avformat: introduce AVStreamGroup

Signed-off-by: James Almer <jamrial@gmail.com>

doc/APIchanges

@@ -2,6 +2,15 @@ The last version increases of all libraries were on 2023-02-09
 
 API changes, most recent first:
 
+2023-12-18 - xxxxxxxxxxx - lavc 60.19.100 - avformat.h
+  Add AVStreamGroup struct.
+  Add AVFormatContext.stream_groups and AVFormatContext.nb_stream_groups
+  Add avformat_stream_group_create(), avformat_stream_group_add_stream(),
+  and av_stream_group_get_class().
+  Add enum AVStreamGroupParamsType with values AV_STREAM_GROUP_PARAMS_NONE,
+  AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT and
+  AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION.
+
 2023-12-18 - xxxxxxxxxxx - lavu 58.35.100 - iamf.h
   Add a new API to support Immersive Audio Model and Formats.
 

doc/fftools-common-opts.texi

@@ -37,9 +37,9 @@ Matches the stream with this index. E.g. @code{-threads:1 4} would set the
 thread count for the second stream to 4. If @var{stream_index} is used as an
 additional stream specifier (see below), then it selects stream number
 @var{stream_index} from the matching streams. Stream numbering is based on the
-order of the streams as detected by libavformat except when a program ID is
+order of the streams as detected by libavformat except when a stream group
-also specified. In this case it is based on the ordering of the streams in the
+specifier or program ID is also specified. In this case it is based on the
-program.
+ordering of the streams in the group or program.
 @item @var{stream_type}[:@var{additional_stream_specifier}]
 @var{stream_type} is one of following: 'v' or 'V' for video, 'a' for audio, 's'
 for subtitle, 'd' for data, and 't' for attachments. 'v' matches all video
@@ -48,6 +48,17 @@ thumbnails or cover arts. If @var{additional_stream_specifier} is used, then
 it matches streams which both have this type and match the
 @var{additional_stream_specifier}. Otherwise, it matches all streams of the
 specified type.
+@item g:@var{group_specifier}[:@var{additional_stream_specifier}]
+Matches streams which are in the group with the specifier @var{group_specifier}.
+if @var{additional_stream_specifier} is used, then it matches streams which both
+are part of the group and match the @var{additional_stream_specifier}.
+@var{group_specifier} may be one of the following:
+@table @option
+@item @var{group_index}
+Match the stream with this group index.
+@item #@var{group_id} or i:@var{group_id}
+Match the stream with this group id.
+@end table
 @item p:@var{program_id}[:@var{additional_stream_specifier}]
 Matches streams which are in the program with the id @var{program_id}. If
 @var{additional_stream_specifier} is used, then it matches streams which both

libavformat/avformat.c

@@ -24,6 +24,7 @@
 #include "libavutil/avstring.h"
 #include "libavutil/channel_layout.h"
 #include "libavutil/frame.h"
+#include "libavutil/iamf.h"
 #include "libavutil/intreadwrite.h"
 #include "libavutil/mem.h"
 #include "libavutil/opt.h"
@@ -80,6 +81,32 @@ FF_ENABLE_DEPRECATION_WARNINGS
     av_freep(pst);
 }
 
+void ff_free_stream_group(AVStreamGroup **pstg)
+{
+    AVStreamGroup *stg = *pstg;
+
+    if (!stg)
+        return;
+
+    av_freep(&stg->streams);
+    av_dict_free(&stg->metadata);
+    av_freep(&stg->priv_data);
+    switch (stg->type) {
+    case AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT: {
+        av_iamf_audio_element_free(&stg->params.iamf_audio_element);
+        break;
+    }
+    case AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION: {
+        av_iamf_mix_presentation_free(&stg->params.iamf_mix_presentation);
+        break;
+    }
+    default:
+        break;
+    }
+
+    av_freep(pstg);
+}
+
 void ff_remove_stream(AVFormatContext *s, AVStream *st)
 {
     av_assert0(s->nb_streams>0);
@@ -88,6 +115,14 @@ void ff_remove_stream(AVFormatContext *s, AVStream *st)
     ff_free_stream(&s->streams[ --s->nb_streams ]);
 }
 
