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  #1  
Old 2020-02-07, 12:34 AM
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The Validity of MD5 Checksums

this is an old article written by site founder RainDawg back in 2004, originally published in sharingthegroove.org technobabble then later on RainDawg's own website (now defunct). we still use md5 for video, but for audio we use st5/ffp for the last 15yrs or so.

In this thread find some lost pages from the past recovered via archive.org. enjoy.
-Five

Quote:
Originally Posted by RainDawg
The Validity of MD5 Checksums

Written By The RainDawg

I've heard several people voice a degree of skepticism as to how reliable the practice of using md5 checksums to validate files is. I mean, just how can a simple 32 digit number tell one file apart from the billions of billions of others on the internet? Well, for the more mathematically minded folks on here, check out this link for a quick description of the actual md5 algorithm:

RFC 1321 - The MD5 Message-Digest Algorithm

Incidentally, the output is actually a 128-bit number, though the output we generally see is encoded to hexadecimal. It is basically a random number ascribed to the particular combination of bits that comprise the file you are making a signature of. This signature is a single "word" that uses 16 characters (0-9 and a-f) and contains 32 places. Using that simple math you learned in high school, this means there are 16^32 combinations, or 3.403*10^38 possible md5 hash values.

Now, to give you an idea of the magnitude of this number, I just rambled off some simple calculations to give comparison. Scientists predict that the universe is 12-14 billion years old. Using the high end of that prediction as a baseline, it's easily calculated that the big bang occured on the order of 4.4*10^17 seconds ago. If you had a computer with the ability to randomly generate files and compute their checksum at 7.7*10^20 per second, it would have taken from the inception of the universe to the current time to randomly generate a file that matches a desired checksum.

Now, you've all verified checksums before, and just checking takes several seconds each, much less the random generation of a file of arbitrary size. Let's assume you had a trillion computers generating files since the beginning of time, you'd still have to have each one capable of randomly generating files at a rate of 770 million per second; impossible by even the most optimistic opinions of the limits of computing, now or in the future.

In fact, if I assume there are 1 trillion computers in the world and that there are 1 trillion files on each computer (both high estimates), there is still only a 1 in 340 trillion chance that there are two files that exist anywhere in the world that contain identical md5 hashes. And, of course, the chance of hitting on these odds is about the same as winning the pick 6 lottery....2 TIMES IN A ROW!

Now, these calculations do not take into account the fact that the file types would have to be compatible. The chance that two files return an identical md5 hash is so small as to be considered impossible. But even if they did, what are the chances that file would be a FLAC file, or even a valid file on a Windows system at all (or Mac, or Linux, or Atari 2600 for that matter). Even if the two files did match, they would be so markedly different that you'd know immediately upon attempting to open the file that wasn't a FLAC or SHN at all.

In conclusion, if you've read this far, this should prove to you more skeptical computers that it is simply impossible to a) create a file from it's md5 hash and b) to have a file pass the md5 hash and NOT be what you're expecting it to be.

Anyone who still doesn't think that md5 is a valid method of fingerprinting files must have a rather profound misunderstanding of the science of random numbers. I would have far more faith in the absurd tenants of tarot cards, the Bible Code, or even Hasidic numerology than to believe that the file I have is different than the one that created the md5 hash I'm verifying against....each of these "arts" has an infinitely higher chance of scoring a "hit".
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  #2  
Old 2020-02-07, 05:14 PM
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Re: The Validity of MD5 Checksums

another dated but useful article from 2004
Quote:
Originally Posted by RainDawg
FLAC Fingerprints

As an alternative to the wholefile md5 scheme required for .shn files, a newer format called the Free Lossless Audio Codec addressed this issue by making an md5 check of just the audio data contained within the file an inherent part of the file's structure. This elegant concept adds a short segment to the header of the FLAC file itself which contains an md5 of the original uncompressed PCM .wav data. This value is called the "fingerprint", a fitting title as it only validates the audio, not the extra data appended to the file. Using the FLAC fingerprint method, users could add or remove tags or change the compression setting and not change the actual audio contained within. Since the fingerprint only checks audio data, traders could change these values at will and they will still verify as identical to the original.

