addd note on modem sound cards to README_fdmdv

git-svn-id: https://svn.code.sf.net/p/freetel/code@413 01035d8c-6547-0410-b346-abe4f91aad63

diff --git a/codec2-dev/README_fdmdv.txt b/codec2-dev/README_fdmdv.txt
index 8f121d5a2ef9885a506b7350b7f6981455d53e19..e67ce80d55fc21594f360e18767370c3d8761b30 100644 (file)
--- a/codec2-dev/README_fdmdv.txt
+++ b/codec2-dev/README_fdmdv.txt
@@ -47,6 +47,15 @@ $ cd src
     $ octave
     octave:1> fdmdv_ut
 
+5. NOTE: If you would like to play modem samples over the air please
+   convert the 8 kHz samples to 48 kHz.  Many PC sound cards have
+   wildly inaccurate sample clock rates when set to 8 kHz, but seem to
+   perform OK when set for 48 kHz.  If playing and recording files you
+   can use the sox utility:
+
+   $ sox -r 8000 -s -2 modem_sample_8kHz.raw -r 48000 modem_sample_48kHz.wav
+
+
 References
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