applications: nrf5340_audio: LC3 Decoder Audio Module

    Implement the LC3 T2 decoder audio module.

Signed-off-by: Graham Wacey <[email protected]>

include/audio_modules/lc3_decoder.h

@@ -0,0 +1,83 @@
+/*
+ * Copyright(c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+#ifndef _LC3_DECODER_H_
+#define _LC3_DECODER_H_
+
+#include "audio_defines.h"
+#include "audio_module.h"
+
+#define LC3_DECODER_PCM_NUM_BYTES_MONO                                                             \
+	((CONFIG_LC3_DECODER_SAMPLE_RATE_HZ * CONFIG_LC3_DECODER_BIT_DEPTH_OCTETS *                \
+	  CONFIG_LC3_DECODER_FRAME_DURATION_US) /                                                  \
+	 1000000)
+
+/**
+ * @brief Private pointer to the module's parameters.
+ */
+extern struct audio_module_description *lc3_decoder_description;
+
+/**
+ * @brief Private pointer to the decoders handle.
+ */
+struct lc3_decoder_handle;
+
+/**
+ * @brief The module configuration structure.
+ */
+struct lc3_decoder_configuration {
+	/* Sample rate for the decoder instance. */
+	uint32_t sample_rate_hz;
+
+	/* Number of valid bits for a sample (bit depth).
+	 * Typically 16 or 24.
+	 */
+	uint8_t bits_per_sample;
+
+	/* Number of bits used to carry a sample of size bits_per_sample.
+	 * For example, say we have a 24 bit sample stored in a 32 bit
+	 * word (int32_t), then:
+	 *     bits_per_sample = 24
+	 *     carrier_size    = 32
+	 */
+	uint32_t carried_bits_per_sample;
+
+	/* Frame duration for this decoder instance. */
+	uint32_t data_len_us;
+
+	/* A flag indicating if the decoded buffer is sample interleaved or not. */
+	bool interleaved;
+
+	/* Channel locations for this decoder instance. */
+	uint32_t locations;
+
+	/* Maximum bitrate supported by the decoder. */
+	uint32_t bitrate_bps_max;
+};
+
+/**
+ * @brief  Private module context.
+ */
+struct lc3_decoder_context {
+	/* Array of decoder channel handles. */
+	struct lc3_decoder_handle *lc3_dec_channel[CONFIG_LC3_DEC_CHANNELS_MAX];
+
+	/* Number of decoder channel handles. */
+	uint32_t dec_handles_count;
+
+	/* The decoder configuration. */
+	struct lc3_decoder_configuration config;
+
+	/* Minimum coded bytes required for this decoder instance. */
+	uint16_t coded_bytes_req;
+
+	/* Audio sample bytes per frame. */
+	size_t sample_frame_bytes;
+
+	/* Number of successive frames to which PLC has been applied. */
+	uint16_t plc_count;
+};
+
+#endif /* _LC3_DECODER_H_ */

subsys/CMakeLists.txt

@@ -69,6 +69,7 @@ add_subdirectory_ifdef(CONFIG_EMDS emds)
 add_subdirectory_ifdef(CONFIG_NET_CORE_MONITOR net_core_monitor)
 add_subdirectory_ifdef(CONFIG_AUDIO_MODULE audio_module)
 add_subdirectory_ifdef(CONFIG_AUDIO_MODULE_TEMPLATE audio_modules/audio_module_template)
+add_subdirectory_ifdef(CONFIG_AUDIO_MODULE_T2_LC3_DECODER audio_modules/lc3/t2/decoder)
 add_subdirectory_ifdef(CONFIG_UART_ASYNC_ADAPTER uart_async_adapter)
 add_subdirectory_ifdef(CONFIG_SDFW_SERVICES_ENABLED sdfw_services)
 add_subdirectory(suit)

subsys/Kconfig

@@ -35,6 +35,7 @@ rsource "nrf_security/Kconfig"
 rsource "net_core_monitor/Kconfig"
 rsource "audio_module/Kconfig"
 rsource "audio_modules/audio_module_template/Kconfig"
+rsource "audio_modules/lc3/t2/decoder/Kconfig"
 rsource "uart_async_adapter/Kconfig"
 rsource "trusted_storage/Kconfig"
 rsource "sdfw_services/Kconfig"

subsys/audio_modules/lc3/CMakeLists.txt

@@ -0,0 +1,8 @@
+#
+# Copyright (c) 2018 Nordic Semiconductor
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+add_subdirectory_ifdef(CONFIG_AUDIO_MODULE_LC3_DECODER_T2 t2/decoder)
+add_subdirectory_ifdef(CONFIG_SW_LC3_ENCODER_T2 t2/encoder)

