diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 41a47597f4..08d0c2a772 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -66,6 +66,7 @@ static const AVOption options[] = {
     { "dash", "Write DASH compatible fragmented MP4", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_DASH}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
     { "frag_discont", "Signal that the next fragment is discontinuous from earlier ones", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_FRAG_DISCONT}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
     { "delay_moov", "Delay writing the initial moov until the first fragment is cut, or until the first fragment flush", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_DELAY_MOOV}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
+    { "global_sidx", "Write a global sidx index at the start of the file", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_GLOBAL_SIDX}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
     { "write_colr", "Write colr atom (Experimental, may be renamed or changed, do not use from scripts)", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_WRITE_COLR}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
     { "write_gama", "Write deprecated gama atom", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_WRITE_GAMA}, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, "movflags" },
     FF_RTP_FLAG_OPTS(MOVMuxContext, rtp_flags),
@@ -3765,7 +3766,7 @@ static int mov_write_moof_tag(AVIOContext *pb, MOVMuxContext *mov, int tracks,
     mov_write_moof_tag_internal(avio_buf, mov, tracks, 0);
     moof_size = ffio_close_null_buf(avio_buf);
 
-    if (mov->flags & FF_MOV_FLAG_DASH && !(mov->flags & FF_MOV_FLAG_FASTSTART))
+    if (mov->flags & FF_MOV_FLAG_DASH && !(mov->flags & FF_MOV_FLAG_GLOBAL_SIDX))
         mov_write_sidx_tags(pb, mov, tracks, moof_size + 8 + mdat_size);
 
     if ((ret = mov_add_tfra_entries(pb, mov, tracks, moof_size + 8 + mdat_size)) < 0)
@@ -3905,7 +3906,7 @@ static int mov_write_ftyp_tag(AVIOContext *pb, AVFormatContext *s)
     else if (mov->mode == MODE_MP4)
         ffio_wfourcc(pb, "mp41");
 
-    if (mov->flags & FF_MOV_FLAG_DASH && mov->flags & FF_MOV_FLAG_FASTSTART)
+    if (mov->flags & FF_MOV_FLAG_DASH && mov->flags & FF_MOV_FLAG_GLOBAL_SIDX)
         ffio_wfourcc(pb, "dash");
 
     return update_size(pb, pos);
@@ -4167,7 +4168,7 @@ static int mov_flush_fragment(AVFormatContext *s)
             return ret;
 
         if (mov->flags & FF_MOV_FLAG_DELAY_MOOV) {
-            if (mov->flags & FF_MOV_FLAG_FASTSTART)
+            if (mov->flags & FF_MOV_FLAG_GLOBAL_SIDX)
                 mov->reserved_header_pos = avio_tell(s->pb);
             avio_flush(s->pb);
             mov->moov_written = 1;
@@ -4181,7 +4182,7 @@ static int mov_flush_fragment(AVFormatContext *s)
         avio_write(s->pb, buf, buf_size);
         av_free(buf);
 
-        if (mov->flags & FF_MOV_FLAG_FASTSTART)
+        if (mov->flags & FF_MOV_FLAG_GLOBAL_SIDX)
             mov->reserved_header_pos = avio_tell(s->pb);
 
         mov->moov_written = 1;
@@ -4460,7 +4461,7 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
              * in sidx/tfrf/tfxd tags; make sure the sidx pts and duration match up with
              * the next fragment. This means the cts of the first sample must
              * be the same in all fragments. */
-            if ((mov->flags & FF_MOV_FLAG_DASH && !(mov->flags & FF_MOV_FLAG_FASTSTART)) ||
+            if ((mov->flags & FF_MOV_FLAG_DASH && !(mov->flags & FF_MOV_FLAG_GLOBAL_SIDX)) ||
                 mov->mode == MODE_ISM)
                 pkt->pts = pkt->dts + trk->end_pts - trk->cluster[trk->entry].dts;
         } else {
@@ -5304,7 +5305,7 @@ static int mov_write_header(AVFormatContext *s)
         if ((ret = mov_write_moov_tag(pb, mov, s)) < 0)
             return ret;
         mov->moov_written = 1;
-        if (mov->flags & FF_MOV_FLAG_FASTSTART)
+        if (mov->flags & FF_MOV_FLAG_GLOBAL_SIDX)
             mov->reserved_header_pos = avio_tell(pb);
     }
 
@@ -5532,7 +5533,7 @@ static int mov_write_trailer(AVFormatContext *s)
         mov_auto_flush_fragment(s);
         for (i = 0; i < mov->nb_streams; i++)
            mov->tracks[i].data_offset = 0;
-        if (mov->flags & FF_MOV_FLAG_FASTSTART) {
+        if (mov->flags & FF_MOV_FLAG_GLOBAL_SIDX) {
             av_log(s, AV_LOG_INFO, "Starting second pass: inserting sidx atoms\n");
             res = shift_data(s);
             if (res == 0) {
diff --git a/libavformat/movenc.h b/libavformat/movenc.h
index 72862f1b10..06adf2b121 100644
--- a/libavformat/movenc.h
+++ b/libavformat/movenc.h
@@ -209,8 +209,9 @@ typedef struct MOVMuxContext {
 #define FF_MOV_FLAG_DASH                  (1 << 11)
 #define FF_MOV_FLAG_FRAG_DISCONT          (1 << 12)
 #define FF_MOV_FLAG_DELAY_MOOV            (1 << 13)
-#define FF_MOV_FLAG_WRITE_COLR            (1 << 14)
-#define FF_MOV_FLAG_WRITE_GAMA            (1 << 15)
+#define FF_MOV_FLAG_GLOBAL_SIDX           (1 << 14)
+#define FF_MOV_FLAG_WRITE_COLR            (1 << 15)
+#define FF_MOV_FLAG_WRITE_GAMA            (1 << 16)
 
 int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt);