RxFax, SIP, Asterisk 1.2.x - native format has changed

Asterisk Asterisk Support
1

I’m trying to make RxFax work with 1.2.1. App_nv_faxdetect detects the fax but RxFax generates the following NOTICE message:

Dec  8 18:51:48 NOTICE[28620]: channel.c:1903 ast_read: Dropping incompatible voice frame on SIP/2504833657-999c of format slin since our native format has changed to ulaw

Here is the full trace

  == Spawn extension (incoming-2504798646, h, 1) exited non-zero on 'Local/s@incoming-2504798646-f0b6,2'
    -- Executing Answer("SIP/2504833657-999c", "") in new stack
    -- Executing NoOp("SIP/2504833657-999c", "incoming extensions 8646") in new stack
    -- Executing PlayTones("SIP/2504833657-999c", "ring") in new stack
    -- Executing NVFaxDetect("SIP/2504833657-999c", "10|dt") in new stack
Dec  8 18:51:48 NOTICE[28620]: app_nv_faxdetect.c:224 nv_detectfax_exec: Redirecting SIP/2504833657-999c to fax extension
    -- Executing NoOp("SIP/2504833657-999c", "Receiving Fax") in new stack
    -- Executing StopPlayTones("SIP/2504833657-999c", "") in new stack
    -- Executing Set("SIP/2504833657-999c", "TIMEOUT(absolute)=35") in new stack
    -- Channel will hangup at 2005-12-09 02:52:23 UTC.
    -- Executing Set("SIP/2504833657-999c", "FAXFILE=/tmp/test.tif") in new stack
    -- Executing RxFAX("SIP/2504833657-999c", "/tmp/test.tif||debug") in new stack
Dec  8 18:51:48 NOTICE[28620]: channel.c:1903 ast_read: Dropping incompatible voice frame on SIP/2504833657-999c of format slin since our native format has changed to ulaw

Any hints on what to do?

Rob