movenc: Add a new flag for writing global sidx indexes for dash

The double meaning of the faststart flag (moving a moov atom
to the start of files, making them streamable, for non-fragmented
files, vs inserting a global sidx index at the start of files
for fragmented files) is confusing - see 40ed1cbf1 for
explanation of its origins.

Since the second meaning of the flag hasn't been part of any
libav release yet, just rename it to get rid of the confusion
without any extra deprecation (which wouldn't get rid of the
potential confusion, of users adding -movflags faststart
even for fragmented files, where it isn't needed for making
them "streamable").

This gets back the old behaviour, where -movflags faststart
doesn't have any effect for fragmented files.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -62,6 +62,7 @@ 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" },
     FF_RTP_FLAG_OPTS(MOVMuxContext, rtp_flags),
     { "skip_iods", "Skip writing iods atom.", offsetof(MOVMuxContext, iods_skip), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM},
     { "iods_audio_profile", "iods audio profile atom.", offsetof(MOVMuxContext, iods_audio_profile), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 255, AV_OPT_FLAG_ENCODING_PARAM},
@@ -2836,7 +2837,7 @@ 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)
@@ -2976,7 +2977,7 @@ 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);
@@ -3228,7 +3229,7 @@ static int mov_flush_fragment(AVFormatContext *s)
         mov_write_moov_tag(s->pb, mov, s);
 
         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;
@@ -3242,7 +3243,7 @@ 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;
@@ -3481,7 +3482,7 @@ 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 {
@@ -4048,7 +4049,7 @@ static int mov_write_header(AVFormatContext *s)
         !(mov->flags & FF_MOV_FLAG_DELAY_MOOV)) {
         mov_write_moov_tag(pb, mov, s);
         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);
     }
 
@@ -4245,7 +4246,7 @@ 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) {

libavformat/movenc.h

@@ -192,6 +192,7 @@ 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_GLOBAL_SIDX           (1 << 14)
 
 int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt);