support elevenlabs options

lib/synth-audio.js

@@ -586,20 +586,24 @@ const synthCustomVendor = async(logger, {credentials, stats, language, voice, te
 };
 
 const synthElevenlabs = async(logger, {credentials, stats, language, voice, text}) => {
-  const {api_key, model_id} = credentials;
+  const {api_key, model_id, options} = credentials;
+  const opts = JSON.parse(options || '{}');
+  const optimize_streaming_latency = opts.optimize_streaming_latency ?
+    `?optimize_streaming_latency=${opts.optimize_streaming_latency}` : '';
   try {
     const post = bent('https://api.elevenlabs.io', 'POST', 'buffer', {
       'xi-api-key': api_key,
       'Accept': 'audio/mpeg',
       'Content-Type': 'application/json'
     });
-    const mp3 = await post(`/v1/text-to-speech/${voice}`, {
+    const mp3 = await post(`/v1/text-to-speech/${voice}${optimize_streaming_latency}`, {
       text,
       model_id,
       voice_settings: {
         stability: 0.5,
         similarity_boost: 0.5
-      }
+      },
+      ...opts
     });
     return mp3;
   } catch (err) {

test/synth.js

@@ -459,7 +459,16 @@ test('Elevenlabs speech synth tests', async(t) => {
       vendor: 'elevenlabs',
       credentials: {
         api_key: process.env.ELEVENLABS_API_KEY,
-        model_id: process.env.ELEVENLABS_MODEL_ID
+        model_id: process.env.ELEVENLABS_MODEL_ID,
+        options: JSON.stringify({
+          optimize_streaming_latency: 1,
+          voice_settings: {
+            similarity_boost: 1,
+            stability: 0.8,
+            style: 1,
+            use_speaker_boost: true
+          }
+        })
       },
       language: 'en-US',
       voice: process.env.ELEVENLABS_VOICE_ID,