I don't think it's "easy" seekable. We cannot move to an arbitrary position: - There is no start-code - The frame size can be variable (not generated by the proposed encoder implementation, but allowed).
The only possibility I see is checking that the frame size looks valid for multiple frames. The range of valid frame sizes is large (20 to 625 Bytes), so I can only validate 6 bits for each 16 bits packet size read. This format is not really designed to be seekable. Do you think we will need it? On Thu, Mar 28, 2024 at 2:33 AM Paul B Mahol <one...@gmail.com> wrote: > This format actually supports seeking. > > The proposed solution here is sub-optimal. > > On Wed, Mar 27, 2024 at 11:22 PM Antoine Soulier via ffmpeg-devel < > ffmpeg-devel@ffmpeg.org> wrote: > >> 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 <asoul...@google.com> >> --- >> doc/muxers.texi | 6 ++ >> libavformat/Makefile | 2 + >> libavformat/allformats.c | 2 + >> libavformat/lc3dec.c | 135 +++++++++++++++++++++++++++++++++++++++ >> libavformat/lc3enc.c | 102 +++++++++++++++++++++++++++++ >> 5 files changed, 247 insertions(+) >> create mode 100644 libavformat/lc3dec.c >> create mode 100644 libavformat/lc3enc.c >> >> 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 e15d0fa6d7..e225354faf 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..9ca9825f1b >> --- /dev/null >> +++ b/libavformat/lc3dec.c >> @@ -0,0 +1,135 @@ >> +/* >> + * LC3 demuxer >> + * Copyright (C) 2024 Antoine Soulier <asoul...@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 frame_samples; >> + int64_t position; >> + 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_us; >> + 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_us = avio_rl16(s->pb) * 10; >> + 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, 32, 1, srate_hz); >> + 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_us); >> + AV_WL16(st->codecpar->extradata + 2, ep_mode); >> + AV_WL16(st->codecpar->extradata + 4, hr_mode); >> + >> + lc3->frame_samples = av_rescale(frame_us, srate_hz, 1000*1000); >> + >> + lc3->position = 0; >> + lc3->length = st->duration + >> + av_rescale(frame_us == 7500 ? 4000 : 2500, srate_hz, 1000*1000); >> + >> + 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->duration = lc3->frame_samples; >> + lc3->position += lc3->frame_samples; >> + if (lc3->position > lc3->length) { >> + pkt->duration -= lc3->position - lc3->length; >> + lc3->position = lc3->length; >> + } >> + >> + 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_NOBINSEARCH | AVFMT_NOGENSEARCH | >> AVFMT_NO_BYTE_SEEK | AVFMT_NOTIMESTAMPS, >> + .priv_data_size = sizeof(LC3DemuxContext), >> + .read_header = lc3_read_header, >> + .read_packet = lc3_read_packet, >> +}; >> diff --git a/libavformat/lc3enc.c b/libavformat/lc3enc.c >> new file mode 100644 >> index 0000000000..a7e3e3f4f7 >> --- /dev/null >> +++ b/libavformat/lc3enc.c >> @@ -0,0 +1,102 @@ >> +/* >> + * LC3 muxer >> + * Copyright (C) 2024 Antoine Soulier <asoul...@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; >> + uint16_t frame_us = 10000; >> + int ep_mode = 0, hr_mode = 0; >> + uint32_t nb_samples = av_rescale_q( >> + st->duration, st->time_base, (AVRational){ 1, srate_hz }); >> + >> + if (st->codecpar->extradata_size >= 2) >> + frame_us = AV_RL16(st->codecpar->extradata + 0); >> + >> + if (st->codecpar->extradata_size >= 6) { >> + ep_mode = AV_RL16(st->codecpar->extradata + 2); >> + hr_mode = AV_RL16(st->codecpar->extradata + 4); >> + } >> + >> + 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 >> >> _______________________________________________ >> ffmpeg-devel mailing list >> ffmpeg-devel@ffmpeg.org >> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> >> To unsubscribe, visit link above, or email >> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". >> > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
