diff --git a/libavformat/Makefile b/libavformat/Makefile
index 472bbaf7cf..70c43ddde3 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -260,6 +260,7 @@ OBJS-$(CONFIG_HLS_DEMUXER)               += hls.o hls_sample_encryption.o
 OBJS-$(CONFIG_HLS_MUXER)                 += hlsenc.o hlsplaylist.o avc.o
 OBJS-$(CONFIG_HNM_DEMUXER)               += hnm.o
 OBJS-$(CONFIG_IAMF_DEMUXER)              += iamfdec.o iamf_parse.o iamf.o
+OBJS-$(CONFIG_IAMF_MUXER)                += iamfenc.o iamf.o
 OBJS-$(CONFIG_ICO_DEMUXER)               += icodec.o
 OBJS-$(CONFIG_ICO_MUXER)                 += icoenc.o
 OBJS-$(CONFIG_IDCIN_DEMUXER)             += idcin.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 63ca44bacd..7529aed4a4 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -213,6 +213,7 @@ extern const AVInputFormat  ff_hls_demuxer;
 extern const FFOutputFormat ff_hls_muxer;
 extern const AVInputFormat  ff_hnm_demuxer;
 extern const AVInputFormat  ff_iamf_demuxer;
+extern const FFOutputFormat ff_iamf_muxer;
 extern const AVInputFormat  ff_ico_demuxer;
 extern const FFOutputFormat ff_ico_muxer;
 extern const AVInputFormat  ff_idcin_demuxer;
diff --git a/libavformat/iamfenc.c b/libavformat/iamfenc.c
new file mode 100644
index 0000000000..29933d56eb
--- /dev/null
+++ b/libavformat/iamfenc.c
@@ -0,0 +1,1085 @@
+/*
+ * IAMF muxer
+ * Copyright (c) 2023 James Almer
+ *
+ * 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
+ */
+
+#include <stdint.h>
+
+#include "libavutil/avassert.h"
+#include "libavutil/common.h"
+#include "libavutil/internal.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/opt.h"
+#include "libavcodec/get_bits.h"
+#include "libavcodec/flac.h"
+#include "libavcodec/mpeg4audio.h"
+#include "libavcodec/put_bits.h"
+#include "avformat.h"
+#include "avio_internal.h"
+#include "iamf.h"
+#include "iamf_internal.h"
+#include "internal.h"
+#include "mux.h"
+
+typedef struct IAMFMuxContext {
+    IAMFContext iamf;
+
+    int first_stream_id;
+} IAMFMuxContext;
+
+static int update_extradata(AVFormatContext *s, IAMFCodecConfig *codec_config)
+{
+    GetBitContext gb;
+    PutBitContext pb;
+    int ret;
+
+    switch(codec_config->codec_id) {
+    case AV_CODEC_ID_OPUS:
+        if (codec_config->extradata_size < 19)
+            return AVERROR_INVALIDDATA;
+        codec_config->extradata_size -= 8;
+        memmove(codec_config->extradata, codec_config->extradata + 8, codec_config->extradata_size);
+        AV_WB8(codec_config->extradata + 1, 2); // set channels to stereo
+        break;
+    case AV_CODEC_ID_FLAC: {
+        uint8_t buf[13];
+
+        init_put_bits(&pb, buf, sizeof(buf));
+        ret = init_get_bits8(&gb, codec_config->extradata, codec_config->extradata_size);
+        if (ret < 0)
+            return ret;
+
+        put_bits32(&pb, get_bits_long(&gb, 32)); // min/max blocksize
+        put_bits64(&pb, 48, get_bits64(&gb, 48)); // min/max framesize
+        put_bits(&pb, 20, get_bits(&gb, 20)); // samplerate
+        skip_bits(&gb, 3);
+        put_bits(&pb, 3, 1); // set channels to stereo
+        ret = put_bits_left(&pb);
+        put_bits(&pb, ret, get_bits(&gb, ret));
+        flush_put_bits(&pb);
+
+        memcpy(codec_config->extradata, buf, sizeof(buf));
+        break;
+    }
+    default:
+        break;
+    }
+
+    return 0;
+}
+
+static int fill_codec_config(AVFormatContext *s, const AVStreamGroup *stg,
+                             IAMFCodecConfig *codec_config)
+{
+    const AVIAMFAudioElement *iamf = stg->params.iamf_audio_element;
+    const AVStream *st = stg->streams[0];
+    int ret;
+
+    av_freep(&codec_config->extradata);
+    codec_config->extradata_size = 0;
+
+    codec_config->codec_config_id = iamf->codec_config_id;
+    codec_config->codec_id = st->codecpar->codec_id;
+    codec_config->sample_rate = st->codecpar->sample_rate;
+    codec_config->codec_tag = st->codecpar->codec_tag;
+    codec_config->nb_samples = st->codecpar->frame_size;
+    codec_config->seek_preroll = st->codecpar->seek_preroll;
+    if (st->codecpar->extradata_size) {
+        codec_config->extradata = av_memdup(st->codecpar->extradata, st->codecpar->extradata_size);
+        if (!codec_config->extradata)
+            return AVERROR(ENOMEM);
+        codec_config->extradata_size = st->codecpar->extradata_size;
+        ret = update_extradata(s, codec_config);
+        if (ret < 0)
+            return ret;
+    }
+
+    return 0;
+}
+
+static IAMFParamDefinition *get_param_definition(AVFormatContext *s, unsigned int parameter_id)
+{
+    const IAMFMuxContext *const c = s->priv_data;
+    const IAMFContext *const iamf = &c->iamf;
+    IAMFParamDefinition *param_definition = NULL;
+
+    for (int i = 0; i < iamf->nb_param_definitions; i++)
+        if (iamf->param_definitions[i].param->parameter_id == parameter_id) {
+            param_definition = &iamf->param_definitions[i];
+            break;
+        }
+
+    return param_definition;
+}
+
+static IAMFParamDefinition *add_param_definition(AVFormatContext *s, AVIAMFParamDefinition *param)
+{
+    IAMFMuxContext *const c = s->priv_data;
+    IAMFContext *const iamf = &c->iamf;
+    IAMFParamDefinition *param_definition = av_dynarray2_add_nofree((void **)&iamf->param_definitions,
+                                                                    &iamf->nb_param_definitions,
