Tuesday, February 17, 2015

Enhanced Audio On The Emacspeak Desktop

Enhanced Audio On The Emacspeak Desktop

1 Enhanced Audio On The Emacspeak Desktop

I recently added a set of modules to Emacspeak to leverage some of the high-end audio functionality available on Linux machines on modern hardware. As an example, applying effects such as 3D spatialization, high-end reverb effects etc. once consumed CPU cycles to the extent where it was not possible to play with these in realtime. All these now take less than 1–5% of the CPU, and that when my laptop is running in power-save mode!

1.1 An Audio Workbench Using SoX

Sound Exchange (SoX), described as the Swiss army knife of sound processing, has been around since the time I was a graduate student. Today it provides a versatile set of tools for editing and manipulating both wave and mp3 files. Module sox.el implements a simple Audio Workbench for the Emacspeak desktop.

1.1.1 Pre-Requisites

SoX with all available auxillary packages for adding support for various filetypes such as mp3. The various Ladspa related packages for installing additional audio effect filters.

1.1.2 Usage Instructions For SoX.el

  • Launch the Audio Workbench via by executing M-x sox.
  • Use f to open a wave or mp3 file you wish to manipulate.
  • Add any of the supported effects using e.
  • Use upper-case E to add more than one effect.
  • Hit p to play the result, s to save the result to a new file.

At present sox.el supports a few effects such as trim for clipping files, reverb for adding a reverb etc., with more to come as I use it.

1.2 Adding High-End Reverb When Playing Media Streams

I use mplayer to play both local and network media streams. MPlayer can apply a wide range of filters to the audio stream; more interestingly it can also apply effects implemented as Ladspa plugins. Package tap-plugins implements a large number of high-quality Ladspa filters, including a versatile Reverb filter.

Once you have package tap-plugins and its dependencies installed, and a relatively new version of MPlayer (with support for Ladspa plugins), you can now apply various Reverb Presets to your media streams via Emacspeak MPlayer command emacspeak-m-player-apply-reverb-preset bound to P in Emacspeak MPlayer. Package tap-plugins defines a total of 42 Reverb Presets, experiment with these when wearing headsets. Once you have applied a Reverb Preset, you can edit its current settings via command emacspeak-m-player-edit-reverb bound to R in Emacspeak MPlayer. Alternatively, you can pick a default effect to use via Emacs' custom interface; see option emacspeak-m-player-reverb-filter.

1.3 Defining Convenient MPLayer Shortcuts

Finally, You can now bind shortcut keys for launching Emacspeak MPlayer from specific locations where you store media, e.g., you can have separate shortcuts for Music vs Audio Books – see command emacspeak-m-player-accelerator. This is best used by customizing Emacspeak option emacspeak-media-location-bindings — just use the Customize interface to specify pairs of shortcut keys and media locations.

Date: <2015-02-17 Tue>

Author: raman

Created: 2015-02-17 Tue 17:37

Emacs (Org mode 8.2.10)