[GreenKeys] Saving RTTY art as audio

[Bob Camp]

Hi

I got a chance to do a little Java research today. It is very possible 
to write a simple program to convert a five level "text" file to tones 
out of your computer's sound card. There is enough of a sound driver in 
standard Java run time environments to do what we would need to do. 
There are some sample sine wave tone generator programs out there on 
the net. The play a wave file approach would not be needed.

Of course I'm not a Java guy, but it certainly looks like you can do it.

	Take Care

		Bob Camp
		KB8TQ


On Feb 14, 2005, at 11:30 PM, David Ross wrote:

> greenkeyers -
>
> Bob Camp wrote:
>> If I have a four hour tape and save it as binary it takes up about 
>> 80K as straight file. If we zip the thing it will drop down to less 
>> than 30K since the mapping is not very dense. A few thousand tapes 
>> will take up 30 Megs on a web site. That's not to tough to find space 
>> for. Zip compression is not lossy you loose nothing in the process.
>> If you do a normal audio CD then the same four hours will soak up 640 
>> meg x 4 = 2.5 gigs. A reasonable compression probably drops that to 
>> 200 Megs. Since sound compression is lossy you don't want to crank it 
>> up to far. MP3's are designed so the compression artifacts are not 
>> audible to the human ear. The same may not be true of a TU ....
>> Run up as MP3's the thousand or so tapes would soak up 200 Gigs on 
>> the web server. That's quite a bit more storage than the zip files.
>> It would be more practical to set up a java app that would take the 
>> binary file and put out tones. That way you would have the best of 
>> both worlds.
>
>
>
> I have been playing with exactly this -  converting ASCII text files 
> to RTTY tones.  I run an ASCII text file through MMTTY to make Baudot 
> audio tones, capture the audio tones to disk as a .WAV file, then 
> convert the .WAV file to a .MP3 file using an .MP3 encoder.
>
>   Running at 60WPM, 46,238 bytes of ASCII text converts into 8,140,640 
> bytes of .MP3 audio, and that is done at 8Kbits/second -  every byte 
> of ASCII text converts to 176 bytes of .MP3 audio.
>   If the .WAV -> .MP3 conversion is done at 16Kbits/sec, then the file 
> size is 16,280,719 bytes.
>   All this for 2 hours and 15 minutes of 60WPM text -  not very 
> efficient as far as disk space goes...
>
>        46,238 bytes of .TXT files converts to
> 1,435,870,862 bytes of .WAV files (44.1 Ksample/sec, 16 bit stereo), or
>     8,140,640 bytes of .MP3 files (at 8Kbits/second)
>
>   The above conversions were made using 850 shift, but I would guess 
> that 170 shift would give the same results.
>
>   With my own conversions, I see no print errors at either 8Kbits/sec 
> or 16Kbits/sec.
>   Nor do I see any errors on George's Internet feed at 24Kbits/sec, 
> either [Winamp -> MMTTY] or [Winamp -> Dovetron -> Model 28].  
> However, George's 24Kbps feed causes consistent underflows here, given 
> a 26.4Kbit ISP connection.
>
>   Using MMTTY to convert ASCII text to Baudot tones is the time 
> bottleneck, being done in realtime as it is.
>   The conversion from .WAV file to .MP3 file is quite fast -  I use 
> the LAME 3.91 encoder -  free & reasonably fast, it runs in a DOS 
> window.
>
>   Is it really possible to do the text-to-tone conversion with a Java 
> application?
>
> Dave Ross    N7EPI
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