Manpages - opus_multistream.3
Table of Contents
- NAME
- SYNOPSIS
- Detailed Description
- Typedef Documentation
- Function Documentation
- int opus_multistream_decode (OpusMSDecoder * st, const unsigned
- int opus_multistream_decode_float (OpusMSDecoder * st, const
- OpusMSDecoder* opus_multistream_decoder_create (opus_int32 Fs,
- int opus_multistream_decoder_ctl (OpusMSDecoder * st, int request,
- void opus_multistream_decoder_destroy (OpusMSDecoder * st)
- opus_int32 opus_multistream_decoder_get_size (int streams, int
- int opus_multistream_decoder_init (OpusMSDecoder * st, opus_int32
- mapping)
- pcm, int frame_size, unsigned char * data, opus_int32
- pcm, int frame_size, unsigned char * data, opus_int32
- OpusMSEncoder* opus_multistream_encoder_create (opus_int32 Fs,
- int opus_multistream_encoder_ctl (*OpusMSEncoder * st, int request,
- void opus_multistream_encoder_destroy (OpusMSEncoder * st)
- *opus_int32 opus_multistream_encoder_get_size (int streams, int
- int opus_multistream_encoder_init (*OpusMSEncoder * st, opus_int32
- mapping, int application)*
- Author
NAME
opus_multistream - The multistream API allows individual Opus streams to be combined into a single packet, enabling support for up to 255 channels. Unlike an elementary Opus stream, the encoder and decoder must negotiate the channel configuration before the decoder can successfully interpret the data in the packets produced by the encoder. Some basic information, such as packet duration, can be computed without any special negotiation.
SYNOPSIS
Typedefs
typedef struct OpusMSEncoder OpusMSEncoder
Opus multistream encoder state.
typedef struct OpusMSDecoder OpusMSDecoder
Opus multistream decoder state.
Multistream encoder functions
opus_int32 opus_multistream_encoder_get_size (int streams, int
coupled_streams)
Gets the size of an OpusMSEncoder structure.
opus_int32 opus_multistream_surround_encoder_get_size (int channels,
int mapping_family)
OpusMSEncoder * opus_multistream_encoder_create (opus_int32 Fs,
int channels, int streams, int coupled_streams, const unsigned char
*mapping, int application, int *error)
Allocates and initializes a multistream encoder state.
OpusMSEncoder * opus_multistream_surround_encoder_create
(opus_int32 Fs, int channels, int mapping_family, int *streams, int
*coupled_streams, unsigned char *mapping, int application, int *error)
int opus_multistream_encoder_init (OpusMSEncoder st, *opus_int32
Fs, int channels, int streams, int coupled_streams, const unsigned char
*mapping, int application)
Initialize a previously allocated multistream encoder state.
int opus_multistream_surround_encoder_init (OpusMSEncoder st,
*opus_int32 Fs, int channels, int mapping_family, int *streams, int
*coupled_streams, unsigned char *mapping, int application)
int opus_multistream_encode (OpusMSEncoder st, const *opus_int16
pcm, int frame_size, unsigned char *data, *opus_int32
max_data_bytes)
Encodes a multistream Opus frame.
int opus_multistream_encode_float (OpusMSEncoder st, const float
*pcm, int frame_size, unsigned char *data, *opus_int32
max_data_bytes)
Encodes a multistream Opus frame from floating point input.
void opus_multistream_encoder_destroy (OpusMSEncoder st)
Frees an OpusMSEncoder
allocated by
*opus_multistream_encoder_create().
int opus_multistream_encoder_ctl (OpusMSEncoder *st, int
request,…)
Perform a CTL function on a multistream Opus encoder.
Multistream decoder functions
opus_int32 opus_multistream_decoder_get_size (int streams, int
coupled_streams)
Gets the size of an OpusMSDecoder
structure.
