding format for transferring data from the MHP television to the laptop is needed. There may well already be some existing system which could be used: that may well be fairly basic knowledge to people who know about the electronic side of transmitting signals, though that is not my field and I do not know at present.

Hopefully this could be achieved using standard MHP hardware and some software. It may well be that certificates are needed from a registration authority for the MHP terminal to make a telephone call as the MHP system has very strong security protection.

Yet, at the time of writing this introduction 2006-04-30 1052Z the MHP to laptop interface is only a possibility. Hopefully experts from both the MHP and laptop communities will comment on the idea and something good will come of it.

Trying to produce an MHP to laptop interface

TCP/IP is the network protocol used by almost all devices with network capabilities nowadays. So for a flexible solution (as opposed to a special-purpose one), it would be good to design it around TCP/IP.

To simplify the problem, we can split it into two parts:

1. How to set up a TCP/IP connection between the MHP TV or set-top box (STB).
2. How to transfer files over the TCP/IP connection.

Let's discuss part 2 first, since it is the easier of the two. For transferring files, there are many existing technologies that could be used. A simple implementation could be an MHP Java application (Xlet) that implements a file server using HTTP. This file server would simply list the contents of the DSMCC object carousel and offer a download URL for each file. On the laptop a web browser is used to see which files are available and to download the interesting files.

Opening a server socket (default HTTP port is port 80) might be blocked by the security mechanism of MHP, but this can probably be solved by using a non-privileged port (above 1024, such as port 8080) or by signing the Xlet (making it trusted by the MHP stack, so it has more permissions).

For part 1, the solution depends on what kind of return channel is used by the MHP TV/STB.

If it is a phone line, it would have to be connected to the laptop somehow, maybe using a USB modem. Or after voltage conversion, the microphone input; this would only work at relatively low baudrates, but if the modem must be usable with noisy phone lines, the baudrate would have to be configurable in a wide range already. To receive data from the MHP TV/STB, a direct cable between the MHP device and the laptop's modem can be used. If the laptop's modem can be configured to ignore dail tones and pick up any connection, the number dialed is irrelevant. The laptop can then start the PPP daemon and act like a small internet provider (Linux has all required tools for this).

Things would be simpler if the MHP TV/STB would have WiFi built-in. An additional advantage would be that multiple laptops could connect to it at the same time. In this scenario the benefits of a file server become clear: every laptop user can download the files he/she wants at soon as the file server is running.

Other connection types such as bluetooth or ethernet are also possible, but would require USB-enabled receivers to connect them to the laptop. Or if MHP device vendors are interested in specifically supporting these laptops, the TV/STB could include a USB plug to make a USB<->USB connection with the laptop.

A post in the forum in the MHP webspace

A post with a link to this page has been placed in the forum in the http://www.mhp.org webspace.

http://www.mhp.org/forum/forum.xml?forum=10&thread=82

In order to use the forum one needs to register. Going to http://www.mhp.org and following the link Discuss MHP Today leads to the registration page.

Here is a transcript of the post mentioned above.

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The possibility of being able to send information to the laptops of the One Laptop per Child project using an MHP broadcasting system is potentially a major application of the MHP system.

I had previously been thinking that this would be using a standard MHP broadcasting system yet would require specially-built reception equipment.

I am now thinking that perhaps this could be a totally software task using a standard MHP broadcasting system together with an ordinary MHP terminal with facilities for what MHP terms the "interactive profile" with the "telephone call" being made using a cable to a laptop a few feet away: I am presently unsure whether that laptop would be a standard laptop from the project or whether a special version of the laptop would be needed.

I remember reading somewhere that in America the telephone area code 555 is unused in systems and that telephone numbers to area code 555 can be used as telephone numbers stated in speech and in signage on the sides of vans and so on in television shows and movies. So maybe an MHP application could be allowed to send telephone messages to 555-1234. The so-called interactive profile of the MHP system is to allow a telephone message to be sent from an MHP television to anywhere, not necessarily back to the central broadcasting computer: for example, to a mail order company which is selling clothing advertised in a television programme. Here, the receiver of the telephone call would be just a few feet away, yet this could be a convenient way to get the information out of the MHP television to a laptop, from where it could be distributed to other laptops by the laptop network.

Would this work? The need would be for the MHP system to run a Java program, which had been broadcast, which Java program would be used to select files of data (which could be software for the laptop, electronic books and whatever) from the object carousel and send it as some form of "telephone message" to 555-1234.

Can this be achieved? I am not expert in the MHP system, though many people who read this forum are experts in the MHP system.

There is a page in the laptop wiki for discussion of this possibility.

http://wiki.laptop.org/wiki/MHP_to_laptop_interface_possibility

Readers are welcome to participate either in this forum or in the wiki or in both as they choose.

Hopefully this interfacing can be achieved and MHP applied in support of the One Laptop per Child project.

The main page of the One Laptop per Child wiki is at the following page.

http://wiki.laptop.org/wiki/Main_Page

The main page of the One Laptop per Child project is at the following page.

http://www.laptop.org/

William Overington

30 April 2006

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Hopefully experts on the MHP system will wish to participate.