+                                                                    sizeof(*iamf->param_definitions), NULL);
+    if (!param_definition)
+        return NULL;
+    param_definition->param = param;
+    param_definition->audio_element = NULL;
+
+    return param_definition;
+}
+
+static int iamf_init(AVFormatContext *s)
+{
+    IAMFMuxContext *const c = s->priv_data;
+    IAMFContext *const iamf = &c->iamf;
+    int stream_id = 0, ret;
+
+    if (!s->nb_streams) {
+        av_log(s, AV_LOG_ERROR, "There must be at least one stream\n");
+        return AVERROR(EINVAL);
+    }
+
+    for (int i = 0; i < s->nb_streams; i++) {
+        if (s->streams[i]->codecpar->codec_type != AVMEDIA_TYPE_AUDIO ||
+            (s->streams[i]->codecpar->codec_tag != MKTAG('m','p','4','a') &&
+             s->streams[i]->codecpar->codec_tag != MKTAG('O','p','u','s') &&
+             s->streams[i]->codecpar->codec_tag != MKTAG('f','L','a','C') &&
+             s->streams[i]->codecpar->codec_tag != MKTAG('i','p','c','m'))) {
+            av_log(s, AV_LOG_ERROR, "Unsupported codec id %s\n",
+                   avcodec_get_name(s->streams[i]->codecpar->codec_id));
+            return AVERROR(EINVAL);
+        }
+
+        if (s->streams[i]->codecpar->ch_layout.nb_channels > 2) {
+            av_log(s, AV_LOG_ERROR, "Unsupported channel layout on stream #%d\n", i);
+            return AVERROR(EINVAL);
+        }
+
+        if (!s->streams[i]->id)
+            s->streams[i]->id = ++stream_id;
+    }
+
+    if (!s->nb_stream_groups) {
+        av_log(s, AV_LOG_ERROR, "There must be at least two stream groups\n");
+        return AVERROR(EINVAL);
+    }
+
+    for (int i = 0; i < s->nb_stream_groups; i++) {
+        AVStreamGroup *stg = s->stream_groups[i];
+
+        if (stg->type == AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT)
+            iamf->nb_audio_elements++;
+        if (stg->type == AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION)
+            iamf->nb_mix_presentations++;
+    }
+    if ((iamf->nb_audio_elements < 1 && iamf->nb_audio_elements > 2) || iamf->nb_mix_presentations < 1) {
+        av_log(s, AV_LOG_ERROR, "There must be >= 1 and <= 2 IAMF_AUDIO_ELEMENT and at least one IAMF_MIX_PRESENTATION stream groups\n");
+        return AVERROR(EINVAL);
+    }
+
+    iamf->audio_elements = av_calloc(iamf->nb_audio_elements, sizeof(*iamf->audio_elements));
+    iamf->mix_presentations = av_calloc(iamf->nb_mix_presentations, sizeof(*iamf->mix_presentations));
+
+    if (!iamf->audio_elements || !iamf->mix_presentations) {
+        iamf->nb_audio_elements = iamf->nb_mix_presentations = 0;
+        return AVERROR(ENOMEM);
+    }
+
+    for (int i = 0, idx = 0; i < s->nb_stream_groups; i++) {
+        const AVStreamGroup *stg = s->stream_groups[i];
+        AVIAMFAudioElement *iamf_audio_element;
+        IAMFAudioElement *audio_element;
+        IAMFCodecConfig *codec_config = NULL;
+
+        if (stg->type != AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT)
+            continue;
+
+        iamf_audio_element = stg->params.iamf_audio_element;
+        if (iamf_audio_element->audio_element_type == AV_IAMF_AUDIO_ELEMENT_TYPE_SCENE) {
+            const AVIAMFLayer *layer = iamf_audio_element->layers[0];
+            if (iamf_audio_element->num_layers != 1) {
+                av_log(s, AV_LOG_ERROR, "Invalid amount of layers for SCENE_BASED audio element. Must be 1\n");
+                return AVERROR(EINVAL);
+            }
+            if (layer->ch_layout.order != AV_CHANNEL_ORDER_CUSTOM &&
+                layer->ch_layout.order != AV_CHANNEL_ORDER_AMBISONIC) {
+                av_log(s, AV_LOG_ERROR, "Invalid channel layout for SCENE_BASED audio element\n");
+                return AVERROR(EINVAL);
+            }
+            for (int j = 0; j < stg->nb_streams; j++) {
+                if (stg->streams[j]->codecpar->ch_layout.nb_channels > 1) {
+                    av_log(s, AV_LOG_ERROR, "PROJECTION mode ambisonics not supported\n");
+                    return AVERROR_PATCHWELCOME;
+                }
+            }
+        } else
+            for (int k, j = 0; j < iamf_audio_element->num_layers; j++) {
+                const AVIAMFLayer *layer = iamf_audio_element->layers[j];
+                for (k = 0; k < FF_ARRAY_ELEMS(ff_iamf_scalable_ch_layouts); k++)
+                    if (!av_channel_layout_compare(&layer->ch_layout, &ff_iamf_scalable_ch_layouts[k]))
+                        break;
+
+                if (k >= FF_ARRAY_ELEMS(ff_iamf_scalable_ch_layouts)) {
+                    av_log(s, AV_LOG_ERROR, "Unsupported channel layout in stream group #%d\n", i);
+                    return AVERROR(EINVAL);
+                }
+            }
+
+        for (int j = 0; j < iamf->nb_codec_configs; j++) {
+            if (iamf->codec_configs[j].codec_config_id == iamf_audio_element->codec_config_id) {
+                codec_config = &iamf->codec_configs[j];
+                break;
+            }
+        }
+
+        if (!codec_config) {
+            codec_config = av_dynarray2_add_nofree((void **)&iamf->codec_configs, &iamf->nb_codec_configs,
+                                                   sizeof(*iamf->codec_configs), NULL);
+            if (!codec_config)
+                return AVERROR(ENOMEM);
+            memset(codec_config, 0, sizeof(*codec_config));
+
+        }
+
+        ret = fill_codec_config(s, stg, codec_config);
