aws/polly: expose ssml-set-max-duration property

With standard voices, AWS polly supports passing a max-duration
attribute.

When the element gets raw text passed in, it can wrap it as SSML and set
the max duration attribute, this to make sure synthesized speech
doesn't overlap.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1930>

docs/plugins/gst_plugins_cache.json

@@ -111,6 +111,18 @@
                         "type": "gchararray",
                         "writable": true
                     },
+                    "ssml-set-max-duration": {
+                        "blurb": "Wrap plain text as SSML and set the max-duration attribute",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "false",
+                        "mutable": "ready",
+                        "readable": true,
+                        "type": "gboolean",
+                        "writable": true
+                    },
                     "voice-id": {
                         "blurb": "Defines what voice id to use",
                         "conditionally-available": false,

net/aws/src/polly/imp.rs

@@ -34,6 +34,7 @@ const DEFAULT_LATENCY: gst::ClockTime = gst::ClockTime::from_seconds(2);
 const DEFAULT_ENGINE: AwsPollyEngine = AwsPollyEngine::Neural;
 const DEFAULT_LANGUAGE_CODE: AwsPollyLanguageCode = AwsPollyLanguageCode::None;
 const DEFAULT_VOICE_ID: AwsPollyVoiceId = AwsPollyVoiceId::Aria;
+const DEFAULT_SSML_SET_MAX_DURATION: bool = false;
 
 #[derive(Debug, Clone)]
 pub(super) struct Settings {
@@ -45,6 +46,7 @@ pub(super) struct Settings {
     language_code: AwsPollyLanguageCode,
     voice_id: AwsPollyVoiceId,
     lexicon_names: gst::Array,
+    ssml_set_max_duration: bool,
 }
 
 impl Default for Settings {
@@ -58,6 +60,7 @@ impl Default for Settings {
             language_code: DEFAULT_LANGUAGE_CODE,
             voice_id: DEFAULT_VOICE_ID,
             lexicon_names: gst::Array::default(),
+            ssml_set_max_duration: DEFAULT_SSML_SET_MAX_DURATION,
         }
     }
 }
@@ -181,13 +184,23 @@ impl Polly {
 
         let job = {
             let settings = self.settings.lock().unwrap();
-
             let mut task = client
                 .synthesize_speech()
                 .engine(settings.engine.into())
                 .output_format(aws_sdk_polly::types::OutputFormat::Pcm)
-                .text_type(in_format)
-                .text(data)
+                .text_type(if settings.ssml_set_max_duration {
+                    aws_sdk_polly::types::TextType::Ssml
+                } else {
+                    in_format
+                })
+                .text(if settings.ssml_set_max_duration {
+                    format!(
+                        "<speak><prosody amazon:max-duration=\"{}ms\">{data}</prosody></speak>",
+                        duration.mseconds()
+                    )
+                } else {
+                    data.to_owned()
+                })
                 .voice_id(settings.voice_id.into())
                 .set_lexicon_names(Some(
                     settings
@@ -217,6 +230,12 @@ impl Polly {
         let mut buf = gst::Buffer::from_slice(blob.into_bytes());
         let mut state = self.state.lock().unwrap();
 
+        let duration = gst::ClockTime::from_nseconds(
+            (buf.size() as u64)
+                .mul_div_round(1_000_000_000, 32_000)
+                .unwrap(),
+        );
+
         let discont = state
             .out_segment
             .position()
@@ -496,6 +515,12 @@ impl ObjectImpl for Polly {
                     )
                     .mutable_ready()
                     .build(),
+                glib::ParamSpecBoolean::builder("ssml-set-max-duration")
+                    .nick("SSML set max duration")
+                    .blurb("Wrap plain text as SSML and set the max-duration attribute")
+                    .default_value(DEFAULT_SSML_SET_MAX_DURATION)
+                    .mutable_ready()
+                    .build(),
             ]
         });
 
@@ -552,6 +577,10 @@ impl ObjectImpl for Polly {
                 let mut settings = self.settings.lock().unwrap();
                 settings.lexicon_names = value.get::<gst::Array>().expect("type checked upstream");
             }
+            "ssml-set-max-duration" => {
+                let mut settings = self.settings.lock().unwrap();
+                settings.ssml_set_max_duration = value.get().expect("type checked upstream");
+            }
             _ => unimplemented!(),
         }
     }
@@ -590,6 +619,10 @@ impl ObjectImpl for Polly {
                 let settings = self.settings.lock().unwrap();
                 settings.lexicon_names.to_value()
             }
+            "ssml-set-max-duration" => {
+                let settings = self.settings.lock().unwrap();
+                settings.ssml_set_max_duration.to_value()
+            }
             _ => unimplemented!(),
         }
     }