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avcodec/liblc3: add encoding/decoding support of LC3 audio codec 

The LC3 audio codec is the default codec of Bluetooth LE audio.
This is a wrapper over the liblc3 library (https://github.com/google/liblc3).

Signed-off-by: Antoine Soulier <asoulier@google.com>
This commit is contained in:
Antoine Soulier via ffmpeg-devel 2024-04-01 21:32:04 +00:00 committed by Stefano Sabatini
parent e3335e9e9e
commit 240fd04db2
10 changed files with 443 additions and 1 deletions
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1
Changelog
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@ -3,6 +3,7 @@ releases are sorted from youngest to oldest.
version <next>:
- Raw Captions with Time (RCWT) closed caption demuxer
- LC3/LC3plus decoding/encoding using external library liblc3
version 7.0:

6
configure vendored
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@ -245,6 +245,7 @@ External library support:
--enable-libjxl enable JPEG XL de/encoding via libjxl [no]
--enable-libklvanc enable Kernel Labs VANC processing [no]
--enable-libkvazaar enable HEVC encoding via libkvazaar [no]
--enable-liblc3 enable LC3 de/encoding via liblc3 [no]
--enable-liblensfun enable lensfun lens correction [no]
--enable-libmodplug enable ModPlug via libmodplug [no]
--enable-libmp3lame enable MP3 encoding via libmp3lame [no]
@ -1927,6 +1928,7 @@ EXTERNAL_LIBRARY_LIST="
libjxl
libklvanc
libkvazaar
liblc3
libmodplug
libmp3lame
libmysofa
@ -3504,6 +3506,9 @@ libilbc_encoder_deps="libilbc"
libjxl_decoder_deps="libjxl libjxl_threads"
libjxl_encoder_deps="libjxl libjxl_threads"
libkvazaar_encoder_deps="libkvazaar"
liblc3_decoder_deps="liblc3"
liblc3_encoder_deps="liblc3"
liblc3_encoder_select="audio_frame_queue"
libmodplug_demuxer_deps="libmodplug"
libmp3lame_encoder_deps="libmp3lame"
libmp3lame_encoder_select="audio_frame_queue mpegaudioheader"
@ -6876,6 +6881,7 @@ enabled libjxl && require_pkg_config libjxl "libjxl >= 0.7.0" jxl/dec
require_pkg_config libjxl_threads "libjxl_threads >= 0.7.0" jxl/thread_parallel_runner.h JxlThreadParallelRunner
enabled libklvanc && require libklvanc libklvanc/vanc.h klvanc_context_create -lklvanc
enabled libkvazaar && require_pkg_config libkvazaar "kvazaar >= 2.0.0" kvazaar.h kvz_api_get
enabled liblc3 && require_pkg_config liblc3 "lc3 >= 1.1.0" lc3.h lc3_hr_setup_encoder
enabled liblensfun && require_pkg_config liblensfun lensfun lensfun.h lf_db_create
if enabled libmfx && enabled libvpl; then

57
doc/encoders.texi
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@ -814,6 +814,63 @@ ffmpeg -i input.wav -c:a libfdk_aac -profile:a aac_he -b:a 64k output.m4a
@end example
@end itemize
@anchor{liblc3-enc}
@section liblc3
liblc3 LC3 (Low Complexity Communication Codec) encoder wrapper.
Requires the presence of the liblc3 headers and library during configuration.
You need to explicitly configure the build with @code{--enable-liblc3}.
This encoder has support for the Bluetooth SIG LC3 codec for the LE Audio
protocol, and the following features of LC3plus:
@itemize
@item
Frame duration of 2.5 and 5ms.
@item
High-Resolution mode, 48 KHz, and 96 kHz sampling rates.
@end itemize
For more information see the liblc3 project at
@url{https://github.com/google/liblc3}.
@subsection Options
The following options are mapped on the shared FFmpeg codec options.
@table @option
@item b @var{bitrate}
Set the bit rate in bits/s. This will determine the fixed size of the encoded
frames, for a selected frame duration.
@item ar @var{frequency}
Set the audio sampling rate (in Hz).
@item channels
Set the number of audio channels.
@item frame_duration
Set the audio frame duration in milliseconds. Default value is 10ms.
Allowed frame durations are 2.5ms, 5ms, 7.5ms and 10ms.
LC3 (Bluetooth LE Audio), allows 7.5ms and 10ms; and LC3plus 2.5ms, 5ms
and 10ms.
The 10ms frame duration is available in LC3 and LC3 plus standard.
In this mode, the produced bitstream can be referenced either as LC3 or LC3plus.
@item high_resolution @var{boolean}
Enable the high-resolution mode if set to 1. The high-resolution mode is
available with all LC3plus frame durations and for a sampling rate of 48 KHz,
and 96 KHz.
The encoder automatically turns off this mode at lower sampling rates and
activates it at 96 KHz.
This mode should be preferred at high bitrates. In this mode, the audio
bandwidth is always up to the Nyquist frequency, compared to LC3 at 48 KHz,
which limits the bandwidth to 20 KHz.
@end table
@anchor{libmp3lame}
@section libmp3lame

