Kicking the tires: CODEC2

Using CODEC2 source from https://github.com/freedv/codec2

[ For more about CODEC2, start with https://en.wikipedia.org/wiki/Codec_2 and https://www.tapr.org/pdf/DCC2011-Codec2-VK5DGR.pdf ]

Here's how I took a test audio file (from the N6NFI repeater 9am talk net) (8000 samples per second), encoded it with CODEC2 at various bitrate configs, and decoded them again.

The CODEC2 c2enc and c2dec commands use PCM (1 channel, 8000 rate, s16le format) as input and output. So I had to first convert the sample qso.ogg file into qso.pcm.

Then so you can hear the results, I converted the final decodes back into .ogg files that many browsers can play.

  # Input is in qso.ogg.  Convert it into raw PCM qso.pcm.
$ mplayer -ao pcm:nowaveheader:file=qso.pcm -format s16le  qso.ogg
[AO PCM] File: qso2.pcm (RAW PCM)
PCM: Samplerate: 8000Hz Channels: Mono Format s16le
[AO PCM] Info: Faster dumping is achieved with -benchmark -vc null -vo null -ao pcm:fast
[AO PCM] Info: To write WAVE files use -ao pcm:waveheader (default).
AO: [pcm] 8000Hz 1ch s16le (2 bytes per sample)
Video: no video
Starting playback...
A: 567.8 (09:27.8) of 567.8 (09:27.7)  0.0%

  # You can play the PCM file with the paplay command:
$ paplay --rate=8000 --channels=1 --format=s16le --raw  qso.pcm

  # Encode at various bitrates.
$ ( set -x ; for x in 3200 2400 1600 1400 1300 1200 700 700B; do time c2enc $x qso.pcm qso.codec2-$x ; done )

  # Then decode.
$ ( set -x ; for x in 3200 2400 1600 1400 1300 1200 700 700B; do time c2dec $x qso.codec2-$x qso.out-$x.pcm ; done )

$ paplay --rate=8000 --channels=1 --format=s16le --raw  qso.out-3200
$ paplay --rate=8000 --channels=1 --format=s16le --raw  qso.out-700

  # Convert the output PCM files to OGG.
$ (set -x ; for x in qso.out-*.pcm ; do oggenc --raw --raw-bit=16 --raw-chan=1 --raw-rate=8000 --raw-endianness=0   -o $x.ogg $x ; done )


$ ls -ls qso.*

1000 -rw-r--r-- 1 strick eng 1023205 Mar 21 23:28 qso.ogg
8872 -rw-r--r-- 1 strick eng 9084928 Mar 21 23:29 qso.pcm

  84 -rw-r--r-- 1 strick eng   85170 Mar 21 23:32 qso.codec2-1200
 100 -rw-r--r-- 1 strick eng   99365 Mar 21 23:31 qso.codec2-1300
 100 -rw-r--r-- 1 strick eng   99365 Mar 21 23:31 qso.codec2-1400
 112 -rw-r--r-- 1 strick eng  113560 Mar 21 23:31 qso.codec2-1600
 168 -rw-r--r-- 1 strick eng  170340 Mar 21 23:31 qso.codec2-2400
 224 -rw-r--r-- 1 strick eng  227120 Mar 21 23:31 qso.codec2-3200
  56 -rw-r--r-- 1 strick eng   56780 Mar 21 23:32 qso.codec2-700
  56 -rw-r--r-- 1 strick eng   56780 Mar 21 23:32 qso.codec2-700B

8872 -rw-r--r-- 1 strick eng 9084800 Mar 21 23:33 qso.out-1200.pcm
8872 -rw-r--r-- 1 strick eng 9084800 Mar 21 23:32 qso.out-1300.pcm
8872 -rw-r--r-- 1 strick eng 9084800 Mar 21 23:32 qso.out-1400.pcm
8872 -rw-r--r-- 1 strick eng 9084800 Mar 21 23:32 qso.out-1600.pcm
8872 -rw-r--r-- 1 strick eng 9084800 Mar 21 23:32 qso.out-2400.pcm
8872 -rw-r--r-- 1 strick eng 9084800 Mar 21 23:32 qso.out-3200.pcm
8872 -rw-r--r-- 1 strick eng 9084800 Mar 21 23:33 qso.out-700.pcm
8876 -rw-r--r-- 1 strick eng 9084800 Mar 21 23:33 qso.out-700B.pcm

1488 -rw-r--r-- 1 strick eng 1522743 Mar 22 00:21 qso.out-1200.pcm.ogg
1472 -rw-r--r-- 1 strick eng 1507117 Mar 22 00:21 qso.out-1300.pcm.ogg
1476 -rw-r--r-- 1 strick eng 1510418 Mar 22 00:21 qso.out-1400.pcm.ogg
1476 -rw-r--r-- 1 strick eng 1507987 Mar 22 00:21 qso.out-1600.pcm.ogg
1476 -rw-r--r-- 1 strick eng 1508638 Mar 22 00:21 qso.out-2400.pcm.ogg
1456 -rw-r--r-- 1 strick eng 1490898 Mar 22 00:21 qso.out-3200.pcm.ogg
1412 -rw-r--r-- 1 strick eng 1442390 Mar 22 00:21 qso.out-700B.pcm.ogg
1344 -rw-r--r-- 1 strick eng 1375254 Mar 22 00:21 qso.out-700.pcm.ogg

If you use Chrome, Firefox, or Opera, you should be able to listen to the *.ogg files. In Crome, if you click on the .ogg file and it downloads, then right-click the download and select 'Open'.

Input:

qso.ogg

Encoded-then-decoded Outputs:

Input to encoder (converted to PCM from qso.ogg):