De-Emphasis

De-Emphasis

JB's DeEmphasis was created because HDSDR still lacks a deemphasis function for FM
It works best with Virtual Audio Cable (VAC) or similar.

Setup:

Set HDSDR Output Soundcard to VAC Line-2

usually you already have done that in order to feed RDSspy

Set DeEmphasis Audio-Input to VAC Line-2

Set DeEmphasis Audio-Output to Microsoft Soundmapper

check Running

Adjust the deemphasis time-constant to 50 or 75 µsec (US / Europe)
You can also set it to max. 400 µsec to reduce annoying hiss with signals near the noise floor, that you encounter during F2-DX, or 2-way communications.

Audio-Delay time:
An additional audio output delay can be set, that comes in handy when comparing the audio with a web-streamed audio. Typically the stream-audio arrives delayed, so comparing gets a bit tough.

Setting the delay time:

set volume levels so that radio-audio is a bit louder than the web-stream

wait for a specific key (a special word or syllable) in the radio-audio

Ctrl-click and keep button S pressed

the radio audio mutes, you now only hear the stream-audio

release button S when hearing the same audio-key again

the radio-audio un-mutes and you will hear both audios with little or no delay

Reset the audio delay to 0 by a brief click on button S

The maximal delay is 9 seconds.

Minimizing this program reduces it to an icon in the system tray.

Starting the program with commandline parameter Minmize will put it right away in the system tray.

This program can he downloaded here
Unzip in a folder of your choice.

How to Unblock the .CHM Help File
If you press F1 or open the Help file and the right pane is empty or shows a warning message,
then do this:

Right-click on the .CHM file in Windows Explorer

select Properties.

On the General tab of the Properties dialog, click Unblock, then click OK.

Example: Using audio-delay:
In this clip I am listening to 30.335 MHz Executiva FM (97.1) Salgueiro, Pernambuco in Brazil.
It's usually very weak and sits mostly in the noise floor.
Radio-audio and stream-audio are set to the same volume level.
Delay is set to 5.1 seconds, that causes an echo when the stream is also audible.

The clip start with the radio audio, a bit later the stream gets added, at the end you hear the stream alone.

The result is remarkable, you immediately hear that both are identical, even when the radio-audio is distorted and in the noise.
So, that's a fast and efficient method to verify whether you're hearing the right stream.

Tip: Sharing your found delay-time with others makes it easier for them when they try that specific stream for the first time.

© 3S design GmbH Zeiterfassungs-Systeme Zugangskontrolle-Systeme BDE-Systeme Ferienwohnung südliche Nordsee