If you have ever wanted to create high quality audio for your videos or projects then Google Cloud Text-to-Speech (TTS) is a great tool to use. But did you know you can take it to the next level with SSML (Speech Synthesis Markup Language)? In this tutorial I will explain how to use SSML effectively to make your audio more engaging, natural and professional.
Understanding SSML Basics for Text-to-Speech
Speech Synthesis Markup Language (SSML) forms the foundation of natural sounding synthetic speech. This XML based markup language was originally developed to give precise control over text to speech conversion.
What is SSML and Why It Matters
SSML works like HTML for web pages and is a standardized way of marking up text for speech synthesis. The markup language lets you control synthetic speech elements with precision. It enables you to manage the formatting of your audio file for things like acronyms, dates and times.
Key Benefits of Using SSML Tags
SSML’s power comes from its extensive customization options. Users can adjust pitch up to 20 semitones, change speaking rates to be 4x faster or slower than normal and control volume from -96db to +16db. It also enables:
- Precise pronunciation control for brand names and technical terms.
- Natural pauses and breaks between words.
- Customised emphasis on specific phrases.
- Multi language support within a single text block.
Getting Started with Google TTS
Google TTS implementation requires understanding three main components:
- AudioConfig: Simple settings like audio encoding and sample rate.
- SynthesisInput: The text that requires conversion.
- VoiceSelectionParams: Selecting a voice based on language and gender priorities.
The root <speak> element must contain all content when applying SSML in Google TTS. This vital tag tells the system that the enclosed text needs speech synthesis processing. Additional elements must be configured inside these speak tags for them to work properly.
Google TTS does the best job with simple punctuation to get the best results. The system adds natural pauses after the periods and changes the intonation of the question marks. This results in a more natural flow of the speech that is produced by the synthesizer.
Essential SSML Tags for Natural Speech
The right combination of SSML tags is important to be able to get the best from your text to speech output. Here is an overview of the core tags that are the basic building blocks of natural sounding speech.
Core Tags for Simple Voice Control
SSML implementation begins with the <speak> tag which is the root element of all SSML documents. This wrapper tag provides several core functions:
- Breaks: Adding pauses to your script.
<break time="500ms"/>
- Prosody: Adjusting pitch, rate and volume.
<prosody rate="90%" pitch="+10%">This sounds great!</prosody>
- Emphasis: Highlighting specific words or phrases.
<emphasis level="strong">Important message!</emphasis>
- Phonemes: Controlling the pronunciation of tricky words.
<phoneme alphabet="ipa" ph="\u02c8eksplorə">explorer</phoneme>
- Multiple Voices: Switching between different voices.
<voice name="en-US-Wavenet-A">Hi!</voice> <voice name="en-US-Wavenet-D">Hello!</voice>
Pronunciation and Emphasis Tags
Pronunciation control is something that needs a little bit of finesse. The <phoneme> tag gives you a precise control over the word pronunciation and it works well with brand names or technical terms. The system also supports language specific pronunciations through the <lang> tag which enables it to easily switch between different languages in the same text.
The <say-as> element is a great way to get better results with things like:
- Numerical expressions.
- Date formats.
- Time expressions.
- Abbreviations.
- Mathematical notations.
Timing and Pause Controls
Natural speech relies upon the use of proper timing and pauses. The <break> tag adds pauses in the synthesized speech through two main methods:
- Strength based pauses: x-weak, weak, medium, strong or x-strong.
- Time based pauses: You can specify the duration in milliseconds or seconds.
Other structural elements like <p> and <s> are used to organize content into proper paragraphs and sentences and to create a natural rhythm of the output speech. These elements also ensure that there are proper pauses between sections of the audio file to enhance its flow.
It’s important to understand how these tags are hierarchically structured. The <speak> tag must contain other elements, and timing controls can be inserted inside the pronunciation tags to create complex speech patterns.
Customizing Voice Output with SSML
Synthetic speech fine tuning is needed to fine tune voice parameters. The prosody tag is useful to create natural sounding audio output.
Pitch and Speed Adjustment
Prosody tag gives you control over voice characteristics. The pitch can be adjusted up to +20 semitones or down to –20 semitones. You can adjust the tone to fit the mood of your content. The rate attribute lets you change the speed from very slow to much faster than normal human speech.
Natural sounding results are obtained from proper application of pitch and speed variations. For example, to create a more authoritative tone, the rate can be slowed down and the pitch can be lowered by 2 semitones: <prosody rate="slow" pitch="-2st">Can you hear me now?</prosody>.
Emphasis and Emotion
SSML tags are used for word emphasis and emotional expression. There are four levels of emphasis that can be used:
- Strong: Makes the speech a little bit louder and a bit slower.
- Moderate: Applied emphasis (default setting).
- Reduced: Softer and quicker.
- None: No emphasis at all.
SSML enhances storytelling and narrative content through emotional expression. The prosody tag works with emphasis tags to create engaging audio experiences.
Voice Selection and Language Control
SSML’s versatility is seen in its language handling and voice selection. The <lang> tag is used to switch between different languages within the same text. This feature is useful for multilingual content or when a specific accent is required.
Voice selection parameters allow you to customize on the basis of:
- Gender priorities.
- Accent variations.
- Speaking styles.
The <voice> tag lets you change voices within a single SSML request. You can create dynamic conversations or vary the narrative style within one audio output.
Results are usually good when these features are properly combined. It is important to switch between voices, adjust the prosody, and use the appropriate emphasis to make your audio content appealing to your audience.
Real-Life Example: Creating Engaging Video Audio
Let’s say you are creating a promotional video. Here’s an SSML example to bring it to life:
<speak> Welcome to <emphasis level="moderate">TTSFree Online</emphasis>, your go to platform for creating <prosody pitch="+20%">amazing</prosody> audio content. <break time="1s"/> Ready to transform your videos with <prosody volume="x-loud">high quality audio</prosody>? Let’s get started! </speak>
This script combines emphasis, pitch adjustments, and pauses to create a professional and engaging introduction.
Tips for Using SSML Effectively
- It’s Natural: Don’t overdo it with the effects; your audio should not sound like a robot. Use tags sparingly for the best results.
- Test Your Scripts: It is important to play back your audio often to ensure that it meets your expectations.
- Experiment: Try different combinations of tags to find what works best for your content.
Using SSML with Google Cloud Text-to-Speech opens up endless possibilities for customizing your audio. Whether you are a content creator, a marketer, or an educator, SSML helps you create professional quality audio that will capture your audience’s attention.
Start experimenting with SSML today and see how it can improve your TTS projects. Happy creating!