OpusMSDecoder * opus_multistream_decoder_create (opus_int32 Fs,
int channels, int streams, int coupled_streams, const unsigned char
*mapping, int *error)
Allocates and initializes a multistream decoder state.
int opus_multistream_decoder_init (OpusMSDecoder st, *opus_int32
Fs, int channels, int streams, int coupled_streams, const unsigned char
*mapping)
Intialize a previously allocated decoder state object.
int opus_multistream_decode (OpusMSDecoder st, const unsigned char
*data, *opus_int32 len, opus_int16 *pcm, int frame_size, int
decode_fec)
Decode a multistream Opus packet.
int opus_multistream_decode_float (OpusMSDecoder st, const unsigned
char *data, *opus_int32 len, float *pcm, int frame_size, int
decode_fec)
Decode a multistream Opus packet with floating point output.
int opus_multistream_decoder_ctl (OpusMSDecoder *st, int
request,…)
Perform a CTL function on a multistream Opus decoder.
void opus_multistream_decoder_destroy (OpusMSDecoder st)
Frees an OpusMSDecoder
allocated by
*opus_multistream_decoder_create().
Detailed Description
The multistream API allows individual Opus streams to be combined into a single packet, enabling support for up to 255 channels. Unlike an elementary Opus stream, the encoder and decoder must negotiate the channel configuration before the decoder can successfully interpret the data in the packets produced by the encoder. Some basic information, such as packet duration, can be computed without any special negotiation.
The format for multistream Opus packets is defined in RFC 7845
and is
based on the self-delimited Opus framing described in Appendix B of
RFC 6716
. Normal Opus packets are just a degenerate case of
multistream Opus packets, and can be encoded or decoded with the
multistream API by setting streams
to 1
when initializing the
encoder or decoder.
Multistream Opus streams can contain up to 255 elementary Opus streams. These may be either ’uncoupled’ or ’coupled’, indicating that the decoder is configured to decode them to either 1 or 2 channels, respectively. The streams are ordered so that all coupled streams appear at the beginning.
A mapping
table defines which decoded channel i
should be used for
each input/output (I/O) channel j
. This table is typically provided as
an unsigned char array. Let i = mapping[j]
be the index for I/O
channel j
. If i < 2*coupled_streams
, then I/O channel j
is encoded
as the left channel of stream (i/2)
if i
is even, or as the right
channel of stream (i/2)
if i
is odd. Otherwise, I/O channel j
is
encoded as mono in stream (i - coupled_streams)
, unless it has the
special value 255, in which case it is omitted from the encoding
entirely (the decoder will reproduce it as silence). Each value i
must
either be the special value 255 or be less than
streams + coupled_streams
.
The output channels specified by the encoder should use the
Vorbis channel ordering
. A decoder may wish to apply an additional
permutation to the mapping the encoder used to achieve a different
output channel order (e.g. for outputing in WAV order).
Each multistream packet contains an Opus packet for each stream, and all of the Opus packets in a single multistream packet must have the same duration. Therefore the duration of a multistream packet can be extracted from the TOC sequence of the first stream, which is located at the beginning of the packet, just like an elementary Opus stream:
int nb_samples; int nb_frames; nb_frames = opus_packet_get_nb_frames(data, len); if (nb_frames < 1) return nb_frames; nb_samples = opus_packet_get_samples_per_frame(data, 48000) * nb_frames;
The general encoding and decoding process proceeds exactly the same as in the normal Opus Encoder and Opus Decoder APIs. See their documentation for an overview of how to use the corresponding multistream functions.
Typedef Documentation
typedef struct OpusMSDecoder OpusMSDecoder
Opus multistream decoder state. This contains the complete state of a multistream Opus decoder. It is position independent and can be freely copied.
See also
opus_multistream_decoder_create
opus_multistream_decoder_init
typedef struct OpusMSEncoder OpusMSEncoder
Opus multistream encoder state. This contains the complete state of a multistream Opus encoder. It is position independent and can be freely copied.
See also
opus_multistream_encoder_create
opus_multistream_encoder_init
Function Documentation
int opus_multistream_decode (OpusMSDecoder * st, const unsigned
char * data, opus_int32 len, opus_int16 * pcm, int frame_size, int decode_fec) Decode a multistream Opus packet.
Parameters
st
OpusMSDecoder*
: Multistream decoder state.
dataconst unsigned char*
: Input payload. Use aNULL
pointer to indicate packet loss.
lenopus_int32
: Number of bytes in payload.
pcmopus_int16*
: Output signal, with interleaved samples. This must contain room forframe_size*channels
samples.
frame_sizeint
: The number of samples per channel of available space in pcm. If this is less than the maximum packet duration (120 ms; 5760 for 48kHz), this function will not be capable of decoding some packets. In the case of PLC (data==NULL) or FEC (decode_fec=1), then frame_size needs to be exactly the duration of audio that is missing, otherwise the decoder will not be in the optimal state to decode the next incoming packet. For the PLC and FEC cases, frame_size must be a multiple of 2.5 ms.
decode_fecint
: Flag (0 or 1) to request that any in-band forward error correction data be decoded. If no such data is available, the frame is decoded as if it were lost.
