El 29/12/17 a las 21:09, Kevin Otte escribió:
> I'd like to experiment with piping FreeDV over the network a la DMR and
> DSTAR reflectors. First step would seem to be how to extract those
> frames from what's coming over the air.
>
> My first testing attempt:
> kjotte@daedalus:~/svn/codec2-dev/build$ ./src/freedv_tx 2400B
> ../raw/hts1a.raw - | ./src/freedv_rx 2400B - /tmp/demod.craw --codecrx
>
> My understanding is that the result of this pipeline would be
> /tmp/demod.craw populated with the raw Codec2 1300 frames that were
> sent. Instead I'm getting the decoded 8KHz PCM.
>
> What have I missed?
Hi Kevin and all,
I've taken a look at this. To rephrase Kevin's question, in case it
wasn't clear:
Assume we have a recording of a FreeDV signal. Extract the
Codec2 frames using the command line tools.
I see no way of doing this with the current command line tools.
There is the undocumented "--codecrx" option in freedv_rx, but this
works as follows:
a) If --codecrx is not used, then freedv_rx uses freedv_rx() from the
API to demodulate the signal and decode the Codec2 frames to obtain
speech samples.
b) If --codecrx is used, then freedv_rx first uses freedv_codecrx() from
the API to demodulated the signal and obtain the Codec2 frames. Then, it
uses codec2_decode() to decode the frames and obtain speech samples.
Maybe there is some subtlety involved, but to me it seems that a) and b)
accomplish the same in different ways. So I don't see the purpose of the
"--codecrx" flag (other than to test the freedv_codecrx() function in
the API).
I have patched freedv_rx to do what Kevin wants (see the patch below):
make freedv_rx output codec2 frames when --codecrx is used.
I'm testing it as follows, and it works fine:
./freedv_tx 2400B ../../raw/hts1a.raw - | \
./freedv_rx 2400B - - --codecrx | \
./c2dec 1300 - - | \
play -t raw -r 8000 -e signed-integer -b 16 -c 1 -
(note that I'm including c2dec in the pipe).
73,
Dani.
---------
Index: src/freedv_rx.c
===================================================================
--- src/freedv_rx.c (revision 3386)
+++ src/freedv_rx.c (working copy)
@@ -205,10 +205,10 @@
unsigned char encoded[bytes_per_codec_frame * codec_frames];
/* Use the freedv_api to demodulate only */
- nout = freedv_codecrx(freedv, encoded, demod_in);
+ nout = freedv_codecrx(freedv, speech_out, demod_in);
/* deccode the speech ourself (or send it to elsewhere,
e.g. network) */
- if (nout) {
+/* if (nout) {
unsigned char *enc_frame = encoded;
short *speech_frame = speech_out;
@@ -220,11 +220,12 @@
nout += samples_per_frame;
}
}
+*/
}
nin = freedv_nin(freedv);
- fwrite(speech_out, sizeof(short), nout, fout);
+ fwrite(speech_out, use_codecrx ? sizeof(char) : sizeof(short),
nout, fout);
freedv_get_modem_stats(freedv, &sync, &snr_est);
freedv_get_modem_extended_stats(freedv,&stats);
total_bit_errors = freedv_get_total_bit_errors(freedv);
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