+        if (ret < 0)
+            return ret;
+
+        audio_element = &iamf->audio_elements[idx++];
+        audio_element->element = iamf_audio_element;
+        audio_element->audio_element_id = stg->id;
+        audio_element->codec_config = codec_config;
+
+        audio_element->substreams = av_calloc(stg->nb_streams, sizeof(*audio_element->substreams));
+        if (!audio_element->substreams)
+            return AVERROR(ENOMEM);
+        audio_element->nb_substreams = stg->nb_streams;
+
+        for (int j = 0, k = 0; j < iamf_audio_element->num_layers; j++) {
+            IAMFLayer *layer = av_dynarray2_add_nofree((void **)&audio_element->layers, &audio_element->nb_layers,
+                                                       sizeof(*audio_element->layers), NULL);
+            int nb_channels = iamf_audio_element->layers[j]->ch_layout.nb_channels;
+
+            if (!layer)
+                return AVERROR(ENOMEM);
+            memset(layer, 0, sizeof(*layer));
+
+            if (j)
+                nb_channels -= iamf_audio_element->layers[j - 1]->ch_layout.nb_channels;
+            for (; nb_channels > 0 && k < stg->nb_streams; k++) {
+                const AVStream *st = stg->streams[k];
+                IAMFSubStream *substream = &audio_element->substreams[k];
+
+                substream->audio_substream_id = st->id;
+                layer->substream_count++;
+                layer->coupled_substream_count += st->codecpar->ch_layout.nb_channels == 2;
+                nb_channels -= st->codecpar->ch_layout.nb_channels;
+            }
+            if (nb_channels) {
+                av_log(s, AV_LOG_ERROR, "Invalid channel count across substreams in layer %u from stream group %u\n",
+                       j, stg->index);
+                return AVERROR(EINVAL);
+            }
+        }
+
+        if (iamf_audio_element->demixing_info) {
+            AVIAMFParamDefinition *param = iamf_audio_element->demixing_info;
+            IAMFParamDefinition *param_definition = get_param_definition(s, param->parameter_id);
+
+            if (param->num_subblocks != 1) {
+                av_log(s, AV_LOG_ERROR, "num_subblocks in demixing_info for stream group %u is not 1\n", stg->index);
+                return AVERROR(EINVAL);
+            }
+            if (!param_definition) {
+                param_definition = add_param_definition(s, param);
+                if (!param_definition)
+                    return AVERROR(ENOMEM);
+            }
+            param_definition->audio_element = iamf_audio_element;
+        }
+        if (iamf_audio_element->recon_gain_info) {
+            AVIAMFParamDefinition *param = iamf_audio_element->recon_gain_info;
+            IAMFParamDefinition *param_definition = get_param_definition(s, param->parameter_id);
+
+            if (param->num_subblocks != 1) {
+                av_log(s, AV_LOG_ERROR, "num_subblocks in recon_gain_info for stream group %u is not 1\n", stg->index);
+                return AVERROR(EINVAL);
+            }
+
+            if (!param_definition) {
+                param_definition = add_param_definition(s, param);
+                if (!param_definition)
+                    return AVERROR(ENOMEM);
+            }
+            param_definition->audio_element = iamf_audio_element;
+        }
+    }
+
+    for (int i = 0, idx = 0; i < s->nb_stream_groups; i++) {
+        const AVStreamGroup *stg = s->stream_groups[i];
+        IAMFMixPresentation *mix_presentation;
+
+        if (stg->type != AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION)
+            continue;
+
+        mix_presentation = &iamf->mix_presentations[idx++];
+        mix_presentation->mix = stg->params.iamf_mix_presentation;
+
+        for (int i = 0; i < stg->params.iamf_mix_presentation->num_submixes; i++) {
+            AVIAMFSubmix *submix = stg->params.iamf_mix_presentation->submixes[i];
+            AVIAMFParamDefinition *param = submix->output_mix_config;
+            IAMFParamDefinition *param_definition;
+
+            if (!param) {
+                av_log(s, AV_LOG_ERROR, "output_mix_config is not present in submix %u from Mix Presentation ID %"PRId64"\n", i, stg->id);
+                return AVERROR(EINVAL);
+            }
+
+            param_definition = get_param_definition(s, param->parameter_id);
+            if (!param_definition) {
+                param_definition = add_param_definition(s, param);
+                if (!param_definition)
+                    return AVERROR(ENOMEM);
+            }
+
+            for (int j = 0; j < submix->num_elements; j++) {
+                const AVIAMFAudioElement *iamf_audio_element = NULL;
+                const AVIAMFSubmixElement *element = submix->elements[j];
+                param = element->element_mix_config;
+
+                if (!param) {
+                    av_log(s, AV_LOG_ERROR, "element_mix_config is not present for element %u in submix %u from Mix Presentation ID %"PRId64"\n", j, i, stg->id);
+                    return AVERROR(EINVAL);
+                }
+                param_definition = get_param_definition(s, param->parameter_id);
+                if (!param_definition) {
+                    param_definition = add_param_definition(s, param);
+                    if (!param_definition)
+                        return AVERROR(ENOMEM);
+                }
+                for (int k = 0; k < iamf->nb_audio_elements; k++)
