Amiga Tools 5/Amiga Tools 5.iso/tools/developer-tools/amos-tools/eaissue3a/text/ripper_3.asc

Text File | 1996-07-13 | 16.7 KB | 349 lines

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                  Multiripper tutorial part 3 - Decrunchers
                  -----------------------------------------

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        Not only is Multi-ripper an excellent module ripper, but it is
    also the best executable ripper that I know of, doing a much better
    job than larger rippers such as ExoticRipper.

        Multiripper allows you to unpack executables into the memory, and
    then examine the uncrunched contents for music modules. Lot's of
    different kinds of decrunchers are detectable, including almost all of
    the classic ones, and all of the exotic decrunchers used by coding
    groups such as Paradox and Red Sector.

        This next part of the tutorial is hopefully going to help you in
    getting your music modules from crunched files. Even better for you, I
    shall show you how to recover modules from Non-DOS disks, which you
    can't access in Workbench. Multi-Ripper is the ONLY shareware ripper
    that will allow you to mess around with the sectors on the disk, as
    with any of the other programs, you must register in order just to be
    able to read the disk.
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        I am also going to explain a bit about the encryption routines
    that some of the programmers use in their code to try and "Hide" the
    prescence of a module, as well as some other ways of deciding if a
    module exists, without having to load Multiripper.

        Remeber, that not all Non-DOS disks are readable in the ripper. If
    you try and use a disk such as Shadow of the Beast 2, then you will see
    that the ripper cannot register it, where if you use disks such as
    R-Type and Red Sector megademo, it has no problems.

        Here are the 2 main things you need to know, starting at the top
    with executable decrunchers.

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                            EXECUTABLE DECRUNCHERS
                            ----------------------

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        Often when you are writing a game, you will find that when
    everything is placed on the disk, the program takes up just a few
    extra K's of space than what you can actually use. When this happens,
    people use a "Cruncher" program, which reads the program in, and
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    squashes it up, so that it takes up less space on the disk. When the
    program is then run, it is unpacked, and then executed.

        When this happens, the module player will not be able to determine
    what is a module, and what is not. It will more than likely keep
    coming up with jargon than any actual modules. Commonly used
    filecrunchers are Stonecracker, PowerPacker and Crunchmania, which all
    three will NOT decrunch in multi-ripper. Many of the old and exotic
    crunchers will work, as they use the same kind of code as regular
    decrunchers, but perhaps have a different on-screen effect as it is
    unpacking.

        There are 2 ways of reading these files into Multiripper. The
    first, being the simple RI (Filename) (address in mem), and then you
    can use a HUNK (adress loaded in) to find the decrunch header.

        The program (if it understands all of the decruncher) will ask you
    if you want to Move, Skip or Unpack the decrunched file. It is a good
    idea to move the decruncher to a place in memory that is not used, as
    anything between the 2 addresses shown is completely overwritten.
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    Pressing U will unpack the file. You may have to wait a while,
    depending on how big the file is. With a lot of the decrunchers, the
    screen will be effected, also an indication that the process is
    working. Once unpacked, the program will tell you the start and finish
    address of the program you have just unpacked. If you use the WI
    command with the 2 addresses, you will save a data-file of the
    uncrunched executable, for use in other programs and rippers etc. NOTE
    that the file saved IS NOT executable, as it is the raw data directly
    from the decruncher. The executable bit of the program is scattered
    around somewhere for the convinience of the decruncher.

        Sometimes, the program will not be able to understand the
    decruncher either fully, or partly. If it does not recognize it at
    all, it will just skip past it. If it partly-recognizes the cruncher,
    then what it displays will depend on what it understands. The common
    ones are "Unable to locate decrunch address" meaning that you cannot
    move the program around, and you also must unpack it to the address
    that is stated/non stated, which usually results in a crash.

        Once you have unpacked the file, you can begin your usual music
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    ripping commands to see if there are any kinds of music modules in
    there at all. Common ways of disguising modules are to make the
    modules look like old Soundtracker modules, which can't be picked in
    in Multi-ripper too well. See the previous part for more information.

        When a module has been located, you can save it in the same way
    you would any other module. It should be OK, but some modules tend to
    get a bit of interference inside them, especially if MR is not too
    familiar with the decruncher that was used.


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                              SECTOR DECRUNCHERS
                              ------------------

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        Sector decrunchers are normally the decrunchers that you find on
    the Non-DOS disks such as games and demos. Multiripper can read and
    examine these kind of disks for both decrunchers and music modules.

