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>

1 files changed, 146 insertions, 0 deletions

diff --git a/libavcodec/liblc3dec.c b/libavcodec/liblc3dec.c
new file mode 100644
index 0000000000..c0a31bc91f
--- /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 "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),
+};