+                    if (iamf->audio_elements[k].audio_element_id == element->audio_element_id) {
+                        iamf_audio_element = iamf->audio_elements[k].element;
+                        break;
+                    }
+                param_definition->audio_element = iamf_audio_element;
+            }
+        }
+    }
+
+    c->first_stream_id = s->streams[0]->id;
+
+    return 0;
+}
+
+static void leb(AVIOContext *pb, unsigned value)
+{
+    int len, i;
+    uint8_t byte;
+
+    len = (av_log2(value) + 7) / 7;
+
+    for (i = 0; i < len; i++) {
+        byte = value >> (7 * i) & 0x7f;
+        if (i < len - 1)
+            byte |= 0x80;
+
+        avio_w8(pb, byte);
+    }
+}
+
+static int iamf_write_codec_config(AVFormatContext *s, const IAMFCodecConfig *codec_config)
+{
+    uint8_t header[MAX_IAMF_OBU_HEADER_SIZE];
+    AVIOContext *dyn_bc;
+    uint8_t *dyn_buf = NULL;
+    PutBitContext pb;
+    int dyn_size;
+
+    int ret = avio_open_dyn_buf(&dyn_bc);
+    if (ret < 0)
+        return ret;
+
+    leb(dyn_bc, codec_config->codec_config_id);
+    avio_wl32(dyn_bc, codec_config->codec_tag);
+
+    leb(dyn_bc, codec_config->nb_samples);
+    avio_wb16(dyn_bc, codec_config->seek_preroll);
+
+    switch(codec_config->codec_id) {
+    case AV_CODEC_ID_OPUS:
+        avio_write(dyn_bc, codec_config->extradata, codec_config->extradata_size);
+        break;
+    case AV_CODEC_ID_AAC:
+        return AVERROR_PATCHWELCOME;
+    case AV_CODEC_ID_FLAC:
+        avio_w8(dyn_bc, 0x80);
+        avio_wb24(dyn_bc, codec_config->extradata_size);
+        avio_write(dyn_bc, codec_config->extradata, codec_config->extradata_size);
+        break;
+    case AV_CODEC_ID_PCM_S16LE:
+        avio_w8(dyn_bc, 0);
+        avio_w8(dyn_bc, 16);
+        avio_wb32(dyn_bc, codec_config->sample_rate);
+        break;
+    case AV_CODEC_ID_PCM_S24LE:
+        avio_w8(dyn_bc, 0);
+        avio_w8(dyn_bc, 24);
+        avio_wb32(dyn_bc, codec_config->sample_rate);
+        break;
+    case AV_CODEC_ID_PCM_S32LE:
+        avio_w8(dyn_bc, 0);
+        avio_w8(dyn_bc, 32);
+        avio_wb32(dyn_bc, codec_config->sample_rate);
+        break;
+    case AV_CODEC_ID_PCM_S16BE:
+        avio_w8(dyn_bc, 1);
+        avio_w8(dyn_bc, 16);
+        avio_wb32(dyn_bc, codec_config->sample_rate);
+        break;
+    case AV_CODEC_ID_PCM_S24BE:
+        avio_w8(dyn_bc, 1);
+        avio_w8(dyn_bc, 24);
+        avio_wb32(dyn_bc, codec_config->sample_rate);
+        break;
+    case AV_CODEC_ID_PCM_S32BE:
+        avio_w8(dyn_bc, 1);
+        avio_w8(dyn_bc, 32);
+        avio_wb32(dyn_bc, codec_config->sample_rate);
+        break;
+    default:
+        break;
+    }
+
+    init_put_bits(&pb, header, sizeof(header));
+    put_bits(&pb, 5, IAMF_OBU_IA_CODEC_CONFIG);
+    put_bits(&pb, 3, 0);
+    flush_put_bits(&pb);
+
+    dyn_size = avio_close_dyn_buf(dyn_bc, &dyn_buf);
+    avio_write(s->pb, header, put_bytes_count(&pb, 1));
+    leb(s->pb, dyn_size);
+    avio_write(s->pb, dyn_buf, dyn_size);
+    av_free(dyn_buf);
+
+    return 0;
+}
+
+static inline int rescale_rational(AVRational q, int b)
+{
+    return av_clip_int16(av_rescale(q.num, b, q.den));
+}
+
+static int scalable_channel_layout_config(AVFormatContext *s, AVIOContext *dyn_bc,
+                                          const IAMFAudioElement *audio_element)
+{
+    const AVIAMFAudioElement *element = audio_element->element;
+    uint8_t header[MAX_IAMF_OBU_HEADER_SIZE];
+    PutBitContext pb;
+
+    init_put_bits(&pb, header, sizeof(header));
+    put_bits(&pb, 3, element->num_layers);
+    put_bits(&pb, 5, 0);
+    flush_put_bits(&pb);
+    avio_write(dyn_bc, header, put_bytes_count(&pb, 1));
+    for (int i = 0; i < element->num_layers; i++) {
+        AVIAMFLayer *layer = element->layers[i];
+        int layout;
+        for (layout = 0; layout < FF_ARRAY_ELEMS(ff_iamf_scalable_ch_layouts); layout++) {
+            if (!av_channel_layout_compare(&layer->ch_layout, &ff_iamf_scalable_ch_layouts[layout]))
+                break;
+        }
+        init_put_bits(&pb, header, sizeof(header));
+        put_bits(&pb, 4, layout);
+        put_bits(&pb, 1, !!layer->output_gain_flags);
+        put_bits(&pb, 1, layer->recon_gain_is_present);
+        put_bits(&pb, 2, 0); // reserved
+        put_bits(&pb, 8, audio_element->layers[i].substream_count);
+        put_bits(&pb, 8, audio_element->layers[i].coupled_substream_count);
+       // av_log(s, AV_LOG_WARNING, "k %d, substream_count %d, coupled_substream_count %d\n", k, layer->substream_count, coupled_substream_count);
+        if (layer->output_gain_flags) {
+            put_bits(&pb, 6, layer->output_gain_flags);
+            put_bits(&pb, 2, 0);
+            put_bits(&pb, 16, rescale_rational(layer->output_gain, 1 << 8));
+        }
+        flush_put_bits(&pb);
+        avio_write(dyn_bc, header, put_bytes_count(&pb, 1));
+    }
+
+    return 0;
+}
+
+static int ambisonics_config(AVFormatContext *s, AVIOContext *dyn_bc,
+                             const IAMFAudioElement *audio_element)
+{
+    const AVIAMFAudioElement *element = audio_element->element;
+    AVIAMFLayer *layer = element->layers[0];
+
+    leb(dyn_bc, 0); // ambisonics_mode
+    leb(dyn_bc, layer->ch_layout.nb_channels); // output_channel_count
+    leb(dyn_bc, audio_element->nb_substreams); // substream_count
+