+void ff_remove_stream_group(AVFormatContext *s, AVStreamGroup *stg)
+{
+    av_assert0(s->nb_stream_groups > 0);
+    av_assert0(s->stream_groups[ s->nb_stream_groups - 1 ] == stg);
+
+    ff_free_stream_group(&s->stream_groups[ --s->nb_stream_groups ]);
+}
+
 /* XXX: suppress the packet queue */
 void ff_flush_packet_queue(AVFormatContext *s)
 {
@@ -118,6 +153,9 @@ void avformat_free_context(AVFormatContext *s)
 
     for (unsigned i = 0; i < s->nb_streams; i++)
         ff_free_stream(&s->streams[i]);
+    for (unsigned i = 0; i < s->nb_stream_groups; i++)
+        ff_free_stream_group(&s->stream_groups[i]);
+    s->nb_stream_groups = 0;
     s->nb_streams = 0;
 
     for (unsigned i = 0; i < s->nb_programs; i++) {
@@ -139,6 +177,7 @@ void avformat_free_context(AVFormatContext *s)
     av_packet_free(&si->pkt);
     av_packet_free(&si->parse_pkt);
     av_freep(&s->streams);
+    av_freep(&s->stream_groups);
     ff_flush_packet_queue(s);
     av_freep(&s->url);
     av_free(s);
@@ -464,7 +503,7 @@ int av_find_best_stream(AVFormatContext *ic, enum AVMediaType type,
  */
 static int match_stream_specifier(const AVFormatContext *s, const AVStream *st,
                                   const char *spec, const char **indexptr,
-                                  const AVProgram **p)
+                                  const AVStreamGroup **g, const AVProgram **p)
 {
     int match = 1;                      /* Stores if the specifier matches so far. */
     while (*spec) {
@@ -493,6 +532,46 @@ static int match_stream_specifier(const AVFormatContext *s, const AVStream *st,
                 match = 0;
             if (nopic && (st->disposition & AV_DISPOSITION_ATTACHED_PIC))
                 match = 0;
+        } else if (*spec == 'g' && *(spec + 1) == ':') {
+            int64_t group_idx = -1, group_id = -1;
+            int found = 0;
+            char *endptr;
+            spec += 2;
+            if (*spec == '#' || (*spec == 'i' && *(spec + 1) == ':')) {
+                spec += 1 + (*spec == 'i');
+                group_id = strtol(spec, &endptr, 0);
+                if (spec == endptr || (*endptr && *endptr++ != ':'))
+                    return AVERROR(EINVAL);
+                spec = endptr;
+            } else {
+                group_idx = strtol(spec, &endptr, 0);
+                /* Disallow empty id and make sure that if we are not at the end, then another specifier must follow. */
+                if (spec == endptr || (*endptr && *endptr++ != ':'))
+                    return AVERROR(EINVAL);
+                spec = endptr;
+            }
+            if (match) {
+                if (group_id > 0) {
+                    for (unsigned i = 0; i < s->nb_stream_groups; i++) {
+                        if (group_id == s->stream_groups[i]->id) {
+                            group_idx = i;
+                            break;
+                        }
+                    }
+                }
+                if (group_idx < 0 || group_idx > s->nb_stream_groups)
+                    return AVERROR(EINVAL);
+                for (unsigned j = 0; j < s->stream_groups[group_idx]->nb_streams; j++) {
+                    if (st->index == s->stream_groups[group_idx]->streams[j]->index) {
+                        found = 1;
+                        if (g)
+                            *g = s->stream_groups[group_idx];
+                        break;
+                    }
+                }
+            }
+            if (!found)
+                match = 0;
         } else if (*spec == 'p' && *(spec + 1) == ':') {
             int prog_id;
             int found = 0;
@@ -591,10 +670,11 @@ int avformat_match_stream_specifier(AVFormatContext *s, AVStream *st,
     int ret, index;
     char *endptr;
     const char *indexptr = NULL;
+    const AVStreamGroup *g = NULL;
     const AVProgram *p = NULL;
     int nb_streams;
 
