qcelpdec.c File Reference

QCELP decoder. More...

#include <stddef.h>
#include "libavutil/avassert.h"
#include "libavutil/channel_layout.h"
#include "libavutil/float_dsp.h"
#include "avcodec.h"
#include "internal.h"
#include "get_bits.h"
#include "qcelpdata.h"
#include "celp_filters.h"
#include "acelp_filters.h"
#include "acelp_vectors.h"
#include "lsp.h"

Go to the source code of this file.

Data Structures
struct	QCELPContext

Enumerations
enum	qcelp_packet_rate {   I_F_Q = -1, SILENCE, RATE_OCTAVE, RATE_QUARTER,   RATE_HALF, RATE_FULL }

Functions
static av_cold int	qcelp_decode_init (AVCodecContext *avctx)
	Initialize the speech codec according to the specification. More...
static int	decode_lspf (QCELPContext *q, float *lspf)
	Decode the 10 quantized LSP frequencies from the LSPV/LSP transmission codes of any bitrate and check for badly received packets. More...
static void	decode_gain_and_index (QCELPContext *q, float *gain)
	Convert codebook transmission codes to GAIN and INDEX. More...
static int	codebook_sanity_check_for_rate_quarter (const uint8_t *cbgain)
	If the received packet is Rate 1/4 a further sanity check is made of the codebook gain. More...
static void	compute_svector (QCELPContext *q, const float *gain, float *cdn_vector)
	Compute the scaled codebook vector Cdn From INDEX and GAIN for all rates. More...
static void	apply_gain_ctrl (float *v_out, const float *v_ref, const float *v_in)
	Apply generic gain control. More...
static const float *	do_pitchfilter (float memory[303], const float v_in[160], const float gain[4], const uint8_t *lag, const uint8_t pfrac[4])
	Apply filter in pitch-subframe steps. More...
static void	apply_pitch_filters (QCELPContext *q, float *cdn_vector)
	Apply pitch synthesis filter and pitch prefilter to the scaled codebook vector. More...
static void	lspf2lpc (const float *lspf, float *lpc)
	Reconstruct LPC coefficients from the line spectral pair frequencies and perform bandwidth expansion. More...
static void	interpolate_lpc (QCELPContext *q, const float *curr_lspf, float *lpc, const int subframe_num)
	Interpolate LSP frequencies and compute LPC coefficients for a given bitrate & pitch subframe. More...
static qcelp_packet_rate	buf_size2bitrate (const int buf_size)
static qcelp_packet_rate	determine_bitrate (AVCodecContext *avctx, const int buf_size, const uint8_t **buf)
	Determine the bitrate from the frame size and/or the first byte of the frame. More...
static void	warn_insufficient_frame_quality (AVCodecContext *avctx, const char *message)
static void	postfilter (QCELPContext *q, float *samples, float *lpc)
static int	qcelp_decode_frame (AVCodecContext *avctx, void *data, int *got_frame_ptr, AVPacket *avpkt)

Variables
AVCodec	ff_qcelp_decoder

Detailed Description

QCELP decoder.

Author

Reynaldo H. Verdejo Pinochet

Remarks

FFmpeg merging spearheaded by Kenan Gillet

Development mentored by Benjamin Larson

Definition in file qcelpdec.c.

Enumeration Type Documentation

qcelp_packet_rate

enum qcelp_packet_rate

Enumerator
I_F_Q	insufficient frame quality
SILENCE
RATE_OCTAVE
RATE_QUARTER
RATE_HALF
RATE_FULL

Definition at line 44 of file qcelpdec.c.

Function Documentation

qcelp_decode_init()

static av_cold int qcelp_decode_init ( AVCodecContext *  avctx )

static

Initialize the speech codec according to the specification.

TIA/EIA/IS-733 2.4.9

Definition at line 85 of file qcelpdec.c.

decode_lspf()

static int decode_lspf ( QCELPContext *  q, float *  lspf  )

static

Decode the 10 quantized LSP frequencies from the LSPV/LSP transmission codes of any bitrate and check for badly received packets.

Parameters

q	the context
lspf	line spectral pair frequencies

Returns

0 on success, -1 if the packet is badly received

TIA/EIA/IS-733 2.4.3.2.6.2-2, 2.4.8.7.3

Definition at line 111 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

decode_gain_and_index()

static void decode_gain_and_index ( QCELPContext *  q, float *  gain  )

static

Convert codebook transmission codes to GAIN and INDEX.

Parameters

q	the context
gain	array holding the decoded gain

TIA/EIA/IS-733 2.4.6.2

Definition at line 195 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

codebook_sanity_check_for_rate_quarter()

static int codebook_sanity_check_for_rate_quarter ( const uint8_t *  cbgain )

static

If the received packet is Rate 1/4 a further sanity check is made of the codebook gain.

Parameters

cbgain

the unpacked cbgain array

Returns

-1 if the sanity check fails, 0 otherwise

TIA/EIA/IS-733 2.4.8.7.3

Definition at line 273 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

compute_svector()

static void compute_svector ( QCELPContext *  q, const float *  gain, float *  cdn_vector  )

static

Compute the scaled codebook vector Cdn From INDEX and GAIN for all rates.

