[FFmpeg-devel] [PATCH] avformat/mov: get the correct fragment stream info when decrypting the sample

[1035567130@qq.com]

From: Wang Yaqiang <wangyaqiang03@kuaishou.com>

When using mov_read_packet get a pkt, and the packet is encrypted,
it will invoke the cenc_filter func for process the decryption.
This function find the frag_stream_info according to frag_index.current,
but the value of frag_index.current is equal to the last read index of moof box,
this will cause pkt and frag_stream_info mismatch

Signed-off-by: Wang Yaqiang <wangyaqiang03@kuaishou.com>
---
 libavformat/isom.h |  2 ++
 libavformat/mov.c  | 33 ++++++++++++++++++++++++++-------
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/libavformat/isom.h b/libavformat/isom.h
index f05c2d9c28..d90e16457b 100644
--- a/libavformat/isom.h
+++ b/libavformat/isom.h
@@ -137,6 +137,8 @@ typedef struct MOVFragmentStreamInfo {
     int64_t next_trun_dts;
     int index_entry;
     MOVEncryptionIndex *encryption_index;
+    int stsd_id; // current fragment stsd_id
+    int64_t max_pos; //current fragment max pos
 } MOVFragmentStreamInfo;
 
 typedef struct MOVFragmentIndexItem {
diff --git a/libavformat/mov.c b/libavformat/mov.c
index a09a762d91..c118072931 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -1182,6 +1182,20 @@ static int mov_read_moov(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     return 0; /* now go for mdat */
 }
 
+static int get_frag_index_with_pkt(MOVFragmentIndex *frag_index, AVPacket *pkt)
+{
+    if (!pkt) return -1;
+    for (int i = 0; i < frag_index->nb_items;i++) {
+        MOVFragmentStreamInfo *frag_stream_info = frag_index->item[i].stream_info;
+        if (frag_stream_info) {
+            if (pkt->pos + pkt->size <= frag_stream_info->max_pos) {
+                return i;
+            }
+        }
+    }
+    return -1;
+}
+
 static MOVFragmentStreamInfo * get_frag_stream_info(
     MOVFragmentIndex *frag_index,
     int index,
@@ -4868,9 +4882,10 @@ static int mov_read_tfhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     av_log(c->fc, AV_LOG_TRACE, "frag flags 0x%x\n", frag->flags);
 
     frag_stream_info = get_current_frag_stream_info(&c->frag_index);
-    if (frag_stream_info)
+    if (frag_stream_info) {
         frag_stream_info->next_trun_dts = AV_NOPTS_VALUE;
-
+        frag_stream_info->stsd_id = frag->stsd_id;
+    }
     return 0;
 }
 
@@ -5335,9 +5350,10 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
         index = update_frag_index(c, offset);
         frag_stream_info = get_frag_stream_info(&c->frag_index, index, track_id);
-        if (frag_stream_info)
+        if (frag_stream_info) {
             frag_stream_info->sidx_pts = timestamp;
-
+            frag_stream_info->max_pos = offset + size;
+        }
         if (av_sat_add64(offset, size) != offset + (uint64_t)size ||
             av_sat_add64(pts, duration) != pts + (uint64_t)duration
         )
@@ -7101,13 +7117,16 @@ static int cenc_filter(MOVContext *mov, AVStream* st, MOVStreamContext *sc, AVPa
     MOVEncryptionIndex *encryption_index;
     AVEncryptionInfo *encrypted_sample;
     int encrypted_index, ret;
-
-    frag_stream_info = get_frag_stream_info(&mov->frag_index, mov->frag_index.current, st->id);
+    int frag_index = get_frag_index_with_pkt(&mov->frag_index,pkt);
+    if (frag_index < 0) {
+        frag_index = mov->frag_index.current;
+    }
+    frag_stream_info = get_frag_stream_info(&mov->frag_index,frag_index, st->id);
     encrypted_index = current_index;
     encryption_index = NULL;
     if (frag_stream_info) {
         // Note this only supports encryption info in the first sample descriptor.
-        if (mov->fragment.stsd_id == 1) {
+        if (frag_stream_info->stsd_id == 1) {
             if (frag_stream_info->encryption_index) {
                 if (!current_index && frag_stream_info->index_entry)
                     sc->cenc.frag_index_entry_base = frag_stream_info->index_entry;
-- 
2.33.0

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