Tagged: digital speech decoder

DSD+ Version 1.5 Released

Note: This post is now old (written in 2014). As of mid 2015 the latest version of DSD+ can be downloaded from www.dsdplus.com. Also note that in 2015 DSD+ changed their version numbers for some reason, so 1.5 is actually older than 1.1.

Version 1.5 of Digital Speech Decoder Plus (DSD+) has been released. DSD+ is a popular Windows software tool used for decoding digital speech such as P25 with the RTL-SDR. The latest version comes with a simple GUI interface that has an event log that shows call target and source ID history and an audio waveform plot which can help determine if DSD+ is receiving audio correctly. This version of DSD+ has the ability to decode the following protocols.

  • D-STAR
  • NXDN4800
  • NXDN9600
  • DMR/MotoTRBO
  • P25 Phase 1
  • X2-TDMA
  • ProVoice

In addition to the above, the new version comes with an LRRP decoder and display program which should allow you to see on a map the GPS location of broadcasting radios.

DSD+ V1.51 can be downloaded from this link (UPDATE: dead link, use www.dsdplus.com now). The forum thread on RadioReference where the developer releases and discusses the DSD+ software can be found here.

This version of DSD+ comes with all the files needed to make it run already. To use DSD+ V1.5 simply extract the zip file into a folder and double click on DSDPlus.EXE. DSD+ will listen to your default audio device that is set in the Windows sound recording properties. Simply tune to a digital voice signal in SDR# or any other SDR receiver and set the output audio settings accordingly. To start the LRRP display program simply open LRRP.exe.

DSDPlusv1p5
DSD+ V1.5 GUI
DSD+ V1.5 LRRP GPS Display
DSD+ V1.5 LRRP GPS Display

Decoding NXDN using DSD+ and an RTL-SDR

Over on YouTube user John Miller has uploaded a video showing an example of DSD+ decoding an NXDN96 voice signal. NXDN is a digital voice protocol by developed by Kenwood that is often used by public safety organizations.

John uses SDR# to receive the NXDN signal and then pipes the audio to DSD+ using Virtual Audio Cable for decoding.

DSD+ Decoding NXDN

New SDR# Plugin: GUI Interface for DSD+

The developer over at rtl-sdr.ru has released a new plugin for SDR# (note in Russian – use Google translate) which allows the digital voice decoder DSD+ to be controlled via a GUI interface from SDR#. To use this plugin you will need to have a copy of DSD+ already downloaded as you will need to point the plugin to the DSD+ install directory. You will also need to have virtual audio cable software such as VAC or VBCable setup.

Information on downloading and setting up DSD+ can be found here.

DSD+ SDR# Plugin GUI
DSD+ SDR# Plugin GUI

RTL-SDR DSD Call Log Recorder

Programmer Tyler Watt has been working on software that automatically logs each call from an RTL-SDR running DSD (Digital Speech Decoder) and then stores it in a time stamped database as an mp3 file. There is also a web front end for the database which allows public users to search and play recorded calls.

Recently Tyler updated his code by rewriting it in PHP and making it multiplatform.

The old version of his web front end in action for his local P25 calls can be viewed here, and the newer one can be found here.

Improved Digital Voice P25 Decoding with DSD+

Update: This post is now very old. The latest version of DSD+ can now to found at www.dsdplus.com.

Over on Reddit we've seen mention of an upgraded Digital Speech Decoder (DSD) program, named DSD+. The original DSD is a program that can be used in conjuction with a SDR receiving program such as SDR#, and an audio piping program like VBCable to decode digital speech, such as P25 and DMR/MOTOTRBO.

DSD+ claims to have improved decoding and audio quality capabilities. An audio sample from a weak P25 sample can be found here for DSD+, and for comparison here for the old DSD.

DSD+ can be downloaded from this megaupload link.

To run DSD+. you will need to place an MP3 encoder file lame_enc.dll into the same folder as the dsd.exe executable. This file is not included with DSD+ due to licencing. For Windows, lame_enc.dll can be downloaded from http://lame1.buanzo.com.ar/#lamewindl (Mega Mirror). Download the ZIP option, and then copy the dll file into the same folder as DSD+.

If you don't know how to use DSD, see our tutorial on using DSD here, and if desired simply use DSD+ instead of the original DSD. (Note cygwin is not required for DSD+)

DSD+ Output
DSD+ Output

New DSD Block Available for GNU Radio

The popular digital speech decoder (DSD) software has now been wrapped into a GNU Radio Companion block. Previously, DSD required use of virtual audio cables to get decoding to work with GNU Radio, but now the signal audio can be passed directly into this block.

Luke Berndt from the HackRF-dev forums has posted his work to make the functionality of DSD available to GNU Radio users in the form of a GRC block. “I have been playing around a bit and found an easy way to receive and playback digital LMR. More and more of the radio systems are going from narrow band FM to Digital. This makes it tough to listen to them on GQRX. DSD is a great program which can decoded the audio you get when you tune in a system in GQRX, but you either have to run it on another machine with a audio cable in between or figure out how to do a virtual audio cable on your machine.

Luckily, someone wrapped the DSD libraries so they can be accessed as GRC blocks. I have put together a GRC file and a Python program that make it a little easier to use the block.

If you have a chance, give them a try and let me know if they work. There is a good chance I have messed up the values in the filters or else where, but I have gotten clean audio out of it.”

Download the files from GitHub.

DSD is a Linux and Windows software program capable of decoding popular digital speech codecs such as APCO P25 and MOTOTRBO/DMR.

Via DangerousPrototypes