How to set options of commands called by browser?

Presently when Speech Synthesis Markup Language (SSML) is set as at text property of SpeechSynthesisUtterance instance at Chromium or Firefox web browsers the SSML is not parsed at *nix as reflected at audio output of speechSynthesis.speak() call. Browsing the source code of the browsers speech-dispatcher appears to be called by .speak() where either spd-say or espeak , if configured to do so, could be called by speech-dispatcher. spd-say has an x option -x, --ssml Set SSML mode on (default: off) espeak has an m option -m Interpret SSML markup, and ignore other tags Have created a user configuration file for speech-dispatcher using spd-conf -u The documentation states that the user configuration file can be used to set parameters for specific clients > **4.1.6 Parameter Settings Commands** > > The following parameter setting commands are available. For > configuration and history clients there are also functions for setting > the value for some other connection and for all connections. They are > listed separately below. > > C API function: `int spd_set_data_mode(SPDConnection *connection, > SPDDataMode mode)` Set Speech Dispatcher data mode. Currently, plain > text and SSML are supported. SSML is especially useful if you want to > use index marks or include changes of voice parameters in the text. > > mode is the requested data mode: SPD_DATA_TEXT or SPD_DATA_SSML. Questions 1. How to set the default option of either or both -x for spd-say and -m for espeak commands at ~/.config/speech-dispatcher/speechd.conf for the clients Chromium and Firefox browsers when .speak() is called? 2. How to adjust the source code at Chromium and Firefox browsers to set the -x or -m options by default for the text set at SpeechSpeechSynthesisUtterance text property which is passed to window.speechSynthesis.speak()?