-    ret = match_stream_specifier(s, st, spec, &indexptr, &p);
+    ret = match_stream_specifier(s, st, spec, &indexptr, &g, &p);
     if (ret < 0)
         goto error;
 
@@ -612,10 +692,11 @@ int avformat_match_stream_specifier(AVFormatContext *s, AVStream *st,
         return (index == st->index);
 
     /* If we requested a matching stream index, we have to ensure st is that. */
-    nb_streams = p ? p->nb_stream_indexes : s->nb_streams;
+    nb_streams = g ? g->nb_streams : (p ? p->nb_stream_indexes : s->nb_streams);
     for (int i = 0; i < nb_streams && index >= 0; i++) {
-        const AVStream *candidate = s->streams[p ? p->stream_index[i] : i];
+        unsigned idx = g ? g->streams[i]->index : (p ? p->stream_index[i] : i);
-        ret = match_stream_specifier(s, candidate, spec, NULL, NULL);
+        const AVStream *candidate = s->streams[idx];
+        ret = match_stream_specifier(s, candidate, spec, NULL, NULL, NULL);
         if (ret < 0)
             goto error;
         if (ret > 0 && index-- == 0 && st == candidate)

libavformat/avformat.h

@@ -1018,6 +1018,83 @@ typedef struct AVStream {
     int pts_wrap_bits;
 } AVStream;
 
+enum AVStreamGroupParamsType {
+    AV_STREAM_GROUP_PARAMS_NONE,
+    AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT,
+    AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION,
+};
+
+struct AVIAMFAudioElement;
+struct AVIAMFMixPresentation;
+
+typedef struct AVStreamGroup {
+    /**
+     * A class for @ref avoptions. Set by avformat_stream_group_create().
+     */
+    const AVClass *av_class;
+
+    void *priv_data;
+
+    /**
+     * Group index in AVFormatContext.
+     */
+    unsigned int index;
+
+    /**
+     * Group type-specific group ID.
+     *
+     * decoding: set by libavformat
+     * encoding: may set by the user
+     */
+    int64_t id;
+
+    /**
+     * Group type
+     *
+     * decoding: set by libavformat on group creation
+     * encoding: set by avformat_stream_group_create()
+     */
+    enum AVStreamGroupParamsType type;
+
+    /**
+     * Group type-specific parameters
+     */
+    union {
+        struct AVIAMFAudioElement *iamf_audio_element;
+        struct AVIAMFMixPresentation *iamf_mix_presentation;
+    } params;
+
+    /**
+     * Metadata that applies to the whole group.
+     *
+     * - demuxing: set by libavformat on group creation
+     * - muxing: may be set by the caller before avformat_write_header()
+     *
+     * Freed by libavformat in avformat_free_context().
+     */
+    AVDictionary *metadata;
+
+    /**
+     * Number of elements in AVStreamGroup.streams.
+     *
+     * Set by avformat_stream_group_add_stream() must not be modified by any other code.
+     */
+    unsigned int nb_streams;
+
+    /**
+     * A list of streams in the group. New entries are created with
+     * avformat_stream_group_add_stream().
+     *
+     * - demuxing: entries are created by libavformat on group creation.
+     *             If AVFMTCTX_NOHEADER is set in ctx_flags, then new entries may also
+     *             appear in av_read_frame().
+     * - muxing: entries are created by the user before avformat_write_header().
+     *
+     * Freed by libavformat in avformat_free_context().
+     */
+    AVStream **streams;
+} AVStreamGroup;
+
 struct AVCodecParserContext *av_stream_get_parser(const AVStream *s);
 
