[sip-comm-dev] iLBC frame size


I'm a student developing a VOIP application for an undergraduate course.
I would like to know if ilbc included in sip-communicator can be used in
both 20ms/ 30ms frame size or only in 30ms.
As you can look below...


    public void open() throws ResourceUnavailableException
        int mode = Constants.ILBC_MODE;
        enc = new ilbc_encoder(mode);

        if(mode == 20)
            ILBC_NO_OF_BYTES = ilbc_constants.NO_OF_BYTES_20MS;
        else if(mode == 30)
            ILBC_NO_OF_BYTES = ilbc_constants.NO_OF_BYTES_30MS;

package net.java.sip.communicator.impl.media.codec;
public class Constants
    public static final String ALAW_RTP = "ALAW/rtp";
    public static final String SPEEX_RTP = "speex/rtp";
    public static final String SPEEX = "speex";
    public static final String ILBC_RTP = "ilbc/rtp";
    public static final String ILBC = "ilbc";

     * mode : Frame size for the encoding/decoding
     * 20 - 20 ms
     * 30 - 30 ms
    public static int ILBC_MODE = 30;

these are the only 2 places where ILBC_MODE is present.
there is no explicit method to change frame size to 20 ms.
I would like to know if this was done because 30ms has still not been
implemented properly or only because sip-comunicator uses only 30ms mode.
Can I freely chose 20ms in my programs?

Thankyou for your time and reply!

(Sorry if this question could be stupid ;))