Hi,

I am evaluating some GSM AMR codec, I needed the following details as
I am writing a wrapper for it.

#define GSM_PCM_SAMPLES_PER_FRAME	
#define GSM_SAMPLES_PER_FRAME		
#define GSM_SAMPLES_PER_SECOND
#define GSM_BYTES_PER_FRAME	
#define GSM_FRAMES_PER_SECOND

I am new to codecs and esp. to GSM AMR, it would help me if anyone can
explain what is the default bitrate, since its a multi bitrate codec(
4.75 to 12.2kbps)...I am not sure which I should be using...

I know that its a 20ms frame with 160 samples...

But I need to know things like:
1.PCM input sample size per frame for encoding
2. Output sample size of encoded GSM data
3. frame size 
4. No. of frames/second
5. No of bytes/frame..



It will help me if you guys can reply ASAP!!



-TIA

Have a look at the ETSI website www.etsi.org They have all the standards
concerning GSM
Wim

> I am evaluating some GSM AMR codec, I needed the following details as
> I am writing a wrapper for it.
>
> #define GSM_PCM_SAMPLES_PER_FRAME

160

> #define GSM_SAMPLES_PER_FRAME

160

> #define GSM_SAMPLES_PER_SECOND

8000


> #define GSM_BYTES_PER_FRAME

this is variable based on the output rate


> #define GSM_FRAMES_PER_SECOND


50


>
> I am new to codecs and esp. to GSM AMR, it would help me if anyone can
> explain what is the default bitrate, since its a multi bitrate codec(
> 4.75 to 12.2kbps)...I am not sure which I should be using...
>

There is no "default" bit rate. Appropriate bit-rate is selected based on
channel quality. Higher bit rates have higher speech quality, lower bit
rates have lower speech quality. What you should be using is totally
dependent on your application. If your application requires just a fixed
rate, don't bother using AMR. It was not developed for landline
applications. EFR may be better suited in such applications.



> I know that its a 20ms frame with 160 samples...
> But I need to know things like:
> 1.PCM input sample size per frame for encoding
> 2. Output sample size of encoded GSM data

This is variable. Take a look at tables in GSM 05.03 and GSM 06.90
(available from ETSI).


> 3. frame size
> 4. No. of frames/second
> 5. No of bytes/frame..

See above.

> It will help me if you guys can reply ASAP!!

I am not sure if you realize that "ASAP" is considered offensive in many
places. People are less likely to respond (forget ASAP) to your questions if
you use words like this. I would recommend not using it in future postings.