Make it possible to restart speech even when audio open failed once

When notably the audio card is busy, we should report the issue to the
application, but still permit the application to retry submitting text
to synth, and eventually succeed to open it.

This change simply fixes the update of the out_samplerate variable to track
whether audio is open, and if not when text is submitted by the application,
try again to open it.

src/libespeak-ng/speech.c

@@ -123,12 +123,12 @@ static int dispatch_audio(short *outbuf, int length, espeak_EVENT *event)
 				if (out_samplerate != 0) {
 					// sound was previously open with a different sample rate
 					audio_object_close(my_audio);
+					out_samplerate = 0;
 #ifdef HAVE_SLEEP
 					sleep(1);
 #endif
 				}
 #endif
-				out_samplerate = voice_samplerate;
 #ifdef HAVE_PCAUDIOLIB_AUDIO_H
 				int error = audio_object_open(my_audio, AUDIO_OBJECT_FORMAT_S16LE, voice_samplerate, 1);
 				if (error != 0) {
@@ -137,6 +137,7 @@ static int dispatch_audio(short *outbuf, int length, espeak_EVENT *event)
 					return -1;
 				}
 #endif
+				out_samplerate = voice_samplerate;
 #ifdef USE_ASYNC
 				if ((my_mode & ENOUTPUT_MODE_SYNCHRONOUS) == 0)
 					event_init();
@@ -144,6 +145,18 @@ static int dispatch_audio(short *outbuf, int length, espeak_EVENT *event)
 			}
 		}
 
+#ifdef HAVE_PCAUDIOLIB_AUDIO_H
+		if (out_samplerate == 0) {
+			int error = audio_object_open(my_audio, AUDIO_OBJECT_FORMAT_S16LE, voice_samplerate, 1);
+			if (error != 0) {
+				fprintf(stderr, "error: %s\n", audio_object_strerror(my_audio, error));
+				err = ENS_AUDIO_ERROR;
+				return -1;
+			}
+			out_samplerate = voice_samplerate;
+		}
+#endif
+
 #ifdef HAVE_PCAUDIOLIB_AUDIO_H
 		if (outbuf && length && a_wave_can_be_played) {
 			int error = audio_object_write(my_audio, (char *)outbuf, 2*length);