The specification lacks some information here.

TIA/EIA/IS-733 has an omission on the codebook index determination formula for RATE_FULL and RATE_HALF frames at section 2.4.8.1.1. It says you have to subtract the decoded index parameter from the given scaled codebook vector index 'n' to get the desired circular codebook index, but it does not mention that you have to clamp 'n' to [0-9] in order to get RI-compliant results.

The reason for this mistake seems to be the fact they forgot to mention you have to do these calculations per codebook subframe and adjust given equation values accordingly.

Parameters

q	the context
gain	array holding the 4 pitch subframe gain values
cdn_vector	array for the generated scaled codebook vector

Definition at line 309 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

apply_gain_ctrl()

static void apply_gain_ctrl ( float *  v_out, const float *  v_ref, const float *  v_in  )

static

Apply generic gain control.

Parameters

v_out	output vector
v_in	gain-controlled vector
v_ref	vector to control gain of

TIA/EIA/IS-733 2.4.8.3, 2.4.8.6

Definition at line 396 of file qcelpdec.c.

Referenced by apply_pitch_filters().

do_pitchfilter()

static const float* do_pitchfilter ( float  memory[303], const float  v_in[160], const float  gain[4], const uint8_t *  lag, const uint8_t  pfrac[4]  )

static

Apply filter in pitch-subframe steps.

Parameters

memory	buffer for the previous state of the filter must be able to contain 303 elements the 143 first elements are from the previous state the next 160 are for output
v_in	input filter vector
gain	per-subframe gain array, each element is between 0.0 and 2.0
lag	per-subframe lag array, each element is between 16 and 143 if its corresponding pfrac is 0, between 16 and 139 otherwise
pfrac	per-subframe boolean array, 1 if the lag is fractional, 0 otherwise

Returns

filter output vector

Definition at line 423 of file qcelpdec.c.

Referenced by apply_pitch_filters().

apply_pitch_filters()

static void apply_pitch_filters ( QCELPContext *  q, float *  cdn_vector  )

static

Apply pitch synthesis filter and pitch prefilter to the scaled codebook vector.

TIA/EIA/IS-733 2.4.5.2, 2.4.8.7.2

Parameters

q	the context
cdn_vector	the scaled codebook vector

Definition at line 467 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

lspf2lpc()

static void lspf2lpc ( const float *  lspf, float *  lpc  )

static

Reconstruct LPC coefficients from the line spectral pair frequencies and perform bandwidth expansion.

Parameters

lspf	line spectral pair frequencies
lpc	linear predictive coding coefficients

Note

: bandwidth_expansion_coeff could be precalculated into a table but it seems to be slower on x86

TIA/EIA/IS-733 2.4.3.3.5

Definition at line 536 of file qcelpdec.c.

Referenced by interpolate_lpc().

interpolate_lpc()

static void interpolate_lpc ( QCELPContext *  q, const float *  curr_lspf, float *  lpc, const int  subframe_num  )

static

Interpolate LSP frequencies and compute LPC coefficients for a given bitrate & pitch subframe.

TIA/EIA/IS-733 2.4.3.3.4, 2.4.8.7.2

Parameters

q	the context
curr_lspf	LSP frequencies vector of the current frame
lpc	float vector for the resulting LPC
subframe_num	frame number in decoded stream

Definition at line 564 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

buf_size2bitrate()

static qcelp_packet_rate buf_size2bitrate ( const int  buf_size )

static

Definition at line 588 of file qcelpdec.c.

Referenced by determine_bitrate().

determine_bitrate()

static qcelp_packet_rate determine_bitrate ( AVCodecContext *  avctx, const int  buf_size, const uint8_t **  buf  )

static

Determine the bitrate from the frame size and/or the first byte of the frame.

Parameters

avctx	the AV codec context
buf_size	length of the buffer
buf	the buffer

Returns

the bitrate on success, I_F_Q if the bitrate cannot be satisfactorily determined

TIA/EIA/IS-733 2.4.8.7.1

Definition at line 613 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

warn_insufficient_frame_quality()

static void warn_insufficient_frame_quality ( AVCodecContext *  avctx, const char *  message  )

static

Definition at line 647 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

postfilter()

static void postfilter ( QCELPContext *  q, float *  samples, float *  lpc  )

static

Definition at line 654 of file qcelpdec.c.

Referenced by qcelp_decode_frame().

qcelp_decode_frame()

static int qcelp_decode_frame ( AVCodecContext *  avctx, void *  data, int *  got_frame_ptr, AVPacket *  avpkt  )

static

Definition at line 686 of file qcelpdec.c.

Variable Documentation

ff_qcelp_decoder

AVCodec ff_qcelp_decoder

Initial value:

= {
    .name           = "qcelp",
    .long_name      = NULL_IF_CONFIG_SMALL("QCELP / PureVoice"),
    .type           = AVMEDIA_TYPE_AUDIO,
    .id             = AV_CODEC_ID_QCELP,
    .init           = qcelp_decode_init,
    .decode         = qcelp_decode_frame,
    .capabilities   = AV_CODEC_CAP_DR1,
    .priv_data_size = sizeof(QCELPContext),
}

Definition at line 793 of file qcelpdec.c.