Reference documentation and code samples for the Cloud Speech V1p1beta1 Client class AudioEncoding.
The encoding of the audio data sent in the request.
All encodings support only 1 channel (mono) audio, unless the
audio_channel_count
and enable_separate_recognition_per_channel
fields
are set.
For best results, the audio source should be captured and transmitted using
a lossless encoding (FLAC
or LINEAR16
). The accuracy of the speech
recognition can be reduced if lossy codecs are used to capture or transmit
audio, particularly if background noise is present. Lossy codecs include
MULAW
, AMR
, AMR_WB
, OGG_OPUS
, SPEEX_WITH_HEADER_BYTE
, MP3
,
and WEBM_OPUS
.
The FLAC
and WAV
audio file formats include a header that describes the
included audio content. You can request recognition for WAV
files that
contain either LINEAR16
or MULAW
encoded audio.
If you send FLAC
or WAV
audio file format in
your request, you do not need to specify an AudioEncoding
; the audio
encoding format is determined from the file header. If you specify
an AudioEncoding
when you send send FLAC
or WAV
audio, the
encoding configuration must match the encoding described in the audio
header; otherwise the request returns an
google.rpc.Code.INVALID_ARGUMENT error
code.
Protobuf type google.cloud.speech.v1p1beta1.RecognitionConfig.AudioEncoding
Namespace
Google \ Cloud \ Speech \ V1p1beta1 \ RecognitionConfigMethods
static::name
Parameter | |
---|---|
Name | Description |
value |
mixed
|
static::value
Parameter | |
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Name | Description |
name |
mixed
|
Constants
ENCODING_UNSPECIFIED
Value: 0
Not specified.
Generated from protobuf enum ENCODING_UNSPECIFIED = 0;
LINEAR16
Value: 1
Uncompressed 16-bit signed little-endian samples (Linear PCM).
Generated from protobuf enum LINEAR16 = 1;
FLAC
Value: 2
FLAC
(Free Lossless Audio
Codec) is the recommended encoding because it is
lossless--therefore recognition is not compromised--and
requires only about half the bandwidth of LINEAR16
. FLAC
stream
encoding supports 16-bit and 24-bit samples, however, not all fields in
STREAMINFO
are supported.
Generated from protobuf enum FLAC = 2;
MULAW
Value: 3
8-bit samples that compand 14-bit audio samples using G.711 PCMU/mu-law.
Generated from protobuf enum MULAW = 3;
AMR
Value: 4
Adaptive Multi-Rate Narrowband codec. sample_rate_hertz
must be 8000.
Generated from protobuf enum AMR = 4;
AMR_WB
Value: 5
Adaptive Multi-Rate Wideband codec. sample_rate_hertz
must be 16000.
Generated from protobuf enum AMR_WB = 5;
OGG_OPUS
Value: 6
Opus encoded audio frames in Ogg container (OggOpus).
sample_rate_hertz
must be one of 8000, 12000, 16000, 24000, or 48000.
Generated from protobuf enum OGG_OPUS = 6;
SPEEX_WITH_HEADER_BYTE
Value: 7
Although the use of lossy encodings is not recommended, if a very low
bitrate encoding is required, OGG_OPUS
is highly preferred over
Speex encoding. The Speex encoding supported by
Cloud Speech API has a header byte in each block, as in MIME type
audio/x-speex-with-header-byte
.
It is a variant of the RTP Speex encoding defined in
RFC 5574.
The stream is a sequence of blocks, one block per RTP packet. Each block
starts with a byte containing the length of the block, in bytes, followed
by one or more frames of Speex data, padded to an integral number of
bytes (octets) as specified in RFC 5574. In other words, each RTP header
is replaced with a single byte containing the block length. Only Speex
wideband is supported. sample_rate_hertz
must be 16000.
Generated from protobuf enum SPEEX_WITH_HEADER_BYTE = 7;
MP3
Value: 8
MP3 audio. MP3 encoding is a Beta feature and only available in
v1p1beta1. Support all standard MP3 bitrates (which range from 32-320
kbps). When using this encoding, sample_rate_hertz
has to match the
sample rate of the file being used.
Generated from protobuf enum MP3 = 8;
WEBM_OPUS
Value: 9
Opus encoded audio frames in WebM container
(OggOpus). sample_rate_hertz
must be
one of 8000, 12000, 16000, 24000, or 48000.
Generated from protobuf enum WEBM_OPUS = 9;