Opus

https://opus-codec.org/docs/
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### Using opus_encoder_ctl with OPUS_SET_BANDWIDTH, OPUS_GET_BANDWIDTH, and OPUS_RESET_STATE

Source: https://opus-codec.org/docs/opus_api-1.6/group__opus__encoderctls.html

Shows how to use opus_encoder_ctl with convenience macros: set bandwidth, get bandwidth, and reset state. The first example checks the return value against OPUS_OK.

```c
int ret;
ret = opus_encoder_ctl(enc_ctx, OPUS_SET_BANDWIDTH(OPUS_AUTO));
if (ret != OPUS_OK) return ret;
```

```c
opus_int32 rate;
opus_encoder_ctl(enc_ctx, OPUS_GET_BANDWIDTH(&rate));
```

```c
opus_encoder_ctl(enc_ctx, OPUS_RESET_STATE);
```

--------------------------------

### OPUS_GET_QEXT

Source: https://opus-codec.org/docs/opus_api-1.6/opus__defines_8h_source.html

Gets the current QEXT setting.

```APIDOC
## OPUS_GET_QEXT

### Description
Gets the current QEXT setting.

### Macro Definition
`#define OPUS_GET_QEXT(x) OPUS_GET_QEXT_REQUEST, opus_check_int_ptr(x)`

### Parameters
- **x** (int*) - Required - Pointer to an integer where the QEXT setting will be stored.

```

--------------------------------

### op_fopen

Source: https://opus-codec.org/docs/opusfile_api-0.12/opusfile_8h_source.html

Opens a file and initializes callbacks for OpusFile.

```APIDOC
## op_fopen

### Description
Opens a file using the standard C library and initializes an OpusFileCallbacks structure for use with OpusFile functions.

### Function Signature
```c
void *op_fopen(OpusFileCallbacks *_cb, const char *_path, const char *_mode);
```

### Parameters
- `_cb` (OpusFileCallbacks*) - Required - Pointer to the callbacks structure to initialize.
- `_path` (const char*) - Required - The file path to open.
- `_mode` (const char*) - Required - The file mode (e.g., "rb").

### Return Value
- Returns a stream handle on success, or NULL on failure.
```

--------------------------------

### opus_multistream_decoder_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/opus__multistream_8h.html

Gets the size of an OpusMSDecoder structure.

```APIDOC
## opus_multistream_decoder_get_size

### Description
Gets the size of an OpusMSDecoder structure.

### Function Signature
`opus_int32 opus_multistream_decoder_get_size(int streams, int coupled_streams)`

### Parameters
- **streams** (int) - Required - Number of streams.
- **coupled_streams** (int) - Required - Number of coupled streams.

### Returns
- **opus_int32** - Size of the OpusMSDecoder structure in bytes.
```

--------------------------------

### opus_server_info_init

Source: https://opus-codec.org/docs/opusfile_api-0.12/opusfile_8h_source.html

Initializes an OpusServerInfo structure.

```APIDOC
## opus_server_info_init

### Description
Initializes an OpusServerInfo structure to its default state.

### Function Signature
```c
void opus_server_info_init(OpusServerInfo *_info);
```

### Parameters
- `_info` (OpusServerInfo*) - Required - Pointer to the OpusServerInfo structure to initialize.
```

--------------------------------

### opus_multistream_encoder_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/opus__multistream_8h.html

Gets the size of an OpusMSEncoder structure.

```APIDOC
## opus_multistream_encoder_get_size

### Description
Gets the size of an OpusMSEncoder structure.

### Function Signature
`opus_int32 opus_multistream_encoder_get_size(int streams, int coupled_streams)`

### Parameters
- **streams** (int) - Required - Number of streams.
- **coupled_streams** (int) - Required - Number of coupled streams.

### Returns
- **opus_int32** - Size of the OpusMSEncoder structure in bytes.
```

--------------------------------

### opus_repacketizer_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/opus_8h.html

Gets the size of an `OpusRepacketizer` structure.

```APIDOC
## opus_repacketizer_get_size

### Description
Gets the size of an `OpusRepacketizer` structure.

### Function Signature
int opus_repacketizer_get_size(void)

### Parameters
None.

### Return Value
- **int** - Size of the structure.
```