Returns
Number of samples decoded on success or a negative error code (see Error codes) on failure.
int opus_multistream_decode_float (OpusMSDecoder * st, const
unsigned char * data, opus_int32 len, float * pcm, int frame_size, int decode_fec) Decode a multistream Opus packet with floating point output.
Parameters
st
OpusMSDecoder*
: Multistream decoder state.
dataconst unsigned char*
: Input payload. Use aNULL
pointer to indicate packet loss.
lenopus_int32
: Number of bytes in payload.
pcmopus_int16*
: Output signal, with interleaved samples. This must contain room forframe_size*channels
samples.
frame_sizeint
: The number of samples per channel of available space in pcm. If this is less than the maximum packet duration (120 ms; 5760 for 48kHz), this function will not be capable of decoding some packets. In the case of PLC (data==NULL) or FEC (decode_fec=1), then frame_size needs to be exactly the duration of audio that is missing, otherwise the decoder will not be in the optimal state to decode the next incoming packet. For the PLC and FEC cases, frame_size must be a multiple of 2.5 ms.
decode_fecint
: Flag (0 or 1) to request that any in-band forward error correction data be decoded. If no such data is available, the frame is decoded as if it were lost.
Returns
Number of samples decoded on success or a negative error code (see Error codes) on failure.
OpusMSDecoder* opus_multistream_decoder_create (opus_int32 Fs,
int channels, int streams, int coupled_streams, const unsigned char * mapping, int * error) Allocates and initializes a multistream decoder state. Call opus_multistream_decoder_destroy() to release this object when finished.
Parameters
Fs
opus_int32
: Sampling rate to decode at (in Hz). This must be one of 8000, 12000, 16000, 24000, or 48000.
channelsint
: Number of channels to output. This must be at most 255. It may be different from the number of coded channels (streams + coupled_streams
).
streamsint
: The total number of streams coded in the input. This must be no more than 255.
coupled_streamsint
: Number of streams to decode as coupled (2 channel) streams. This must be no larger than the total number of streams. Additionally, The total number of coded channels (streams + coupled_streams
) must be no more than 255.
mappingconst unsigned char[channels]
: Mapping from coded channels to output channels, as described in Opus Multistream API.
errorint *
: Returns OPUS_OK on success, or an error code (see Error codes) on failure.
int opus_multistream_decoder_ctl (OpusMSDecoder * st, int request,
…) Perform a CTL function on a multistream Opus decoder. Generally the request and subsequent arguments are generated by a convenience macro.
Parameters
st
OpusMSDecoder*
: Multistream decoder state.
request This and all remaining parameters should be replaced by one of the convenience macros in Generic CTLs, Decoder related CTLs, or Multistream specific encoder and decoder CTLs.
See also
Generic CTLs
Decoder related CTLs
Multistream specific encoder and decoder CTLs
void opus_multistream_decoder_destroy (OpusMSDecoder * st)
Frees an OpusMSDecoder
allocated by
opus_multistream_decoder_create().
Parameters
st
OpusMSDecoder
: Multistream decoder state to be freed.
opus_int32 opus_multistream_decoder_get_size (int streams, int
coupled_streams)
Gets the size of an OpusMSDecoder
structure.
Parameters
streams
int
: The total number of streams coded in the input. This must be no more than 255.
coupled_streamsint
: Number streams to decode as coupled (2 channel) streams. This must be no larger than the total number of streams. Additionally, The total number of coded channels (streams + coupled_streams
) must be no more than 255.
Returns
The size in bytes on success, or a negative error code (see Error codes) on error.
int opus_multistream_decoder_init (OpusMSDecoder * st, opus_int32
Fs, int channels, int streams, int coupled_streams, const unsigned char
mapping)
Intialize a previously allocated decoder state object. The memory pointed to by st must be at least the size returned by opus_multistream_encoder_get_size(). This is intended for applications which use their own allocator instead of malloc. To reset a previously initialized state, use the OPUS_RESET_STATE CTL.
