support riva tts stream

lib/synth-audio.js

@@ -215,7 +215,8 @@ async function synthAudio(client, createHash, retrieveHash, logger, stats, { acc
         audioData = await synthNuance(client, logger, {credentials, stats, voice, model, text});
         break;
       case 'nvidia':
-        audioData = await synthNvidia(client, logger, {credentials, stats, language, voice, model, text});
+        audioData = await synthNvidia(client, logger, {credentials, stats, language, voice, model, text,
+          renderForCaching, disableTtsStreaming});
         break;
       case 'ibm':
         audioData = await synthIbm(logger, {credentials, stats, voice, text});
@@ -708,8 +709,24 @@ const synthNuance = async(client, logger, {credentials, stats, voice, model, tex
   });
 };
 
-const synthNvidia = async(client, logger, {credentials, stats, language,  voice, model, text}) => {
+const synthNvidia = async(client, logger, {
+  credentials, stats, language,  voice, model, text, renderForCaching, disableTtsStreaming
+}) => {
   const {riva_server_uri} = credentials;
+  if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
+    let params = '';
+    params += `{riva_server_uri=${riva_server_uri}`;
+    params += `,voice=${voice}`;
+    params += `,language=${language}`;
+    params += ',write_cache_file=1';
+    params += '}';
+
+    return {
+      filePath: `say:${params}${text.replace(/\n/g, ' ')}`,
+      servedFromCache: false,
+      rtt: 0
+    };
+  }
   let rivaClient, request;
   const sampleRate = 8000;
   try {