.flac gained rapid support of lossless traders over .shn for several other reasons. First, the filetype is both seekable and seamless, meaning no seek table data had to be appended to the file to use it in your favorite media player. It also contains a check during decoding that actually performs a check of the stored fingerprint value to what's actually inside the file, and if they don't match, the file will not decode. This double-checking ensures that files corrupted during transfer are unusable and therefore the error will not be passed on.

FLAC's use of the fingerprint allows users much more versatility while still maintaining the same core functionality : verifiying that the audio in your files has not altered since it was seeded. Of course, a user may still use wholefile md5 checks on .flac files if they see fit, but this is a practice performed out of ignorance rather than functionality. Using FLAC's fingerprinting is much more useful than wholefile md5 checking, and should be used 100% of the time.
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Quote:
Originally posted by oxymoron
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  #3  
Old 2020-02-07, 05:23 PM
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Re: The Validity of MD5 Checksums

FLAC Frontend FFP Tutorial, 2004
Quote:
Originally Posted by RainDawg
Creating a FLAC Fingerprint File with FLAC Frontend

FLAC fingerprints represent the most versatile form of lossless audio verification currently available. To better understand what a FLAC fingerprint is, read this. To proceed with a step-through for creating a FLAC fingerprint file (ffp) with FLAC Frontend, read on.

Note: Due to serious inadequacies in older versions of FLAC Frontend (mainly it it's handling of sector boundary correction), please make sure that you are using version 1.7.1 or later, downloadable here.

First, you'll need to have a complete set of properly named FLAC files. Open an explorer window and browse to the directory containing these files.

[image missing]

Open up a FLAC Frontend window. Drag the files from the explorer window into the FLAC frontend window.

[image missing]

Press the "Fingerprint" button, at which point a browse window will open. Direct this window to the same directory as the FLAC files are included. Note that this will output a .txt file which will contain the md5 fingerpring of just the raw audio data contained within the FLAC file. Name this file appropriately and press "OK".

[image missing]

A command line window will be opened by Frontend which will run the command necessary to grab the fingerprint data from the FLAC header and place it into a text file. After it has run, it will automatically close the command line window and the .ffp.txt file will apear in the original explorer window.

[image missing]

Open this file to see what the accepted format for a .ffp.txt file looks like. It should have written one line for each file contained within the folder you selected. If it doesn't, you didn't correctly add all of the files to the FLAC Frontend window and you should start over. If it does, you've successfully create a FLAC Fingerprint file.

[image missing]

Make sure to distribute this file with any sets that you trade or seed to an internet distribution site. This will help traders track and verify their files against the originals.
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Quote:
Originally posted by oxymoron
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  #4  
Old 2020-02-07, 05:30 PM
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Re: The Validity of MD5 Checksums

FLAC Frontend FFP Tutorial 2, 2004
Quote:
Originally Posted by RainDawg
Testing a set of FLAC files with FLAC Frontend

FLAC has the unique ability to store information about it's audio content within the header. The FLAC Fingerprint feature takes an md5 checksum of just the audio data contained within the file. FLAC stores this number inside the header of the file itself, and thus each file can be independantly "tested" to confirm that it has not been corrupted. When you "test" a FLAC file it will take the md5 checksum of the audio contained within the file, compare it to the result stored in the header (put there when the file was originally encoded) and return a pass/fail. This is a simple way to confirm that the file you have has not not corrupted. This is also useful when you've downloaded a file off the internet either with BitTorrent or any other transfer protocall. Run a quick test on your file; if it fails you did not complete the download correctly. If it passes, you're good to go.

Note: Due to serious inadequacies in older versions of FLAC Frontend (mainly it it's handling of sector boundary correction), please make sure that you are using version 1.7.1 or later, downloadable here.

Testing FLAC files is an incredibly easy process, but a necessary step in confirming files after a download has completed. To run a test, simply browse to a collection of FLAC files with a given folder.

[image missing]

Drag all of the files into the fresh FLAC Frontend window. Press the "Test" button located towards the bottom right. This will open a command prompt window and begin displaying the results as it checks each file. It will take several seconds to perform each check, depending on the length of the file.