 #if FF_API_GET_END_PTS
@@ -1726,6 +1803,26 @@ typedef struct AVFormatContext {
      * @return 0 on success, a negative AVERROR code on failure
      */
     int (*io_close2)(struct AVFormatContext *s, AVIOContext *pb);
+
+    /**
+     * Number of elements in AVFormatContext.stream_groups.
+     *
+     * Set by avformat_stream_group_create(), must not be modified by any other code.
+     */
+    unsigned int nb_stream_groups;
+
+    /**
+     * A list of all stream groups in the file. New groups are created with
+     * avformat_stream_group_create(), and filled with avformat_stream_group_add_stream().
+     *
+     * - demuxing: groups may be created by libavformat in avformat_open_input().
+     *             If AVFMTCTX_NOHEADER is set in ctx_flags, then new groups may also
+     *             appear in av_read_frame().
+     * - muxing: groups may be created by the user before avformat_write_header().
+     *
+     * Freed by libavformat in avformat_free_context().
+     */
+    AVStreamGroup **stream_groups;
 } AVFormatContext;
 
 /**
@@ -1844,6 +1941,37 @@ const AVClass *avformat_get_class(void);
  */
 const AVClass *av_stream_get_class(void);
 
+/**
+ * Get the AVClass for AVStreamGroup. It can be used in combination with
+ * AV_OPT_SEARCH_FAKE_OBJ for examining options.
+ *
+ * @see av_opt_find().
+ */
+const AVClass *av_stream_group_get_class(void);
+
+/**
+ * Add a new empty stream group to a media file.
+ *
+ * When demuxing, it may be called by the demuxer in read_header(). If the
+ * flag AVFMTCTX_NOHEADER is set in s.ctx_flags, then it may also
+ * be called in read_packet().
+ *
+ * When muxing, may be called by the user before avformat_write_header().
+ *
+ * User is required to call avformat_free_context() to clean up the allocation
+ * by avformat_stream_group_create().
+ *
+ * New streams can be added to the group with avformat_stream_group_add_stream().
+ *
+ * @param s media file handle
+ *
+ * @return newly created group or NULL on error.
+ * @see avformat_new_stream, avformat_stream_group_add_stream.
+ */
+AVStreamGroup *avformat_stream_group_create(AVFormatContext *s,
+                                            enum AVStreamGroupParamsType type,
+                                            AVDictionary **options);
+
 /**
  * Add a new stream to a media file.
  *
@@ -1863,6 +1991,31 @@ const AVClass *av_stream_get_class(void);
  */
 AVStream *avformat_new_stream(AVFormatContext *s, const struct AVCodec *c);
 
+/**
+ * Add an already allocated stream to a stream group.
+ *
+ * When demuxing, it may be called by the demuxer in read_header(). If the
+ * flag AVFMTCTX_NOHEADER is set in s.ctx_flags, then it may also
+ * be called in read_packet().
+ *
+ * When muxing, may be called by the user before avformat_write_header() after
+ * having allocated a new group with avformat_stream_group_create() and stream with
+ * avformat_new_stream().
+ *
+ * User is required to call avformat_free_context() to clean up the allocation
+ * by avformat_stream_group_add_stream().
+ *
+ * @param stg stream group belonging to a media file.
+ * @param st  stream in the media file to add to the group.
+ *
+ * @retval 0                 success
+ * @retval AVERROR(EEXIST)   the stream was already in the group
+ * @retval "another negative error code" legitimate errors
+ *
+ * @see avformat_new_stream, avformat_stream_group_create.
+ */
+int avformat_stream_group_add_stream(AVStreamGroup *stg, AVStream *st);
+
 #if FF_API_AVSTREAM_SIDE_DATA
 /**
  * Wrap an existing array as stream side data.

libavformat/dump.c

@@ -24,6 +24,7 @@
 
 #include "libavutil/channel_layout.h"
 #include "libavutil/display.h"
+#include "libavutil/iamf.h"
 #include "libavutil/intreadwrite.h"
 #include "libavutil/log.h"
 #include "libavutil/mastering_display_metadata.h"
@@ -134,12 +135,15 @@ static void print_fps(double d, const char *postfix)
         av_log(NULL, AV_LOG_INFO, "%1.0fk %s", d / 1000, postfix);
 }
 
