Add new LC3 decoder am: 1fdc954d8b (977495cf) · Commits · e / os / android_packages_modules_Bluetooth

system/embdrv/lc3/include/lc3.h

+60 −19

Original line number	Diff line number	Diff line
		@@ -24,7 +24,7 @@
		* Bluetooth Specification v1.0
		*
		*
		* The LC3 is an efficient, low latency, audio codec.
		* The LC3 is an efficient low latency audio codec.
		*
		* - Unlike most other codecs, the LC3 codec is focused on audio streaming
		* in constrained (on packet sizes and interval) tranport layer.
		@@ -35,8 +35,8 @@
		* the user (or transport layer).
		*
		* However, the bitrate (bytes budget for encoding a frame) can be
		* freely changed at any time. BUT it does never rely on signal
		* complexity, it can follow a temporary bandwidth increase or reduction.
		* freely changed at any time. But will not rely on signal complexity,
		* it can follow a temporary bandwidth increase or reduction.
		*
		* - Unlike classic codecs, the LC3 codecs does not run on fixed amount
		* of samples as input. It operate only on fixed frame duration, for
		@@ -54,8 +54,8 @@
		* 1. The frame size will not be 7.5 ms or 10 ms, but is scaled
		* by 'supported samplerate' / 'input samplerate'
		*
		* 2. The bandwith will be hard limited (to 20 KHz) if you select 48 KHz.
		* The encoded bandwith will also be affected by the above inverse
		* 2. The bandwidth will be hard limited (to 20 KHz) if you select 48 KHz.
		* The encoded bandwidth will also be affected by the above inverse
		* factor of 20 KHz.
		*
		* Applied to 44.1 KHz, we get :
		@@ -63,23 +63,23 @@
		* 1. About 8.16 ms frame duration, instead of 7.5 ms
		* About 10.88 ms frame duration, instead of 10 ms
		*
		* 2. The bandwith becomes limited to 18.375 KHz
		* 2. The bandwidth becomes limited to 18.375 KHz
		*
		*
		* --- How to encode ---
		* --- How to encode / decode ---
		*
		* An encoder context need to be setup. This context keep states on
		* the current stream to encode, and samples that overlapped accross
		* An encoder / decoder context need to be setup. This context keep states
		* on the current stream to proceed, and samples that overlapped across
		* frames.
		*
		* You have two ways to setup the encoder :
		* You have two ways to setup the encoder / decoder :
		*
		* - Using static memory allocation (this module does not rely on
		* any dynamic memory allocation). The types `lc3_encoder_mem_16k_t`,
		* and `lc3_encoder_mem_48k_t` have size of the memory needed for
		* any dynamic memory allocation). The types `lc3_xxcoder_mem_16k_t`,
		* and `lc3_xxcoder_mem_48k_t` have size of the memory needed for
		* encoding up to 16 KHz or 48 KHz.
		*
		* - Using dynamic memory allocation. The `lc3_encoder_size()` procedure
		* - Using dynamic memory allocation. The `lc3_xxcoder_size()` procedure
		* returns the needed memory size, for a given configuration. The memory
		* space must be aligned to a pointer size. As an example, you can setup
		* encoder like this :
		@@ -149,6 +149,7 @@ extern "C" {
		*/

		typedef struct lc3_encoder *lc3_encoder_t;
		typedef struct lc3_decoder *lc3_decoder_t;


		/**
		@@ -156,18 +157,22 @@ typedef struct lc3_encoder *lc3_encoder_t;
		*
		* Propose types suitable for static memory allocation, supporting
		* any frame duration, and maximum samplerates 16k and 48k respectively
		* You can customize your type using the `LC3_ENCODER_MEM_T` macro.
		* You can customize your type using the `LC3_ENCODER_MEM_T` or
		* `LC3_DECODER_MEM_T` macro.
		*/

		typedef LC3_ENCODER_MEM_T(10000, 16000) lc3_encoder_mem_16k_t;
		typedef LC3_ENCODER_MEM_T(10000, 48000) lc3_encoder_mem_48k_t;

		typedef LC3_DECODER_MEM_T(10000, 16000) lc3_decoder_mem_16k_t;
		typedef LC3_DECODER_MEM_T(10000, 48000) lc3_decoder_mem_48k_t;