[image missing]

When done, the window will pause so that you can review the results of each file's "test". Once you're satisfied that all files have been tested successfully, press any key to close the window. The ability to self-test is something that is incredibly easy yet extremely useful for lossless file trading. Always be sure to run a test of your files every time you transfer them off of a CD, DVD, through the internet, or between computers.

[image missing]
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Quote:
Originally posted by oxymoron
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  #5  
Old 2020-02-07, 06:04 PM
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Re: The Validity of MD5 Checksums

important early document about "shntool md5s" (now called .st5) from 2004. shntool like the engine inside Trader's Little Helper, and is even more powerful when run directly from the command console.

for clarity, I have changed each mention of "shntool md5" to "st5", and the outdated "md5" command to current "hash".

Quote:
Originally Posted by RainDawg
Using st5s

As opposed to traditional "wholefile md5" checks, the fantastic audio file utility shntool has the ability to create an md5 check of just the encoded PCM wav data contained within a given lossless file. st5 can perform an anlysis of virtually any lossless file type you have installed on your system. The clear advantage is that users can change from one format to another, add file tags, add or update seek tags, or any other number of things that perviously would have changed the wholefile md5 check. Yet using the st5, files with identical audio content will have the same checksum regardless of what extra, format changes, etc it has been through so long as the audio remains the same, the container can change at the will of any trader. Before proceeding with this tutorial, please ensure you have shntool installed. If you do not have it installed, please do; it's simply priceless software.

Indicendtally, the st5 of a FLAC file is identical to it's FLAC fingerprint, as both are checking for the same thing: pure audio content [the hash values are also identical, only formatting is different]. If you use the FLAC fingerprint (ffp) for FLAC seeds, st5 is redundant. [st5 is the best choice of the two, or both okay. md5 not necessary.]

The st5 function is most easily run with a DOS batch file to automate the command line switches. Create a new batch file with the following text. This will run and st5 check on every shn, flac, wav, or ape file within the folder and report the result to a file named st5.txt which will be placed in the same folder. Note that sometimes this can can be somewhat slow, epscially with ape files. To ensure that every file is checked, please wait until "Press Any Key To Continue" appears in the command line window running the script.

Code:
@echo off
%~d1 & cd %*
for %%T in (shn flac wav ape) do if exist *.%%T shntool hash *.%%T>>st5.txt
pause
Save and close the batch file. Now simply take any folder that contains any shn, flac, ape, or wav files that you'd like to check and drag it onto the batch file. A command line window will pop up yet remain blank during the time that it is testing and recording the st5. After completion, you can check the st5.txt file and/or rename it however you see fit.

Circulating an st5 with your original seeds will allow traders to track and confirm their source without being restricted to any given format to tagging scheme. It will allow traders to focus on the only important thing: the perfect duplication of audio content from trade to trade. Though shntool is somewhat tricky to setup, st5s are a big help to traders and always a welcome addition to any seed.
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Quote:
Originally posted by oxymoron
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  #6  
Old 2020-02-07, 06:09 PM
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Re: The Validity of MD5 Checksums

legacy software article, 2004
Quote:
Originally Posted by RainDawg
Creating a DOS batch file.

Many of us on a Windows PC today take for granted the ease of use which comes with a graphical user interface (GUI). This makes using programs easier, prettier, and more efficient. Yet before the creation of graphical interfaces, computers required the use of "command line" programming: simple text commands given to the operating system. There are many programs still in use today that are either exclusively command line applications or permit the use of command line options to increase the functionality. One such example is shntool, an incredibly powerful audio file application which I use quite frequently.

To automate the use of command line applications, something called a "batch file" was create to send a series of commands, one at a time, to a list of programs. For repetitive work, it can save quite a bit of typing. Batch files can also be used for any commonly used function, preventing the user from having to manually type it each time they wish to use it.

Creating a batch file is really quite simple. There are sections of this website that will refer to creating and using batch files, so I've setup this quick guide for creating and using one. This is not, however, a guide for coding a batch file. There is an enormous amount of information on this topic available on the internet and I'd prefer to not re-create the wheel.