-static void dump_metadata(void *ctx, const AVDictionary *m, const char *indent)
+static void dump_dictionary(void *ctx, const AVDictionary *m,
+                            const char *name, const char *indent)
 {
-    if (m && !(av_dict_count(m) == 1 && av_dict_get(m, "language", NULL, 0))) {
     const AVDictionaryEntry *tag = NULL;
 
-        av_log(ctx, AV_LOG_INFO, "%sMetadata:\n", indent);
+    if (!m)
+        return;
+
+    av_log(ctx, AV_LOG_INFO, "%s%s:\n", indent, name);
     while ((tag = av_dict_iterate(m, tag)))
         if (strcmp("language", tag->key)) {
             const char *p = tag->value;
@@ -155,7 +159,12 @@ static void dump_metadata(void *ctx, const AVDictionary *m, const char *indent)
             }
             av_log(ctx, AV_LOG_INFO, "\n");
         }
-    }
+}
+
+static void dump_metadata(void *ctx, const AVDictionary *m, const char *indent)
+{
+    if (m && !(av_dict_count(m) == 1 && av_dict_get(m, "language", NULL, 0)))
+        dump_dictionary(ctx, m, "Metadata", indent);
 }
 
 /* param change side data*/
@@ -509,7 +518,7 @@ static void dump_sidedata(void *ctx, const AVStream *st, const char *indent)
 
 /* "user interface" functions */
 static void dump_stream_format(const AVFormatContext *ic, int i,
-                               int index, int is_output)
+                               int group_index, int index, int is_output)
 {
     char buf[256];
     int flags = (is_output ? ic->oformat->flags : ic->iformat->flags);
@@ -517,6 +526,8 @@ static void dump_stream_format(const AVFormatContext *ic, int i,
     const FFStream *const sti = cffstream(st);
     const AVDictionaryEntry *lang = av_dict_get(st->metadata, "language", NULL, 0);
     const char *separator = ic->dump_separator;
+    const char *group_indent = group_index >= 0 ? "    " : "";
+    const char *extra_indent = group_index >= 0 ? "        " : "      ";
     AVCodecContext *avctx;
     int ret;
 
@@ -543,7 +554,8 @@ static void dump_stream_format(const AVFormatContext *ic, int i,
     avcodec_string(buf, sizeof(buf), avctx, is_output);
     avcodec_free_context(&avctx);
 
-    av_log(NULL, AV_LOG_INFO, "  Stream #%d:%d", index, i);
+    av_log(NULL, AV_LOG_INFO, "%s  Stream #%d", group_indent, index);
+    av_log(NULL, AV_LOG_INFO, ":%d", i);
 
     /* the pid is an important information, so we display it */
     /* XXX: add a generic system */
@@ -621,9 +633,89 @@ static void dump_stream_format(const AVFormatContext *ic, int i,
         av_log(NULL, AV_LOG_INFO, " (non-diegetic)");
     av_log(NULL, AV_LOG_INFO, "\n");
 
-    dump_metadata(NULL, st->metadata, "    ");
+    dump_metadata(NULL, st->metadata, extra_indent);
 