+    if (layer->ch_layout.order == AV_CHANNEL_ORDER_AMBISONIC)
+        for (int i = 0; i < layer->ch_layout.nb_channels; i++)
+            avio_w8(dyn_bc, i);
+    else
+        for (int i = 0; i < layer->ch_layout.nb_channels; i++)
+            avio_w8(dyn_bc, layer->ch_layout.u.map[i].id);
+
+    return 0;
+}
+
+static int param_definition(AVFormatContext *s, AVIOContext *dyn_bc,
+                            AVIAMFParamDefinition *param)
+{
+    leb(dyn_bc, param->parameter_id);
+    leb(dyn_bc, param->parameter_rate);
+    avio_w8(dyn_bc, !!param->param_definition_mode << 7); // param_definition_mode
+    if (!param->param_definition_mode) {
+        leb(dyn_bc, param->duration); // duration
+        leb(dyn_bc, param->constant_subblock_duration); // constant_subblock_duration
+        if (param->constant_subblock_duration == 0) {
+            leb(dyn_bc, param->num_subblocks);
+            for (int i = 0; i < param->num_subblocks; i++) {
+                const void *subblock = avformat_iamf_param_definition_get_subblock(param, i);
+
+                switch (param->param_definition_type) {
+                case AV_IAMF_PARAMETER_DEFINITION_MIX_GAIN: {
+                    const AVIAMFMixGainParameterData *mix = subblock;
+                    leb(dyn_bc, mix->subblock_duration);
+                    break;
+                }
+                case AV_IAMF_PARAMETER_DEFINITION_DEMIXING: {
+                    const AVIAMFDemixingInfoParameterData *demix = subblock;
+                    leb(dyn_bc, demix->subblock_duration);
+                    break;
+                }
+                case AV_IAMF_PARAMETER_DEFINITION_RECON_GAIN: {
+                    const AVIAMFReconGainParameterData *recon = subblock;
+                    leb(dyn_bc, recon->subblock_duration);
+                    break;
+                }
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int iamf_write_audio_element(AVFormatContext *s, const IAMFAudioElement *audio_element)
+{
+    uint8_t header[MAX_IAMF_OBU_HEADER_SIZE];
+    const AVIAMFAudioElement *element = audio_element->element;
+    AVIOContext *dyn_bc;
+    uint8_t *dyn_buf = NULL;
+    PutBitContext pb;
+    int param_definition_types = AV_IAMF_PARAMETER_DEFINITION_DEMIXING, dyn_size;
+
+    int ret = avio_open_dyn_buf(&dyn_bc);
+    if (ret < 0)
+        return ret;
+
+    leb(dyn_bc, audio_element->audio_element_id);
+
+    init_put_bits(&pb, header, sizeof(header));
+    put_bits(&pb, 3, element->audio_element_type);
+    put_bits(&pb, 5, 0);
+    flush_put_bits(&pb);
+    avio_write(dyn_bc, header, put_bytes_count(&pb, 1));
+
+    leb(dyn_bc, audio_element->codec_config->codec_config_id);
+    leb(dyn_bc, audio_element->nb_substreams);
+
+    for (int i = 0; i < audio_element->nb_substreams; i++)
+        leb(dyn_bc, audio_element->substreams[i].audio_substream_id);
+
+    if (audio_element->nb_layers == 1)
+        param_definition_types &= ~AV_IAMF_PARAMETER_DEFINITION_DEMIXING;
+    if (audio_element->nb_layers > 1)
+        param_definition_types |= AV_IAMF_PARAMETER_DEFINITION_RECON_GAIN;
+    if (audio_element->codec_config->codec_tag == MKTAG('f','L','a','C') ||
+        audio_element->codec_config->codec_tag == MKTAG('i','p','c','m'))
+        param_definition_types &= ~AV_IAMF_PARAMETER_DEFINITION_RECON_GAIN;
+
+    leb(dyn_bc, av_popcount(param_definition_types)); // num_parameters
+
+    if (param_definition_types & 1) {
+        AVIAMFParamDefinition *param = element->demixing_info;
+        AVIAMFDemixingInfoParameterData *demix;
+
+        if (!param) {
+            av_log(s, AV_LOG_ERROR, "demixing_info needed but not set in Stream Group #%u\n",
+                   audio_element->audio_element_id);
+            return AVERROR(EINVAL);
+        }
+
+        demix = avformat_iamf_param_definition_get_subblock(param, 0);
+        leb(dyn_bc, AV_IAMF_PARAMETER_DEFINITION_DEMIXING); // param_definition_type
+        param_definition(s, dyn_bc, param);
+
+        avio_w8(dyn_bc, demix->dmixp_mode << 5); // dmixp_mode
+        avio_w8(dyn_bc, element->default_w << 4); // default_w
+    }
+    if (param_definition_types & 2) {
+        AVIAMFParamDefinition *param = element->recon_gain_info;
+
+        if (!param) {
+            av_log(s, AV_LOG_ERROR, "recon_gain_info needed but not set in Stream Group #%u\n",
+                   audio_element->audio_element_id);
+            return AVERROR(EINVAL);
+        }
+        leb(dyn_bc, AV_IAMF_PARAMETER_DEFINITION_RECON_GAIN); // param_definition_type
+        param_definition(s, dyn_bc, param);
+    }
+
+    if (element->audio_element_type == AV_IAMF_AUDIO_ELEMENT_TYPE_CHANNEL) {
+        ret = scalable_channel_layout_config(s, dyn_bc, audio_element);
+        if (ret < 0)
+            return ret;
+    } else {
+        ret = ambisonics_config(s, dyn_bc, audio_element);
+        if (ret < 0)
+            return ret;
+    }
+
+    init_put_bits(&pb, header, sizeof(header));
+    put_bits(&pb, 5, IAMF_OBU_IA_AUDIO_ELEMENT);
+    put_bits(&pb, 3, 0);
+    flush_put_bits(&pb);
+
+    dyn_size = avio_close_dyn_buf(dyn_bc, &dyn_buf);
+    avio_write(s->pb, header, put_bytes_count(&pb, 1));
+    leb(s->pb, dyn_size);
+    avio_write(s->pb, dyn_buf, dyn_size);
+    av_free(dyn_buf);
+
+    return 0;
+}
+
+static int iamf_write_mixing_presentation(AVFormatContext *s, const IAMFMixPresentation *mix_presentation)
+{
