Glossary and abbreviations

[ddboy]

UPDATE: This is superceded by the Tivo Series 2 Handbook (http://geocities.com/todd2222a) at http://geocities.com/todd2222a


A lot of the terms used in this forum are confusing to new members -- who may be smart people but just coming late to the dicussion. Here is my guess at when everybody is talking about:

SA -- StandAlone, a Tivo that connects to cable tv or antenna
not integrated with a digital satellite receiver.
HDVR2 -- Hughes Digital Video Recorder, series 2. A Tivo
integrated with a DirectTV satellite receiver.
Series 1 -- An older Tivo that uses the IBM PowerPC processor
Series 2 -- A newer Tivo based on the MIPS processor
combo -- A Tivo (recorder) integrated with a satellite receiver
PowerPC -- An IBM microprocessor chip used in early Tivos
MIPS -- Another microprocessor (with an instruction set that is
incompatible with the PowerPC or Intel archiectures)

37 -- A version of a PROM (programmable read only memory)
chip that cannot be reprogrammed electronically while
installed in a circuit board
39 -- Another version of the PROM chip that can be rewritten
under software control while still installed in the circuit.
flash To update, write or rewrite the contents of the PROM
PM -- Private Message, to send the person a message that is not seen in the forum

Send me a private message if I got any of this wrong

[ddboy]

Implicit in these forums are a lot of things that old timers expect
you to know. So, I'd like to collect some of these things here to
get up to speed quickly.

Series 1 vs Series 2 -- From a computer programming point of view the key difference is that Series 1 units use the PowerPC
processor and Series 2 uses the MIPS processor. Therefore C programs need to compiled for one processor or the other and
you have to the right version for your Tivo.

The Other Forum -- Most of the Tivo forums started on http://tivocommunity.com/tivo-vb/. However that forum, although not part of the Tivo company has members with an
association with Tivo and they want to avoid ill will with Tivo, so
they eschew any discussions about:

Extracting video (getting video/audio from the Tivo in MPEG format
Stealing the nightly program guide update service
Avoiding security features of the Tivo (ie modifying software on the Series 2 units

The tivocommunity.com forum coyly refers to this forum as
'the other' forum and prevents the character string 'dealdatabase'
from occuring in forum entries or private messages to prevent
people from finding this site.

PROM checksum checking -- The Series 2 Tivo bootstrap program that is the first thing executed when the machine is plugged in, checks to see if the Linux Operating System kernel
(initial part of the operating system in the Tivo) has been
modified. This is done by doing a complicated algorithm on all the bytes in the kernel file and comparing it against the value it knows the kernel should have. This is called verifying a checksum
or cryptographic message digest. (I guess that)The kernel then checks all checksums for all the other programs and files it will use to verify that they have not been changed. It erases any
other files (on the root partition). The implication of this is that in a Series 2 Tivo you can't add new functionality to your box (such as being able to telnet to the Tivo. The principle solution to this is to modify the PROM so that the checksum test(s) is not performed, or, more precisely by jumping to the 'checksumOkay'
part of the code even if the checksum wasn't what was expected.

BASH -- A 'console' command prompt program in UNIX, the Bourne Again SHell. Shell is the UNIX/Linux word for command
prompt loop (like the windows cmd.exe program). The purpose is to allow the owner to log into his Tivo and use it like a computer
with some video hardware on it -- which is what it is.

Serial BASH -- Tivos have a miniture phone jack on the back intended for connecting the Tivo to external equipment like satellite receivers. This jack connects to a serial port on the Tivo processor. You can connect this to the serial port (aka RS-232 or Com port) on your PC to login. A program is run on the Tivo that implements the PPP (Point to Point Protocol) which provides internet like IP (or TCP/IP) communication over the serial port. Another set of programs (tnlited, in the Tivo, and telnet in the PC) are used create a terminal (log in) session to the Tivo. The alternative is to use an Ethernet adapter.

Ethernet AdapterThe prefered alternative to using the slow,
serial port is to install an Ethernet Adapter. On a Series 2 this is
usually done by connecting a small Ethernet adapter external to the box on the USB connector. See http://www.tivo.com/ for a list of compatible USB/Ethernet adapters. Series 1 machines don't offer USB connector, so people who want the faster ethernet connections need to install an ethernet adapter
card in their machines.