11
doc/general_contents.texi
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@ -237,6 +237,14 @@ Go to @url{http://sourceforge.net/projects/opencore-amr/} and follow the
instructions for installing the library.
Then pass @code{--enable-libfdk-aac} to configure to enable it.
@subsection LC3 library
FFmpeg can make use of the Google LC3 library for LC3 decoding & encoding.
Go to @url{https://github.com/google/liblc3/} and follow the instructions for
installing the library.
Then pass @code{--enable-liblc3} to configure to enable it.
@section OpenH264
FFmpeg can make use of the OpenH264 library for H.264 decoding and encoding.
@ -1300,7 +1308,8 @@ following image formats are supported:
@tab encoding and decoding supported through external library libilbc
@item IMC (Intel Music Coder) @tab @tab X
@item Interplay ACM @tab @tab X
@item MACE (Macintosh Audio Compression/Expansion) 3:1 @tab @tab X
@item LC3 @tab E @tab E
@tab supported through external library liblc3
@item MACE (Macintosh Audio Compression/Expansion) 6:1 @tab @tab X
@item Marian's A-pac audio @tab @tab X
@item MI-SC4 (Micronas SC-4 Audio) @tab @tab X

2
libavcodec/Makefile
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@ -1122,6 +1122,8 @@ OBJS-$(CONFIG_LIBILBC_ENCODER) += libilbc.o
OBJS-$(CONFIG_LIBJXL_DECODER) += libjxldec.o libjxl.o
OBJS-$(CONFIG_LIBJXL_ENCODER) += libjxlenc.o libjxl.o
OBJS-$(CONFIG_LIBKVAZAAR_ENCODER) += libkvazaar.o
OBJS-$(CONFIG_LIBLC3_ENCODER) += liblc3enc.o
OBJS-$(CONFIG_LIBLC3_DECODER) += liblc3dec.o
OBJS-$(CONFIG_LIBMP3LAME_ENCODER) += libmp3lame.o
OBJS-$(CONFIG_LIBOPENCORE_AMRNB_DECODER) += libopencore-amr.o
OBJS-$(CONFIG_LIBOPENCORE_AMRNB_ENCODER) += libopencore-amr.o

2
libavcodec/allcodecs.c
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@ -776,6 +776,8 @@ extern const FFCodec ff_libilbc_encoder;
extern const FFCodec ff_libilbc_decoder;
extern const FFCodec ff_libjxl_decoder;
extern const FFCodec ff_libjxl_encoder;
extern const FFCodec ff_liblc3_encoder;
extern const FFCodec ff_liblc3_decoder;
extern const FFCodec ff_libmp3lame_encoder;
extern const FFCodec ff_libopencore_amrnb_encoder;
extern const FFCodec ff_libopencore_amrnb_decoder;

7
libavcodec/codec_desc.c
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@ -3425,6 +3425,13 @@ static const AVCodecDescriptor codec_descriptors[] = {
.long_name = NULL_IF_CONFIG_SMALL("QOA (Quite OK Audio)"),
.props = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
},
{
.id = AV_CODEC_ID_LC3,
.type = AVMEDIA_TYPE_AUDIO,
.name = "lc3",
.long_name = NULL_IF_CONFIG_SMALL("LC3 (Low Complexity Communication Codec)"),
.props = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
},
/* subtitle codecs */
{

1
libavcodec/codec_id.h
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@ -543,6 +543,7 @@ enum AVCodecID {
AV_CODEC_ID_AC4,
AV_CODEC_ID_OSQ,
AV_CODEC_ID_QOA,
AV_CODEC_ID_LC3,
/* subtitle codecs */
AV_CODEC_ID_FIRST_SUBTITLE = 0x17000, ///< A dummy ID pointing at the start of subtitle codecs.