See also
opus_multistream_decoder_create
opus_multistream_deocder_get_size
Parameters
st
OpusMSEncoder*
: Multistream encoder state to initialize.
Fsopus_int32
: Sampling rate to decode at (in Hz). This must be one of 8000, 12000, 16000, 24000, or 48000.
channelsint
: Number of channels to output. This must be at most 255. It may be different from the number of coded channels (streams + coupled_streams
).
streamsint
: The total number of streams coded in the input. This must be no more than 255.
coupled_streamsint
: Number of streams to decode as coupled (2 channel) streams. This must be no larger than the total number of streams. Additionally, The total number of coded channels (streams + coupled_streams
) must be no more than 255.
mappingconst unsigned char[channels]
: Mapping from coded channels to output channels, as described in Opus Multistream API.
Returns
OPUS_OK on success, or an error code (see Error codes) on failure.
int opus_multistream_encode (OpusMSEncoder * st, const opus_int16
pcm, int frame_size, unsigned char * data, opus_int32
max_data_bytes) Encodes a multistream Opus frame.
Parameters
st
OpusMSEncoder*
: Multistream encoder state.
pcmconst opus_int16*
: The input signal as interleaved samples. This must containframe_size*channels
samples.
frame_sizeint
: Number of samples per channel in the input signal. This must be an Opus frame size for the encoder’s sampling rate. For example, at 48 kHz the permitted values are 120, 240, 480, 960, 1920, and 2880. Passing in a duration of less than 10 ms (480 samples at 48 kHz) will prevent the encoder from using the LPC or hybrid modes.
dataunsigned char*
: Output payload. This must contain storage for at least max_data_bytes.
max_data_bytesopus_int32
: Size of the allocated memory for the output payload. This may be used to impose an upper limit on the instant bitrate, but should not be used as the only bitrate control. Use OPUS_SET_BITRATE to control the bitrate.
Returns
The length of the encoded packet (in bytes) on success or a negative error code (see Error codes) on failure.
int opus_multistream_encode_float (OpusMSEncoder * st, const float
pcm, int frame_size, unsigned char * data, opus_int32
max_data_bytes) Encodes a multistream Opus frame from floating point input.
Parameters
st
OpusMSEncoder*
: Multistream encoder state.
pcmconst float*
: The input signal as interleaved samples with a normal range of +/-1.0. Samples with a range beyond +/-1.0 are supported but will be clipped by decoders using the integer API and should only be used if it is known that the far end supports extended dynamic range. This must containframe_size*channels
samples.
frame_sizeint
: Number of samples per channel in the input signal. This must be an Opus frame size for the encoder’s sampling rate. For example, at 48 kHz the permitted values are 120, 240, 480, 960, 1920, and 2880. Passing in a duration of less than 10 ms (480 samples at 48 kHz) will prevent the encoder from using the LPC or hybrid modes.
dataunsigned char*
: Output payload. This must contain storage for at least max_data_bytes.
max_data_bytesopus_int32
: Size of the allocated memory for the output payload. This may be used to impose an upper limit on the instant bitrate, but should not be used as the only bitrate control. Use OPUS_SET_BITRATE to control the bitrate.
Returns
The length of the encoded packet (in bytes) on success or a negative error code (see Error codes) on failure.
OpusMSEncoder* opus_multistream_encoder_create (opus_int32 Fs,
int channels, int streams, int coupled_streams, const unsigned char * mapping, int application, int * error) Allocates and initializes a multistream encoder state. Call opus_multistream_encoder_destroy() to release this object when finished.
Parameters
Fs
opus_int32
: Sampling rate of the input signal (in Hz). This must be one of 8000, 12000, 16000, 24000, or 48000.
channelsint
: Number of channels in the input signal. This must be at most 255. It may be greater than the number of coded channels (streams + coupled_streams
).
streamsint
: The total number of streams to encode from the input. This must be no more than the number of channels.
coupled_streamsint
: Number of coupled (2 channel) streams to encode. This must be no larger than the total number of streams. Additionally, The total number of encoded channels (streams + coupled_streams
) must be no more than the number of input channels.
mappingconst unsigned char[channels]
: Mapping from encoded channels to input channels, as described in Opus Multistream API. As an extra constraint, the multistream encoder does not allow encoding coupled streams for which one channel is unused since this is never a good idea.
applicationint
: The target encoder application. This must be one of the following:
- OPUS_APPLICATION_VOIP
- Process signal for improved speech intelligibility.
