Voice receiver

[derek]

Hi,

I want to make an electronic device which receives voice data over
ethernet in real time and then output to a loudspeaker. The sound is
mono and the sampling rate is 8K bytes per second. The voice data is
encoded as MP3 format to decrease the data size.

I want to ask whether there exists something I need to pay attention if
I used MCU to do that. I just have experience to implement ethernet
product and TCP/IP protocol stack.

Thanks!

 

[James Meyer]

On 27 Dec 2004 17:34:30 -0800, "derek" <dereklai2k@yahoo.com.hk> wroth:

Hi,

I want to make an electronic device which receives voice data over
ethernet in real time and then output to a loudspeaker. The sound is
mono and the sampling rate is 8K bytes per second. The voice data is
encoded as MP3 format to decrease the data size.

I want to ask whether there exists something I need to pay attention if
I used MCU to do that. I just have experience to implement ethernet
product and TCP/IP protocol stack.

Thanks!

Ethernet is not a "deterministic" transmission medium. You can assume
that all the data you transmit over ethernet will eventually get to its
destination, but you can't assume how long it will take.

I would design in a buffer area at the receiver so that the data can be
transmitted a little faster than your 8K BPS and then clocked out to the decoder
at a steady rate. Otherwise you may get a lot of "jitter" in the data rate.

Jim

 

[derek]

Actually the ethernet is used in LAN but not internet. So I think the
delay is small.

And today I have done an experiment to see whether my old device can
afford how much data rate locing. I find that it is only about 8bps. I
think this number is quite marginal. I will locate which is the
bottleneck and fine tunes the device. The MCU is just 8 bits.