[FFmpeg-devel] [PATCH 1/6] avcodec/liblc3: Add encoding/decoding support of LC3 audio codec

[Antoine Soulier via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

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>
Signed-off-by: Antoine SOULIER <asoulier@google.com>
---
 libavcodec/Makefile     |   3 +
 libavcodec/allcodecs.c  |   3 +
 libavcodec/codec_desc.c |  14 +++
 libavcodec/codec_id.h   |   2 +
 libavcodec/liblc3dec.c  | 146 ++++++++++++++++++++++++++++++
 libavcodec/liblc3enc.c  | 191 ++++++++++++++++++++++++++++++++++++++++
 6 files changed, 359 insertions(+)
 create mode 100644 libavcodec/liblc3dec.c
 create mode 100644 libavcodec/liblc3enc.c

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 708434ac76..7d2cf3076d 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -1123,6 +1123,9 @@ 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_LC3_DECODER)         += liblc3dec.o
+OBJS-$(CONFIG_LIBLC3_LC3PLUS_DECODER)     += liblc3dec.o
 OBJS-$(CONFIG_LIBMP3LAME_ENCODER)         += libmp3lame.o
 OBJS-$(CONFIG_LIBOPENCORE_AMRNB_DECODER)  += libopencore-amr.o
 OBJS-$(CONFIG_LIBOPENCORE_AMRNB_ENCODER)  += libopencore-amr.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index 2386b450a6..29aedaeac6 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -776,6 +776,9 @@ 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_lc3_decoder;
+extern const FFCodec ff_liblc3_lc3plus_decoder;
 extern const FFCodec ff_libmp3lame_encoder;
 extern const FFCodec ff_libopencore_amrnb_encoder;
 extern const FFCodec ff_libopencore_amrnb_decoder;
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index 3bab86db62..230bba2a09 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -3425,6 +3425,20 @@ 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,
+    },
+    {
+        .id        = AV_CODEC_ID_LC3_PLUS,
+        .type      = AVMEDIA_TYPE_AUDIO,
+        .name      = "lc3_plus",
+        .long_name = NULL_IF_CONFIG_SMALL("LC3plus (Low Complexity Communication Codec plus)"),
+        .props     = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
+    },
 
     /* subtitle codecs */
     {
diff --git a/libavcodec/codec_id.h b/libavcodec/codec_id.h
index c8dc21da74..7e4cb39049 100644
--- a/libavcodec/codec_id.h
+++ b/libavcodec/codec_id.h
@@ -543,6 +543,8 @@ enum AVCodecID {
     AV_CODEC_ID_AC4,
     AV_CODEC_ID_OSQ,
     AV_CODEC_ID_QOA,
+    AV_CODEC_ID_LC3,
+    AV_CODEC_ID_LC3_PLUS,
 