146
libavcodec/liblc3dec.c Normal file
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@ -0,0 +1,146 @@
/*
* LC3 decoder wrapper
* Copyright (C) 2024 Antoine Soulier <asoulier@google.com>
*
* This file is part of FFmpeg.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <lc3.h>
#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#include "avcodec.h"
#include "codec.h"
#include "codec_internal.h"
#include "decode.h"
#include "internal.h"
#define DECODER_MAX_CHANNELS 2
typedef struct LibLC3DecContext {
int frame_us, srate_hz, hr_mode;
void *decoder_mem;
lc3_decoder_t decoder[DECODER_MAX_CHANNELS];
int64_t length;
} LibLC3DecContext;
static av_cold int liblc3_decode_init(AVCodecContext *avctx)
{
LibLC3DecContext *liblc3 = avctx->priv_data;
int channels = avctx->ch_layout.nb_channels;
int ep_mode;
unsigned decoder_size;
if (avctx->extradata_size < 10)
return AVERROR_INVALIDDATA;
liblc3->frame_us = AV_RL16(avctx->extradata + 0) * 10;
liblc3->srate_hz = avctx->sample_rate;
ep_mode = AV_RL16(avctx->extradata + 2);
liblc3->hr_mode = AV_RL16(avctx->extradata + 4);
liblc3->length = AV_RL32(avctx->extradata + 6);
if (ep_mode != 0) {
av_log(avctx, AV_LOG_ERROR,
"Error protection mode is not supported.\n");
return AVERROR(EINVAL);
}
av_log(avctx, AV_LOG_INFO,
"Decoding %.1f ms frames.\n", liblc3->frame_us / 1000.f);
if (liblc3->hr_mode)
av_log(avctx, AV_LOG_INFO, "High-resolution mode enabled.\n");
decoder_size = lc3_hr_decoder_size(
liblc3->hr_mode, liblc3->frame_us, liblc3->srate_hz);
if (!decoder_size)
return AVERROR_INVALIDDATA;
liblc3->decoder_mem = av_malloc_array(channels, decoder_size);
if (!liblc3->decoder_mem)
return AVERROR(ENOMEM);
for (int ch = 0; ch < channels; ch++) {
liblc3->decoder[ch] = lc3_hr_setup_decoder(
liblc3->hr_mode, liblc3->frame_us, liblc3->srate_hz, 0,
(char *)liblc3->decoder_mem + ch * decoder_size);
}
avctx->sample_fmt = AV_SAMPLE_FMT_FLTP;
avctx->delay = lc3_hr_delay_samples(
liblc3->hr_mode, liblc3->frame_us, liblc3->srate_hz);
avctx->internal->skip_samples = avctx->delay;
return 0;
}
static av_cold int liblc3_decode_close(AVCodecContext *avctx)
{
LibLC3DecContext *liblc3 = avctx->priv_data;
av_freep(&liblc3->decoder_mem);
return 0;
}
static int liblc3_decode(AVCodecContext *avctx, AVFrame *frame,
int *got_frame_ptr, AVPacket *avpkt)
{
LibLC3DecContext *liblc3 = avctx->priv_data;
int channels = avctx->ch_layout.nb_channels;
uint8_t *in = avpkt->data;
int block_bytes, ret;
frame->nb_samples = av_rescale(
liblc3->frame_us, liblc3->srate_hz, 1000*1000);
if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
return ret;
block_bytes = avpkt->size;
for (int ch = 0; ch < channels; ch++) {
int nbytes = block_bytes / channels + (ch < block_bytes % channels);
ret = lc3_decode(liblc3->decoder[ch], in, nbytes,
LC3_PCM_FORMAT_FLOAT, frame->data[ch], 1);
if (ret < 0)
return AVERROR_INVALIDDATA;
in += nbytes;
}
if (liblc3->length > 0) {
int64_t end_pts = liblc3->length + avctx->delay;
frame->nb_samples = FFMIN(frame->nb_samples,
FFMAX(end_pts - frame->pts, 0));
}
*got_frame_ptr = 1;
return avpkt->size;
}
const FFCodec ff_liblc3_decoder = {
.p.name = "liblc3",
CODEC_LONG_NAME("LC3 (Low Complexity Communication Codec)"),
.p.type = AVMEDIA_TYPE_AUDIO,
.p.id = AV_CODEC_ID_LC3,
.p.capabilities = AV_CODEC_CAP_DR1,
.p.wrapper_name = "liblc3",
.priv_data_size = sizeof(LibLC3DecContext),
.caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
.init = liblc3_decode_init,
.close = liblc3_decode_close,
FF_CODEC_DECODE_CB(liblc3_decode),
};

