[FFmpeg-cvslog] avformat/mov: fix encryption index in the case of multiple trun

[Zhao Zhili]

ffmpeg | branch: master | Zhao Zhili <zhilizhao at tencent.com> | Sun Jul 31 01:14:12 2022 +0800| [1af7797d212eee9aa86a54f558bcfe6abb22949b] | committer: Zhao Zhili

avformat/mov: fix encryption index in the case of multiple trun

frag_stream_info->index_entry isn't the first sample/trun index.
cenc.frag_index_entry_base failed to catch the case since
current_index > 0.

Fix ticket #9807.

Signed-off-by: Zhao Zhili <zhilizhao at tencent.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=1af7797d212eee9aa86a54f558bcfe6abb22949b
---

 libavformat/isom.h |  3 ++-
 libavformat/mov.c  | 10 ++++++----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/libavformat/isom.h b/libavformat/isom.h
index 9d8646d2ea..fd236b985f 100644
--- a/libavformat/isom.h
+++ b/libavformat/isom.h
@@ -135,6 +135,8 @@ typedef struct MOVFragmentStreamInfo {
     int64_t first_tfra_pts;
     int64_t tfdt_dts;
     int64_t next_trun_dts;
+    // Index of the first sample/trun in the fragment.
+    int index_base;
     int index_entry;
     MOVEncryptionIndex *encryption_index;
 } MOVFragmentStreamInfo;
@@ -253,7 +255,6 @@ typedef struct MOVStreamContext {
     struct {
         struct AVAESCTR* aes_ctr;
         struct AVAES *aes_ctx;
-        unsigned int frag_index_entry_base;
         unsigned int per_sample_iv_size;  // Either 0, 8, or 16.
         AVEncryptionInfo *default_encrypted_sample;
         MOVEncryptionIndex *encryption_index;
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 46731fe22c..31f3249ca6 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -1369,6 +1369,7 @@ static int update_frag_index(MOVContext *c, int64_t offset)
         frag_stream_info[i].tfdt_dts = AV_NOPTS_VALUE;
         frag_stream_info[i].next_trun_dts = AV_NOPTS_VALUE;
         frag_stream_info[i].first_tfra_pts = AV_NOPTS_VALUE;
+        frag_stream_info[i].index_base = -1;
         frag_stream_info[i].index_entry = -1;
         frag_stream_info[i].encryption_index = NULL;
     }
@@ -5202,8 +5203,11 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     sc->ctts_count = sti->nb_index_entries;
 
     // Record the index_entry position in frag_index of this fragment
-    if (frag_stream_info)
+    if (frag_stream_info) {
         frag_stream_info->index_entry = index_entry_pos;
+        if (frag_stream_info->index_base < 0)
+            frag_stream_info->index_base = index_entry_pos;
+    }
 
     if (index_entry_pos > 0)
         prev_dts = sti->index_entries[index_entry_pos-1].timestamp;
@@ -7211,9 +7215,7 @@ static int cenc_filter(MOVContext *mov, AVStream* st, MOVStreamContext *sc, AVPa
         // Note this only supports encryption info in the first sample descriptor.
         if (mov->fragment.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;
-                encrypted_index = current_index - (frag_stream_info->index_entry - sc->cenc.frag_index_entry_base);
+                encrypted_index = current_index - frag_stream_info->index_base;
                 encryption_index = frag_stream_info->encryption_index;
             } else {
                 encryption_index = sc->cenc.encryption_index;