		/**
		* Return the number of PCM samples in a frame
		* dt_us Frame duration in us, 7500 or 10000
		* sr_hz Samplerate in Hz, 8000, 16000, 24000, 32000 or 48000
		* return Number of PCM samples, 0 on bad parameter
		* return Number of PCM samples, -1 on bad parameters
		*/
		int lc3_frame_samples(int dt_us, int sr_hz);

		@@ -175,7 +180,7 @@ int lc3_frame_samples(int dt_us, int sr_hz);
		* Return the size of frames, from bitrate
		* dt_us Frame duration in us, 7500 or 10000
		* bitrate Target bitrate in bit per seconds
		* return The floor size in bytes of the frames
		* return The floor size in bytes of the frames, -1 on bad parameters
		*/
		int lc3_frame_bytes(int dt_us, int bitrate);

		@@ -183,10 +188,18 @@ int lc3_frame_bytes(int dt_us, int bitrate);
		* Resolve the bitrate, from the size of frames
		* dt_us Frame duration in us, 7500 or 10000
		* nbytes Size in bytes of the frames
		* return The according bitrate in bps
		* return The according bitrate in bps, -1 on bad parameters
		*/
		int lc3_resolve_bitrate(int dt_us, int nbytes);

		/**
		* Return algorithmic delay, as a number of samples
		* dt_us Frame duration in us, 7500 or 10000
		* sr_hz Samplerate in Hz, 8000, 16000, 24000, 32000 or 48000
		* return Number of algorithmic delay samples, -1 on bad parameters
		*/
		int lc3_delay_samples(int dt_us, int sr_hz);

		/**
		* Return size needed for an encoder
		* dt_us Frame duration in us, 7500 or 10000
		@@ -208,11 +221,39 @@ lc3_encoder_t lc3_setup_encoder(int dt_us, int sr_hz, void *mem);
		* Encode a frame
		* encoder Handle of the encoder
		* pcm, pitch Input PCM samples, and count between two consecutives
		* out, nbytes Output buffer, and size in bytes (20 to 400)
		* nbytes Target size, in bytes, of the frame (20 to 400)
		* out Output buffer of `nbytes` size
		* return 0: On success -1: Wrong parameters
		*/
		int lc3_encode(lc3_encoder_t encoder,
		const int16_t pcm, int pitch, void out, int nbytes);
		const int16_t pcm, int pitch, int nbytes, void out);

		/**
		* Return size needed for an decoder
		* dt_us Frame duration in us, 7500 or 10000
		* sr_hz Samplerate in Hz, 8000, 16000, 24000, 32000 or 48000
		* return Size of then decoder in bytes, 0 on bad parameters
		*/
		unsigned lc3_decoder_size(int dt_us, int sr_hz);

		/**
		* Setup decoder
		* dt_us Frame duration in us, 7500 or 10000
		* sr_hz Samplerate in Hz, 8000, 16000, 24000, 32000 or 48000
		* mem Decoder memory space, aligned to pointer type
		* return Decoder as an handle, NULL on bad parameters
		*/
		lc3_decoder_t lc3_setup_decoder(int dt_us, int sr_hz, void *mem);

		/**
		* Decode a frame
		* decoder Handle of the decoder
		* in, nbytes Input bitstream, and size in bytes, NULL performs PLC
		* pcm, pitch Output PCM samples, and count between two consecutives
		* return 0: On success 1: PLC operated -1: Wrong parameters
		*/
		int lc3_decode(lc3_decoder_t decoder,
		const void in, int nbytes, int16_t pcm, int pitch);


		#ifdef __cplusplus

system/embdrv/lc3/include/lc3_private.h

+52 −15

Original line number	Diff line number	Diff line
		@@ -19,12 +19,14 @@
		#ifndef __LC3_PRIVATE_H
		#define __LC3_PRIVATE_H

		#include <stdint.h>
		#include <stdbool.h>


		/**
		* Return number of samples, delayed samples and
		* encoded spectrum coefficients within a frame
		* For decoding, add number of samples of 18 ms history
		*/

		#define __LC3_NS(dt_us, sr_hz) \
		@@ -34,6 +36,9 @@
		( (dt_us) == 7500 ? 23 * __LC3_NS(dt_us, sr_hz) / 30 \
		: 5 * __LC3_NS(dt_us, sr_hz) / 8 )

		#define __LC3_NH(sr_hz) \
		( (18 * sr_hz) / 1000 )


