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Author Topic: Creating CW MP3 Files?  (Read 1125 times)
N0JZQ
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« on: January 14, 2003, 05:32:27 PM »

Howdy,

Does anyone have any experience creating CW MP3 files? I would like to be able to create MP3 practice files for use in my portable MP3 player. If you know of any software or can give any guidance I would appreciate the help. Thanks in advance.

Scott
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K1ZC
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« Reply #1 on: January 14, 2003, 06:51:13 PM »

Scott,

This is fairly easy to do.  NuMorse Pro lets you use any standard text file as input, and you can output the sound to a WAV file on your PC.  If you have some other software that can read a text file and output CW, you can use "Sound Recorder" which is a standard component on Windows based systems to create the WAV files.

From there, take any good CD burning software (I use Roxio CD-Creator) to burn the disk.  Most importantly, know that different CD players, especially the older ones like in some cars, cannot read all formats.  The Roxio web site has a lot of information on which formats to use.
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N0PP
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« Reply #2 on: January 14, 2003, 08:45:29 PM »

There are normally two steps involved to do this:
 
1. create a WAV file
2. encode the WAV file into an MP3 file

Many PC-based morse code programs will be able to produce WAV files.

MP3 encoders are readily available. "lame" (http://lame.sourceforge.net/) and "blade" (http://bladeenc.mp3.no/) are two examples. But I am not sure if they are available for Microsoft Windows or Mac (I run Linux). If needed you will certainly find Windows or Mac-based MP3 encoders by doing a Google search.

There is one big problem: MP3 is a lossy compression scheme that is physiologically optimized (optimized for the average "human ear Bode plot", and for music). The developers of MP3 did not have Morse code in mind. The result depends on the MP3 encoder and player you are using, but because of the hard-keying and no-noise nature of the Morse code you may experience a lot of distortions (it sounds horrible and is pretty much useless).

The solution is to make the Morse-WAV file more real-world like. Means you may have to add some noise, and/or you may want to lowpass-filter the WAV file before encoding it into MP3. I used Matlab to add some noise, which solved the problem. Unfortunately I don't know about any freely available program that does this. Let me know if you find one. Of course you could also write your own program.

Another possibility would be to record code from the air, for example from the W1AW code practice runs, and then encode that into MP3.

BTW, ARRL has code-practice MP3 files on their webpage, see http://www.arrl.org/w1aw/morse.html
But these files also have the hard-keying / non-noise problem, means they will playback distorted on many players.
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N0JZQ
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« Reply #3 on: January 14, 2003, 11:15:57 PM »

Thanks K1ZC and N0PP. Good advice. It gives me something to work with. I won't be trying to do any programming myself. Took BASIC programming back in the 80's!

Scott N0JZQ
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KB9WQJ
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« Reply #4 on: January 15, 2003, 11:51:21 AM »

re: Hard keying distortion
Wow! I was wondering why the mp3's I downloaded from ARRL sounded like that...kind of a hollow, honking noise.  That explains it.  Thanks for some useful info.
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N0JZQ
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« Reply #5 on: January 15, 2003, 02:39:07 PM »

UPDATE:

With all the info I got from my posting, here is what I came up with and it works great.

I am now using NuMorse Pro. It will save practice files as wav files. I then convert the wav file to an MP3 file with software called Cool Edit. It reduces the size considerably of the wav file and it sounds just fine on my MP3 player. Thanks again for the response and advice.

Scott N0JZQ
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KF6UEB
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« Reply #6 on: January 15, 2003, 08:49:51 PM »

I assume that you want the MP3 files for code practice and not to prove/demonstrate sound file conversion capabilities.

While you could certainly create your own CW MP3, why not download and use the ARRL's MP3 code practice files? They are created in a variety of speeds and are of good quality.

The ARRL's MP3 files work best in Media Player. Here is the link:

http://www.arrl.org/w1aw/morse.html

73,

Rick KF6UEB

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N0JZQ
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« Reply #7 on: January 16, 2003, 08:24:48 PM »

Rick KF6UEB,

Thanks for the response.

I have used the ARRL MP3 files and they are very good. I just wanted variety in my practice and I found what I was looking for with the advice I was given in this post. Anything to keep the mind active!

By the way, I was stationed at Marine Corps Air Station El Toro from 1984 - 1988. I lived on the Marine Base in Tustin. I miss the area, not Los Angeles though! Used to ride my bike to El Toro from Tustin daily and back. Loved riding through the orange groves. I hear most of them are gone now.

Was hoping to see the 49ers and the Raiders in the Super Bowl!

73

Scott N0JZQ
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