Voice transmission

suga.masanobu · External Since: Aug 08, 2007 Posts: 3

Hi,

I need to make project, generaly based on voice/sound transmition. I
have two intercoms that can connect with each other. After connection
is established two people should be albe to speak with each other
(something like phone call). All this using C, linux, LAN voip, g711
coding, rs485. Any ideas where can I find any materials that could
help me with my work? I'll be very grateful for any kind of help.

As far as I manage to look around on internet I found OSS (Open Sound
System). Is it good idea to go deeper in this thema?

Thanks in advice,
Suga

Jan Panteltje · External Since: Jun 03, 2004 Posts: 308

On a sunny day (Wed, 08 Aug 2007 07:04:25 -0700) it happened
suga.masanobu DeleteThis @gmail.com wrote in
<1186581865.830693.293310 DeleteThis @r34g2000hsd.googlegroups.com>:

>Hi,
>
>I need to make project, generaly based on voice/sound transmition. I
>have two intercoms that can connect with each other. After connection
>is established two people should be albe to speak with each other
>(something like phone call). All this using C, linux, LAN voip, g711
>coding, rs485. Any ideas where can I find any materials that could
>help me with my work? I'll be very grateful for any kind of help.
>
>As far as I manage to look around on internet I found OSS (Open Sound
>System). Is it good idea to go deeper in this thema?
>
>Thanks in advice,
>Suga

OK, lets see, maybe we need no C.
We need on each side: soundcard, netcat, sox, lame, mpg123.

# Listening part (start first):
netcat -l -p 1234 | mpg123 /dev/stdin &
# That reads port 1234 TCP and decodes as mp3

# Transmitting part:
rec -d /dev/dsp -r 44100 -c 1 -s w -t raw - | lame -r -s 44.1 -m m -x - - | netcat -w 100 HOSTNAME 1234 &
# That takes the sound from the soundcard, codes it to mp3 with lame, and sends it to HOSTNAME.

Something like that, have not tested this, and you need it 2x, can be simple script.
Probably can be done even simpler.

Wolfgang Draxinger · External Since: Jun 01, 2004 Posts: 101

suga.masanobu DeleteThis @gmail.com wrote:

> As far as I manage to look around on internet I found OSS (Open
> Sound System). Is it good idea to go deeper in this thema?

So your question is, how to access the soundcard under Linux?

Well, googling "Linux Sound" should have brought you
http://www.alsa-project.org which is THE ONE sound API of Linux
you want really to use.

OSS is an obsolete API, which is nowadays being emulated by ALSA.
But using ALSA natively is the far better choice.

Wolfgang Draxinger
--
E-Mail address works, Jabber: hexarith DeleteThis @jabber.org, ICQ: 134682867

suga.masanobu · External Since: Aug 08, 2007 Posts: 3

On 8 Sie, 17:16, Wolfgang Draxinger <wdraxin....TakeThisOut@darkstargames.de>
wrote:
> OSS is an obsolete API, which is nowadays being emulated by ALSA.
> But using ALSA natively is the far better choice.

I underestimated ALSA as I read somewhere that it's worse choice than
OSS. I'll have to look on it more closely.

Thank you for tip.

suga.masanobu · External Since: Aug 08, 2007 Posts: 3

On 8 Sie, 16:49, Jan Panteltje <pNaonStpealm... RemoveThis @yahoo.com> wrote:
> OK, lets see, maybe we need no C.
> We need on each side: soundcard, netcat, sox, lame, mpg123.

As I answered you private by mistake, I'll try to reconstruct what I
mean there so everyone can see what I didn't mention earlier.

I forgot to say that the destination of this project is to use more
than 2 intercoms. The main one (let's say server) should be able to
answer calls from exact client, call to exact client etc. That's why I
said I need it to be written in C, as I have to build some kind of GUI
for it.

Again thank you for your answer and idea.