		/**
		* Frame duration 7.5ms or 10ms
		@@ -62,19 +67,19 @@ enum lc3_srate {


		/**
		* Encoder state
		* Encoder state and memory
		*/

		typedef struct lc3_attdet_state {
		typedef struct lc3_attdet_analysis {
		float en1, an1;
		int p_att;
		} lc3_attdet_state_t;
		} lc3_attdet_analysis_t;

		struct lc3_ltpf_hp50_state {
		float s1, s2;
		};

		typedef struct lc3_ltpf_state {
		typedef struct lc3_ltpf_analysis {
		bool active;
		int pitch;
		float nc[2];
		@@ -83,29 +88,24 @@ typedef struct lc3_ltpf_state {
		float x_12k8[384];
		float x_6k4[178];
		int tc;
		} lc3_ltpf_state_t;
		} lc3_ltpf_analysis_t;

		typedef struct lc3_quant_state {
		typedef struct lc3_spec_analysis {
		float nbits_off;
		int nbits_spare;
		} lc3_quant_state_t;
		} lc3_spec_analysis_t;

		struct lc3_encoder {
		enum lc3_dt dt;
		enum lc3_srate sr;

		lc3_attdet_state_t attdet;
		lc3_ltpf_state_t ltpf;
		lc3_quant_state_t quant;
		lc3_attdet_analysis_t attdet;
		lc3_ltpf_analysis_t ltpf;
		lc3_spec_analysis_t spec;

		float xs, xf, s[0];
		};


		/**
		* Encoder memory
		*/

		#define LC3_ENCODER_BUFFER_COUNT(dt_us, sr_hz) \
		( 2*__LC3_NS(dt_us, sr_hz) + __LC3_ND(dt_us, sr_hz) )

		@@ -116,4 +116,41 @@ struct lc3_encoder {
		}


		/**
		* Decoder state and memory
		*/

		typedef struct lc3_ltpf_synthesis {
		bool active;
		int pitch;
		float c[12][2], x[12];
		} lc3_ltpf_synthesis_t;

		typedef struct lc3_plc_state {
		uint16_t seed;
		int count;
		float alpha;
		} lc3_plc_state_t;

		struct lc3_decoder {
		enum lc3_dt dt;
		enum lc3_srate sr;

		lc3_ltpf_synthesis_t ltpf;
		lc3_plc_state_t plc;

		float xs, xd, *xg, s[0];
		};

		#define LC3_DECODER_BUFFER_COUNT(dt_us, sr_hz) \
		( __LC3_NH(sr_hz) + __LC3_NS(dt_us, sr_hz) + \
		__LC3_ND(dt_us, sr_hz) + __LC3_NS(dt_us, sr_hz) )

		#define LC3_DECODER_MEM_T(dt_us, sr_hz) \
		struct { \
		struct lc3_decoder __d; \
		float __s[LC3_DECODER_BUFFER_COUNT(dt_us, sr_hz)]; \
		}


		#endif /* __LC3_PRIVATE_H */

system/embdrv/lc3/src/attdet.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -23,11 +23,11 @@
		* Time domain attack detector
		*/
		bool lc3_attdet_run(enum lc3_dt dt, enum lc3_srate sr,
		unsigned nbytes, struct lc3_attdet_state state, const float x)
		int nbytes, struct lc3_attdet_analysis attdet, const float x)
		{
		/* --- Check enabling --- */

		const unsigned nbytes_ranges[LC3_NUM_DT][LC3_NUM_SRATE - LC3_SRATE_32K][2] = {
		const int nbytes_ranges[LC3_NUM_DT][LC3_NUM_SRATE - LC3_SRATE_32K][2] = {
		[LC3_DT_7M5] = { { 61, 149 }, { 75, 149 } },
		[LC3_DT_10M] = { { 81, INT_MAX }, { 100, INT_MAX } },
		};
		@@ -78,15 +78,15 @@ bool lc3_attdet_run(enum lc3_dt dt, enum lc3_srate sr,
		float a[4];

		for (int i = 0; i < nblk; i++) {
		a[i] = fmaxf(0.25 * state->an1, state->en1);
		state->en1 = e[i], state->an1 = a[i];
		a[i] = fmaxf(0.25 * attdet->an1, attdet->en1);
		attdet->en1 = e[i], attdet->an1 = a[i];

		if (e[i] > 8.5 * a[i])
		p_att = i + 1;
		}

		int att = state->p_att >= 1 + (nblk >> 1) \|\| p_att > 0;
		state->p_att = p_att;
		int att = attdet->p_att >= 1 + (nblk >> 1) \|\| p_att > 0;
		attdet->p_att = p_att;

