diff mbox series

[FFmpeg-devel,v3,1/3,PoC] avformat: introduce AVStreamGroup

Message ID 20231030152354.2818-1-jamrial@gmail.com
State New
Headers show
Series [FFmpeg-devel,v3,1/3,PoC] avformat: introduce AVStreamGroup | expand

Checks

Context Check Description
yinshiyou/make_fate_loongarch64 success Make fate finished
yinshiyou/make_loongarch64 warning New warnings during build
andriy/make_fate_x86 success Make fate finished
andriy/make_x86 warning New warnings during build

Commit Message

James Almer Oct. 30, 2023, 3:23 p.m. UTC
Signed-off-by: James Almer <jamrial@gmail.com>
---
No changes since last version. I'm resending this for the IAMF demuxer.

I need opinions or reviews for this. We need to get this right from the start
and i don't want to push something that will afterwards be considered unoptimal

 libavformat/avformat.c |  31 +++++++++
 libavformat/avformat.h | 146 +++++++++++++++++++++++++++++++++++++++++
 libavformat/dump.c     |  35 ++++++++--
 libavformat/internal.h |  33 ++++++++++
 libavformat/options.c  |  77 ++++++++++++++++++++++
 5 files changed, 316 insertions(+), 6 deletions(-)

Comments

Anton Khirnov Nov. 6, 2023, 11:37 a.m. UTC | #1
Hi,
Quoting James Almer (2023-10-30 16:23:52)
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
> No changes since last version. I'm resending this for the IAMF demuxer.
> 
> I need opinions or reviews for this. We need to get this right from the start
> and i don't want to push something that will afterwards be considered unoptimal

The API generally looks good to me.

> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> index 9e7eca007e..9b2ee7ff14 100644
> --- a/libavformat/avformat.h
> +++ b/libavformat/avformat.h
> @@ -1018,6 +1018,77 @@ typedef struct AVStream {
>      int pts_wrap_bits;
>  } AVStream;
>  
> +enum AVStreamGroupParamsType {
> +    AV_STREAM_GROUP_PARAMS_NONE,
> +};
> +
> +typedef struct AVStreamGroup {
> +    /**
> +     * A class for @ref avoptions. Set on group creation.
> +     */
> +    const AVClass *av_class;
> +
> +    void *priv_data;
> +
> +    /**
> +     * Group index in AVFormatContext.
> +     */
> +    unsigned int index;
> +
> +    /**
> +     * Group-specific group ID.

type-specific?

> +     *
> +     * decoding: set by libavformat
> +     * encoding: set by the user, replaced by libavformat if left unset

'may be set' is the terminology we use for optional values

> +     */
> +    int64_t id;
> +
> +    /**
> +     * Group-specific type

drop '-specific', I don't see what it adds to the meaning.

> +     *
> +     * decoding: set by libavformat on group creation
> +     * encoding: set by the user on group creation

Could just say 'set by avformat_stream_group_create()', the user should
never set it manually.

> +     */
> +    enum AVStreamGroupParamsType type;
> +
> +    /**
> +     * Group-specific type parameters

type-specific?

> +     */
> +    union {
> +        uintptr_t dummy; // Placeholder
> +    } params;
> +
> +    /**
> +     * Metadata that applies to the whole file.

s/file/group

> +     *
> +     * - demuxing: set by libavformat in avformat_open_input()

Set on group creation, that does not have to be in
avformat_open_input().

> +     * - 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 in avformat_open_input().
> +     *             If AVFMTCTX_NOHEADER is set in ctx_flags, then new entries may also
> +     *             appear in av_read_frame().

We might want to make this type-specific, i.e. some group types are
guaranteed to never change.

> +     * - muxing: entries are created by the user before avformat_write_header().
> +     *
> +     * Freed by libavformat in avformat_free_context().
> +     */
> +    const AVStream **streams;

Is this const useful? I imagine some code might reasonably want to
modify the stream through this pointer.