--------------------------------

### opus_repacketizer_create

Source: https://opus-codec.org/docs/opus_api-1.6/opus_8h.html

Allocates memory and initializes the new repacketizer with opus_repacketizer_init().

```APIDOC
## opus_repacketizer_create

### Description
Allocates memory and initializes the new repacketizer with opus_repacketizer_init().

### Function Signature
OpusRepacketizer *opus_repacketizer_create(void)

### Parameters
None.

### Return Value
- **OpusRepacketizer*** - Pointer to the newly created repacketizer.
```

--------------------------------

### opus_packet_get_bandwidth

Source: https://opus-codec.org/docs/opus_api-1.6/opus_8h.html

Gets the bandwidth of an Opus packet.

```APIDOC
## opus_packet_get_bandwidth

### Description
Gets the bandwidth of an Opus packet.

### Function Signature
int opus_packet_get_bandwidth(const unsigned char *data)

### Parameters
- **data** (const unsigned char*) - Required - Pointer to the packet data.

### Return Value
- **int** - Bandwidth value or error code.
```

--------------------------------

### ope_encoder_deferred_init_with_mapping

Source: https://opus-codec.org/docs/libopusenc_api-0.3/opusenc_8h_source.html

Deferred initialization with explicit channel mapping.

```APIDOC
## ope_encoder_deferred_init_with_mapping

### Description
Deferred initialization of the encoder to force an explicit channel mapping.

### Function Signature
`OPE_EXPORT int ope_encoder_deferred_init_with_mapping(OggOpusEnc *enc, int family, int streams, int coupled_streams, const unsigned char *mapping)`

### Parameters
- `enc` (OggOpusEnc*) - Required - The encoder instance.
- `family` (int) - Required - Family parameter.
- `streams` (int) - Required - Number of streams.
- `coupled_streams` (int) - Required - Number of coupled streams.
- `mapping` (const unsigned char*) - Required - Channel mapping array.

### Returns
- `int` - 0 on success, or an error code.

```

--------------------------------

### opus_dred_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/opus_8h.html

Gets the size of an OpusDRED structure.

```APIDOC
## opus_dred_get_size

### Description
Gets the size of an `OpusDRED` structure.

### Function Signature
`int opus_dred_get_size(void)`

### Return Value
- (int) - Size of the DRED state structure in bytes.
```

--------------------------------

### ope_encoder_deferred_init_with_mapping

Source: https://opus-codec.org/docs/libopusenc_api-0.3/opusenc_8h_source.html

Initializes an encoder with a custom channel mapping.

```APIDOC
## ope_encoder_deferred_init_with_mapping

### Description
Initializes an encoder with a custom channel mapping.

### Function Signature
`OPE_EXPORT int ope_encoder_deferred_init_with_mapping(OggOpusEnc *enc, int family, int streams, int coupled_streams, const unsigned char *mapping)`

### Parameters
- **enc** (OggOpusEnc*) - The encoder.
- **family** (int) - Family (0 for audio, 1 for voice).
- **streams** (int) - Number of streams.
- **coupled_streams** (int) - Number of coupled streams.
- **mapping** (const unsigned char*) - Channel mapping.

### Returns
- **int** - 0 on success, or a negative error code on failure.

```

--------------------------------

### opus_repacketizer_init

Source: https://opus-codec.org/docs/opus_api-1.6/opus_8h.html

(Re)initializes a previously allocated repacketizer state.

```APIDOC
## opus_repacketizer_init

### Description
(Re)initializes a previously allocated repacketizer state.

### Function Signature
OpusRepacketizer *opus_repacketizer_init(OpusRepacketizer *rp)

### Parameters
- **rp** (OpusRepacketizer*) - Required - Pointer to the repacketizer state.

### Return Value
- **OpusRepacketizer*** - Pointer to the initialized state.
```