USB -- Universal Serial Bus, a newer, faster communications connection. The Series 2 has 2 USB connectors on it. People connect an Ethernet Adapter to the USB port. This allows IP (Internet Protocol) communication between the Tivo
and the a LAN (Local Area Network). If you connect this ethernet
adapter to a house LAN with a connection to the Internet, the Tivo can get its updates over the internet rather than using the
phone line. Because it is a normal Internet connection you can use it to login (via telnet) or use other internet applications like
FTP (File Transfer Protocol) or HTTP (Web server).

37 versus 39 -- The PROM chips used in Series 2 Tivos come
in serveral versions. The part number containing 37, cannot be rewritten electronically under the program control of the processor. The part number containing 39 can be updated by a program running in machine. (Or do I have that backwards?) The implication is that if you need to change the contents of the PROM to avoid the kernel checksum check, that you have physicall remove the chip (messy unsoldering) rather than running a program.



Please send any additions or corrections via private message.

[ddboy]

Tivo video format -- The video and audio recorded in the
Tivo is encoded in a compressed digital format called MPEG 2
(Motion Picture Experts Group, standard number 2). DVDs also
use MPEG 2, however they use a slightly different form. Tivo
keeps the audio and video in separate files. DVD (and satellite
or cable transmission of digital video) interleave the audio and
video data into one 'multiplexed' stream. Also DVD use a higher sampling rate for the audio than the Tivo does. So, part of the process of making recordings in the Tivo useful in your PC is converting one form of MPEG to the other. (MPEG 1 is an earlier,
less compressed, poorer quality version of digital video that uses less than 1.5 Mbits/sec. MPEG 2 is typically run at 5 Mbits/sec.)

Serial ConnectionsThe physical jack for the serial connections (asynchronous, start-stop serial) is a 1/8" diameter
"stereo miniture phone jack". The plug has three connections, 'ring', 'sleeve' and 'tip' (in order from the cable to the tip of the plug. The ring is the ___ connection, the sleeve is the ___ connection and the tip is the _____.

How to use serial -- The serial port can be used directly by
connecting it to your PC serial port and using a terminal emulator proram. To do this you must tell Linux to redirect input and output from the Tivo serial port to a copy of the Linux command processing shell. A simple way of doing this is with the command:
"bash <> /dev/ttyS2" (or replace the 2 with a 3 for some machines?). This tells the BASH 'command shell' to send its output (indicated with the '>') to the /dev/ttySx device, and to
pass any input from the serial device (indicated by the '<') back
to the input of the BASH program. (Now how do you execute
this command if you don't have bash access yet? Put it in rc.sysinit?)

Alternatively, the serial port can be used to emulate a internet connection by using PPP (Point to Point Protocol), which allows
'IP packets' to be sent back and forth over the serial port. This
allows any internet applications to be used over serial port. Because asynchronous serial communication is slow, people usually install and Ethernet connection (USB or ethernet card
such as the turbonet card). (info from David Bought)

Send additions or corrections via private message.

[ddboy]

It is frequently hard to tell if solutions people are discussing apply to your model of Tivo. This is a list (under construction) of brands and models of Tivos in an attempt to identify how they are related.

Series 1 units
sa -- Tivo brand, standalone series 1
dsr6k -- Philips, combo
gxceb0t -- Hughes, combo, same insides as dsr6k
t60 -- Sony, combo, same insides as dsr6k, different remote, includes 'VCR IR Blasting'

Series 2 units
-- Stand Alone (connect to antenna or cable, not satellite)
sas2 -- Tivo StandAlone, Series 2
-- Combo (Video recorder integrated with satellite receiver)
hdvr2 -- Hughes Digital Video Recorder, combo
dsr7k -- Philips, Series 2, combo, same inside as hdvr2

(info update from David Bought)
Series 2 units are then subdivided into whether or not they have PROMs that can be reprogrammed in place.

[ddboy]

This information is being inserted in the Tivo Series 2 Handbook (http://geocities/todd2222a) at http://geocities.com/todd2222a

[baudrate]

links dead?

[manzwa]

As mentioned, the links are broken for the glossary. What are the chances of getting a glossary on DDB so us newbies in training to have something to refer and clarify understanding of material presented. All the abbreviations make the material difficult to keep up with. Begging everyones pardon if one exists. I did a search and found none that was extensive. Such a glossary/abbreviations would be great to sticky in the newbie section or somewhere appropriate.

Thanks,
Manzwa

[fredfillis]

A list of which kernels go with which software versions would be helpful. I've tried to find such a list here and on the other forum with no luck.