-    dump_sidedata(NULL, st, "    ");
+    dump_sidedata(NULL, st, extra_indent);
+}
+
+static void dump_stream_group(const AVFormatContext *ic, uint8_t *printed,
+                              int i, int index, int is_output)
+{
+    const AVStreamGroup *stg = ic->stream_groups[i];
+    int flags = (is_output ? ic->oformat->flags : ic->iformat->flags);
+    char buf[512];
+    int ret;
+
+    av_log(NULL, AV_LOG_INFO, "  Stream group #%d:%d", index, i);
+    if (flags & AVFMT_SHOW_IDS)
+        av_log(NULL, AV_LOG_INFO, "[0x%"PRIx64"]", stg->id);
+    av_log(NULL, AV_LOG_INFO, ":");
+
+    switch (stg->type) {
+    case AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT: {
+        const AVIAMFAudioElement *audio_element = stg->params.iamf_audio_element;
+        av_log(NULL, AV_LOG_INFO, " IAMF Audio Element\n");
+        dump_metadata(NULL, stg->metadata, "    ");
+        for (int j = 0; j < audio_element->nb_layers; j++) {
+            const AVIAMFLayer *layer = audio_element->layers[j];
+            int channel_count = layer->ch_layout.nb_channels;
+            av_log(NULL, AV_LOG_INFO, "    Layer %d:", j);
+            ret = av_channel_layout_describe(&layer->ch_layout, buf, sizeof(buf));
+            if (ret >= 0)
+                av_log(NULL, AV_LOG_INFO, " %s", buf);
+            av_log(NULL, AV_LOG_INFO, "\n");
+            for (int k = 0; channel_count > 0 && k < stg->nb_streams; k++) {
+                AVStream *st = stg->streams[k];
+                dump_stream_format(ic, st->index, i, index, is_output);
+                printed[st->index] = 1;
+                channel_count -= st->codecpar->ch_layout.nb_channels;
+            }
+        }
+        break;
+    }
+    case AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION: {
+        const AVIAMFMixPresentation *mix_presentation = stg->params.iamf_mix_presentation;
+        av_log(NULL, AV_LOG_INFO, " IAMF Mix Presentation\n");
+        dump_metadata(NULL, stg->metadata, "    ");
+        dump_dictionary(NULL, mix_presentation->annotations, "Annotations", "    ");
+        for (int j = 0; j < mix_presentation->nb_submixes; j++) {
+            AVIAMFSubmix *sub_mix = mix_presentation->submixes[j];
+            av_log(NULL, AV_LOG_INFO, "    Submix %d:\n", j);
+            for (int k = 0; k < sub_mix->nb_elements; k++) {
+                const AVIAMFSubmixElement *submix_element = sub_mix->elements[k];
+                const AVStreamGroup *audio_element = NULL;
+                for (int l = 0; l < ic->nb_stream_groups; l++)
+                    if (ic->stream_groups[l]->type == AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT &&
+                        ic->stream_groups[l]->id   == submix_element->audio_element_id) {
+                        audio_element = ic->stream_groups[l];
+                        break;
+                    }
+                if (audio_element) {
+                    av_log(NULL, AV_LOG_INFO, "      IAMF Audio Element #%d:%d",
+                           index, audio_element->index);
+                    if (flags & AVFMT_SHOW_IDS)
+                        av_log(NULL, AV_LOG_INFO, "[0x%"PRIx64"]", audio_element->id);
+                    av_log(NULL, AV_LOG_INFO, "\n");
+                    dump_dictionary(NULL, submix_element->annotations, "Annotations", "        ");
+                }
+            }
+            for (int k = 0; k < sub_mix->nb_layouts; k++) {
+                const AVIAMFSubmixLayout *submix_layout = sub_mix->layouts[k];
+                av_log(NULL, AV_LOG_INFO, "      Layout #%d:", k);
+                if (submix_layout->layout_type == 2) {
+                    ret = av_channel_layout_describe(&submix_layout->sound_system, buf, sizeof(buf));
+                    if (ret >= 0)
+                        av_log(NULL, AV_LOG_INFO, " %s", buf);
+                } else if (submix_layout->layout_type == 3)
+                    av_log(NULL, AV_LOG_INFO, " Binaural");
+                av_log(NULL, AV_LOG_INFO, "\n");
+            }
+        }
+        break;
+    }
+    default:
+        break;
+    }
 }
 
 void av_dump_format(AVFormatContext *ic, int index,
@@ -699,7 +791,7 @@ void av_dump_format(AVFormatContext *ic, int index,
             dump_metadata(NULL, program->metadata, "    ");
             for (k = 0; k < program->nb_stream_indexes; k++) {
                 dump_stream_format(ic, program->stream_index[k],
-                                   index, is_output);
+                                   -1, index, is_output);
                 printed[program->stream_index[k]] = 1;
             }
             total += program->nb_stream_indexes;
@@ -708,9 +800,12 @@ void av_dump_format(AVFormatContext *ic, int index,
             av_log(NULL, AV_LOG_INFO, "  No Program\n");
     }
 
