M-Back v0.80 help index
M-Back v0.81 help index

Thank you for using M-Back version 0.81 written by Alex Mayrhofer in 1995. Contact me for the latest version of M-Back or for any bug reports, suggestions or questions.

What's M-Back?

How to decode MPEG files

Playback and saving

How to register

How to get the latest version

Frequently asked questions

You may copy and freely use the unregistered version of M-Back if all the files are distributed together and if they are not modified.

M-Back comes without any warranty and is provided "as is". You are using and distributing it at your own risk.

Vienna, September 1st 1995


What's M-Back?

M-Back features full quality decoding of MPEG-audio layer I and II streams (an international standard for audio data compression, MPEG-audio is one of the most frequently used audio formats on the internet). After having decoded the stream, the resulting PCM-file can be played back through a standard 16bit soundcard or it can be saved as Windows PCM (*.wav) file.

M-Back is still under development! Upcoming versions will feature options to reduce decoding time, have support for 8-bit soundcards, have improved playback timing and (I hope) also decode layer III streams. Contact me to get the latest version.


How to decode MPEG files

When you start M-Back, "No MPEG file opened." will be displayed in the program's main window. To decode MPEG audio files, you will first have to open the file using the menu "File/Open". After having successully read the parameters from the stream, M-Back displays them in it's window. If you get an error message, the selected file is not a MPEG-audio stream, or the file is corrupt (Note that M-Back can only play back files which start with a syncword, streams which start somewhere else will not be accepted).

Now that you can see the parameters, it's time to start the decoding process using the menu item "File/Decode". The progress bar in the middle of the window indicates how far the stream is already decoded. Located under the progress bar, the "Stop-Button" allows you to cancel the decoding process. You will then be able to play and save the so far decoded part, but you will not be able to continue decoding from this position (You can, of course, decode the whole file again).

Related Topics:

Play and save


How to register your copy

If you are think M-Back is worth using it regularly, please do register your copy of M-Back. You will get the following benefits:

1. Unrestricted decoding and playback (decode files of any length)

2. The annoying "UNREGISTERED"-Dialog will not appear any more

3. You will be notified via eMail when new versions are out (if you have an Internet-eMail-address)

4. The registration number will be valid for future updates too, you will not have to re-register.

To register, send ATS 100,- (or US$ 10.- or DM 15.-, please no other currencies) together with your name, address and an self-addressed envelope to:

Alex Mayrhofer

"M-Back registration"

Kroellgasse 7/8

A-1150 Wien

Austria

You may also enclose your Internet eMail address to get the registration information faster (You will, however, receive it in written form, too). In this case, please state if you want to be notified of program updates via eMail (If you state nothing, you will NOT be notified).

Please consider the registration fee being a small donation for the dozens of days I have invested (and will invest) in writing M-Back.

Related Topics:

The registration dialog


The registration dialog

Here you can turn your unregistered copy of M-Back into a registered one by typing in your personal registration name and number. If you didn't register yet, please read how to register.

Type in your registration name into the upper Editfield, your registration number into the lower. Be sure to type them exactly as written in your registration form (Capitalization, no space between first name and surname). Press the "OK"-Button when you've finished. Your copy is now registered.

Related Topics:

How to register


Playing back and saving

Playing back:

Once you have a file (partly) decoded, you can listen to it be selecing the menu item "File/Play". The window will display "playing..." while playback is active. If playback fails, your soundcard does not support the format of the stream or 16bit PCM (M-Back requires an 16bit soundcard at the moment, future versions will also support 8bit).

Saving WAV-files:

You can save the decoded part ("File/Save WAV") in windows 16bit PCM format (*.wav). Please keep in mind that decoded files require lots of diskspace (at 44.1kHz stereo 16 bit: 10 megs per minute). After you have saved the sample to an WAV-file, you can play it back with an external utility (MediaPlayer or an waveform editor).

Related Topics:

How to decode files


Frequently Asked Questions

Q: Where can I get MPEG-audio-files?

A: The best source for MPEG-audio-files is the Internet. Check one of the search engines for "MPEG audio", surf trough the Internet Underground Music Archive (http://www.iuma.com) or have a look at my homepage (http://stud1.tuwien.ac.at/%7Ee9426164/index.html) where I try to collect nice MPEG-audio-places on the net.

Q: How can I encode my own MPEG-audio-files?

A: You can use AMPEG or CoolEdit with it's MPEG-filter. Both are available on the Internet for free or as shareware.

Q: M-Back does only decode the first 20 seconds. What's wrong?

A: This is the main restriction of the unregistered version. If you register M-Back, you will be able to decode files of any length (if you have enough diskspace...).

Q: Playback fails with my soundcard. How can I listen to the files?

A: M-Back supports only 16bit soundcards at the moment. It has been tested with the ProSonic16 and Soundblaster16. If you have only an 8 bit card, you can convert the saved WAV-files to 8 bit and/or lower sampling frequencies with your favourite waveform editor. The next version of M-Back will support 8 bit soundcards, too.

Q: M-Back does not accept my registration number. Why?

A: Be sure that you typed in your registration name and number exactly as written in the registration form. No spaces are allowed between first name and surname, and the capitalization must be exactly the same. M-Back will then accept your registration.

Q: Why is M-Back so slow?

A: You mean, why is XingPlayer faster, don't you? Well, M-Back decodes all channels, in full quality and to the full sampling frequency. So M-Back has to perform millions of multiplications and additions for every second of music, so it becomes a bit slow. In future versions, there will be options to reduce decoding time (e.g. decode to half sampling frequency, only one channel, ...).

Q: What's about Layer III streams?

A: Version 0.81 can open such streams and display it's parameters, but it does not support layer III decoding. The reason is that the coding scheme is much more complex than layer I or II, and I didn't have the time yet to write a fully working decoder. Perhaps future versions will decode them.


Contact me!

M-Back is still being under development. If you found any bugs, or you have an idea how to enhance M-Back, or you just have a question, please mail your feedback to the following address:

eMail:

e9426164@student.tuwien.ac.at

For the latest version of M-Back (M-Back is updated nearly every month), have a look at the "Software Library"-page of my WorldWideWeb-site. If you have a registration number, it will also work with updates of M-Back:

My homepage in the World Wide Web:

http://stud1.tuwien.ac.at/%7Ee9426164/index.html

My "real" address (please ONLY if you have no access to the Internet):

snail mail:

Alex Mayrhofer

Kroellgasse 7/8

A-1150 Wien

Austria