--------------------------------

### opus_dred_decoder_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/opus_8h.html

Gets the size of an OpusDREDDecoder structure.

```APIDOC
## opus_dred_decoder_get_size

### Description
Gets the size of an `OpusDREDDecoder` structure.

### Function Signature
`int opus_dred_decoder_get_size(void)`

### Return Value
- (int) - Size of the DRED decoder structure in bytes.
```

--------------------------------

### opus_decoder_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/opus_8h.html

Gets the size of an OpusDecoder structure.

```APIDOC
## opus_decoder_get_size

### Description
Gets the size of an `OpusDecoder` structure.

### Function Signature
`int opus_decoder_get_size(int channels)`

### Parameters
- **channels** (int) - Required - Number of channels.

### Return Value
- (int) - Size of the decoder structure in bytes.
```

--------------------------------

### op_fopen

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__stream__callbacks.html

Opens a stream with fopen() and fills in a set of callbacks for accessing it. Useful for portable 64-bit seeking and avoiding cross-module linking issues on Windows.

```APIDOC
## op_fopen

### Description
Opens a stream with `fopen()` and fills in a set of callbacks that can be used to access it. This is useful to avoid writing your own portable 64-bit seeking wrappers, and also avoids cross-module linking issues on Windows, where a `FILE *` must be accessed by routines defined in the same module that opened it.

### Function Signature
```c
OP_WARN_UNUSED_RESULT void* op_fopen(OpusFileCallbacks *__cb_, const char *__path_, const char *__mode_)
```

### Parameters
- **__cb_** (OpusFileCallbacks *) - Output - The callbacks to use for this file. If there is an error opening the file, nothing will be filled in here.
- **__path_** (const char *) - Input - The path to the file to open. On Windows, this string must be UTF-8 (to allow access to files whose names cannot be represented in the current MBCS code page). All other systems use the native character encoding.
- **__mode_** (const char *) - Input - The mode to open the file in.

### Returns
A stream handle to use with the callbacks, or `NULL` on error.
```

--------------------------------

### opus_encoder_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/group__opus__encoder.html

Gets the size of an OpusEncoder structure.

```APIDOC
## opus_encoder_get_size

### Description
Gets the size of an `OpusEncoder` structure.

### Function Signature
int opus_encoder_get_size(int channels)

### Parameters
- **channels** (int) - Number of channels.

### Returns
- **int** - Size of the OpusEncoder structure in bytes.
```

--------------------------------

### Allocate and initialize an OpusRepacketizer with malloc

Source: https://opus-codec.org/docs/opus_api-1.6/group__opus__repacketizer.html

Shows how to manually allocate memory for an OpusRepacketizer using opus_repacketizer_get_size() and then initialize it with opus_repacketizer_init(). This is an alternative to calling opus_repacketizer_create().

```c
OpusRepacketizer *rp;
rp = (OpusRepacketizer*)malloc(opus_repacketizer_get_size());
if (rp != NULL)
opus_repacketizer_init(rp);
```

--------------------------------

### opus_custom_decoder_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/opus__custom_8h.html

Gets the size of an OpusCustomDecoder structure.

```APIDOC
## opus_custom_decoder_get_size

### Description
Gets the size of an OpusCustomDecoder structure.

### Function Signature
`int opus_custom_decoder_get_size(const OpusCustomMode *mode, int channels)`

### Parameters
- **mode** (const OpusCustomMode*) - Required - The mode to use.
- **channels** (int) - Required - Number of channels.

### Return Value
- **int** - Size in bytes of the decoder structure.
```

--------------------------------

### Live stream to Icecast using arecord, opusenc, and oggfwd

Source: https://opus-codec.org/docs/opus-tools/opusenc.html

Records and sends a live stream to an Icecast HTTP streaming server using oggfwd.

```shell
arecord -c 2 -r 48000 -twav - | opusenc --bitrate 96 - - | oggfwd icecast.somewhere.org 8000 password /stream.opus
```