+    for (i = 0; i < ic->nb_stream_groups; i++)
+         dump_stream_group(ic, printed, i, index, is_output);
+
     for (i = 0; i < ic->nb_streams; i++)
         if (!printed[i])
-            dump_stream_format(ic, i, index, is_output);
+            dump_stream_format(ic, i, -1, index, is_output);
 
     av_free(printed);
 }

libavformat/internal.h

@@ -202,6 +202,7 @@ typedef struct FFStream {
      */
     AVStream pub;
 
+    AVFormatContext *fmtctx;
     /**
      * Set to 1 if the codec allows reordering, so pts can be different
      * from dts.
@@ -427,6 +428,26 @@ static av_always_inline const FFStream *cffstream(const AVStream *st)
     return (const FFStream*)st;
 }
 
+typedef struct FFStreamGroup {
+    /**
+     * The public context.
+     */
+    AVStreamGroup pub;
+
+    AVFormatContext *fmtctx;
+} FFStreamGroup;
+
+
+static av_always_inline FFStreamGroup *ffstreamgroup(AVStreamGroup *stg)
+{
+    return (FFStreamGroup*)stg;
+}
+
+static av_always_inline const FFStreamGroup *cffstreamgroup(const AVStreamGroup *stg)
+{
+    return (const FFStreamGroup*)stg;
+}
+
 #ifdef __GNUC__
 #define dynarray_add(tab, nb_ptr, elem)\
 do {\
@@ -608,6 +629,18 @@ void ff_free_stream(AVStream **st);
  */
 void ff_remove_stream(AVFormatContext *s, AVStream *st);
 
+/**
+ * Frees a stream group without modifying the corresponding AVFormatContext.
+ * Must only be called if the latter doesn't matter or if the stream
+ * is not yet attached to an AVFormatContext.
+ */
+void ff_free_stream_group(AVStreamGroup **pstg);
+/**
+ * Remove a stream group from its AVFormatContext and free it.
+ * The group must be the last stream of the AVFormatContext.
+ */
+void ff_remove_stream_group(AVFormatContext *s, AVStreamGroup *stg);
+
 unsigned int ff_codec_get_tag(const AVCodecTag *tags, enum AVCodecID id);
 
 enum AVCodecID ff_codec_get_id(const AVCodecTag *tags, unsigned int tag);

libavformat/options.c

@@ -26,6 +26,7 @@
 #include "libavcodec/codec_par.h"
 
 #include "libavutil/avassert.h"
+#include "libavutil/iamf.h"
 #include "libavutil/internal.h"
 #include "libavutil/intmath.h"
 #include "libavutil/opt.h"
@@ -271,6 +272,7 @@ AVStream *avformat_new_stream(AVFormatContext *s, const AVCodec *c)
     if (!st->codecpar)
         goto fail;
 
+    sti->fmtctx = s;
     sti->avctx = avcodec_alloc_context3(NULL);
     if (!sti->avctx)
         goto fail;
@@ -325,6 +327,143 @@ fail:
     return NULL;
 }
 