To create a batch file, open Notepad. Click File > Save As. Browse to the directory you'd like to save the file in. In the "Save as type" input box, select the "All Files" option. Then type in a filename ending in .bat instead of .txt. This will identify it as a batch file. Once the file is save, add valid DOS batch file commands, save, and close the file when done.

[image missing]

Once the batch file has been completed, it can be run by double clicking. If the batch file requires another file or a folder as and input it can be triggered by dragging the file/folder onto the batch file in a Windows Explorer window. The batch file will run whatever commands you have programmed it to do and automatically display the necessary results.

[image missing]
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Quote:
Originally posted by oxymoron
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  #7  
Old 2020-02-07, 06:26 PM
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Re: The Validity of MD5 Checksums

command line software article, 2004.

latest version of shntool here:
http://shnutils.freeshell.org/shntool/


cygwin1.dll no longer required in 2020, everything else is the same.
Quote:
Originally Posted by RainDawg
shntool

Shntool is the ultimate audio file checking and simple conversion utility. The most commonly used feature is it's ability to check audio files of virtually any lossless format for sector boundary errors and, if necessary, fix those errors. Fluency in shntool should be a pre-requisite for anyone who wishes to do lossless audio file trading. Since it's a command-line only application, many users shy away from it's use out of sheer intimidation caused by a lack of a GUI. Allow me to dissuade you from feeling scared any longer....

The first step to using shntool is installing the program and the binaries for each file format you wish to use. This tutorial assumes you're using a Windows-32 based system, though many of the terms here carry over to the Mac OSX environment. If Linux is your OS of choice, I'll assume you're comfortable enough with the command line to not need this page at all. All of necessary program files and file format binaries can be found downloaded free of charge here. You'll want to place a copy of shntool.exe and each .exe codec you plan on using into your Windows PATH directory (on most systems, unless configured otherwise, this will be C:\Windows directory).

Note: In order to run shntool, you will need an updated copy of cygwin1.dll in your PATH as well. This comes packaged in the .zip file if you download shntool from the main www.etree.org page, but also can be obtained as the last item in the list linked above.

Once you've got all the files placed into the PATH directory, you're ready to go. It's that easy. You may want to read through the shntool documentation to get a firm grasp on the powerful utilities that lie at your fingertips, but if you're just interested in running a few simple commands, here's some quick guides that may help you out.
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Quote:
Originally posted by oxymoron
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  #8  
Old 2020-02-07, 06:38 PM
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Re: The Validity of MD5 Checksums

shntool tutorial, 2004. Trader's Little Helper also performs this function. FLAC Frontend can correct without preview using checkboxes.

we are still observing the rule of 588 sample sectors for cd compatibility into 2020, even though not so many people burn audio cdrs these days.
Quote:
Originally Posted by RainDawg
Checking for sector boundary errors and CD compatibility with shntool

It is good practice to only trade CD quality, sector aligned data files. To check a set of files for sector boundary errors (files that are not aligned to sector boundaries) and CD compliance, run then shntool -len command. Using command prompt, navigate to the the folder containing files that you would like to check and type "shntool len *.shn" to check all shn files in that directory. Of course, to check any other file types, substitute ape, flac, wav, or whatever lossless codec your files employ. shntool will then output a summary of qualities pertaining to each of the files checked. Before proceeding with this tutorial, please ensure you have shntool installed. If you do not have it installed, please do; it's simply priceless software.

This command is most easily run from a DOS batch file, and for the command line dummy, you'll want to do this right away. Open a Windows Explorer window and create a new file named shnlen.bat. Now right click on the file and select "edit" from the list; a blank window should open in Notepad. Copy and paste this text to the window:

Code:
@echo off
%~d1 & cd %*
for %%T in (shn flac wav ape) do if exist *.%%T shntool len -u mb *.%%T
pause
Save and close the batch file. Now simply take any folder that contains any shn, flac, ape, or wav files that you'd like to check and drag it onto the batch file. A command line window will pop up and show the results for each file within the folder:

[image missing]

In this particular case there are sector boundary errors on several of the files. You can notice that in the cdr column there is a 'b' noted for track 9 and 10. This set needs to be fixed to be properly sector aligned before burning this set to a CDR.