211
libavcodec/liblc3enc.c Normal file
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@ -0,0 +1,211 @@
/*
* LC3 encoder wrapper
* Copyright (C) 2024 Antoine Soulier <asoulier@google.com>
*
* This file is part of FFmpeg.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <lc3.h>
#include "libavutil/intreadwrite.h"
#include "libavutil/opt.h"
#include "libavutil/mem.h"
#include "avcodec.h"
#include "codec.h"
#include "codec_internal.h"
#include "encode.h"
#define ENCODER_MAX_CHANNELS 2
typedef struct LibLC3EncOpts {
float frame_duration;
int hr_mode;
} LibLC3EncOpts;
typedef struct LibLC3EncContext {
const AVClass *av_class;
LibLC3EncOpts opts;
int block_bytes;
void *encoder_mem;
lc3_encoder_t encoder[ENCODER_MAX_CHANNELS];
int delay_samples;
int remaining_samples;
} LibLC3EncContext;
static av_cold int liblc3_encode_init(AVCodecContext *avctx)
{
LibLC3EncContext *liblc3 = avctx->priv_data;
bool hr_mode = liblc3->opts.hr_mode;
int frame_us = liblc3->opts.frame_duration * 1000;
int srate_hz = avctx->sample_rate;
int channels = avctx->ch_layout.nb_channels;
int effective_bit_rate;
unsigned encoder_size;
if (frame_us != 2500 && frame_us != 5000 &&
frame_us != 7500 && frame_us != 10000 ) {
av_log(avctx, AV_LOG_ERROR,
"Unsupported frame duration %.1f ms.\n", frame_us / 1000.f);
return AVERROR(EINVAL);
}
hr_mode |= srate_hz > 48000;
hr_mode &= srate_hz >= 48000;
if (frame_us == 7500 && hr_mode) {
av_log(avctx, AV_LOG_ERROR,
"High-resolution mode is not supported with 7.5 ms frames.\n");
return AVERROR(EINVAL);
}
av_log(avctx, AV_LOG_INFO, "Encoding %.1f ms frames.\n", frame_us / 1000.f);
if (hr_mode)
av_log(avctx, AV_LOG_INFO, "High-resolution mode is enabled.\n");
liblc3->block_bytes = lc3_hr_frame_block_bytes(
hr_mode, frame_us, srate_hz, channels, avctx->bit_rate);
effective_bit_rate = lc3_hr_resolve_bitrate(
hr_mode, frame_us, srate_hz, liblc3->block_bytes);
if (avctx->bit_rate != effective_bit_rate)
av_log(avctx, AV_LOG_WARNING,
"Bitrate changed to %d bps.\n", effective_bit_rate);
avctx->bit_rate = effective_bit_rate;
encoder_size = lc3_hr_encoder_size(hr_mode, frame_us, srate_hz);
if (!encoder_size)
return AVERROR(EINVAL);
liblc3->encoder_mem = av_malloc_array(channels, encoder_size);
if (!liblc3->encoder_mem)
return AVERROR(ENOMEM);
for (int ch = 0; ch < channels; ch++) {
liblc3->encoder[ch] = lc3_hr_setup_encoder(
hr_mode, frame_us, srate_hz, 0,
(char *)liblc3->encoder_mem + ch * encoder_size);
}
avctx->extradata = av_mallocz(6 + AV_INPUT_BUFFER_PADDING_SIZE);
if (!avctx->extradata)
return AVERROR(ENOMEM);
AV_WL16(avctx->extradata + 0, frame_us / 10);
AV_WL16(avctx->extradata + 2, 0);
AV_WL16(avctx->extradata + 4, hr_mode);
