Reads and writes audio from a file.
Code sample
C++
To learn how to install and use the client library for Speech-to-Text, see Speech-to-Text client libraries .
To authenticate to Speech-to-Text, set up Application Default Credentials. For more information, see Set up authentication for a local development environment .
namespace
speech
=
::
google
::
cloud
::
speech
;
using
RecognizeStream
=
::
google
::
cloud
::
AsyncStreamingReadWriteRpc
<
speech
::
v1
::
StreamingRecognizeRequest
,
speech
::
v1
::
StreamingRecognizeResponse
> ;
auto
constexpr
kUsage
=
R
"
""(
Usage:
streaming_transcribe [--bitrate N] audio.(raw|ulaw|flac|amr|awb)
)""
"
;
// Write the audio in 64k chunks at a time, simulating audio content arriving
// from a microphone.
void
MicrophoneThreadMain
(
RecognizeStream
&
stream
,
std
::
string
const
&
file_path
)
{
speech
::
v1
::
StreamingRecognizeRequest
request
;
std
::
ifstream
file_stream
(
file_path
,
std
::
ios
::
binary
);
auto
constexpr
kChunkSize
=
64
*
1024
;
std
::
vector<char>
chunk
(
kChunkSize
);
while
(
true
)
{
// Read another chunk from the file.
file_stream
.
read
(
chunk
.
data
(),
chunk
.
size
());
auto
const
bytes_read
=
file_stream
.
gcount
();
// And write the chunk to the stream.
if
(
bytes_read
>
0
)
{
request
.
set_audio_content
(
chunk
.
data
(),
bytes_read
);
std
::
cout
<<
"Sending "
<<
bytes_read
/
1024
<<
"k bytes."
<<
std
::
endl
;
if
(
!
stream
.
Write
(
request
,
grpc
::
WriteOptions
()).
get
())
break
;
}
if
(
!
file_stream
)
{
// Done reading everything from the file, so done writing to the stream.
stream
.
WritesDone
().
get
();
break
;
}
// Wait a second before writing the next chunk.
std
::
this_thread
::
sleep_for
(
std
::
chrono
::
seconds
(
1
));
}
}
int
main
(
int
argc
,
char
**
argv
)
try
{
// Create a Speech client with the default configuration
auto
client
=
speech
::
SpeechClient
(
speech
::
MakeSpeechConnection
());
// Parse command line arguments.
auto
args
=
ParseArguments
(
argc
,
argv
);
auto
const
file_path
=
args
.
path
;
speech
::
v1
::
StreamingRecognizeRequest
request
;
auto
&
streaming_config
=
*
request
.
mutable_streaming_config
();
*
streaming_config
.
mutable_config
()
=
args
.
config
;
// Begin a stream.
auto
stream
=
client
.
AsyncStreamingRecognize
();
// The stream can fail to start, and `.get()` returns an error in this case.
if
(
!
stream
-
> Start
().
get
())
throw
stream
-
> Finish
().
get
();
// Write the first request, containing the config only.
if
(
!
stream
-
> Write
(
request
,
grpc
::
WriteOptions
{}).
get
())
{
// Write().get() returns false if the stream is closed.
throw
stream
-
> Finish
().
get
();
}
// Simulate a microphone thread using the file as input.
auto
microphone
=
std
::
thread
(
MicrophoneThreadMain
,
std
::
ref
(
*
stream
),
file_path
);
// Read responses.
auto
read
=
[
& stream
]
{
return
stream
-
> Read
().
get
();
};
for
(
auto
response
=
read
();
response
.
has_value
();
response
=
read
())
{
// Dump the transcript of all the results.
for
(
auto
const
&
result
:
response
-
> results
())
{
std
::
cout
<<
"Result stability: "
<<
result
.
stability
()
<<
"
\n
"
;
for
(
auto
const
&
alternative
:
result
.
alternatives
())
{
std
::
cout
<<
alternative
.
confidence
()
<<
"
\t
"
<<
alternative
.
transcript
()
<<
"
\n
"
;
}
}
}
auto
status
=
stream
-
> Finish
().
get
();
microphone
.
join
();
if
(
!
status
.
ok
())
throw
status
;
return
0
;
}
catch
(
google
::
cloud
::
Status
const
&
s
)
{
std
::
cerr
<<
"Recognize stream finished with an error: "
<<
s
<<
"
\n
"
;
return
1
;
}
catch
(
std
::
exception
const
&
ex
)
{
std
::
cerr
<<
"Standard C++ exception thrown: "
<<
ex
.
what
()
<<
"
\n
"
<<
kUsage
<<
"
\n
"
;
return
1
;
}
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