Here's a list, from the shntool documentation, of what each section's error code means (note that the "x" here is because of the fact the source files were compressed and not decoded PCM data...if this were a .wav file, this would have been a "-" as well):

'-' this particular entry is OK
'x' this particular entry is not applicable or cannot be determined

cdr column:
'c' data is not [C]D-quality
'b' CD-quality WAVE data is not cut on a sector [b]oundary
's' CD-quality WAVE data is too [s]hort to be burned

WAVE column:
'h' WAVE [h]eader is not canonical
'e' WAVE file contains [e]xtra chunks

problems column:
'3' file contains an ID[3]v2 tag
'i' WAVE header is [i]nconsistent about data size and/or file size
't' WAVE file seems to be [t]runcated
'j' WAVE file seems to have [j]unk appended to it

After using the shntool -fix command, the set becomes properly aligned to sector boundaries. Here's a plot from the same list of files after running shntool -fix on the set. Notice how the 'b' in the cdr column is now gone and no errors occur. This set is now suitable for seeding or burning to CDR.

[image missing]
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Quote:
Originally posted by oxymoron
Here you are in a place of permanent madness, be careful!
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  #9  
Old 2020-02-07, 07:06 PM
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Re: The Validity of MD5 Checksums

legacy software tutorial, 2004
Quote:
Originally Posted by RainDawg
Creating st5s on a Macintosh using xACT

As opposed to traditional "wholefile md5" checks, the fantastic audio file utility shntool has the ability to create an md5 check of just the encoded PCM wav data contained within a given lossless file. st5 can perform an anlysis of virtually any file lossless file type you have installed on your system. The clear advantage is that users can change from one format to another, add file tags, add or update seek tags, or any other number of things that perviously would have changed the wholefile md5 check. Yet using the st5, files with identical audio content will have the same checksum regardless of what extra, format changes, etc it has been through so long as the audio remains the same, the container can change at the will of any trader.

Indicendtally, the st5 of a FLAC file is identical to it's FLAC fingerprint, as both are checking for the same thing: pure audio content. If you use the FLAC fingerprint (ffp) for FLAC seeds, st5 is redundant.

The following tutorial was written by U2Lynne

1. Locate files on your computer.

[image missing]

2. Open xACT to the checksum tab and drag the files into the window.

[image missing]

3. Hit the Checksum button.

[image missing]

4. Hit the st5 button (verify is the default).

[image missing]

5. It prompts you to save it somewhere, find the same folder.

[image missing]

6. Name the st5 you are creating properly and hit Save.

[image missing]

7. It makes the st5s (it will take a couple of minutes).

[image missing]
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Quote:
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  #10  
Old 2020-02-07, 07:17 PM
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Re: The Validity of MD5 Checksums

video tutorial, 2004
Quote:
Originally Posted by RainDawg
Checking Video Statistics with GSpot

GSpot is a fantastic little utility for Windows systems which can take most common video formats and test all of the codec stats, including audio, video, length, etc. The latest version (still in Beta at the writing of this guide) can read MPEG formats. Since DVD employs the MPEG-2 video codec, this program is perfect for testing the stream info for your DVD-Video discs. To download the latest version, head to the GSpot 2.52 Download Page. Make sure to grab 2.52 or later, as 2.51 and previous versions did not work with MPEG files.

To use this program to check a single file, simply open GSpot and the open the file you wish to check. To find out the pertinent information on a DVD-Video disc, place the disc into your DVD-Drive and browse to the VIDEO_TS folder, which contains the .vob (authored MPEG-2) video files.

[image missing]

Open a new instance of GSpot. Drag the file named VTS_01_1.VOB info the GSpot window. This will scan the file and load all of the relevant stats. Some DVDs may have multiple "titles" included, in which there will also be a VTS_02_1.VOB, etc. In most cases, the statistics for these titles will be the same, though sometimes the codec/bitrates can be different. They will, however, always use the same video system. When seeding DVDs on the internet, the most pertinent stats are:
  • 1. Audio Codec
  • 2. Audio Bitrate in Kilobits per second (kb/s)
  • 3. Video System - The only way to tell this is to look at the framerate (frms/sec) of the video. 25.00 is used for PAL and 29.97 is used for NTSC.
  • 4. Video Bitrate in Kilobits per second (kbps)

