MHP to laptop interface possibility

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This page is for investigating the possibility of interfacing an MHP (Multimedia Home Platform) DVB (Digital Video Broadcasting) Satellite or Terrestrial TV receiver to the laptop network, for the purpose of receiving software, files and information.


Contents

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.

The following subsections explore these two parts.

Creating a TCP/IP Connection

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 dial tones and pick up any connection, the number dialed is irrelevant. The laptop can then start the PPP daemon and a TCP/IP connection will be established.

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.

Other connection types such as bluetooth or ethernet are also possible, but would require USB-enabled receivers to connect them to the laptop.

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.

File Transfer over TCP/IP

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).

There are several advantages to running a file server on the MHP device and making the laptop download the files instead of pushing the files to the laptop:

  • After setting up the connection once, multiple laptop users can download the files they want. Even if the connection is only with one laptop, that laptop could share its connection with others over WiFi.
  • The user interface for selecting files to download is on the laptop, which is more convenient than using the remote control of the TV.
  • The TV can be used like normal, except that it must not be zapped to a channel on a different transport stream (which might not include the same object carousel).

Can it be done?

Can it use an ordinary MHP television?

In the section Creating a TCP/IP Connection above the following text, shown here in italics, is written.

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.

Other connection types such as bluetooth or ethernet are also possible, but would require USB-enabled receivers to connect them to the laptop.

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.

It would be wonderful and a great step forward if one or more of the manufacturers of MHP equipment becomes interested in specifically supporting these laptops. However, it may be that that does not happen and it may be that the only realistic way of implementing the use of MHP broadcasts to distribute software and data to the laptops will be to use at each school an ordinary MHP television or an ordinary MHP set-top box. So at present there could be an attempt to implement a system using the regularly available reception equipment, though hoping that one or more of the manufacturers will start to supply equipment which would make for a better system.

Using a Multimedia PC as the MHP Receiver to access the data

It should be possible to find an MHP Satellite Receiver with connectors for networking (Ethernet or USB). If not, then here is another solution using a Multi-media PC.

The MHP system allows applications and data to be received on various types of equipment, including set-top-boxes, TVs with built in receiver/decoders and Multimedia PCs. Each piece of equipment provides an identical 'virtual machine' API (Application Programming Interface), a built-in software platform that allows identical downloaded programs to run on any MHP appliance. Downloaded programs can call a standard set of functions and procedures for display and interface/communication, etc, as if they were running on a single standard hardware platform, without knowing any details of the specific hardware chip-sets.

Instead of using a Satellite Receiver box with MHP and struggling to interface it to the OLPC server, a Multi-media PC with MHP Reception hardware/software could be used. This would be connected to the server by Ethernet, USB or Wi-Fi and allow the server to access the data more easily.

To receive information or software via MHP, an OLPC school would use an MS Windows/Linux Multimedia-computer. The cable from the satellite dish would be connected to an internal-card Satellite Receiver/MHP decoder.

The Receiver turns the satellite signal into an MPEG-2 video stream, then extracts the MHP Data from it. Software on the PC would send the data via an Ethernet/USB cable or Wi-Fi to the OLPC server computer. If a version of the hardware and software is available for linux machines, like the server, and the server has a spare card-slot, we could dispense with the seperate multi-media computer and do it all on the server.

MHP is a fairly recent development. If the equipment isn't available just yet (in 2007), it should be available in the next year or so.

For more details of MHP, including Data Carousel broadcasting and IP tunneling (data in MPEG-2 streams), see the standard ETSI EN 301 192 V1.4.1 (2004-11) on the ETSI European Telecommunications Standards Institute website (free registration required).

--Ricardo 15:04, 21 August 2007 (EDT)

Would an ordinary laptop be suitable?

Other aspects - please add sections as you wish

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.

--

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

--

Hopefully experts on the MHP system will wish to participate.

Return channel for interactive services

In the near future (beyond 2007), Interactive TV will become more commonplace in a lot of countries, over Satellite, Cable, Terrestrial TV and Internet IP TV. MHP is built on DVB and allows people to receive data. To provide interactivity, people need a 'Return Channel' (or 'Back Channel') to send data back to the broadcaster to select information, and for quizzes, polls, surveys, teleshopping, email and even web-browsing.

The options for a Return Channel include...

Dial-up/broadband internet

The user selects things via the TV/Satellite remote-control and the set-top box connects to the internet via a cable to a phone/DSL/ADSL socket.

Touch-tone phone system

The user dials an automated phone-system and selects things using the keypad on their phone. Commands are sent by the phone using DTMF tones.

DVB-RCT

DVB-RCT is short for Digital Video Broadcasting - Return Channel Terrestrial, specified by ETSI EN 301 958, available for download (search for 301 958) from the ETSI European Telecommunications Standards Institute website.

It is a system for sending data back to the broadcaster wirelessly using VHF/UHF radio signals. Each user can send data at several Kbps. The range is up to 65KM.

See the dvb.org DVB-RCT Fact Sheet (.pdf file) for a brief overview.

See 'Wikipedia: DVB' for background and more links to standards and info sites.

DVB-RCS

DVB-RCS is short for Digital Video Broadcasting - Return Channel Satellite, and specifies return channels back to the satellite at up to 2 Mbit/s. It is specified in ETSI standard EN 301 790.

--Ricardo 15:41, 21 August 2007 (EDT)

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