- OPUS_APPLICATION_AUDIO
- Favor faithfulness to the original input.
- OPUS_APPLICATION_RESTRICTED_LOWDELAY
- Configure the minimum possible coding delay by disabling certain modes of operation.
/error/*int *
: Returns OPUS_OK on success, or an error code (see Error codes) on failure. *
int opus_multistream_encoder_ctl (*OpusMSEncoder * st, int request,
…)* Perform a CTL function on a multistream Opus encoder. Generally the request and subsequent arguments are generated by a convenience macro.
Parameters
/st/*
OpusMSEncoder*
: Multistream encoder state.
request This and all remaining parameters should be replaced by one of the convenience macros in Generic CTLs, Encoder related CTLs, or Multistream specific encoder and decoder CTLs. *
See also
*Generic CTLs *
*Encoder related CTLs *
*Multistream specific encoder and decoder CTLs *
void opus_multistream_encoder_destroy (OpusMSEncoder * st)
Frees an =OpusMSEncoder=* allocated by opus_multistream_encoder_create(). *
Parameters
/st/*
OpusMSEncoder*
: Multistream encoder state to be freed. *
*opus_int32 opus_multistream_encoder_get_size (int streams, int
coupled_streams)* Gets the size of an OpusMSEncoder structure.
Parameters
/streams/*
int
: The total number of streams to encode from the input. This must be no more than 255.
coupled_streamsint
: Number of coupled (2 channel) streams to encode. This must be no larger than the total number of streams. Additionally, The total number of encoded channels (streams + coupled_streams
) must be no more than 255. *
Returns
The size in bytes on success, or a negative error code (see *Error codes) on error. *
int opus_multistream_encoder_init (*OpusMSEncoder * st, opus_int32
Fs, int channels, int streams, int coupled_streams, const unsigned char
mapping, int application)*
Initialize a previously allocated multistream encoder state. The memory pointed to by /st/* must be at least the size returned by opus_multistream_encoder_get_size(). This is intended for applications which use their own allocator instead of malloc. To reset a previously initialized state, use the OPUS_RESET_STATE CTL. *
See also
*opus_multistream_encoder_create *
*opus_multistream_encoder_get_size *
Parameters
/st/*
OpusMSEncoder*
: Multistream encoder state to initialize.
Fsopus_int32
: Sampling rate of the input signal (in Hz). This must be one of 8000, 12000, 16000, 24000, or 48000.
channelsint
: Number of channels in the input signal. This must be at most 255. It may be greater than the number of coded channels (streams + coupled_streams
).
streamsint
: The total number of streams to encode from the input. This must be no more than the number of channels.
coupled_streamsint
: Number of coupled (2 channel) streams to encode. This must be no larger than the total number of streams. Additionally, The total number of encoded channels (streams + coupled_streams
) must be no more than the number of input channels.
mappingconst unsigned char[channels]
: Mapping from encoded channels to input channels, as described in Opus Multistream API. As an extra constraint, the multistream encoder does not allow encoding coupled streams for which one channel is unused since this is never a good idea.
applicationint
: The target encoder application. This must be one of the following: *
- OPUS_APPLICATION_VOIP
- Process signal for improved speech intelligibility.
- OPUS_APPLICATION_AUDIO
- Favor faithfulness to the original input.
- OPUS_APPLICATION_RESTRICTED_LOWDELAY
- Configure the minimum possible coding delay by disabling certain modes of operation.
Returns
*OPUS_OK on success, or an error code (see Error codes) on failure. *
OpusMSEncoder opus_multistream_surround_encoder_create (opus_int32
Fs, int channels, int mapping_family, int * streams, int * coupled_streams, unsigned char * mapping, int application, int * error)*
*opus_int32 opus_multistream_surround_encoder_get_size (int channels,
int mapping_family)*
int opus_multistream_surround_encoder_init (*OpusMSEncoder * st,
opus_int32 Fs, int channels, int mapping_family, int * streams, int * coupled_streams, unsigned char * mapping, int application)*
Author
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