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Digital Speech Decoder (software package)


Contents

Overview

Digital Speech Decoder is an open source software package that decodes several digital speech formats. It uses the mbelib library (a separate open source package) to synthesize the decoded digital speech. It does not allow decoding of encrypted communications. It can save the compressed digital audio bits to "mbe" data files (.imb and .amb extensions) and play back those saved files. It's discussed in this forum.

The latest version (1.6) supports the following formats and modulation types:

  • P25 Phase 1
  • ProVoice EDACS Digital voice
  • X2-TDMA - Motorola public safety TDMA system with P25 style signaling (mostly based on DMR)
  • DMR/MOTOTRBO - Digital Mobile Radio standard
  • NXDN - 9600 baud (12.5 kHz) NEXEDGE and 4800 baud (6.25 kHz) NEXEDGE/IDAS
  • D-STAR - The Github version of dsd/mbelib can parse and play back D-STAR traffic.
  • C4FM modulation
  • GFSK modulation (including GMSK and other filtered 2/4 level FSK)
  • QPSK modulation (sometimes marketed as "LSM")

The following formats are currently under investigation or development:

  • P25 Phase 2 - standard not finalized yet, vocoder is supported by mbelib
  • OpenSky - four slot format vocoder may be supported by mbelib. Will not be supportable if it is determined that voice encryption is standard
  • Other formats will only be considered if high quality samples of the signals are made available for download by the developers. Samples must be from a discriminator tap, .wav format, 48000Hz, 16 bits per sample, mono.

DSD and mbelib should compile on Linux and *BSD operating systems. Any linux distribution should work as long as it has support for your audio devices. DSD version 1.3 and later requires mbelib 1.2 or later.

The forum for discussion of this package can be found here.

Copyright License

DSD and mbelib are both released under a BSD style copyright license. This means that as far as copyrights are concerned it can be freely copied and used, including for commercial products as long as the original copyright notice is included. (However, see important patent issues section below.)

Patent Issues with mbelib

While DSD was intended to be patent-free, mbelib describes functions that may be covered by one or more U.S. patents owned by DVSI Inc. The source code itself should not be infringing as it merely describes possible methods of implementation. Compiling or using mbelib may infringe on patents rights and/or require licensing. It is unknown if DVSI will sell licenses for software that uses mbelib. If you do not have a license and are in a jurisdiction protected by the DVSI patents you should not compile or use this source code.

Help Page for Windows

DSD For Windows Basic Setup - Easy Instructions Noobs Guide

Downloads

dsd-1.6.0

dsd-1.6.0 source download in zip format

mbelib-1.2.5

mbelib-1.2.5 source download in zip format

Windows Binary 1.4.1

Windows Binary

Windows Binary with P25/DMR Filter 1.5.1

Windows Binary

Windows Binary with P25/DMR Filter 1.6.0 Beta

Windows Binary

RTL-SDR.com instructions and download location for DSD+ 1.51 released October 1, 2014 (shows as 1.051 upon execution)

Be careful. Download site is rife with adware and false download links.


  • Note: You'll need cygwin1.dll for all but DSD+. Go to cygwin.com and install it.
  • Note: Cygwin 1.7.26 is broken (/dev/dsp audio device doesn't work)

Known Working Hardware Setups

If this list gets large enough I will move it to its own page so as not to detract from the overview of DSD.

