When you send audio data to the Speech-to-Text API, you can either send the data
directly (within the request's content
field) or have the API perform recognition remotely on data stored in a
Cloud Storage bucket by specifying the storage object in the request's uri
field.
Any audio data in the content
field in HTTP requests must be in base64 format.
This page describes how to convert audio from a binary file to base64-encoded
data.
Using the command line
Within a gRPC request, you can simply write binary data out directly; however, JSON is used when making a REST request. JSON is a text format that does not directly support binary data, so you will need to convert such binary data into text using Base64 encoding.
Most development environments contain a native base64
utility to
encode a binary into ASCII text data. To encode a file:
Linux
Encode the file using the base64
command line tool, making sure to
prevent line-wrapping by using the -w 0
flag:
base64 INPUT_FILE -w 0 > OUTPUT_FILE
macOS
Encode the file using the base64
command line tool:
base64 -i INPUT_FILE -o OUTPUT_FILE
Windows
Encode the file using the Base64.exe
tool:
Base64.exe -e INPUT_FILE > OUTPUT_FILE
PowerShell
Encode the file using the Convert.ToBase64String
method:
[Convert]::ToBase64String([IO.File]::ReadAllBytes("./ INPUT_FILE ")) > OUTPUT_FILE
Create a JSON request file, inlining the base64-encoded data:
JSON
{
"recognizer"
:
"projects/ PROJECT_ID
/locations/global/recognizers/_"
,
"content"
:
"ZkxhQwAAACIQABAAAAUJABtAA+gA8AB+W8FZndQvQAyjv..."
}
Using client libraries
Embedding binary data into requests through text editors is neither desirable or practical. In practice, you will be embedding base64 encoded files within client code. All supported programming languages have built-in mechanisms for base64 encoding content.
Python
In Python, base64 encode audio files as follows:
# Import the base64 encoding library.
import
base64
# Pass the audio data to an encoding function.
def
encode_audio
(
audio_file
):
with
open
(
audio_file
,
"rb"
)
as
f
:
encoded_content
=
base64
.
b64encode
(
f
.
read
())
return
encoded_content
Node.js
// Read the file into memory.
var
fs
=
require
(
'fs'
);
var
audioFile
=
fs
.
readFileSync
(
' /full/path/to/audio/file.wav
'
);
// Convert the audio data to a Buffer and base64 encode it.
var
encoded
=
Buffer
.
from
(
audioFile
).
toString
(
'base64'
);
Java
// Import the Base64 encoding library.
import
org.apache.commons.codec.binary.Base64
;
// Encode the audio.
byte
[]
audioData
=
Base64
.
encodeBase64
(
audioFile
.
getBytes
());
String
encodedString
=
Base64
.
getEncoder
().
encodeToString
(
audioData
);
Go
import
(
"bufio"
"encoding/base64"
"io"
"os"
)
// Open audio file.
f
,
_
:=
os
.
Open
(
" /full/path/to/audio/file.wav
"
)
// Read entire audio into byte slice.
reader
:=
bufio
.
NewReader
(
f
)
content
,
_
:=
io
.
ReadAll
(
reader
)
// Encode audio as base64.
base64
.
StdEncoding
.
EncodeToString
(
content
)