subsys/audio_modules/lc3/Kconfig

@@ -0,0 +1,132 @@
+#
+# Copyright (c) 2023 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+menu "Audio Modules"
+
+config AUDIO_MODULE_LC3_DECODER_T2
+	bool "Select the T2 software LC3 Decoder"
+	depends on AUDIO_MODULE
+
+#----------------------------------------------------------------------------#
+menu "Log levels"
+
+module = AUDIO_MODULE_LC3_DECODER_T2
+module-str = lc3_decoder_t2
+source "subsys/logging/Kconfig.template.log_config"
+
+endmenu # Log levels
+#----------------------------------------------------------------------------#
+
+menu "LC3"
+visible if SW_CODEC_LC3
+
+config SW_LC3_PLC_DISABLED
+	bool "Skip PLC on a bad frame and fill the output buffer(s) with zeros instead"
+	default n
+	select LC3_PLC_DISABLED
+
+config SW_LC3_BITRATE_MAX
+	int "Max bitrate"
+	default 124000
+
+config SW_LC3_BITRATE_MIN
+	int "Min bitrate"
+	default 32000
+
+config SW_LC3_BITRATE
+	int
+	range SW_LC3_BITRATE_MIN SW_LC3_BITRATE_MAX
+	default 96000
+
+choice SW_LC3_FRAME_DURATION
+	prompt "Select frame duration - 7.5 ms frame duration is not tested"
+	default SW_LC3_FRAME_DURATION_10_MS
+	help
+	  LC3 supports frame duration of 7.5 and 10 ms.
+	  If USB is selected as audio source, we should
+	  have a frame duration of 10 ms since USB sends 1ms at a time.
+
+config SW_LC3_FRAME_DURATION_7_5_MS
+	bool "7.5 ms"
+
+config SW_LC3_FRAME_DURATION_10_MS
+	bool "10 ms"
+endchoice
+
+config SW_LC3_FRAME_DURATION_US
+	int
+	default 7500 if SW_LC3_FRAME_DURATION_7_5_MS
+	default 10000 if SW_LC3_FRAME_DURATION_10_MS
+	help
+	  Audio frame duration in µs.
+
+choice SW_LC3_SAMPLE_RATE
+	prompt "Audio sample rate"
+	default SW_LC3_SAMPLE_RATE_16000_HZ if BT_BAP_BROADCAST_16_2_1 || BT_BAP_BROADCAST_16_2_2 || BT_BAP_UNICAST_16_2_1
+	default SW_LC3_SAMPLE_RATE_24000_HZ if BT_BAP_BROADCAST_24_2_1 || BT_BAP_BROADCAST_24_2_2 || BT_BAP_UNICAST_24_2_1
+	default SW_LC3_SAMPLE_RATE_48000_HZ
+	help
+	  This will be selected based on the BAP settings.
+
+config SW_LC3_SAMPLE_RATE_16000_HZ
+	bool "16 kHz"
+	help
+	  Sample rate of 16kHz is currently only valid for I2S/line-in.
+
+config SW_LC3_SAMPLE_RATE_24000_HZ
+	bool "24 kHz"
+	help
+	  Sample rate of 24kHz is currently only valid for I2S/line-in.
+
+config SW_LC3_SAMPLE_RATE_48000_HZ
+	bool "48 kHz"
+	help
+	  Sample rate of 48kHz is valid for both I2S/line-in and USB.
+endchoice
+
+config SW_LC3_SAMPLE_RATE_HZ
+	int
+	default 16000 if SW_LC3_SAMPLE_RATE_16000_HZ
+	default 24000 if SW_LC3_SAMPLE_RATE_24000_HZ
+	default 48000 if SW_LC3_SAMPLE_RATE_48000_HZ
+	help
+	  I2S supports 16, 24, and 48 kHz sample rates for both input and output.
+	  USB supports only 48 kHz for input.
+
+choice SW_LC3_BIT_DEPTH
+	prompt "Audio bit depth"
+	default SW_LC3_BIT_DEPTH_16
+	help
+	  Select the bit depth for audio.
+
+config SW_LC3_BIT_DEPTH_16
+	bool "16 bit audio"
+
+config SW_LC3_BIT_DEPTH_32
+	bool "32 bit audio"
+endchoice
+
+config SW_LC3_BIT_DEPTH_BITS
+	int
+	default 16 if SW_LC3_BIT_DEPTH_16
+	default 32 if SW_LC3_BIT_DEPTH_32
+	help
+	  Bit depth of one sample in storage.
+
+config SW_LC3_BIT_DEPTH_OCTETS
+	int
+	default 2 if SW_LC3_BIT_DEPTH_16
+	default 4 if SW_LC3_BIT_DEPTH_32
+	help
+	  Bit depth of one sample in storage given in octets.
+
+#----------------------------------------------------------------------------#
+
+osource "../nrfxlib/lc3/Kconfig"
+
+endmenu # LC3
+endmenu # SW Codec
+endmenu # Audio

subsys/audio_modules/lc3/t2/decoder/CMakeLists.txt

@@ -0,0 +1,9 @@
+#
+# Copyright (c) 2023 Nordic Semiconductor
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+target_sources(app PRIVATE
+	       ${CMAKE_CURRENT_SOURCE_DIR}/lc3_decoder.c
+)