Encoding and decoding

Functions
CELTMode *	celt_mode_create (celt_int32_t Fs, int channels, int frame_size, int lookahead, int *error)
void	celt_mode_destroy (CELTMode *mode)
int	celt_mode_info (const CELTMode *mode, int request, celt_int32_t *value)
CELTEncoder *	celt_encoder_create (const CELTMode *mode)
void	celt_encoder_destroy (CELTEncoder *st)
int	celt_encode (CELTEncoder *st, celt_int16_t *pcm, unsigned char *compressed, int nbCompressedBytes)
CELTDecoder *	celt_decoder_create (const CELTMode *mode)
void	celt_decoder_destroy (CELTDecoder *st)
int	celt_decode (CELTDecoder *st, unsigned char *data, int len, celt_int16_t *pcm)

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Detailed Description

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Function Documentation

int celt_decode	(	CELTDecoder *	st,
		unsigned char *	data,
		int	len,
		celt_int16_t *	pcm
	)

Decodes a frame of audio.

Parameters:

	st	Decoder state
	data	Compressed data produced by an encoder
	len	Number of bytes to read from "data". This MUST be exactly the number of bytes returned by the encoder. Using a larger value WILL NOT WORK.
	pcm	One frame (frame_size samples per channel) of decoded PCM will be returned here.

Returns:

Error code.

CELTDecoder* celt_decoder_create

(

const CELTMode *

mode

)

Creates a new decoder state. Each stream needs its own decoder state (can't be shared across simultaneous streams).

Parameters:

mode

Contains all the information about the characteristics of the stream (must be the same characteristics as used for the encoder)

Returns:

Newly created decoder state.

void celt_decoder_destroy

(

CELTDecoder *

st

)

Destroys a a decoder state.

Parameters:

st

Decoder state to be destroyed

int celt_encode	(	CELTEncoder *	st,
		celt_int16_t *	pcm,
		unsigned char *	compressed,
		int	nbCompressedBytes
	)

Encodes a frame of audio.

Parameters:

	st	Encoder state
	pcm	PCM audio in signed 16-bit format (native endian). There must be exactly frame_size samples per channel. The input data is overwritten by a copy of what the remote decoder would decode.
	compressed	The compressed data is written here
	nbCompressedBytes	Number of bytes to use for compressing the frame (can change from one frame to another)

Returns:

Number of bytes written to "compressed". Should be the same as "nbCompressedBytes" unless the stream is VBR. If negative, an error has occured (see error codes). It is IMPORTANT that the length returned be somehow transmitted to the decoder. Otherwise, no decoding is possible.

CELTEncoder* celt_encoder_create

(

const CELTMode *

mode

)

Creates a new encoder state. Each stream needs its own encoder state (can't be shared across simultaneous streams).

Parameters:

mode

Contains all the information about the characteristics of the stream (must be the same characteristics as used for the decoder)

Returns:

Newly created encoder state.

void celt_encoder_destroy

(

CELTEncoder *

st

)

Destroys a an encoder state.

Parameters:

st

Encoder state to be destroyed

CELTMode* celt_mode_create	(	celt_int32_t	Fs,
		int	channels,
		int	frame_size,
		int	lookahead,
		int *	error
	)

Creates a new mode struct. This will be passed to an encoder or decoder. The mode MUST NOT BE DESTROYED until the encoders and decoders that use it are destroyed as well.

Parameters:

	Fs	Sampling rate (32000 to 64000 Hz)
	channels	Number of channels
	frame_size	Number of samples (per channel) to encode in each packet (64 - 256)
	lookahead	Extra latency (in samples per channel) in addition to the frame size (between 32 and frame_size). The larger that value, the better the quality (at the expense of latency)
	error	Returned error code (if NULL, no error will be returned)

Returns:

A newly created mode

void celt_mode_destroy

(

CELTMode *

mode

)

Destroys a mode struct. Only call this after all encoders and decoders using this mode are destroyed as well.

Parameters:

mode

Mode to be destroyed

int celt_mode_info	(	const CELTMode *	mode,
		int	request,
		celt_int32_t *	value
	)

Query information from a mode