[FFmpeg-devel] [PR] [release/8.0] Backport IAMF in mp4 fixes (PR #22312)

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

PR #22312 opened by James Almer (jamrial)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22312
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22312.patch


>From 415c801ab54e520524fd3388e5a201cf52dcfc4c 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 f3945c2be2..d722fc3deb 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -10573,7 +10573,7 @@ static int mov_parse_lcevc_streams(AVFormatContext *s)
 
 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];
@@ -10581,7 +10581,21 @@ 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 f092a66b5ac1d0db12a8cebba7afb2a64558c431 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 f7abdf4207..2098f264aa 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 d722fc3deb..49498eda77 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -11153,7 +11153,7 @@ 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",
@@ -11189,6 +11189,12 @@ 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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