> @@ -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);

ff_stream_group_free()

Also, I'd prefer a dedicated header for this, internal.h is an
abomination.
James Almer Nov. 6, 2023, 2:04 p.m. UTC | #2
On 11/6/2023 8:37 AM, Anton Khirnov wrote:
> Hi,
> Quoting James Almer (2023-10-30 16:23:52)
>> Signed-off-by: James Almer <jamrial@gmail.com>
>> ---
>> No changes since last version. I'm resending this for the IAMF demuxer.
>>
>> I need opinions or reviews for this. We need to get this right from the start
>> and i don't want to push something that will afterwards be considered unoptimal
> 
> The API generally looks good to me.
> 
>> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
>> index 9e7eca007e..9b2ee7ff14 100644
>> --- a/libavformat/avformat.h
>> +++ b/libavformat/avformat.h
>> @@ -1018,6 +1018,77 @@ typedef struct AVStream {
>>       int pts_wrap_bits;
>>   } AVStream;
>>   
>> +enum AVStreamGroupParamsType {
>> +    AV_STREAM_GROUP_PARAMS_NONE,
>> +};
>> +
>> +typedef struct AVStreamGroup {
>> +    /**
>> +     * A class for @ref avoptions. Set on group creation.
>> +     */
>> +    const AVClass *av_class;
>> +
>> +    void *priv_data;
>> +
>> +    /**
>> +     * Group index in AVFormatContext.
>> +     */
>> +    unsigned int index;
>> +
>> +    /**
>> +     * Group-specific group ID.
> 
> type-specific?
> 
>> +     *
>> +     * decoding: set by libavformat
>> +     * encoding: set by the user, replaced by libavformat if left unset
> 
> 'may be set' is the terminology we use for optional values
> 
>> +     */
>> +    int64_t id;
>> +
>> +    /**
>> +     * Group-specific type
> 
> drop '-specific', I don't see what it adds to the meaning.
> 
>> +     *
>> +     * decoding: set by libavformat on group creation
>> +     * encoding: set by the user on group creation
> 
> Could just say 'set by avformat_stream_group_create()', the user should
> never set it manually.
> 
>> +     */
>> +    enum AVStreamGroupParamsType type;
>> +
>> +    /**
>> +     * Group-specific type parameters
> 
> type-specific?
> 
>> +     */
>> +    union {
>> +        uintptr_t dummy; // Placeholder
>> +    } params;
>> +
>> +    /**
>> +     * Metadata that applies to the whole file.
> 
> s/file/group
> 
>> +     *
>> +     * - demuxing: set by libavformat in avformat_open_input()
> 
> Set on group creation, that does not have to be in
> avformat_open_input().
> 
>> +     * - 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 in avformat_open_input().
>> +     *             If AVFMTCTX_NOHEADER is set in ctx_flags, then new entries may also
>> +     *             appear in av_read_frame().
> 
> We might want to make this type-specific, i.e. some group types are
> guaranteed to never change.
> 
>> +     * - muxing: entries are created by the user before avformat_write_header().
>> +     *
>> +     * Freed by libavformat in avformat_free_context().
>> +     */
>> +    const AVStream **streams;
> 
> Is this const useful? I imagine some code might reasonably want to
> modify the stream through this pointer.

True. Will change.

> 
>> @@ -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);
> 
> ff_stream_group_free()
> 
> Also, I'd prefer a dedicated header for this, internal.h is an
> abomination.

Should i move the AVStream related functions to it too?
diff mbox series

Patch

diff --git a/libavformat/avformat.c b/libavformat/avformat.c
index 5b8bb7879e..05d9837b97 100644
--- a/libavformat/avformat.c
+++ b/libavformat/avformat.c
@@ -80,6 +80,25 @@  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) {
+    // Structs in the union are freed here
+    default:
+        break;
+    }
+
+    av_freep(pstg);
+}
+
 void ff_remove_stream(AVFormatContext *s, AVStream *st)
 {
     av_assert0(s->nb_streams>0);
@@ -88,6 +107,14 @@  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 +145,9 @@  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++) {
@@ -138,6 +168,7 @@  void avformat_free_context(AVFormatContext *s)
     av_dict_free(&si->id3v2_meta);
     av_packet_free(&si->pkt);
     av_packet_free(&si->parse_pkt);
+    av_freep(&s->stream_groups);
     av_freep(&s->streams);
     ff_flush_packet_queue(s);
     av_freep(&s->url);
diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 9e7eca007e..9b2ee7ff14 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1018,6 +1018,77 @@  typedef struct AVStream {
     int pts_wrap_bits;
 } AVStream;
 