--------------------------------

### opus_custom_encoder_get_size

Source: https://opus-codec.org/docs/opus_api-1.6/opus__custom_8h.html

Gets the size of an OpusCustomEncoder structure.

```APIDOC
## opus_custom_encoder_get_size

### Description
Gets the size of an OpusCustomEncoder structure.

### Function Signature
`int opus_custom_encoder_get_size(const OpusCustomMode *mode, int channels)`

### Parameters
- **mode** (const OpusCustomMode*) - Required - The mode to use.
- **channels** (int) - Required - Number of channels.

### Return Value
- **int** - Size in bytes of the encoder structure.
```

--------------------------------

### op_bitrate_instant

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__stream__info.html

Compute the instantaneous bitrate, measured as the ratio of bits to playable samples decoded since a) the last call to op_bitrate_instant(), b) the last seek, or c) the start of playback, whichever was most recent.

```APIDOC
## op_bitrate_instant

### Description
Compute the instantaneous bitrate, measured as the ratio of bits to playable samples decoded since a) the last call to op_bitrate_instant(), b) the last seek, or c) the start of playback, whichever was most recent.

### Function Signature
```c
opus_int32 op_bitrate_instant(OggOpusFile *_of) OP_ARG_NONNULL(1)
```

### Parameters
- `_of` (OggOpusFile*) - Required - The OggOpusFile handle.

### Return Value
Returns the instantaneous bitrate in bits per second.
```

--------------------------------

### OPUS_GET_GAIN

Source: https://opus-codec.org/docs/opus_api-1.6/opus__defines_8h_source.html

Gets the current gain setting.

```APIDOC
## OPUS_GET_GAIN

### Description
Gets the current gain setting.

### Macro Definition
`#define OPUS_GET_GAIN(x) OPUS_GET_GAIN_REQUEST, opus_check_int_ptr(x)`

### Parameters
- **x** (int*) - Required - Pointer to an integer where the gain will be stored.

```

--------------------------------

### op_fopen

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__stream__callbacks.html

Opens a stream with fopen() and fills in a set of callbacks.

```APIDOC
## op_fopen

### Description
Opens a stream with `fopen()` and fills in a set of callbacks that can be used to access it.

### Signature
```c
OP_WARN_UNUSED_RESULT void * op_fopen(OpusFileCallbacks *_cb, const char *_path, const char *_mode)
```

### Parameters
- **_cb** (OpusFileCallbacks*) - Callbacks structure to fill in.
- **_path** (const char*) - Path to the file to open.
- **_mode** (const char*) - File open mode (e.g., "rb").

### Returns
- (void*) - A stream handle, or NULL on failure.
```

--------------------------------

### OPUS_GET_BANDWIDTH

Source: https://opus-codec.org/docs/opus_api-1.6/opus__defines_8h_source.html

Gets the bandwidth of the encoded signal.

```APIDOC
## OPUS_GET_BANDWIDTH

### Description
Gets the bandwidth of the encoded signal.

### Macro Definition
`#define OPUS_GET_BANDWIDTH(x) OPUS_GET_BANDWIDTH_REQUEST, opus_check_int_ptr(x)`

### Parameters
- **x** (int*) - Required - Pointer to an integer where the bandwidth will be stored.

```

--------------------------------

### op_fdopen

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__stream__callbacks.html

Opens a stream with fdopen() and fills in a set of callbacks.

```APIDOC
## op_fdopen

### Description
Opens a stream with `fdopen()` and fills in a set of callbacks that can be used to access it.

### Signature
```c
OP_WARN_UNUSED_RESULT void * op_fdopen(OpusFileCallbacks *_cb, int _fd, const char *_mode)
```

### Parameters
- **_cb** (OpusFileCallbacks*) - Callbacks structure to fill in.
- **_fd** (int) - File descriptor to open.
- **_mode** (const char*) - File open mode (e.g., "rb").

### Returns
- (void*) - A stream handle, or NULL on failure.
```

--------------------------------

### OPUS_GET_FINAL_RANGE

Source: https://opus-codec.org/docs/opus_api-1.6/opus__defines_8h_source.html

Gets the final range of the coder.

```APIDOC
## OPUS_GET_FINAL_RANGE

### Description
Gets the final range of the coder.

### Macro Definition
`#define OPUS_GET_FINAL_RANGE(x) OPUS_GET_FINAL_RANGE_REQUEST, opus_check_uint_ptr(x)`

### Parameters
- **x** (unsigned int*) - Required - Pointer to an unsigned integer where the final range will be stored.