+    IAMFMuxContext *const c = s->priv_data;
+    IAMFContext *const iamf = &c->iamf;
+    uint8_t header[MAX_IAMF_OBU_HEADER_SIZE];
+    AVIAMFMixPresentation *mix = mix_presentation->mix;
+    const AVDictionaryEntry *tag = NULL;
+    PutBitContext pb;
+    AVIOContext *dyn_bc;
+    uint8_t *dyn_buf = NULL;
+    int dyn_size;
+
+    int ret = avio_open_dyn_buf(&dyn_bc);
+    if (ret < 0)
+        return ret;
+
+    leb(dyn_bc, mix_presentation->mix_presentation_id); // mix_presentation_id
+    leb(dyn_bc, av_dict_count(mix->annotations)); // count_label
+
+    while ((tag = av_dict_iterate(mix->annotations, tag)))
+        avio_put_str(dyn_bc, tag->key);
+    while ((tag = av_dict_iterate(mix->annotations, tag)))
+        avio_put_str(dyn_bc, tag->value);
+
+    leb(dyn_bc, mix->num_submixes);
+    for (int i = 0; i < mix->num_submixes; i++) {
+        const AVIAMFSubmix *sub_mix = mix->submixes[i];
+
+        leb(dyn_bc, sub_mix->num_elements);
+        for (int j = 0; j < sub_mix->num_elements; j++) {
+            const IAMFAudioElement *audio_element = NULL;
+            const AVIAMFSubmixElement *submix_element = sub_mix->elements[j];
+
+            for (int k = 0; k < iamf->nb_audio_elements; k++)
+                if (iamf->audio_elements[k].audio_element_id == submix_element->audio_element_id) {
+                    audio_element = &iamf->audio_elements[k];
+                    break;
+                }
+
+            av_assert0(audio_element);
+            leb(dyn_bc, submix_element->audio_element_id);
+
+            if (av_dict_count(submix_element->annotations) != av_dict_count(mix->annotations)) {
+                av_log(s, AV_LOG_ERROR, "Inconsistent amount of labels in submix %d from Mix Presentation id #%u\n",
+                       j, audio_element->audio_element_id);
+                return AVERROR(EINVAL);
+            }
+            while ((tag = av_dict_iterate(submix_element->annotations, tag)))
+                avio_put_str(dyn_bc, tag->value);
+
+            init_put_bits(&pb, header, sizeof(header));
+            put_bits(&pb, 2, submix_element->headphones_rendering_mode);
+            put_bits(&pb, 6, 0); // reserved
+            flush_put_bits(&pb);
+            avio_write(dyn_bc, header, put_bytes_count(&pb, 1));
+            leb(dyn_bc, 0); // rendering_config_extension_size
+            param_definition(s, dyn_bc, submix_element->element_mix_config);
+            avio_wb16(dyn_bc, rescale_rational(submix_element->default_mix_gain, 1 << 8));
+        }
+        param_definition(s, dyn_bc, sub_mix->output_mix_config);
+        avio_wb16(dyn_bc, rescale_rational(sub_mix->default_mix_gain, 1 << 8));
+
+        leb(dyn_bc, sub_mix->num_layouts); // num_layouts
+        for (int i = 0; i < sub_mix->num_layouts; i++) {
+            AVIAMFSubmixLayout *submix_layout = sub_mix->layouts[i];
+            int layout, info_type;
+            int dialogue = submix_layout->dialogue_anchored_loudness.num &&
+                           submix_layout->dialogue_anchored_loudness.den;
+            int album = submix_layout->album_anchored_loudness.num &&
+                        submix_layout->album_anchored_loudness.den;
+
+            if (layout == FF_ARRAY_ELEMS(ff_iamf_sound_system_map)) {
+                av_log(s, AV_LOG_ERROR, "Invalid Sound System value in a submix\n");
+                return AVERROR(EINVAL);
+            }
+
+            if (submix_layout->layout_type == AV_IAMF_SUBMIX_LAYOUT_TYPE_LOUDSPEAKERS) {
+                for (layout = 0; layout < FF_ARRAY_ELEMS(ff_iamf_sound_system_map); layout++) {
+                    if (!av_channel_layout_compare(&submix_layout->sound_system, &ff_iamf_sound_system_map[layout].layout))
+                        break;
+                }
+                if (layout == FF_ARRAY_ELEMS(ff_iamf_sound_system_map)) {
+                    av_log(s, AV_LOG_ERROR, "Invalid Sound System value in a submix\n");
+                    return AVERROR(EINVAL);
+                }
+            }
+            init_put_bits(&pb, header, sizeof(header));
+            put_bits(&pb, 2, submix_layout->layout_type); // layout_type
+            if (submix_layout->layout_type == AV_IAMF_SUBMIX_LAYOUT_TYPE_LOUDSPEAKERS) {
+                put_bits(&pb, 4, ff_iamf_sound_system_map[layout].id); // sound_system
+                put_bits(&pb, 2, 0); // reserved
+            } else
+                put_bits(&pb, 6, 0); // reserved
+            flush_put_bits(&pb);
+            avio_write(dyn_bc, header, put_bytes_count(&pb, 1));
+
+            info_type  = (submix_layout->true_peak.num && submix_layout->true_peak.den);
+            info_type |= (dialogue || album) << 1;
+            avio_w8(dyn_bc, info_type);
+            avio_wb16(dyn_bc, rescale_rational(submix_layout->integrated_loudness, 1 << 8));
+            avio_wb16(dyn_bc, rescale_rational(submix_layout->digital_peak, 1 << 8));
+            if (info_type & 1)
+                avio_wb16(dyn_bc, rescale_rational(submix_layout->true_peak, 1 << 8));
+            if (info_type & 2) {
+                avio_w8(dyn_bc, dialogue + album); // num_anchored_loudness
+                if (dialogue) {
+                    avio_w8(dyn_bc, IAMF_ANCHOR_ELEMENT_DIALOGUE);
+                    avio_wb16(dyn_bc, rescale_rational(submix_layout->dialogue_anchored_loudness, 1 << 8));
+                }
+                if (album) {