+enum AVStreamGroupParamsType {
+    AV_STREAM_GROUP_PARAMS_NONE,
+};
+
+typedef struct AVStreamGroup {
+    /**
+     * A class for @ref avoptions. Set on group creation.
+     */
+    const AVClass *av_class;
+
+    void *priv_data;
+
+    /**
+     * Group index in AVFormatContext.
+     */
+    unsigned int index;
+
+    /**
+     * Group-specific group ID.
+     *
+     * decoding: set by libavformat
+     * encoding: set by the user, replaced by libavformat if left unset
+     */
+    int64_t id;
+
+    /**
+     * Group-specific type
+     *
+     * decoding: set by libavformat on group creation
+     * encoding: set by the user on group creation
+     */
+    enum AVStreamGroupParamsType type;
+
+    /**
+     * Group-specific type parameters
+     */
+    union {
+        uintptr_t dummy; // Placeholder
+    } params;
+
+    /**
+     * Metadata that applies to the whole file.
+     *
+     * - demuxing: set by libavformat in avformat_open_input()
+     * - 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 in avformat_open_input().
+     *             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().
+     */
+    const AVStream **streams;
+} AVStreamGroup;
+
 struct AVCodecParserContext *av_stream_get_parser(const AVStream *s);
 
 #if FF_API_GET_END_PTS
@@ -1726,6 +1797,26 @@  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 +1935,36 @@  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);
+
 /**
  * Add a new stream to a media file.
  *
@@ -1863,6 +1984,31 @@  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, const AVStream *st);
+
 #if FF_API_AVSTREAM_SIDE_DATA
 /**
  * Wrap an existing array as stream side data.
diff --git a/libavformat/dump.c b/libavformat/dump.c
index c0868a1bb3..7713415cae 100644
--- a/libavformat/dump.c
+++ b/libavformat/dump.c
@@ -509,7 +509,7 @@  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 +517,8 @@  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 +545,10 @@  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);
+    if (group_index >= 0)
+        av_log(NULL, AV_LOG_INFO, ":%d", group_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 +626,24 @@  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];
+    char buf[512];
+    int ret;
+
+    av_log(NULL, AV_LOG_INFO, "  Stream group #%d:%d:", index, i);
+
+    switch (stg->type) {
+    default:
+        break;
+    }
 }
 
 void av_dump_format(AVFormatContext *ic, int index,
@@ -699,7 +719,7 @@  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 +728,12 @@  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);
 }
diff --git a/libavformat/internal.h b/libavformat/internal.h
index 7702986c9c..c6181683ef 100644
--- a/libavformat/internal.h
+++ b/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);
diff --git a/libavformat/options.c b/libavformat/options.c
index 1d8c52246b..b3998bae43 100644
--- a/libavformat/options.c
+++ b/libavformat/options.c
@@ -271,6 +271,7 @@  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 +326,82 @@  fail:
     return NULL;
 }
 
+static const AVClass stream_group_class = {
+    .class_name     = "AVStreamGroup",
+    .item_name      = av_default_item_name,
+    .version        = LIBAVUTIL_VERSION_INT,
+};
+
+const AVClass *av_stream_group_get_class(void)
+{
+    return &stream_group_class;
+}
+
+AVStreamGroup *avformat_stream_group_create(AVFormatContext *s,
+                                            enum AVStreamGroupParamsType type)
+{
+    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;
+    stg->type = type;
+    switch (type) {
+    // Structs in the union are allocated here
+    default:
+        break;
+    }
+
+    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, const AVStream *st)
+{
+    const 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, const 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 &&