     /* subtitle codecs */
     AV_CODEC_ID_FIRST_SUBTITLE = 0x17000,          ///< A dummy ID pointing at the start of subtitle codecs.
diff --git a/libavcodec/liblc3dec.c b/libavcodec/liblc3dec.c
new file mode 100644
index 0000000000..e97cecc68f
--- /dev/null
+++ b/libavcodec/liblc3dec.c
@@ -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 "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;
+    bool hr_mode;
+    lc3_decoder_t decoder[DECODER_MAX_CHANNELS];
+} LibLC3DecContext;
+
+static av_cold int liblc3_decode_init(AVCodecContext *avctx)
+{
+    LibLC3DecContext *liblc3 = avctx->priv_data;
+    int channels = avctx->ch_layout.nb_channels;
+    unsigned decoder_size;
+
+    if (avctx->extradata_size < 2)
+        return AVERROR_INVALIDDATA;
+
+    liblc3->frame_us = AV_RL16(avctx->extradata + 0);
+    liblc3->srate_hz = avctx->sample_rate;
+    liblc3->hr_mode  = avctx->extradata_size >= 6 &&
+                       AV_RL16(avctx->extradata + 4);
+
+    av_log(avctx, AV_LOG_INFO,
+        "Decoding %.1f ms frames\n", liblc3->frame_us / 1e3f);
+    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;
+
+    for (int ch = 0; ch < channels; ch++) {
+        liblc3->decoder[ch] = lc3_hr_setup_decoder(liblc3->hr_mode,
+            liblc3->frame_us, liblc3->srate_hz, 0, av_malloc(decoder_size));
+        if (!liblc3->decoder[ch])
+            return AVERROR(ENOMEM);
+    }
+
+    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;
+    int channels = avctx->ch_layout.nb_channels;
+
+    for (int ch = 0; ch < channels; ch++)
+        av_free(liblc3->decoder[ch]);
+
+    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 = lc3_hr_frame_samples(
+        liblc3->hr_mode, liblc3->frame_us, liblc3->srate_hz);
+    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+        return ret;
+
+    block_bytes = avpkt->size;
+    for (int ch = 0; ch < channels; ch++) {
+        int frame_bytes = block_bytes / channels
+            + (ch < block_bytes % channels);
+
+
+        ret = lc3_decode(liblc3->decoder[ch], in, frame_bytes,
+                LC3_PCM_FORMAT_FLOAT, frame->data[ch], 1);
+        if (ret < 0)
+            return AVERROR_INVALIDDATA;
+
+        in += frame_bytes;
+    }
+
+    frame->nb_samples = FFMIN(frame->nb_samples, avpkt->duration);
+
+    *got_frame_ptr = 1;
+
+    return avpkt->size;
+}
+
+const FFCodec ff_liblc3_lc3_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),
+    .init           = liblc3_decode_init,
+    .close          = liblc3_decode_close,
+    FF_CODEC_DECODE_CB(liblc3_decode),
+};
+
+const FFCodec ff_liblc3_lc3plus_decoder = {
+    .p.name         = "liblc3",
+    CODEC_LONG_NAME("LC3plus (Low Complexity Communication Codec plus)"),
+    .p.type         = AVMEDIA_TYPE_AUDIO,
+    .p.id           = AV_CODEC_ID_LC3_PLUS,
+    .p.capabilities = AV_CODEC_CAP_DR1,
+    .p.wrapper_name = "liblc3",
+    .priv_data_size = sizeof(LibLC3DecContext),
+    .init           = liblc3_decode_init,
+    .close          = liblc3_decode_close,
+    FF_CODEC_DECODE_CB(liblc3_decode),
+};
diff --git a/libavcodec/liblc3enc.c b/libavcodec/liblc3enc.c
new file mode 100644
index 0000000000..6495742c04
--- /dev/null
+++ b/libavcodec/liblc3enc.c
@@ -0,0 +1,191 @@
+/*
+ * 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 "avcodec.h"
+#include "codec.h"
+#include "codec_internal.h"
+#include "encode.h"
+
+#define ENCODER_MAX_CHANNELS  2
+
+typedef struct LibLC3EncOpts {
+    float frame_duration;
+    bool hr_mode;
+} LibLC3EncOpts;
+
+typedef struct LibLC3EncContext {
+    AVClass *av_class;
+    LibLC3EncOpts opts;
+    int block_bytes;
+    lc3_encoder_t encoder[ENCODER_MAX_CHANNELS];
+} 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 / 1e3f);
+        return AVERROR(EINVAL);
+    }
+
+    hr_mode |= srate_hz > 48000;
+    hr_mode &= srate_hz >= 48000;
+
+    if (frame_us <= 5000 || hr_mode)
+        avctx->codec_id = AV_CODEC_ID_LC3_PLUS;
+
+    if (frame_us == 7500 && hr_mode) {
+        av_log(avctx, AV_LOG_ERROR,
+            "High-reolution mode not supported with 7.5 ms frames\n");
+        return AVERROR(EINVAL);
+    }
+
+    av_log(avctx, AV_LOG_INFO, "Encoding %.1f ms frames\n", frame_us / 1e3f);
+    if (hr_mode)
+        av_log(avctx, AV_LOG_INFO, "High-resolution mode 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(frame_us, frame_us, srate_hz);
+    if (!encoder_size)
+        return AVERROR(EINVAL);
+
+    for (int ch = 0; ch < channels; ch++) {
+        liblc3->encoder[ch] = lc3_hr_setup_encoder(
+            hr_mode, frame_us, srate_hz, 0, av_malloc(encoder_size));
+        if (!liblc3->encoder[ch])
+            return AVERROR(ENOMEM);
+    }
+
+    avctx->extradata = av_mallocz(6);
+    if (!avctx->extradata)
+        return AVERROR(ENOMEM);
+
+    AV_WL16(avctx->extradata + 0, frame_us);
+    AV_WL16(avctx->extradata + 2, 0);
+    AV_WL16(avctx->extradata + 4, hr_mode);
+    avctx->extradata_size = 6;
+
+    avctx->frame_size = lc3_hr_frame_samples(hr_mode, frame_us, srate_hz);
+
+    return 0;
+}
+
+static av_cold int liblc3_encode_close(AVCodecContext *avctx)
+{
+    LibLC3EncContext *liblc3 = avctx->priv_data;
+    int channels = avctx->ch_layout.nb_channels;
+
+    for (int ch = 0; ch < channels; ch++)
+        av_free(liblc3->encoder[ch]);
+
+    return 0;
+}
+
+static int liblc3_encode(AVCodecContext *avctx, AVPacket *avpkt,
+                         const AVFrame *av_frame, int *got_packet_ptr)
+{
+    LibLC3EncContext *liblc3 = avctx->priv_data;
+    int block_bytes = liblc3->block_bytes;
+    int channels = avctx->ch_layout.nb_channels;
+    uint8_t *data_ptr;
+    int ret;
+
+    if ((ret = ff_alloc_packet(avctx, avpkt, block_bytes)) < 0)
+        return ret;
+
+    data_ptr = avpkt->data;
+    for (int ch = 0; ch < channels; ch++) {
+        int frame_bytes = block_bytes / channels
+                + (ch < block_bytes % channels);
+
+        lc3_encode(liblc3->encoder[ch],
+            LC3_PCM_FORMAT_FLOAT, av_frame->data[ch], 1,
+            frame_bytes, data_ptr);
+
+        data_ptr += frame_bytes;
+    }
+
+    *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,
+    .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),
+};
-- 
2.44.0.396.g6e790dbe36-goog

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