avctx->extradata_size = 6;
avctx->frame_size = av_rescale(frame_us, srate_hz, 1000*1000);
liblc3->delay_samples = lc3_hr_delay_samples(hr_mode, frame_us, srate_hz);
liblc3->remaining_samples = 0;
return 0;
}
static av_cold int liblc3_encode_close(AVCodecContext *avctx)
{
LibLC3EncContext *liblc3 = avctx->priv_data;
av_freep(&liblc3->encoder_mem);
return 0;
}
static int liblc3_encode(AVCodecContext *avctx, AVPacket *pkt,
const AVFrame *frame, int *got_packet_ptr)
{
LibLC3EncContext *liblc3 = avctx->priv_data;
int block_bytes = liblc3->block_bytes;
int channels = avctx->ch_layout.nb_channels;
void *zero_frame = NULL;
uint8_t *data_ptr;
int ret;
if ((ret = ff_get_encode_buffer(avctx, pkt, block_bytes, 0)) < 0)
return ret;
if (frame) {
int padding = frame->nb_samples - frame->duration;
liblc3->remaining_samples = FFMAX(liblc3->delay_samples - padding, 0);
} else {
if (!liblc3->remaining_samples)
return 0;
liblc3->remaining_samples = 0;
zero_frame = av_mallocz(avctx->frame_size * sizeof(float));
if (!zero_frame)
return AVERROR(ENOMEM);
}
data_ptr = pkt->data;
for (int ch = 0; ch < channels; ch++) {
const float *pcm = zero_frame ? zero_frame : frame->data[ch];
int nbytes = block_bytes / channels + (ch < block_bytes % channels);
lc3_encode(liblc3->encoder[ch],
LC3_PCM_FORMAT_FLOAT, pcm, 1, nbytes, data_ptr);
data_ptr += nbytes;
}
if (zero_frame)
av_free(zero_frame);
*got_packet_ptr = 1;
return 0;
}
#define OFFSET(x) offsetof(LibLC3EncContext, opts.x)
#define FLAGS AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
{ "frame_duration", "Duration of a frame in milliseconds",
OFFSET(frame_duration), AV_OPT_TYPE_FLOAT,
{ .dbl = 10.0 }, 2.5, 10.0, FLAGS },
{ "high_resolution", "Enable High-Resolution mode (48 KHz or 96 KHz)",
OFFSET(hr_mode), AV_OPT_TYPE_BOOL,
{ .i64 = 0 }, 0, 1, FLAGS },
{ NULL }
};
static const AVClass class = {
.class_name = "liblc3 encoder",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
const FFCodec ff_liblc3_encoder = {
.p.name = "liblc3",
CODEC_LONG_NAME("LC3 (Low Complexity Communication Codec)"),
.p.type = AVMEDIA_TYPE_AUDIO,
.p.id = AV_CODEC_ID_LC3,
.p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY,
.p.ch_layouts = (const AVChannelLayout[])
{ { AV_CHANNEL_ORDER_UNSPEC, 1 },
{ AV_CHANNEL_ORDER_UNSPEC, 2 }, { 0 } },
.p.supported_samplerates = (const int [])
{ 96000, 48000, 32000, 24000, 16000, 8000, 0 },
.p.sample_fmts = (const enum AVSampleFormat[])
{ AV_SAMPLE_FMT_FLTP, AV_SAMPLE_FMT_NONE },
.p.priv_class = &class,
.p.wrapper_name = "liblc3",
.priv_data_size = sizeof(LibLC3EncContext),
.init = liblc3_encode_init,
.close = liblc3_encode_close,
FF_CODEC_ENCODE_CB(liblc3_encode),
};