        Firstly, in order for you to do anything, there are 2 commands
    that you can use to look on the disk. The first, and easiest, is the
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    SCAN command, which will scan the disk in the internal drive for
    modules and decrunchers. The addresses of any possibilities found are
    displayed on the screen. The list of all the decrunchers that have
    been found can be called at any time using the LDEC command. With the
    modules however, I think it would be best if you wrote down what you
    find, as they will not be listed on-screen with the LDEC command. Now,
    when you have these numbers, they can be used in conjunction with the
    RS command, as they are the sector numbers the Amiga recognized
    something at. It is always a good idea to add a few numbers to the end
    of the last sector number to make sure that you load all of the needed
    data into memory. Once you have read in the information, you can then
    go onto using the HUNK command and the HUNT command to try and recover
    the data even further. If you manage to find a module/decrunch header
    and the data is not all there, then add a few more to the final
    address of the RS sector, as the information is not being read in to
    be played. With decrunchers, you will be always unpacking lots of 0's,
    or the system could crash, although that has not happened on me yet,
    and I don't really want it to.

        The second command is a bit more difficult, and you will need at
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    least 2Mb of RAM in order to pull it off. If you have set your disk up
    the way I told you in the first part of the tutorial, you should see
    that the program kicks in at the beginning of the memory, making the
    startplace of memory at 45000 (disk users) and 75000 (Amiga's with a
    HD). Now, insert the disk and type RS 0 6E0 75000 and hit return. This
    will read the entire disk into memory, up to about 150000, allowing
    you a bit of space for any decrunchers that you should find. If the
    program happents to hit a read error, then the operation will be
    aborted where it is on the disk, and not read any further. Once
    finished reading, you can use a direct HUNT command to look into the
    memory for any modules, or a HUNK command to try and locate a
    decruncher. NOTE that some modules will be messed up slightly from the
    RS method, depending on the cruncher systems that the disk uses. One
    example of a module that will come straight from an RS is the rather
    good title tune from Zool 2. It will rip it clean, and all samples
    too. For more examples of modules that I have ripped, then see further
    down in the document, where I shall give a few working examples.
    Remember, it is illegal to try and sell modules you have ripped from
    any commercial game under your own name, so don't do it !!

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        Both of the above methods do exactly the same job, except maybe
    the second method is probably a bit more reliable, as you know then
    that you have all the data needed to play a complete module, or unpack
    a full decruncher.

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                              HIDING THE MODULES
                              ------------------

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        Don't sneeze whilst typing on the keyboard, and brushing your
    teeth at the same time. You get toothpaste all over the monitor and
    keyboard. Anyhow, enough of my little accident, and back to the
    tutorial. A lot of software houses try and hide their modules by
    putting a form of an encrypter into their modules, to try and stop top
    rippers like myself from extracting them successfully. I have managed
    to crack quite a few of these, but there are the odd few which still
    stump me for a while.

        The most common one, which does not really encrypt the module, but
    stumps Multiripper, is to store the module as an old Soundtracker
    module, which uses the standard 15 presets instead of the newer 31
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    presets. The best way around this, is to save the data file you have
    unpacked, and load it into another ripper such as ExtoicRipper, which
    does rip the old Soundtracker modules, and convert them to 31 using
    Protracker or Soundtracker module makers.

        Another good one is to alter the way the actual module is read by
    a music player. Let me try and build a picture of the header into your
    head. A music module name consists of 20-22 characters consisting of
    CHR$(0). The name of the module can be no more than 20 characters
    long, as is stored in the first 20 characters of the header. Then, the
    names of all the samples are stored after this, and finally, the song
    and sample data. Now, if you were to change all the 0's in the name to
    a set variable, or just to random numbers, then the module ripper
    would not be able to pick it up because it could not find that final
    0. Ways around this are to edit the file in a binary editor such as
    DekSID, but you have to know what you are looking for first. The
    sample names are usually kept in, although these can be changed to
    disguise the module a bit too.

        Another good way, is to store the song and the samples at
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    different parts of the program. Then, when the program is run, the 2
    parts are pasted together as one in order to play. This is a method
    that I use, and is fairly effective, as you will only be able to rip
    the song information, without any samples.