[image missing]
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Quote:
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  #11  
Old 2020-02-07, 07:22 PM
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Re: The Validity of MD5 Checksums

legacy software tutorial, 2004
Quote:
Originally Posted by RainDawg
Creating a .torrent file with Azureus

Azureus is alltogether one of the most robust and visually appealing BitTorrent clients, but also provides remarkably simple wizard for creating a new .torrent file for seeding on any public tracker. Even better, this program will run equally as nicely on Windows, Macintosh, and Linux. I highly recommend that BitTorrent veterans and newbies alike give this client a try.

Before you start this step-through, you'll need to make sure every file in your torrent has ben saved and is not currently being used by your system. Any file changes after the creation of the .torrent file will cause all peers to be unable to properly finish the download from you. So finish editing and .txt or .nfo files, close your media players that may be using a files you're downloading, etc.

Once you're ready to go, open up Azureus. Click on "File" in the menu and select the "Create a Torrent" feature.

[image missing]

The first window is the wizard will ask you for four pieces of information.
1. First, you'll need to select the "Use an external tracker" opetion. Type in the announce URL for the tracker you wish to seed to. Azureus will save this URL so that future torrents to that tracker can be created more easily.
2. The second section asks you if you want to use multiple trackers or include md5 hashes for some other filesharing networks. Unless you know what these mean and have a specific use for doing such an action, I recommend that you uncheck these boxes.
3. I always seed a directory of files with an informational .txt file, but if you're just seeding one file, you can choose that option as well.
4. Comments are optional. Use them to make a short description of the contents of your seed.

[image missing]

Type in the directory you wish to create a .torrent file or use the "Browse..." button to pick from an explorer window.

[image missing]

Select a location and filename for the new .torrent file. It's best to allow Azureus to pick the best piece size but selecting "Auto" from the pull-down menu.

[image missing]

It will take a few seconds to create the md5 hashes for the files in your torrent, and may even take up to several minutes for "larger" torrents. Once it's done, simply take the created torrent file and upload it to the tracker you're seeding to in whatever manner specified by their admins.
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  #12  
Old 2020-02-07, 07:28 PM
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Re: The Validity of MD5 Checksums

legacy software tutorial, 2004
Quote:
Originally Posted by RainDawg
Winamp Configuration for Lossless File Types

The following tutorial was written by Five

www.winamp.com

[image missing]

I prefer v2.81, old versions are available from these sites:

http://www.winampheaven.net
http://www.oldversion.com

WINAMP SUPPORT FOR SHN - FLAC - APES

Shorten:
http://forums.winamp.com/showthread.php?t=257776

FLAC:
http://www.winamp.com/plugins/details.php?id=131643

FLAC frontend also comes with it as I recall:
http://flac.sourceforge.net/

Monkey's Audio:
You have to install the frontend then install the plugin, in your D:\Program Files\Monkey's Audio\MAC Winamp Plugin (PIMP).exe. You can copy this and uninstall the frontend afterward if you just want the winamp plugin.

http://www.monkeysaudio.com/

Or...

It asks whether to install the plugin when you install the program. That's the easiest way I guess. If you chose not to do it then you can also open up the program, go to the general settings and press the button there.

***Gapless playback!
Also very important is to configure WinAmp for gapless audio playback for a seamless listening experience. There's a couple ways to do this:

You do not need any external gapless plugins for Winamp. Just use the default directsound/waveout plugin, go to preferences/plugins/output/configure/buffering and set the 'buffer ahead on track change' to something like 1 or 2s. Also select the fading tab and disable all fades. There, completely gapless playback without any flashy external plugins.

The other alternative (you guessed it) is to use a gapless audio plugin:

I believe Shnamp 2.02 comes with this one:

http://www.winamp.com/plugins/details.php?id=24303

I use this one:

http://www.winamp.com/plugins/details.php?id=107818

To activate after installation, use <Ctrl+P>, then go to "Output", then select one of these two.

