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

[Stefano Sabatini <stefasab@gmail.com>]

On date Wednesday 2024-04-10 16:46:55 -0700, ffmpeg-devel Mailing List wrote:
> Sure, I thought these warnings were disabled while looking at codec2.c
> Sorry for the bad merge of the doc.

> From 975040408f32431efc3fae0a0b8c048f02159515 Mon Sep 17 00:00:00 2001
> From: Antoine SOULIER <asoulier@google.com>
> Date: Thu, 4 Apr 2024 22:38:03 +0000
> Subject: [PATCH] avformat/lc3: Add file format for LC3/LC3plus transport
> 
> A file format is described in Bluetooth SIG LC3 and ETSI TS 103 634, for
> test purpose. This is the format implemented here.
> ---
>  Changelog                |   1 +
>  doc/muxers.texi          |   6 +
>  libavformat/Makefile     |   2 +
>  libavformat/allformats.c |   2 +
>  libavformat/lc3.c        | 253 +++++++++++++++++++++++++++++++++++++++
>  5 files changed, 264 insertions(+)
>  create mode 100644 libavformat/lc3.c
> 
> diff --git a/Changelog b/Changelog
> index b7a1af4083..5c8f505211 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -5,6 +5,7 @@ version <next>:
>  - Raw Captions with Time (RCWT) closed caption demuxer
>  - LC3/LC3plus decoding/encoding using external library liblc3
>  - ffmpeg CLI filtergraph chaining
> +- LC3/LC3plus demuxer and muxer
>  
>  
>  version 7.0:
> diff --git a/doc/muxers.texi b/doc/muxers.texi
> index 4b30970b78..4c14323d50 100644
> --- a/doc/muxers.texi
> +++ b/doc/muxers.texi
> @@ -2725,6 +2725,12 @@ games such as "Real War", and "Real War: Rogue States".
>  
>  This muxer accepts a single @samp{adpcm_ima_ssi} audio stream.
>  
> +@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.

nit++: @samp{lc3} for consistency

> +
>  @section lrc
>  LRC lyrics file format muxer.
>  
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index 9981799cc9..8efe26b6df 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-$(CONFIG_LC3_DEMUXER)               += lc3.o
> +OBJS-$(CONFIG_LC3_MUXER)                 += lc3.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 ae925dcf60..305fa46532 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/lc3.c b/libavformat/lc3.c
> new file mode 100644
> index 0000000000..e27727145b
> --- /dev/null
> +++ b/libavformat/lc3.c
> @@ -0,0 +1,253 @@
> +/*
> + * LC3 demuxer

nit: LC3 demuxer and 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 "config_components.h"
> +
> +#include "libavcodec/packet.h"
> +#include "libavutil/intreadwrite.h"
> +
> +#include "avformat.h"
> +#include "avio.h"
> +#include "demux.h"
> +#include "internal.h"
> +#include "mux.h"
> +
> +static int check_frame_length(int srate_hz, int frame_us)
> +{
> +    if (srate_hz !=  8000 && srate_hz != 16000 && srate_hz != 24000 &&
> +        srate_hz != 32000 && srate_hz != 48000 && srate_hz != 96000)
> +        return -1;
> +
> +    if (frame_us != 2500 && frame_us !=  5000 &&
> +        frame_us != 7500 && frame_us != 10000)
> +        return -1;
> +
> +    return 0;
> +}
> +
> +#if CONFIG_LC3_DEMUXER
> +
> +typedef struct LC3DemuxContext {
> +    int frame_samples;
> +    int64_t end_dts;
> +} LC3DemuxContext;
> +
> +static int lc3_read_probe(const AVProbeData *p)
> +{
> +    int frame_us, srate_hz;
> +
> +    if (p->buf_size < 12)
> +        return 0;
> +
> +    if (AV_RB16(p->buf + 0) != 0x1ccc ||
> +        AV_RL16(p->buf + 2) <  9 * sizeof(uint16_t))
> +        return 0;
> +
> +    srate_hz = AV_RL16(p->buf + 4) * 100;
> +    frame_us = AV_RL16(p->buf + 10) * 10;
> +    if (check_frame_length(srate_hz, frame_us) < 0)
> +        return 0;
> +
> +    return AVPROBE_SCORE_MAX;
> +}
> +
> +static int lc3_read_header(AVFormatContext *s)
> +{
> +    LC3DemuxContext *lc3 = s->priv_data;
> +    AVStream *st = NULL;
> +    uint16_t tag, hdr_size;
> +    uint32_t length;
> +    int srate_hz, frame_us, channels, bit_rate;
> +    int ep_mode, hr_mode;
> +    int num_extra_params;
> +    int delay, 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);
> +
> +    if (check_frame_length(srate_hz, frame_us) < 0) {

> +        av_log(s, AV_LOG_ERROR, "Invalid LC3 sample rate: %d Hz, "
> +                                "frame duration: %.1f ms.\n",
> +               srate_hz, frame_us / 1000.f);

you can move the log to the function, by passing a log context (this
way you can provide more context in the error message and specify what
failed between rate and duration) - or skip the log in case a NULL log
context is provided for the probe case

but I don't think this is really blocking

[...]

Looks good to me otherwise, thanks.
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