        Sometimes, however, modules just cannot be ripped cleanly.
    Sometimes you can rip the song with no problems, but you will have to
    put the samples in the right place yourselves using a program such as
    Protracker. The samples are often corrupted, but using a professional
    sample editor, you should still be able to remove the individual
    samples without too much hassle.

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                 WAYS OF DETECTING A MOD WITHOUT MULTIRIPPER
                 -------------------------------------------

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        Now, although Multiripper is very good at ripping modules, it can
    be very tiresome when it comes to loading in loads of files only to
    discover you cannot locate a module.

        Any kind of program which has a RAW sample player within it can be
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    used. I have a few small programs in the AMOS library which do the
    same job. The way it works is quite simple. You load in the file you
    wish to examine, and begin playing. If it is not a module, you will
    hear lots of mess in the background. If the program starts playing
    samples from the module you are looking for, such as drum beats,
    cymbals etc., then you are onto a roll. If the file only plays the one
    sample, the chances are that the file you are listening to is a raw
    sample anyway.

        You can then load the file into Multiripper and try and extract a
    module from it. Note that you cannot determine if a decruncher exists
    if you use the Directory Opus method.

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                 EXAMPLE MODULES TO TANTALIZE YOUR TITBITS !!
                 --------------------------------------------

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        Well, here it is. Some examples from the hundreds of games that I
    have managed to rip tunes from. I have just put the basic instructions
    for use in Multiripper, plus any other instructions that you will need
    in external programs. Here goes :
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          NAME OF PROGRAM         METHOD OF EXTRACTION
      ----------------------|----------------------------------------------
           Budbrain 2 demo  |   Run the demo, and when the tune you want
                            |   begins to play, reset the computer and use
                            |   the HUNT command. The modules should
                            |   appear entact.
             Jaguar XJ 220  |   Again, wait till the tune appears and use
                            |   a standard HUNT command. All the CD tracks
                            |   are rippable in MR except the first.
                    Zool 2  |   RS data disk 1 into memory, and use a
                            |   standard HUNT command to locate the title
                            |   tune.
       Red Sector Megademo  |   Locate all the decruncher addresses using
                            |   one of the above-mentioned methods. Unpack
                            |   each file in turn, and use a HUNT command.
                            |   If HUNT fails, save the data file and use
                            |   ExoticRipper to locate old Soundtracker
                            |   modules. Not all decrunchers contain
                            |   modules.

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                Funny demo  |   Uncrunch the executable into memory, and
                            |   save the data file. Use DekSID to find a
                            |   sample named BELLS. Change the character
                            |   21 characters behind to an ASCII value
                            |   above 0, and re-write the file. You should
                            |   be able to rip an old ST module with
                            |   ExoticRipper. If there are no samples,
                            |   use a good sample editor to recover them
                            |   from the data file.

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        Well, that is about it. All the others are just the same, so there
    is no point in adding loads of the same kind of rip.

        It also brings us to the end of this tutorial. If you are still
    stuck on Multiripper, and need some advice, or perhaps a shareware
    copy of the program, then why not drop me a line. If you want a copy
    of the program, along with any other of the Shareware programs used,
    then send me a disk and a letter telling me what you want, and I will
    be happy to return it to you. If you are interested in AMOS
    programming, then also let me know. Fill the disk with some of your
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    programs so I can include them in the library. The address to send all
    your stuff to is :

ú
                          Andrew "Mushroom" Kellett
                                 Mushroom PD
                            32 Castleton Crescent
                                   Gamesley
                                   Glossop
                                  Derbyshire
                                   SK13 9TH
                                   ENGLAND


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        Several thanx must go out in this tutorial, the main going to
    Erland Simonsen, author of the amazing Multiripper. Here is a list of
    all programs which you should have in your posession in order to rip
    modules on a high basis :



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                          MultiRipper V3 (Shareware)
                           ExoticRipper (Shareware)
                              DekSID (Shareware)
                                Directory Opus
                         PRO Sample Player (Freeware)
                            Noiseplayer (Freeware)
                             Smartplay (Freeware)

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        I have several other tutorials available. These include routines
    for AMOS and AMOSPro, and consist of Graphic equalizers, and how to
    make tracker demos, as well as being able to recognize tracker modules
    from within AMOS. If you want any of these, then please ensure that
    you enclose a disk for me to include them on.

        So, until we happen to meet again, it is goodbye from me, and
    goodbye from Millie.

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    [Andrew "Mushroom" Kellett]

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EOF