		return att;
		}

system/embdrv/lc3/src/attdet.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -33,12 +33,12 @@
		* Time domain attack detector
		* dt, sr Duration and samplerate of the frame
		* nbytes Size in bytes of the frame
		* state State of the Attack Detector
		* attdet Context of the Attack Detector
		* x [-6..-1] Previous, [0..ns-1] Current samples
		* return 1: Attack detected 0: Otherwise
		*/
		bool lc3_attdet_run(enum lc3_dt dt, enum lc3_srate sr,
		unsigned nbytes, lc3_attdet_state_t state, const float x);
		int nbytes, lc3_attdet_analysis_t attdet, const float x);


		#endif /* __LC3_ATTDET_H */

system/embdrv/lc3/src/bits.c

+208 −81

Original line number	Diff line number	Diff line
		@@ -20,18 +20,127 @@
		#include "common.h"


		/* ----------------------------------------------------------------------------
		* Common
		* -------------------------------------------------------------------------- */

		static inline int ac_get(struct lc3_bits_buffer *);
		static inline void accu_load(struct lc3_bits_accu , struct lc3_bits_buffer );

		/**
		* Arithmetic coder return range bits
		* ac Arithmetic coder
		* return 1 + log2(ac->range)
		*/
		static int ac_get_range_bits(const struct lc3_bits_ac *ac)
		{
		int nbits = 0;

		for (unsigned r = ac->range; r; r >>= 1, nbits++);

		return nbits;
		}

		/**
		* Arithmetic coder return pending bits
		* ac Arithmetic coder
		* return Pending bits
		*/
		static int ac_get_pending_bits(const struct lc3_bits_ac *ac)
		{
		return 26 - ac_get_range_bits(ac) +
		((ac->cache >= 0) + ac->carry_count) * 8;
		}

		/**
		* Return number of bits left in the bitstream
		* bits Bitstream context
		* return >= 0: Number of bits left < 0: Overflow
		*/
		static int get_bits_left(const struct lc3_bits *bits)
		{
		const struct lc3_bits_buffer *buffer = &bits->buffer;
		const struct lc3_bits_accu *accu = &bits->accu;
		const struct lc3_bits_ac *ac = &bits->ac;

		uintptr_t end = (uintptr_t)buffer->p_bw +
		(bits->mode == LC3_BITS_MODE_READ ? LC3_ACCU_BITS/8 : 0);

		uintptr_t start = (uintptr_t)buffer->p_fw -
		(bits->mode == LC3_BITS_MODE_READ ? LC3_AC_BITS/8 : 0);

		return 8 * (end - start) -
		(accu->n + accu->nover + ac_get_pending_bits(ac));
		}

		/**
		* Setup bitstream writing
		*/
		void lc3_setup_bits(struct lc3_bits *bits,
		enum lc3_bits_mode mode, void *buffer, int len)
		{
		*bits = (struct lc3_bits){
		.mode = mode,
		.accu = {
		.n = mode == LC3_BITS_MODE_READ ? LC3_ACCU_BITS : 0,
		},
		.ac = {
		.range = 0xffffff,
		.cache = -1
		},
		.buffer = {
		.start = (uint8_t )buffer, .end = (uint8_t )buffer + len,
		.p_fw = (uint8_t )buffer, .p_bw = (uint8_t )buffer + len,
		}
		};

		if (mode == LC3_BITS_MODE_READ) {
		struct lc3_bits_ac *ac = &bits->ac;
		struct lc3_bits_accu *accu = &bits->accu;
		struct lc3_bits_buffer *buffer = &bits->buffer;

		ac->low = ac_get(buffer) << 16;
		ac->low \|= ac_get(buffer) << 8;
		ac->low \|= ac_get(buffer);

		accu_load(accu, buffer);
		}
		}

		/**
		* Return number of bits left in the bitstream
		*/
		int lc3_get_bits_left(const struct lc3_bits *bits)
		{
		return LC3_MAX(get_bits_left(bits), 0);
		}

		/**
		* Return number of bits left in the bitstream
		*/
		int lc3_check_bits(const struct lc3_bits *bits)
		{
		const struct lc3_bits_ac *ac = &bits->ac;

		return -(get_bits_left(bits) < 0 \|\| ac->error);
		}


		/* ----------------------------------------------------------------------------
		* Writing
		* -------------------------------------------------------------------------- */