+static void *stream_group_child_next(void *obj, void *prev)
+{
+    AVStreamGroup *stg = obj;
+    if (!prev) {
+        switch(stg->type) {
+        case AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT:
+            return stg->params.iamf_audio_element;
+        case AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION:
+            return stg->params.iamf_mix_presentation;
+        default:
+            break;
+        }
+    }
+    return NULL;
+}
+
+static const AVClass *stream_group_child_iterate(void **opaque)
+{
+    uintptr_t i = (uintptr_t)*opaque;
+    const AVClass *ret = NULL;
+
+    switch(i) {
+    case AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT:
+        ret = av_iamf_audio_element_get_class();
+        break;
+    case AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION:
+        ret = av_iamf_mix_presentation_get_class();
+        break;
+    default:
+        break;
+    }
+
+    if (ret)
+        *opaque = (void*)(i + 1);
+    return ret;
+}
+
+static const AVOption stream_group_options[] = {
+    {"id", "Set group id", offsetof(AVStreamGroup, id), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, AV_OPT_FLAG_ENCODING_PARAM },
+    { NULL }
+};
+
+static const AVClass stream_group_class = {
+    .class_name     = "AVStreamGroup",
+    .item_name      = av_default_item_name,
+    .version        = LIBAVUTIL_VERSION_INT,
+    .option         = stream_group_options,
+    .child_next     = stream_group_child_next,
+    .child_class_iterate = stream_group_child_iterate,
+};
+
+const AVClass *av_stream_group_get_class(void)
+{
+    return &stream_group_class;
+}
+
+AVStreamGroup *avformat_stream_group_create(AVFormatContext *s,
+                                            enum AVStreamGroupParamsType type,
+                                            AVDictionary **options)
+{
+    AVStreamGroup **stream_groups;
+    AVStreamGroup *stg;
+    FFStreamGroup *stgi;
+
+    stream_groups = av_realloc_array(s->stream_groups, s->nb_stream_groups + 1,
+                                     sizeof(*stream_groups));
+    if (!stream_groups)
+        return NULL;
+    s->stream_groups = stream_groups;
+
+    stgi = av_mallocz(sizeof(*stgi));
+    if (!stgi)
+        return NULL;
+    stg = &stgi->pub;
+
+    stg->av_class = &stream_group_class;
+    av_opt_set_defaults(stg);
+    stg->type = type;
+    switch (type) {
+    case AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT:
+        stg->params.iamf_audio_element = av_iamf_audio_element_alloc();
+        if (!stg->params.iamf_audio_element)
+            goto fail;
+        break;
+    case AV_STREAM_GROUP_PARAMS_IAMF_MIX_PRESENTATION:
+        stg->params.iamf_mix_presentation = av_iamf_mix_presentation_alloc();
+        if (!stg->params.iamf_mix_presentation)
+            goto fail;
+        break;
+    default:
+        goto fail;
+    }
+
+    if (options) {
+        if (av_opt_set_dict2(stg, options, AV_OPT_SEARCH_CHILDREN))
+            goto fail;
+    }
+
+    stgi->fmtctx = s;
+    stg->index   = s->nb_stream_groups;
+
+    s->stream_groups[s->nb_stream_groups++] = stg;
+
+    return stg;
+fail:
+    ff_free_stream_group(&stg);
+    return NULL;
+}
+
+static int stream_group_add_stream(AVStreamGroup *stg, AVStream *st)
+{
+    AVStream **streams = av_realloc_array(stg->streams, stg->nb_streams + 1,
+                                          sizeof(*stg->streams));
+    if (!streams)
+        return AVERROR(ENOMEM);
+
+    stg->streams = streams;
+    stg->streams[stg->nb_streams++] = st;
+
+    return 0;
+}
+
+int avformat_stream_group_add_stream(AVStreamGroup *stg, AVStream *st)
+{
+    const FFStreamGroup *stgi = cffstreamgroup(stg);
+    const FFStream *sti = cffstream(st);
+
+    if (stgi->fmtctx != sti->fmtctx)
+        return AVERROR(EINVAL);
+
+    for (int i = 0; i < stg->nb_streams; i++)
+        if (stg->streams[i]->index == st->index)
+            return AVERROR(EEXIST);
+
+    return stream_group_add_stream(stg, st);
+}
+
 static int option_is_disposition(const AVOption *opt)
 {
     return opt->type == AV_OPT_TYPE_CONST &&

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFORMAT_VERSION_MINOR  18
+#define LIBAVFORMAT_VERSION_MINOR  19
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \