[FFmpeg-devel] [PATCH 2/2] avformat/lc3: Add file format for LC3/LC3plus transport

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

A file format is described in Bluetooth SIG LC3 and ETSI TS 103 634, for
test purpose. This is the format implemented here.

Signed-off-by: Antoine Soulier <asoulier@google.com>
---
 Changelog                |   1 +
 doc/muxers.texi          |   6 ++
 libavformat/Makefile     |   2 +
 libavformat/allformats.c |   2 +
 libavformat/lc3dec.c     | 164 +++++++++++++++++++++++++++++++++++++++
 libavformat/lc3enc.c     | 100 ++++++++++++++++++++++++
 6 files changed, 275 insertions(+)
 create mode 100644 libavformat/lc3dec.c
 create mode 100644 libavformat/lc3enc.c

diff --git a/Changelog b/Changelog
index 83a4cf7888..08c200a41d 100644
--- a/Changelog
+++ b/Changelog
@@ -2,6 +2,7 @@ Entries are sorted chronologically from oldest to youngest within each release,
 releases are sorted from youngest to oldest.
 
 version <next>:
+- LC3/LC3plus demuxer and muxer
 - LC3/LC3plus decoding/encoding using external library liblc3
 
 
diff --git a/doc/muxers.texi b/doc/muxers.texi
index a10a8e216f..9687746c30 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -2612,6 +2612,12 @@ WebDAV server every second:
 ffmpeg -f x11grab -framerate 1 -i :0.0 -q:v 6 -update 1 -protocol_opts method=PUT http://example.com/desktop.jpg
 @end example
 
+@section lc3
+Bluetooth SIG Low Complexity Communication Codec audio (LC3), or
+ETSI TS 103 634 Low Complexity Communication Codec plus (LC3plus).
+
+This muxer accepts a single @code{lc3} audio stream.
+
 @section matroska
 
 Matroska container muxer.
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 44aa485029..4961c42852 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -332,6 +332,8 @@ OBJS-$(CONFIG_KVAG_DEMUXER)              += kvag.o
 OBJS-$(CONFIG_KVAG_MUXER)                += kvag.o rawenc.o
 OBJS-$(CONFIG_LAF_DEMUXER)               += lafdec.o
 OBJS-$(CONFIG_LATM_MUXER)                += latmenc.o rawenc.o
+OBJS-$(CONFIG_LC3_DEMUXER)               += lc3dec.o
+OBJS-$(CONFIG_LC3_MUXER)                 += lc3enc.o
 OBJS-$(CONFIG_LMLM4_DEMUXER)             += lmlm4.o
 OBJS-$(CONFIG_LOAS_DEMUXER)              += loasdec.o rawdec.o
 OBJS-$(CONFIG_LUODAT_DEMUXER)            += luodatdec.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 9df42bb87a..0b36a7c3eb 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -252,6 +252,8 @@ extern const FFInputFormat  ff_kvag_demuxer;
 extern const FFOutputFormat ff_kvag_muxer;
 extern const FFInputFormat  ff_laf_demuxer;
 extern const FFOutputFormat ff_latm_muxer;
+extern const FFInputFormat  ff_lc3_demuxer;
+extern const FFOutputFormat ff_lc3_muxer;
 extern const FFInputFormat  ff_lmlm4_demuxer;
 extern const FFInputFormat  ff_loas_demuxer;
 extern const FFInputFormat  ff_luodat_demuxer;
diff --git a/libavformat/lc3dec.c b/libavformat/lc3dec.c
new file mode 100644
index 0000000000..74d6794d00
--- /dev/null
+++ b/libavformat/lc3dec.c
@@ -0,0 +1,164 @@
+/*
+ * LC3 demuxer
+ * Copyright (C) 2024  Antoine Soulier <asoulier@google.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Based on the file format specified by :
+ *
+ * - Bluetooth SIG - Low Complexity Communication Codec Test Suite
+ *   https://www.bluetooth.org/docman/handlers/downloaddoc.ashx?doc_id=502301
+ *   3.2.8.2 Reference LC3 Codec Bitstream Format
+ *
+ * - ETSI TI 103 634 V1.4.1 - Low Complexity Communication Codec plus
+ *   https://www.etsi.org/deliver/etsi_ts/103600_103699/103634/01.04.01_60/ts_103634v010401p.pdf
+ *   LC3plus conformance script package
+ */
+
+#include "libavcodec/packet.h"
+#include "libavutil/intreadwrite.h"
+
+#include "avformat.h"
+#include "avio.h"
+#include "demux.h"
+#include "internal.h"
+
+typedef struct LC3DemuxContext {
+    int dt, delay;
+    int64_t timestamp;
+    int64_t length;
+} LC3DemuxContext;
+
+static int lc3_read_header(AVFormatContext *s)
+{
+    LC3DemuxContext *lc3 = s->priv_data;
+    AVStream *st = NULL;
+    uint16_t tag, hdr_size;
+    uint16_t frame_10us;
+    uint32_t length;
+    int ep_mode, hr_mode;
+    int srate_hz, channels, bit_rate;
+    int num_extra_params, ret;
+
+    tag = avio_rb16(s->pb);
+    hdr_size = avio_rl16(s->pb);
+
+    if (tag != 0x1ccc || hdr_size < 9 * sizeof(uint16_t))
+        return AVERROR_INVALIDDATA;
+
+    num_extra_params = hdr_size / sizeof(uint16_t) - 9;
+
+    srate_hz   = avio_rl16(s->pb) * 100;
+    bit_rate   = avio_rl16(s->pb) * 100;
+    channels   = avio_rl16(s->pb);
+    frame_10us = avio_rl16(s->pb);
+    ep_mode    = avio_rl16(s->pb) != 0;
+    length     = avio_rl32(s->pb);
+    hr_mode    = num_extra_params >= 1 && avio_rl16(s->pb);
+
+    st = avformat_new_stream(s, NULL);
+    if (!st)
+        return AVERROR(ENOMEM);
+
+    avpriv_set_pts_info(st, 64, 1, srate_hz);
+    st->start_time = 0;
+    st->duration = length;
+
+    st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
+    st->codecpar->codec_id = AV_CODEC_ID_LC3;
+    st->codecpar->sample_rate = srate_hz;
+    st->codecpar->bit_rate = bit_rate;
+    st->codecpar->ch_layout.nb_channels = channels;
+
+    if ((ret = ff_alloc_extradata(st->codecpar, 6)) < 0) {
+        av_log(s, AV_LOG_ERROR, "Could not allocate extradata.\n");
+        return ret;
+    }
+
+    AV_WL16(st->codecpar->extradata + 0, frame_10us);
+    AV_WL16(st->codecpar->extradata + 2, ep_mode);
+    AV_WL16(st->codecpar->extradata + 4, hr_mode);
+
+    lc3->dt = av_rescale(frame_10us, srate_hz, 100*1000);
+    lc3->delay = av_rescale(frame_10us == 750 ? 400 : 250, srate_hz, 100*1000);
+
+    lc3->timestamp = -lc3->delay;
+    lc3->length = st->duration;
+
+    return 0;
+}
+
+static int lc3_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    LC3DemuxContext *lc3 = s->priv_data;
+    AVIOContext *pb = s->pb;
+    int ret;
+