		/**
		* Flush the bits accumulator
		* accu Bitstream accumulator
		* buffer Bitstream buffer
		*/
		static void accu_flush(struct lc3_bits_accu *accu,
		struct lc3_bits_buffer *buffer)
		static inline void accu_flush(
		struct lc3_bits_accu accu, struct lc3_bits_buffer buffer)
		{
		unsigned nbytes = LC3_MIN(accu->n >> 3, buffer->nleft);
		int nbytes = LC3_MIN(accu->n >> 3, buffer->p_bw - buffer->p_fw);

		accu->n -= 8 * nbytes;
		buffer->nleft -= nbytes;

		for ( ; nbytes; accu->v >>= 8, nbytes--)
		*(--buffer->p_bw) = accu->v & 0xff;
		@@ -45,15 +154,10 @@ static void accu_flush(struct lc3_bits_accu *accu,
		* buffer Bitstream buffer
		* byte Byte to output
		*/
		static void ac_put(struct lc3_bits_buffer *buffer, unsigned byte)
		static inline void ac_put(struct lc3_bits_buffer *buffer, int byte)
		{
		buffer->overflow \|= (buffer->nleft_fw <= 0);
		if (buffer->overflow)
		return;

		if (buffer->p_fw < buffer->end)
		*(buffer->p_fw++) = byte;
		buffer->nleft_fw--;
		buffer->nleft--;
		}

		/**
		@@ -61,8 +165,8 @@ static void ac_put(struct lc3_bits_buffer *buffer, unsigned byte)
		* ac Arithmetic coder
		* buffer Bitstream buffer
		*/
		static void ac_shift(struct lc3_bits_ac *ac,
		struct lc3_bits_buffer *buffer)
		static inline void ac_shift(
		struct lc3_bits_ac ac, struct lc3_bits_buffer buffer)
		{
		if (ac->low < 0xff0000 \|\| ac->carry)
		{
		@@ -76,38 +180,11 @@ static void ac_shift(struct lc3_bits_ac *ac,
		ac->carry = 0;
		}
		else
		{
		ac->carry_count++;
		}

		ac->low = (ac->low << 8) & 0xffffff;
		}

		/**
		* Arithmetic coder return range bits
		* ac Arithmetic coder
		* return 1 + log2(ac->range)
		*/
		static int ac_get_range_bits(const struct lc3_bits_ac *ac)
		{
		int nbits = 0;

		for (unsigned r = ac->range; r; r >>= 1, nbits++);

		return nbits;
		}

		/**
		* Arithmetic coder return pending bits
		* ac Arithmetic coder
		* return Pending bits
		*/
		static int ac_get_pending_bits(const struct lc3_bits_ac *ac)
		{
		return 26 - ac_get_range_bits(ac) +
		((ac->cache >= 0) + ac->carry_count) * 8;
		}

		/**
		* Arithmetic coder termination
		* ac Arithmetic coder
		@@ -155,44 +232,12 @@ static void ac_terminate(struct lc3_bits_ac *ac,
		end_val = nbits < 8 ? 0 : 0xff;
		}

		if (buffer->nleft_fw > 0) {
		if (buffer->p_fw < buffer->end) {
		*buffer->p_fw &= 0xff >> nbits;
		*buffer->p_fw \|= end_val << (8 - nbits);
		}
		}

		/**
		* Setup bitstream writing
		*/
		void lc3_setup_bits(struct lc3_bits bits, void buffer, unsigned len)
		{
		*bits = (struct lc3_bits){

		.ac = {
		.range = 0xffffff,
		.cache = -1
		},

		.buffer = {
		.p_fw = (uint8_t *)buffer,
		.p_bw = (uint8_t *)buffer + len,
		.nleft_fw = len, .nleft = len
		}
		};
		}