+                    avio_w8(dyn_bc, IAMF_ANCHOR_ELEMENT_ALBUM);
+                    avio_wb16(dyn_bc, rescale_rational(submix_layout->album_anchored_loudness, 1 << 8));
+                }
+            }
+        }
+    }
+
+    init_put_bits(&pb, header, sizeof(header));
+    put_bits(&pb, 5, IAMF_OBU_IA_MIX_PRESENTATION);
+    put_bits(&pb, 3, 0);
+    flush_put_bits(&pb);
+
+    dyn_size = avio_close_dyn_buf(dyn_bc, &dyn_buf);
+    avio_write(s->pb, header, put_bytes_count(&pb, 1));
+    leb(s->pb, dyn_size);
+    avio_write(s->pb, dyn_buf, dyn_size);
+    av_free(dyn_buf);
+
+    return 0;
+}
+
+static int iamf_write_header(AVFormatContext *s)
+{
+    IAMFMuxContext *const c = s->priv_data;
+    IAMFContext *const iamf = &c->iamf;
+    uint8_t header[MAX_IAMF_OBU_HEADER_SIZE];
+    PutBitContext pb;
+    AVIOContext *dyn_bc;
+    uint8_t *dyn_buf = NULL;
+    int dyn_size;
+
+    int ret = avio_open_dyn_buf(&dyn_bc);
+    if (ret < 0)
+        return ret;
+
+    // Sequence Header
+    init_put_bits(&pb, header, sizeof(header));
+    put_bits(&pb, 5, IAMF_OBU_IA_SEQUENCE_HEADER);
+    put_bits(&pb, 3, 0);
+    flush_put_bits(&pb);
+
+    avio_write(dyn_bc, header, put_bytes_count(&pb, 1));
+    leb(dyn_bc, 6);
+    avio_wb32(dyn_bc, MKBETAG('i','a','m','f'));
+    avio_w8(dyn_bc, iamf->nb_audio_elements > 1); // primary_profile
+    avio_w8(dyn_bc, iamf->nb_audio_elements > 1); // additional_profile
+
+    dyn_size = avio_close_dyn_buf(dyn_bc, &dyn_buf);
+    avio_write(s->pb, dyn_buf, dyn_size);
+    av_free(dyn_buf);
+
+    for (int i; i < iamf->nb_codec_configs; i++) {
+        ret = iamf_write_codec_config(s, &iamf->codec_configs[i]);
+        if (ret < 0)
+            return ret;
+    }
+
+    for (int i; i < iamf->nb_audio_elements; i++) {
+        ret = iamf_write_audio_element(s, &iamf->audio_elements[i]);
+        if (ret < 0)
+            return ret;
+    }
+
+    for (int i; i < iamf->nb_mix_presentations; i++) {
+        ret = iamf_write_mixing_presentation(s, &iamf->mix_presentations[i]);
+        if (ret < 0)
+            return ret;
+    }
+
+    return 0;
+}
+
+static int write_parameter_block(AVFormatContext *s, AVIAMFParamDefinition *param)
+{
+    uint8_t header[MAX_IAMF_OBU_HEADER_SIZE];
+    IAMFParamDefinition *param_definition = get_param_definition(s, param->parameter_id);
+    PutBitContext pb;
+    AVIOContext *dyn_bc;
+    uint8_t *dyn_buf = NULL;
+    int dyn_size, ret;
+
+    if (param->param_definition_type > AV_IAMF_PARAMETER_DEFINITION_RECON_GAIN) {
+        av_log(s, AV_LOG_DEBUG, "Ignoring side data with unknown param_definition_type %u\n",
+               param->param_definition_type);
+        return 0;
+    }
+
+    if (!param_definition) {
+        av_log(s, AV_LOG_ERROR, "Non-existent Parameter Definition with ID %u referenced by a packet\n",
+               param->parameter_id);
+        return AVERROR(EINVAL);
+    }
+
+    if (param->param_definition_type != param_definition->param->param_definition_type ||
+        param->param_definition_mode != param_definition->param->param_definition_mode) {
+        av_log(s, AV_LOG_ERROR, "Inconsistent param_definition_mode or param_definition_type values "
+                                "for Parameter Definition with ID %u in a packet\n",
+               param->parameter_id);
+        return AVERROR(EINVAL);
+    }
+
+    ret = avio_open_dyn_buf(&dyn_bc);
+    if (ret < 0)
+        return ret;
+
+    // Sequence Header
+    init_put_bits(&pb, header, sizeof(header));
+    put_bits(&pb, 5, IAMF_OBU_IA_PARAMETER_BLOCK);
+    put_bits(&pb, 3, 0);
+    flush_put_bits(&pb);
+    avio_write(s->pb, header, put_bytes_count(&pb, 1));
+
+    leb(dyn_bc, param->parameter_id);
+    if (param->param_definition_mode) {
+        leb(dyn_bc, param->duration);
+        leb(dyn_bc, param->constant_subblock_duration);
+        if (param->constant_subblock_duration == 0)
+            leb(dyn_bc, param->num_subblocks);
+    }
+
+    for (int i = 0; i < param->num_subblocks; i++) {
+        const void *subblock = avformat_iamf_param_definition_get_subblock(param, i);
+
+        switch (param->param_definition_type) {
+        case AV_IAMF_PARAMETER_DEFINITION_MIX_GAIN: {
+            const AVIAMFMixGainParameterData *mix = subblock;
+            if (param->param_definition_mode && param->constant_subblock_duration == 0)
+                leb(dyn_bc, mix->subblock_duration);
+
+            leb(dyn_bc, mix->animation_type);
+
+            avio_wb16(dyn_bc, rescale_rational(mix->start_point_value, 1 << 8));
+            if (mix->animation_type >= AV_IAMF_ANIMATION_TYPE_LINEAR)
+                avio_wb16(dyn_bc, rescale_rational(mix->end_point_value, 1 << 8));
+            if (mix->animation_type == AV_IAMF_ANIMATION_TYPE_BEZIER) {
+                avio_wb16(dyn_bc, rescale_rational(mix->control_point_value, 1 << 8));
+                avio_w8(dyn_bc, mix->control_point_relative_time);
+            }
+            break;
+        }
+        case AV_IAMF_PARAMETER_DEFINITION_DEMIXING: {
+            const AVIAMFDemixingInfoParameterData *demix = subblock;
+            if (param->param_definition_mode && param->constant_subblock_duration == 0)
+                leb(dyn_bc, demix->subblock_duration);
+
+            avio_w8(dyn_bc, demix->dmixp_mode << 5);
+            break;
+        }
+        case AV_IAMF_PARAMETER_DEFINITION_RECON_GAIN: {