*thanks to Kotti for showing me how to configure WinAmp for gapless playback without plugins and pointing out that Monkey's Audio Frontend asks you if you want to install the WinAmp plugin when you first install it.
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  #13  
Old 2020-02-07, 07:59 PM
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Re: The Validity of MD5 Checksums

legacy Cool Edit Pro / Adobe Audition tutorial, 2004
Quote:
Originally Posted by RainDawg
Removing gaps between tracks on TAO CDs or CDs sourced from non-sector aligned WAV files.

Two of the more common problems that arise in CDR trading are Track-at-Once (TAO) burned discs and discs that are burned from WAV files that are not aligned to a proper sector boundary. Luckily, these two problems are fixed fairly easily using Cool Edit Pro and some of the fantastic features it has. I still use Cool Edit version 2.1, but I think the features are pretty much the same in it's new incarnation, Adobe Audition. There are several other programs that do this, but none quite as nicely as it's done here. Cool Edit is able to open a set of WAV files and piece them together into one long segment, allowing you to see exactly where a silence begins and ends. Second, Cool Edit has an auto-smoothing feature that will blend together two sections of audio that are joined together by the deletion of what's between them. This ensures that when you remove the silence the two portions around it flow smoothly; other programs without this ability can leave a small click at the junction.

First, and most importantly, make sure that auto-smoothing is enabled. Go to Options > Settings > Data. The default settings shown here should be sufficient for removing silence and smoothing the audio.

[image missing]

As the first step to removing the gaps, open an entire set of WAV files that are intended to flow together using the Open Append command. If you're unsure how to do this, there is a quick tutorial over here. Once you've got a whole set opened, the window will show the long WAV file with cue list data storing the track splits. Your silences will be near these points.

[image missing]

When zoomed all the way out, it doesn't look like there are gaps between the tracks, but when we zoom in a bit we'll start to see the offending silence. So, go ahead and go to the first cue point and begin zooming in on it. A tip for those of you with a wheel-mouse: place the cursor on top of the cue point and spin up to zoom in and spin down to zoom out. This is quite handy for big files like this. Note that in this example the silence falls all within a single track, but many times the silence will span two tracks and the cue list split will be in the middle. Just follow this example exactly the same, and the cue point will be moved to the audio just outside of the portion you delete so that the track split stays in the same place.

[image missing]

Now that we've zoomed in far enough to see the silence, we can go ahead and select it to remove it. Keep zooming in on one side of the gap until you can see the individual samples. Select the exact point and where the silence begins and drag over to create a selection.

[image missing]

Now zoom start zooming back out a few steps at a time, continuously stretching the selected region as you go.

[image missing]

Keep zooming out until you get to the other side of the gap. Now stretch the selection until it covers the entire gap PLUS a little bit more.

[image missing]

Now you can start zooming in on the end of the silence, slowly shrinking the selected area to get closer and closer to the end of the silence. Eventually, you'll be close enough to position the end of the selection to the exact sample where the silence end.

[image missing]

Now that we have the silence and ONLY the silence selected, go ahead and press the delete button. The entire silence will be deleted and the two sections of audio surrounding them automatically smoothed. Some other audio editing packages will not do this smoothing. Now, all you'll need to do is zoom back out and repeat this feature for every spot where there should be continuous audio that has been separated with silence. It can be somewhat time consuming, but it one of the simpler techniques in audio editing, and repairs a rather common problem.
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Quote:
Originally posted by oxymoron
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  #14  
Old 2020-02-07, 08:04 PM
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Re: The Validity of MD5 Checksums

legacy Cool Edit Pro / Adobe Audition tutorial, 2004
my personal opinion is to take this opinion with a grain of salt. I admit that some shows need help with this. my old ipod recordings needed this (poor a>d).
Quote:
Originally Posted by RainDawg
Correcting the DC Offset

A musical waveform, as with any other waveform, contains spectral components of varying frequencies. Part of this spectrum is known as the direct current component; basically a 0Hz signal. Ideally, there should be zero spectral activity as the signal approaches 0Hz, for several reasons, which are beyond the scope of this tutorial. Simply speaking, if there is a portion of the signal power contained at close to DC frequencies, it can adversely affect the sound quality of your recording and, at very high levels, can cause damage to your speakers or amplifiers. While it’s highly unlikely that you should worry about equipment damage, sound quality degradation as a result of DC offset problems is actually quite common, is very simple to fix, and can give your recording just a little more crispness and clarity. DC components as part of your musical waveform is often called an offset because it evidences itself as the overall waveform not being centered around 0 amplitude, but by either being above or below the horizontal axis in a simple waveform plot. If it is large enough, you will be able to observe an “offset” as the wav sits above or below the 0-amplitude centerline

Note: If you are going to be remastering a recording, DC offset correction should be the first step. Always apply this before any other steps, including fade-ins and fade-outs, as well as more complicated procedures.