```

--------------------------------

### op_freopen()

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__stream__callbacks.html

Documentation for the op_freopen() function, which opens a stream using freopen() and fills in callbacks for accessing it.

```APIDOC
## op_freopen()

### Description
Opens a stream with `freopen()` and fills in a set of callbacks that can be used to access it. This is useful to avoid writing your own portable 64-bit seeking wrappers, and also avoids cross-module linking issues on Windows, where a `FILE *` must be accessed by routines defined in the same module that opened it.

### Signature
```c
OP_WARN_UNUSED_RESULT void* op_freopen(OpusFileCallbacks *__cb_, const char *__path_, const char *__mode_, void *__stream_);
```

### Parameters
- **__cb_** (OpusFileCallbacks*) - [out] The callbacks to use for this file. If there is an error opening the file, nothing will be filled in here.
- **__path_** (const char*) - The path to the file to open. On Windows, this string must be UTF-8 (to allow access to files whose names cannot be represented in the current MBCS code page). All other systems use the native character encoding.
- **__mode_** (const char*) - The mode to open the file in.
- **__stream_** (void*) - A stream previously returned by op_fopen(), op_fdopen(), or op_freopen().

### Returns
A stream handle to use with the callbacks, or `NULL` on error.
```

--------------------------------

### Create Opus decoder with opus_decoder_create

Source: https://opus-codec.org/docs/opus_api-1.6/group__opus__decoder.html

Allocates and initializes a decoder state. Fs must be 8000, 12000, 16000, 24000, or 48000; channels must be 1 or 2. On failure, error holds the error code; on success it is OPUS_OK. The return value is a newly created decoder state.

```c
int error;
OpusDecoder *dec;
dec = opus_decoder_create(Fs, channels, &error);
```

--------------------------------

### OPUS_GET_DRED_DURATION

Source: https://opus-codec.org/docs/opus_api-1.6/opus__defines_8h_source.html

Gets the current DRED duration.

```APIDOC
## OPUS_GET_DRED_DURATION

### Description
Gets the current DRED duration.

### Macro Definition
`#define OPUS_GET_DRED_DURATION(x) OPUS_GET_DRED_DURATION_REQUEST, opus_check_int_ptr(x)`

### Parameters
- **x** (int*) - Required - Pointer to an integer where the DRED duration will be stored.

```

--------------------------------

### ope_get_version_string

Source: https://opus-codec.org/docs/libopusenc_api-0.3/opusenc_8h_source.html

Returns the version string of the library.

```APIDOC
## ope_get_version_string

### Description
Returns the version string of the library.

### Function Signature
`OPE_EXPORT const char *ope_get_version_string(void)`

### Parameters
None.

### Returns
- **const char*** - The version string.

