How to get SSML <mark> timestamps from Google Cloud text-to-speech API - markers

Question

I want to use SSML markers through the Google Cloud text-to-speech API to request the timing of these markers in the audio stream. These timestamps are necessary in order to provide cues for effects, word/section highlighting and feedback to the user.
I found this question which is relevant, although the question refers to the timestamps for each word and not the SSML <mark> tag.
The following API request returns OK but shows the lack of the requested marker data. This is using the Cloud Text-to-Speech API v1.
{
"voice": {
"languageCode": "en-US"
},
"input": {
"ssml": "<speak>First, <mark name=\"a\"/> second, <mark name=\"b\"/> third.</speak>"
},
"audioConfig": {
"audioEncoding": "mp3"
}
}
Response:
{
"audioContent":"//NExAAAAANIAAAAABcFAThYGJqMWA..."
}
Which only provides the synthesized audio without any contextual information.
Is there an API request that I am overlooking which can expose information about these markers such as is the case with IBM Watson and Amazon Polly?

Answer 1

Looks like this is supported in Cloud Text-to-Speech API v1beta1: https://cloud.google.com/text-to-speech/docs/reference/rest/v1beta1/text/synthesize#TimepointType
You can use https://texttospeech.googleapis.com/v1beta1/text:synthesize. Set TimepointType to SSML_MARK. If this field is not set, timepoints are not returned by default.

Answer 2

At the time of writing, the timepoint data is available in the v1beta1 release of Google cloud text-to-speech.
I didn't need to sign on to any extra developer program in order to access the beta, beyond the default access.
Importing in Python (for example) went from:
from google.cloud import texttospeech as tts
to:
from google.cloud import texttospeech_v1beta1 as tts
Nice and simple.
I needed to modify the default way I was sending the synthesis request to include the enable_time_pointing flag.
I found that with a mix of poking around the machine-readable API description here and reading the Python library code, which I had already downloaded.
Thankfully, the source in the generally available version also includes the v1beta version - thank you Google!
I've put a runnable sample below. Running this needs the same auth and setup you'll need for a general text-to-speech sample, which you can get by following the official documentation.
Here's what it does for me (with slight formatting for readability):
$ python tools/try-marks.py
Marks content written to file: .../demo.json
Audio content written to file: .../demo.mp3
$ cat demo.json
[
{"sec": 0.4300000071525574, "name": "here"},
{"sec": 0.9234582781791687, "name": "there"}
]
Here's the sample:
import json
from pathlib import Path
from google.cloud import texttospeech_v1beta1 as tts
def go_ssml(basename: Path, ssml):
client = tts.TextToSpeechClient()
voice = tts.VoiceSelectionParams(
language_code="en-AU",
name="en-AU-Wavenet-B",
ssml_gender=tts.SsmlVoiceGender.MALE,
)
response = client.synthesize_speech(
request=tts.SynthesizeSpeechRequest(
input=tts.SynthesisInput(ssml=ssml),
voice=voice,
audio_config=tts.AudioConfig(audio_encoding=tts.AudioEncoding.MP3),
enable_time_pointing=[
tts.SynthesizeSpeechRequest.TimepointType.SSML_MARK]
)
)
# cheesy conversion of array of Timepoint proto.Message objects into plain-old data
marks = [dict(sec=t.time_seconds, name=t.mark_name)
for t in response.timepoints]
name = basename.with_suffix('.json')
with name.open('w') as out:
json.dump(marks, out)
print(f'Marks content written to file: {name}')
name = basename.with_suffix('.mp3')
with name.open('wb') as out:
out.write(response.audio_content)
print(f'Audio content written to file: {name}')
go_ssml(Path.cwd() / 'demo', """
<speak>
Go from <mark name="here"/> here, to <mark name="there"/> there!
</speak>
""")