The easiest and most effective way of correcting the DC offset is to use Cool Edit Pro. As with many of my tutorials, I recommend using the "Open Append" command and run the correction on an entire set all at once. This will ensure that each track is shifted together. Otherwise, it's possible that the shift will be greater on one track than on an adjacent one, and the resulting change in amplitude between the tracks may cause a small click to appear. To ensure your recording stays perfectly smooth between the tracks, and to save yourself time, apply the DC offset correction on the whole set. For a quick instructions on using Open Append, click here.

Note: Only apply this on recordings from a single source. If two separate sources with difference DC offset values are fixed at once, your correction will not be as effective and may actually be worse.

First, analyze the WAV to see if correction is necessary. There are two ways to do this:

1. Select the entire WAV (<Ctrl>+A), then go to Analyze > Statistics. Look at the value for "DC Offset". If it is not zero, this recording could benefit from dc offset correction.

[image missing]

[image missing]

2. If the DC offset is large enough, zooming in on a quiet portion of the audio will reveal that the DC offset is high enough to cause the waveform to ride above or below the red centerline.

[image missing]

If your recording needs to have the DC offset corrected, simply select the entire WAV (<Ctrl>+A). Go to Effects > Amplitude. A window will pop up with a set of preset templates to process the amplitude of your waveform. Select the "Center Wave" option, and press OK.

[image missing]

It's that simple. You can see that the wav is now centered about the red centerline. Compare the plot below to the one above, and notice the huge difference. Your ears will thank you.

[image missing]
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Quote:
Originally posted by oxymoron
Here you are in a place of permanent madness, be careful!
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  #15  
Old 2020-02-07, 08:05 PM
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Five Five is offline
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Re: The Validity of MD5 Checksums

legacy Cool Edit Pro / Adobe Audition tutorial, 2004
Quote:
Originally Posted by RainDawg
Opening a set of files using "Open Append"

The "Open Append" command is a remarkably useful tool for remastering a group of WAV files at once. This command will open a selection of WAV files, combine them together into one long track, and store cue data into the WAV file to remember where the original track splits were. I use this feature for many of my remastering examples because, generally, you want to apply the same effects to entire sets. It is also useful in making sure multiple tracks that flow together remain seamless; editing files one at a time can result in discrepancies between the amplitudes on the track splits, causing a click if these tracks are played together. Here's a quick tutorial for opening and exporting a set of WAV files.

Head to File > Open Append. Select all of the files you are going to be working on in the dialog box that opens. Before you press OK, make sure to go to the "File Name:" box and make sure everything is listed in the right order.

[image missing]

It will take a few minutes to open up all of the WAVs, but when it's done, you'll see one long waveform split apart by cue list data, with the original file names shown along the top. Below the waveform there should be a window in which this cue data is displayed. This will take a form of a list with each of the original file names and the start/end points of the sections they cover.

[image missing]

At this point, go ahead and perform whatever editing you wish to do to your set. When you're done, and ready to export the long track back to individual WAV files, go ahead to the rest of this tutorial.



Once you're done editing, go to the cue list info window, and select the entire list. Press the "Batch" button to bring up the output. First, select the "Use Cue Label as Filename Prefix" to have the output files named the same as your source files. Choose an output directory that is different to the location where the original WAVs are stored and select PCM from the "Output Format" dropdown menu.

[image missing]

Press OK and watch as Cool Edit writes your newly smoothed WAV files to the selected directory. Note that the output files will not be sector aligned. You will need to use shntool or FLAC Frontend version 1.7.1 or later to correct this before burning to CD or you will recreate the very problem you just fixed!
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