```

--------------------------------

### URL Reading Options

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__url__options.html

This snippet documents the URL reading options for op_url_stream_create(), including functions to initialize and clear server info structures, and macros to configure proxy settings, SSL certificate checks, and server info retrieval.

```APIDOC
## opus_server_info_init

### Description
Initializes an OpusServerInfo structure. This function must be called before using the structure.

### Method
Function

### Signature
void opus_server_info_init(OpusServerInfo *_info) OP_ARG_NONNULL(1)

### Parameters
- **_info** (OpusServerInfo*) - Required - Pointer to the structure to initialize.

### Return Value
None.
```

```APIDOC
## opus_server_info_clear

### Description
Clears the OpusServerInfo structure, releasing any allocated resources.

### Method
Function

### Signature
void opus_server_info_clear(OpusServerInfo *_info) OP_ARG_NONNULL(1)

### Parameters
- **_info** (OpusServerInfo*) - Required - Pointer to the structure to clear.

### Return Value
None.
```

```APIDOC
## OP_SSL_SKIP_CERTIFICATE_CHECK

### Description
Skip the certificate check when connecting via TLS/SSL (https). This option is a macro that can be passed to op_url_stream_create().

### Method
Macro

### Signature
#define OP_SSL_SKIP_CERTIFICATE_CHECK(_b)

### Parameters
- **_b** (int) - Required - Boolean flag: non-zero to skip certificate check, zero to perform it.

### Return Value
None (macro expands to an option value).
```

```APIDOC
## OP_HTTP_PROXY_HOST

### Description
Proxy connections through the given host. This option is a macro that can be passed to op_url_stream_create().

### Method
Macro

### Signature
#define OP_HTTP_PROXY_HOST(_host)

### Parameters
- **_host** (const char*) - Required - Hostname of the proxy server.

### Return Value
None (macro expands to an option value).
```

```APIDOC
## OP_HTTP_PROXY_PORT

### Description
Use the given port when proxying connections. This option is a macro that can be passed to op_url_stream_create().

### Method
Macro

### Signature
#define OP_HTTP_PROXY_PORT(_port)

### Parameters
- **_port** (int) - Required - Port number of the proxy server.

### Return Value
None (macro expands to an option value).
```

```APIDOC
## OP_HTTP_PROXY_USER

### Description
Use the given user name for authentication when proxying connections. This option is a macro that can be passed to op_url_stream_create().

### Method
Macro

### Signature
#define OP_HTTP_PROXY_USER(_user)

### Parameters
- **_user** (const char*) - Required - User name for proxy authentication.

### Return Value
None (macro expands to an option value).
```

```APIDOC
## OP_HTTP_PROXY_PASS

### Description
Use the given password for authentication when proxying connections. This option is a macro that can be passed to op_url_stream_create().

### Method
Macro

### Signature
#define OP_HTTP_PROXY_PASS(_pass)

### Parameters
- **_pass** (const char*) - Required - Password for proxy authentication.

### Return Value
None (macro expands to an option value).
```

```APIDOC
## OP_GET_SERVER_INFO

### Description
Parse information about the streaming server (if any) and return it. This option is a macro that can be passed to op_url_stream_create().

### Method
Macro

### Signature
#define OP_GET_SERVER_INFO(_info)

### Parameters
- **_info** (OpusServerInfo*) - Required - Pointer to an OpusServerInfo structure to receive the server information.

### Return Value
None (macro expands to an option value).
```

--------------------------------

### opus_get_version_string

Source: https://opus-codec.org/docs/opus_api-1.6/opus__defines_8h_source.html

Gets the libopus version string.

```APIDOC
## opus_get_version_string

### Description
Gets the libopus version string.

### Function Signature
`const char *opus_get_version_string(void)`

### Parameters
None.

### Returns
- **const char*** - A pointer to a null-terminated string containing the version information.

```

--------------------------------

### op_fdopen

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__stream__callbacks.html

Opens a stream with fdopen() and fills in a set of callbacks for accessing it. Useful for portable 64-bit seeking and avoiding cross-module linking issues on Windows.

```APIDOC
## op_fdopen

### Description
Opens a stream with `fdopen()` and fills in a set of callbacks that can be used to access it. This is useful to avoid writing your own portable 64-bit seeking wrappers, and also avoids cross-module linking issues on Windows, where a `FILE *` must be accessed by routines defined in the same module that opened it.

### Function Signature
```c
OP_WARN_UNUSED_RESULT void* op_fdopen(OpusFileCallbacks *__cb_, int __fd_, const char *__mode_)
```

### Parameters
- **__cb_** (OpusFileCallbacks *) - Output - The callbacks to use for this file. If there is an error opening the file, nothing will be filled in here.
- **__fd_** (int) - Input - The file descriptor to open.
- **__mode_** (const char *) - Input - The mode to open the file in.

### Returns
A stream handle to use with the callbacks, or `NULL` on error.
```

--------------------------------

### ope_encoder_get_page

Source: https://opus-codec.org/docs/libopusenc_api-0.3/opusenc_8h_source.html

Gets a page of encoded data.

```APIDOC
## ope_encoder_get_page

### Description
Gets a page of encoded data.

### Function Signature
`OPE_EXPORT int ope_encoder_get_page(OggOpusEnc *enc, unsigned char **page, opus_int32 *len, int flush)`

### Parameters
- **enc** (OggOpusEnc*) - The encoder.
- **page** (unsigned char**) - Pointer to store the page data.
- **len** (opus_int32*) - Pointer to store the page length.
- **flush** (int) - Whether to flush the encoder.

### Returns
- **int** - 0 on success, or a negative error code on failure.