		/**
		* Return number of bits left in the bitstream
		*/
		int lc3_get_bits_left(const struct lc3_bits *bits)
		{
		int nbits_left = 8 * bits->buffer.nleft;
		nbits_left -= LC3_MIN(bits->accu.n, nbits_left);
		nbits_left -= LC3_MIN(ac_get_pending_bits(&bits->ac), nbits_left);

		return nbits_left;
		}

		/**
		* Flush and terminate bitstream
		*/
		@@ -202,7 +247,8 @@ void lc3_flush_bits(struct lc3_bits *bits)
		struct lc3_bits_accu *accu = &bits->accu;
		struct lc3_bits_buffer *buffer = &bits->buffer;

		for (int n = 8 * buffer->nleft - accu->n; n > 0; n -= 32)
		int nleft = buffer->p_bw - buffer->p_fw;
		for (int n = 8 * nleft - accu->n; n > 0; n -= 32)
		lc3_put_bits(bits, 0, LC3_MIN(n, 32));

		accu_flush(accu, buffer);
		@@ -211,19 +257,19 @@ void lc3_flush_bits(struct lc3_bits *bits)
		}

		/**
		* Write from 0 to 32 bits,
		* Write from 1 to 32 bits,
		* exceeding the capacity of the accumulator
		*/
		void __lc3_put_bits_over(struct lc3_bits *bits, unsigned v, int n)
		void lc3_put_bits_generic(struct lc3_bits *bits, unsigned v, int n)
		{
		struct lc3_bits_accu *accu = &bits->accu;

		/* --- Fullfill accumulator and flush -- */
		/* --- Fulfill accumulator and flush -- */

		int n1 = LC3_MIN(ACCU_BITS - accu->n, n);
		int n1 = LC3_MIN(LC3_ACCU_BITS - accu->n, n);
		if (n1) {
		accu->v \|= v << accu->n;
		accu->n = ACCU_BITS;
		accu->n = LC3_ACCU_BITS;
		}

		accu_flush(accu, &bits->buffer);
		@@ -237,10 +283,91 @@ void __lc3_put_bits_over(struct lc3_bits *bits, unsigned v, int n)
		/**
		* Arithmetic coder renormalization
		*/
		void __lc3_renorm_ac(struct lc3_bits *bits)
		void lc3_ac_write_renorm(struct lc3_bits *bits)
		{
		struct lc3_bits_ac *ac = &bits->ac;

		for ( ; ac->range < 0x10000; ac->range <<= 8)
		ac_shift(ac, &bits->buffer);
		}


		/* ----------------------------------------------------------------------------
		* Reading
		* -------------------------------------------------------------------------- */

		/**
		* Arithmetic coder get byte
		* buffer Bitstream buffer
		* return Byte read, 0 on overflow
		*/
		static inline int ac_get(struct lc3_bits_buffer *buffer)
		{
		return buffer->p_fw < buffer->end ? *(buffer->p_fw++) : 0;
		}

		/**
		* Load the accumulator
		* accu Bitstream accumulator
		* buffer Bitstream buffer
		*/
		static inline void accu_load(struct lc3_bits_accu *accu,
		struct lc3_bits_buffer *buffer)
		{
		int nbytes = LC3_MIN(accu->n >> 3, buffer->p_bw - buffer->start);

		accu->n -= 8 * nbytes;

		for ( ; nbytes; nbytes--) {
		accu->v >>= 8;
		accu->v \|= *(--buffer->p_bw) << (LC3_ACCU_BITS - 8);
		}

		if (accu->n >= 8) {
		accu->nover = LC3_MIN(accu->nover + accu->n, LC3_ACCU_BITS);
		accu->v >>= accu->n;
		accu->n = 0;
		}
		}

		/**
		* Read from 1 to 32 bits,
		* exceeding the capacity of the accumulator
		*/
		unsigned lc3_get_bits_generic(struct lc3_bits *bits, int n)
		{
		struct lc3_bits_accu *accu = &bits->accu;
		struct lc3_bits_buffer *buffer = &bits->buffer;

		/* --- Fulfill accumulator and read -- */

		accu_load(accu, buffer);

		int n1 = LC3_MIN(LC3_ACCU_BITS - accu->n, n);
		unsigned v = (accu->v >> accu->n) & ((1u << n1) - 1);
		accu->n += n1;

		/* --- Second round --- */

		int n2 = n - n1;

		if (n2) {
		accu_load(accu, buffer);

		v \|= ((accu->v >> accu->n) & ((1u << n2) - 1)) << n1;
		accu->n += n2;
		}

		return v;
		}

		/**
		* Arithmetic coder renormalization
		*/
		void lc3_ac_read_renorm(struct lc3_bits *bits)
		{
		struct lc3_bits_ac *ac = &bits->ac;

		for ( ; ac->range < 0x10000; ac->range <<= 8)
		ac->low = ((ac->low << 8) \| ac_get(&bits->buffer)) & 0xffffff;
		}