Discriminator SourceInputInput Sound DeviceOutput Sound DeviceOperating System/ Linux FlavorComputer SpecsAudio Successfully Decoded
GRE PSR-500 Direct TapiMic mic portiMicOnboard audioUbuntu 10.04Dell Mini 1012 netbook N450(1.66GHz)ProVoice
TV28T v2 DVB-T USB Stick (R820T)What You HearSoundblaster Audigy (PCI)Onboard AudioWindows XP ProIntel DG41TY mobo w/ Intel Core2 Quad CPU Q9400 (2.66GHz)P25 Phase 1, MotoTRBO
RadioShack Pro-97 Direct TapLine InRealtek HD AudioRealtek HD AudioUbuntu 10.04Acer Aspire One Netbook D150 (1.7 GHz)P25 Phase I
RadioShack Pro-95 Direct Tap w/10k ResistorLine IniMic & Realtek HD AudioiMic & Realtek HD AudioUbuntu 10.04Custom Built/ Gigabyte MotherboardP25 Phase I, Provoice
RadioShack Pro-95 Disc TapLine inG110 KeyboardG110 KeyboardWindows 7EVGA x58/i7 920Provoice
RadioShack Pro-94 Direct TapLine InRealtek HD AudioRealtek HD AudioUbuntu 10.04Custom Built/ Gigabyte MotherboardP25 Phase I
RadioShack Pro-90 Disc TapLine InAC97AC97Ubuntu 10.43 GHz 1.5MBP25 Phase I
RadioShack Pro-79 Direct TapLine InAnalog Devices ADI 198x Integrated Audio/SoundBlaster Live!32Analog Devices ADI 198x Integrated Audio/SoundBlaster Live!32Xubuntu 9.10/Ubuntu 10.04Dell GX270 (P4 2.6 GHz)/Lenovo Thinkpad X61 (Core 2 Duo)/Dell Precision 300 (P4 3.2 GHz)P25 Phase I, ProVoice, MotoTRBO
RadioShack Pro-2067 Direct TapLine InAnalog Devices ADI 198x Integrated AudioAnalog Devices ADI 198x Integrated AudioUbuntu 10.04Dell GX520 (2.8 GHz - 3.4 GHz)MotoTRBO, ProVoice
RadioShack Pro-433 Disc TapLine inIntel HD AudioIntel HD AudioUbuntu 11.04Dell Inspiron 1525 Core 2 DuoMotoTRBO
Icom IC-PCR1000 Packet out w/100k ohm resistor and 10uf capacitor built into cableLine InAC97Diamond XS71Ubuntu 10.04Amd Athlon 64 (1.8 GHz - 2.4 GHz)P25 Phase I, MotoTRBO
Icom IC-PCR1000 Packet outputLine InAC97Sound Blaster X-FiDebian LennyAthlon 64 3000+ (2.0 GHz)Provoice, MotoTRBO, P25 Phase I
Uniden BCT15XLine InAC97Sound Blaster X-Fi Debian LennyAthlon 64 3000+ (2.0 GHz)Provoice, MotoTRBO, P25 Phase I
Uniden BCT-15X Disc TapMic In (DC Bias removed)C-Media CM108 ($1.87 on eBay)C-Media CM108 ($1.87 on eBay)Windows 7 ProIBM x336 dual Xeon 3.0GHzProVoice, DMR, P25 Phase I
Uniden BCT-15 Disc TapMic inATISound MaxUbuntu 10.42.4 GHz Core 2 Duo 4.0MBP25 Phase I
Uniden BCT-8 Disc TapLine InRealtek HD AudioSound Blaster X-FiWindows 7i7-3960X 3.30GHzMotoTRBO
Uniden BC796D Disc TapLine inSound Blaster X-FiSound Blaster X-FiWindows 7HP Pavillion Elite, Intel i7 quad coreP25 Phase 1, ProVoice, MotoTRBO
Uniden BC350A Direct TapLine InRealTek HD AudioRealTek HD AudioUbuntu 10.04 32-bitAMD Turion 64 X2 (2.0 GHz)MotoTRBO, NXDN 4800
Uniden BC246T Disc Tap w/100k ohm resistor and 10uf capacitor built into cableLine InAC97AC97Ubuntu 10.04 on flash driveDell Dimension 2400 (2.4 GHz - 2.8 GHz)P25 Phase I
Uniden BC245xlt Direct TapiMic mic portiMicOnboard audioUbuntu 10.04Dell Mini 1012 netbook N450(1.66GHz)ProVoice
Uniden BC235xlt Direct TapiMic mic portiMicOnboard audioUbuntu 10.04Dell Mini 1012 netbook N450(1.66GHz)ProVoice
Yaesu ft857 packet socketLine Insnd_hda_intelsnd_usb_audioUbuntu 9.1 32bitAMD Athlon 64x2 8400+ (2.1 GHz)MotoTRBO
Yaesu FT8800 Disc TapLine InAC97AC97Debian (no GUI)1.7 GHz AthlonMotoTRBO, P25 Phase I
AOR AR-2515 Disc TapLine InAC97AC97Ubuntu 10.43 GHz 1.5MBP25 Phase I
Kenwood TH-F6A 9600 baud out w/100k ohm resistor and 10uf capacitor built into cableMic inAC97AC97Ubuntu 10.04Acer Aspire OneP25 Phase I, MotoTRBO
Uniden BCT15X Disc Tap 10k ohm resistor and 10uf capacitorLine InSoundMAX Integrated Digital HD AudioSoundMAX Integrated Digital HD AudioWindows 8 ProAthlon 64 6400+ (3.1 GHz)P25 Phase I NXDN 9600
Uniden BC346XT Disc Tap 10k ohm resistorLine InRealtek HD AudioRealtek HD AudioWindows 7 64Intel i5-2500 (3.3 GHz)Provoice, P25 Phase I, DMR
ICOM IC-7100 USB Sound output USB USB Audio Codec Realtek HD AudioWindows 7 32Intel P9700 (2.8 GHz) P25 Phase I, DMR
DVT-SDR with , Unitrunker 1.0.27.19,or SDR#USBVB Audio Virtual CableOnboard AudioWindows 8.1 ProMicrosoft Surface Pro (first gen). Intel i5.MotoTRBO, P25

Frequently Asked Questions

Q: Do I need a radio with discriminator tap?

A: Yes, if you want to listen live or save mbe data files. No radio or discriminator tap is required to play saved mbe data files.

Q: Where can I get information on the discriminator tap for my radio?

A: Wiki information is available here for the Discriminator_output.

Q: Will this work on Windows?

A: As of December 7, 2011 binaries for Windows have been added.

Q: Will this work on a Mac?

A: No, because OS X does not use the traditional Unix-like /dev/audio interface. It should be easy for someone familiar with Mac audio programming to port it to the Mac.

Q: Will you support decryption if I lawfully posess the encryption keys?

A: From the Readme file:

        Decryption of speech is NOT supported, even if you lawfully posess the
        encryption keys.  Decryption support will not be added in the future as
        the authors wish to steer as far away from the legal issues associated
        with encryption as possible.

Q: Who are the author(s)?'

A: The author(s) are anonymous but PGP keys are provided inside the packages so future releases/communications can be verified.


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