+    ret = av_get_packet(s->pb, pkt, avio_rl16(pb));
+    if (ret < 0)
+        return ret;
+
+    pkt->pos -= 2;
+    pkt->pts = FFMAX(lc3->timestamp, 0);
+    pkt->duration = lc3->dt;
+
+    lc3->timestamp += lc3->dt;
+    if (lc3->timestamp > lc3->length) {
+        pkt->duration -= lc3->timestamp - lc3->length;
+        lc3->timestamp = lc3->length;
+    }
+
+    return 0;
+}
+
+static int lc3_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
+{
+    AVStream *st = s->streams[stream_index];
+    FFStream *const sti = ffstream(st);
+    LC3DemuxContext *lc3 = s->priv_data;
+    const AVIndexEntry *ie;
+    int index;
+
+    timestamp = FFMAX(timestamp - lc3->delay, 0);
+    if (timestamp >= lc3->length)
+        return AVERROR_EOF;
+
+    index = av_index_search_timestamp(st, timestamp, flags);
+    ie = index < 0 ? NULL : &sti->index_entries[index];
+    if (!ie || avio_seek(s->pb, ie->pos, SEEK_SET) < 0)
+        return -1;
+
+    lc3->timestamp = ie->timestamp;
+    if (lc3->timestamp == 0)
+      lc3->timestamp -= lc3->delay;
+
+    return 0;
+}
+
+const FFInputFormat ff_lc3_demuxer = {
+    .p.name         = "lc3",
+    .p.long_name    = NULL_IF_CONFIG_SMALL("LC3 (Low Complexity Communication Codec)"),
+    .p.extensions   = "lc3",
+    .p.flags        = AVFMT_GENERIC_INDEX,
+    .priv_data_size = sizeof(LC3DemuxContext),
+    .read_header    = lc3_read_header,
+    .read_packet    = lc3_read_packet,
+    .read_seek      = lc3_read_seek,
+};
diff --git a/libavformat/lc3enc.c b/libavformat/lc3enc.c
new file mode 100644
index 0000000000..e768212f63
--- /dev/null
+++ b/libavformat/lc3enc.c
@@ -0,0 +1,100 @@
+/*
+ * LC3 muxer
+ * Copyright (C) 2024  Antoine Soulier <asoulier@google.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Based on the file format specified by :
+ *
+ * - Bluetooth SIG - Low Complexity Communication Codec Test Suite
+ *   https://www.bluetooth.org/docman/handlers/downloaddoc.ashx?doc_id=502301
+ *   3.2.8.2 Reference LC3 Codec Bitstream Format
+ *
+ * - ETSI TI 103 634 V1.4.1 - Low Complexity Communication Codec plus
+ *   https://www.etsi.org/deliver/etsi_ts/103600_103699/103634/01.04.01_60/ts_103634v010401p.pdf
+ *   LC3plus conformance script package
+ */
+
+#include "libavutil/intreadwrite.h"
+
+#include "avformat.h"
+#include "avio.h"
+#include "mux.h"
+#include "internal.h"
+
+static av_cold int lc3_init(AVFormatContext *s)
+{
+    if (s->nb_streams != 1) {
+        av_log(s, AV_LOG_ERROR, "This muxer only supports a single stream.\n");
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
+static int lc3_write_header(AVFormatContext *s)
+{
+    AVStream *st = s->streams[0];
+    int channels = st->codecpar->ch_layout.nb_channels;
+    int srate_hz = st->codecpar->sample_rate;
+    int bit_rate = st->codecpar->bit_rate;
+    int frame_us, ep_mode, hr_mode;
+    uint32_t nb_samples = av_rescale_q(
+        st->duration, st->time_base, (AVRational){ 1, srate_hz });
+
+    if (st->codecpar->extradata_size < 6)
+        return AVERROR_INVALIDDATA;
+
+    frame_us = AV_RL16(st->codecpar->extradata + 0) * 10;
+    ep_mode = AV_RL16(st->codecpar->extradata + 2) != 0;
+    hr_mode = AV_RL16(st->codecpar->extradata + 4) != 0;
+
+    avio_wb16(s->pb, 0x1ccc);
+    avio_wl16(s->pb, (9 + hr_mode) * sizeof(uint16_t));
+    avio_wl16(s->pb, srate_hz / 100);
+    avio_wl16(s->pb, bit_rate / 100);
+    avio_wl16(s->pb, channels);
+    avio_wl16(s->pb, frame_us / 10);
+    avio_wl16(s->pb, ep_mode);
+    avio_wl32(s->pb, nb_samples);
+    if (hr_mode)
+        avio_wl16(s->pb, hr_mode);
+
+    return 0;
+}
+
+static int lc3_write_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    avio_wl16(s->pb, pkt->size);
+    avio_write(s->pb, pkt->data, pkt->size);
+    return 0;
+}
+
+const FFOutputFormat ff_lc3_muxer = {
+    .p.name        = "lc3",
+    .p.long_name   = NULL_IF_CONFIG_SMALL("LC3 (Low Complexity Communication Codec)"),
+    .p.extensions  = "lc3",
+    .p.audio_codec = AV_CODEC_ID_LC3,
+    .p.video_codec = AV_CODEC_ID_NONE,
+    .p.flags       = AVFMT_NOTIMESTAMPS,
+    .init          = lc3_init,
+    .write_header  = lc3_write_header,
+    .write_packet  = lc3_write_packet,
+};
-- 
2.44.0.478.gd926399ef9-goog

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