[FFmpeg-devel] [PR] [release/7.1] Backport IAMF in mp4 fixes (PR #22313)

[James Almer via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #22313 opened by James Almer (jamrial)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22313
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22313.patch


>From 37deee5cab866a6694414524f6ec67cba43fb880 Mon Sep 17 00:00:00 2001
From: James Almer <jamrial@gmail.com>
Date: Fri, 27 Feb 2026 10:38:14 -0300
Subject: [PATCH 1/2] avformat/mov: fix setting iamf stream id offsets

If we were to add the highest id of a non iamf stream as offset to iamf stream
ids, and one of the latter was 0, then an id overlap would ocurr.

Signed-off-by: James Almer <jamrial@gmail.com>
(cherry picked from commit 51aef95ba156b7848eca5445f0f59b091c3b1004)
---
 libavformat/mov.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 7c7aced6ca..6fddce9552 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -10182,7 +10182,7 @@ static AVStream *mov_find_reference_track(AVFormatContext *s, AVStream *st,
 
 static void fix_stream_ids(AVFormatContext *s)
 {
-    int highest_id = 0;
+    int highest_id = 0, lowest_iamf_id = INT_MAX;
 
     for (int i = 0; i < s->nb_streams; i++) {
         const AVStream *st = s->streams[i];
@@ -10190,7 +10190,21 @@ static void fix_stream_ids(AVFormatContext *s)
         if (!sc->iamf)
             highest_id = FFMAX(highest_id, st->id);
     }
-    highest_id += !highest_id;
+
+    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)
+            continue;
+        for (int j = 0; j < stg->nb_streams; j++) {
+            AVStream *st = stg->streams[j];
+            lowest_iamf_id = FFMIN(lowest_iamf_id, st->id);
+        }
+    }
+
+    if (highest_id < lowest_iamf_id)
+        return;
+
+    highest_id += !lowest_iamf_id;
     for (int i = 0; highest_id > 1 && i < s->nb_stream_groups; i++) {
         AVStreamGroup *stg = s->stream_groups[i];
         if (stg->type != AV_STREAM_GROUP_PARAMS_IAMF_AUDIO_ELEMENT)
-- 
2.52.0


>From 654607e18c10fed40e08c143f9dc40a51ecd201c Mon Sep 17 00:00:00 2001
From: James Almer <jamrial@gmail.com>
Date: Fri, 27 Feb 2026 10:41:31 -0300
Subject: [PATCH 2/2] avformat/mov: fix cases where we discard iamf packets
 from enabled streams

Given the entire iamf struct is inside a single Track, if the first iamf stream
(which is the one sharing the index and id from the Track) was to be disabled,
then packets from every iamf stream would be discarded.
Fix this by actually going through the entire iamf Sample and discarding those
from the disabled streams only.

Signed-off-by: James Almer <jamrial@gmail.com>
(cherry picked from commit 16ee3d8d99a2f2e83a2559e958e19ede813b29f8)
---
 libavformat/iamf_reader.c | 3 +++
 libavformat/mov.c         | 8 +++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/libavformat/iamf_reader.c b/libavformat/iamf_reader.c
index 5cbe89ca68..9a8371d9e3 100644
--- a/libavformat/iamf_reader.c
+++ b/libavformat/iamf_reader.c
@@ -95,6 +95,9 @@ static int audio_frame_obu(AVFormatContext *s, const IAMFDemuxContext *c,
         memcpy(side_data, c->recon, c->recon_size);
     }
 
+    if (st->discard == AVDISCARD_ALL)
+        pkt->flags |= AV_PKT_FLAG_DISCARD;
+
     pkt->stream_index = st->index;
     return 0;
 }
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 6fddce9552..f025487baf 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -10729,7 +10729,7 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
         sample->size = FFMIN(sample->size, (mov->next_root_atom - sample->pos));
     }
 
-    if (st->discard != AVDISCARD_ALL) {
+    if (st->discard != AVDISCARD_ALL || sc->iamf) {
         int64_t ret64 = avio_seek(sc->pb, sample->pos, SEEK_SET);
         if (ret64 != sample->pos) {
             av_log(mov->fc, AV_LOG_ERROR, "stream %d, offset 0x%"PRIx64": partial file\n",
@@ -10765,6 +10765,12 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
                     return ret;
                 }
                 size -= ret;
+
+                if (pkt->flags & AV_PKT_FLAG_DISCARD) {
+                    av_packet_unref(pkt);
+                    ret = 0;
+                    continue;
+                }
                 pkt->pts = pts; pkt->dts = dts;
                 pkt->pos = pos; pkt->flags |= flags;
                 pkt->duration = duration;
-- 
2.52.0

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