avformat/mov: get the correct fragment stsd_id when decrypting the sample

When determining whether a packet should be decrypted,
should use the stsd_id of the fragment where the current packet is located.

Reviewed-by: Zhao Zhili <zhilizhao@tencent.com>
Signed-off-by: Wang Yaqiang <wangyaqiang03@kuaishou.com>

libavformat/isom.h

@@ -139,6 +139,7 @@ typedef struct MOVFragmentStreamInfo {
     int index_base;
     int index_entry;
     MOVEncryptionIndex *encryption_index;
+    int stsd_id; // current fragment stsd_id
 } MOVFragmentStreamInfo;
 
 typedef struct MOVFragmentIndexItem {

libavformat/mov.c

@@ -4958,9 +4958,10 @@ 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;
 }
 
@@ -7225,7 +7226,7 @@ static int cenc_filter(MOVContext *mov, AVStream* st, MOVStreamContext *sc, AVPa
     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) {
                 encrypted_index = current_index - frag_stream_info->index_base;
                 encryption_index = frag_stream_info->encryption_index;