[Icecast] Low-bitrate audio encode/stream application

[david feldman]

Hello Thomas,

You are correct - the application is basically for secure remote access to 
ham CW (morse code) station. I believe the solution will be based on low bit 
rate MP3 streaming for receiver side (MP3 allows use with existing CODEC in 
client side, which could include Win CE or Linux palmtop type form factor, 
and the audio source would just be "voice grade" material on a mono, not 
stereo, connection). I am investigating options to build small 
morse-to-IRDA/Serial encoder that would accept key/paddle input, encode and 
timestamp into serial message format, and be transmitted back to server 
using the client machine's serial/IRDA port and then through telnet or 
similar text-oriented session to the server. This seems to hold promise in 
that it would require very little or no client side software development 
(I'm hoping to do this with a HP Jornada 720 windows CE client, which is 
about 5 years old, out of production, so other CODEC development seems very 
unlikely.)

Do you know if any books have been published that address icecast? It 
appears from reading traffic on this reflector that a single (mono) 22000 
bps encoding rate carried over a 32000 bps is feasible, and while this would 
be a bit much for dial-up serial access, it would be adequate for any 
broadband client connection.

73 Dave WB0GAZ wb0gaz at hotmail.com

>From: "Thomas B. R?cker" 	<dm8tbr at afthd.tu-darmstadt.de>
>Subject: Re: [Icecast] Low-bitrate audio encode/stream application
>To: david feldman <wb0gaz at hotmail.com>, icecast at xiph.org
>Message-ID: <41CB4DD3.6020602 at afthd.tu-darmstadt.de>
>Content-Type: text/plain; charset=ISO-8859-15; format=flowed
>
>Hi David,
>
>trying to put pieces together...
>judging by your email-adress you must be an radio amateur.
>lets try an "educated guess" ;)
>
>hope you're not going to try running digimodes through that... ;)
>
>Short wave audio should be fine. I use darkice myself for exactly that
>purpose: remote RX at dl0td while travelling around europe.
>
>One thing you should remember is: there is a considerable delay you wont
>be able to reduce below a minimum (depending on network and client
>software). This makes tuning bit harder on ssb.
>
>Oh before i forget: there is a mediaplayer capable of streaming mp3 and
>ogg/vorbis for WinCE (HPC/PPC). I've been using it for quite some time
>before i switched towards embedded linux. It is a bit tricky to get it
>running (you have to prepare a special playlist file containing the
>stream adress in a weird char encoding)
>Hopefully this is fixed by now. would make it more useable. ;)
>you should be able to find it either at corecodec.com or while looking
>for pocket-divx (its an descendant of the abandoned pocket-divx
>sourcecode).
>
>bitrates can be pushed quite low while using ogg/vorbis. quality -1 at
>22kHz mono should already give you around 20kbit or so with drops to
>nearly zero when there is very low noise-level and no signal. A downside
>could be increased time-shift due to buffers filling up slowly.
>
>vy 73 es merry x-mas es happy nw yr de Thomas, dm8tbr