```

--------------------------------

### opus_tags_get_track_gain

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__header__info.html

Gets the track gain from an R128_TRACK_GAIN tag.

```APIDOC
## opus_tags_get_track_gain

### Description
Get the track gain from an R128_TRACK_GAIN tag, if one was specified.

### Function Signature
`int opus_tags_get_track_gain(const OpusTags *_tags, int *_gain_q8) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2)`

### Parameters
- `_tags` (const OpusTags*) - Required - Pointer to the OpusTags structure.
- `_gain_q8` (int*) - Required - Pointer to an integer to receive the gain in Q8 format.

### Return Value
Returns 0 on success, or a negative error code if no track gain tag is present.
```

--------------------------------

### Basic opusenc usage: input.wav to output.opus

Source: https://opus-codec.org/docs/opus-tools/opusenc.html

Simplest usage. Takes input.wav and produces output.opus.

```shell
opusenc input.wav output.opus
```

--------------------------------

### opus_tags_get_album_gain

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__header__info.html

Gets the album gain from an R128_ALBUM_GAIN tag.

```APIDOC
## opus_tags_get_album_gain

### Description
Get the album gain from an R128_ALBUM_GAIN tag, if one was specified.

### Function Signature
`int opus_tags_get_album_gain(const OpusTags *_tags, int *_gain_q8) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2)`

### Parameters
- `_tags` (const OpusTags*) - Required - Pointer to the OpusTags structure.
- `_gain_q8` (int*) - Required - Pointer to an integer to receive the gain in Q8 format.

### Return Value
Returns 0 on success, or a negative error code if no album gain tag is present.
```

--------------------------------

### op_freopen

Source: https://opus-codec.org/docs/opusfile_api-0.12/group__stream__callbacks.html

Opens a stream with freopen() and fills in a set of callbacks.

```APIDOC
## op_freopen

### Description
Opens a stream with `freopen()` and fills in a set of callbacks that can be used to access it.

### Signature
```c
OP_WARN_UNUSED_RESULT void * op_freopen(OpusFileCallbacks *_cb, const char *_path, const char *_mode, void *_stream)
```

### Parameters
- **_cb** (OpusFileCallbacks*) - Callbacks structure to fill in.
- **_path** (const char*) - Path to the file to open.
- **_mode** (const char*) - File open mode (e.g., "rb").
- **_stream** (void*) - Existing stream to reuse.

### Returns
- (void*) - A stream handle, or NULL on failure.
```

--------------------------------

### OPUS_GET_COMPLEXITY

Source: https://opus-codec.org/docs/opus_api-1.6/group__opus__encoderctls.html

Gets the encoder's complexity configuration.

```APIDOC
## OPUS_GET_COMPLEXITY

### Description
Gets the encoder's complexity configuration.

### Parameters
#### Output Parameters
- **x** (`opus_int32 *`) - Required - Returns a value in the range 0-10, inclusive.

### See Also
- OPUS_SET_COMPLEXITY
```

--------------------------------

### OPUS_GET_BITRATE

Source: https://opus-codec.org/docs/opus_api-1.6/group__opus__encoderctls.html

Gets the encoder's bitrate configuration.

```APIDOC
## OPUS_GET_BITRATE

### Description
Gets the encoder's bitrate configuration.

### Parameters
#### Output Parameters
- **x** (`opus_int32 *`) - Required - Returns the bitrate in bits per second. The default is determined based on the number of channels and the input sampling rate.

### See Also
- OPUS_SET_BITRATE
```
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