+            const AVIAMFReconGainParameterData *recon = subblock;
+            const AVIAMFAudioElement *audio_element = param_definition->audio_element;
+
+            if (param->param_definition_mode && param->constant_subblock_duration == 0)
+                leb(dyn_bc, recon->subblock_duration);
+
+            if (!audio_element) {
+                av_log(s, AV_LOG_ERROR, "Invalid Parameter Definition with ID %u referenced by a packet\n", param->parameter_id);
+                return AVERROR(EINVAL);
+            }
+
+            for (int j = 0; j < audio_element->num_layers; j++) {
+                const AVIAMFLayer *layer = audio_element->layers[j];
+
+                if (layer->recon_gain_is_present) {
+                    unsigned int recon_gain_flags = 0;
+                    int k = 0;
+
+                    for (; k < 7; k++)
+                        recon_gain_flags |= (1 << k) * !!recon->recon_gain[j][k];
+                    for (; k < 12; k++)
+                        recon_gain_flags |= (2 << k) * !!recon->recon_gain[j][k];
+                    if (recon_gain_flags >> 8)
+                        recon_gain_flags |= (1 << k);
+
+                    leb(dyn_bc, recon_gain_flags);
+                    for (k = 0; k < 12; k++) {
+                        if (recon->recon_gain[j][k])
+                            avio_w8(dyn_bc, recon->recon_gain[j][k]);
+                    }
+                }
+            }
+            break;
+        }
+        default:
+            av_assert0(0);
+        }
+    }
+
+    dyn_size = avio_close_dyn_buf(dyn_bc, &dyn_buf);
+    leb(s->pb, dyn_size);
+    avio_write(s->pb, dyn_buf, dyn_size);
+    av_free(dyn_buf);
+
+    return 0;
+}
+
+static int iamf_write_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    const IAMFMuxContext *const c = s->priv_data;
+    AVStream *st = s->streams[pkt->stream_index];
+    uint8_t header[MAX_IAMF_OBU_HEADER_SIZE];
+    PutBitContext pb;
+    AVIOContext *dyn_bc;
+    uint8_t *dyn_buf = NULL;
+    int dyn_size;
+    int ret, type = st->id <= 17 ? st->id + IAMF_OBU_IA_AUDIO_FRAME_ID0 : IAMF_OBU_IA_AUDIO_FRAME;
+
+    if (s->nb_stream_groups && st->id == c->first_stream_id) {
+        AVIAMFParamDefinition *mix =
+            (AVIAMFParamDefinition *)av_packet_get_side_data(pkt, AV_PKT_DATA_IAMF_MIX_GAIN_PARAM, NULL);
+        AVIAMFParamDefinition *demix =
+            (AVIAMFParamDefinition *)av_packet_get_side_data(pkt, AV_PKT_DATA_IAMF_DEMIXING_INFO_PARAM, NULL);
+        AVIAMFParamDefinition *recon =
+            (AVIAMFParamDefinition *)av_packet_get_side_data(pkt, AV_PKT_DATA_IAMF_RECON_GAIN_INFO_PARAM, NULL);
+
+        if (mix) {
+            ret = write_parameter_block(s, mix);
+            if (ret < 0)
+               return ret;
+        }
+        if (demix) {
+            ret = write_parameter_block(s, demix);
+            if (ret < 0)
+               return ret;
+        }
+        if (recon) {
+            ret = write_parameter_block(s, recon);
+            if (ret < 0)
+               return ret;
+        }
+    }
+
+    ret = avio_open_dyn_buf(&dyn_bc);
+    if (ret < 0)
+        return ret;
+
+    init_put_bits(&pb, header, sizeof(header));
+    put_bits(&pb, 5, type);
+    put_bits(&pb, 3, 0);
+    flush_put_bits(&pb);
+    avio_write(s->pb, header, put_bytes_count(&pb, 1));
+
+    if (st->id > 17)
+        leb(dyn_bc, st->id);
+
+    dyn_size = avio_close_dyn_buf(dyn_bc, &dyn_buf);
+    leb(s->pb, dyn_size + pkt->size);
+    avio_write(s->pb, dyn_buf, dyn_size);
+    av_free(dyn_buf);
+    avio_write(s->pb, pkt->data, pkt->size);
+
+    return 0;
+}
+
+static void iamf_deinit(AVFormatContext *s)
+{
+    IAMFMuxContext *const c = s->priv_data;
+    IAMFContext *const iamf = &c->iamf;
+
+    for (int i = 0; i < iamf->nb_audio_elements; i++) {
+        IAMFAudioElement *audio_element = &iamf->audio_elements[i];
+        audio_element->element = NULL;
+    }
+
+    for (int i = 0; i < iamf->nb_mix_presentations; i++) {
+        IAMFMixPresentation *mix_presentation = &iamf->mix_presentations[i];
+        mix_presentation->mix = NULL;
+    }
+
+    ff_iamf_uninit_context(iamf);
+
+    return;
+}
+
+static const AVCodecTag iamf_codec_tags[] = {
+    { AV_CODEC_ID_AAC,       MKTAG('m','p','4','a') },
+    { AV_CODEC_ID_FLAC,      MKTAG('f','L','a','C') },
+    { AV_CODEC_ID_OPUS,      MKTAG('O','p','u','s') },
+    { AV_CODEC_ID_PCM_S16LE, MKTAG('i','p','c','m') },
+    { AV_CODEC_ID_PCM_S16BE, MKTAG('i','p','c','m') },
+    { AV_CODEC_ID_PCM_S24LE, MKTAG('i','p','c','m') },
+    { AV_CODEC_ID_PCM_S24BE, MKTAG('i','p','c','m') },
+    { AV_CODEC_ID_PCM_S32LE, MKTAG('i','p','c','m') },
+    { AV_CODEC_ID_PCM_S32BE, MKTAG('i','p','c','m') },
+    { AV_CODEC_ID_NONE,      MKTAG('i','p','c','m') }
+};
+
+const FFOutputFormat ff_iamf_muxer = {
+    .p.name            = "iamf",
+    .p.long_name       = NULL_IF_CONFIG_SMALL("Raw Immersive Audio Model and Formats"),
+    .p.extensions      = "iamf",
+    .priv_data_size    = sizeof(IAMFMuxContext),
+    .p.audio_codec     = AV_CODEC_ID_OPUS,
+    .init              = iamf_init,
+    .deinit            = iamf_deinit,
+    .write_header      = iamf_write_header,
+    .write_packet      = iamf_write_packet,
+    .p.codec_tag       = (const AVCodecTag* const []){ iamf_codec_tags, NULL },
+    .p.flags           = AVFMT_GLOBALHEADER | AVFMT_NOTIMESTAMPS,
+   // .p.priv_class      = &iamf_class,
+};
