avformat/mov: add option to use tfdt for fragment timestamps.

doc/demuxers.texi

@@ -665,6 +665,12 @@ Set mfra timestamps as PTS
 Don't use mfra box to set timestamps
 @end table
 
+@item use_tfdt
+For fragmented input, set fragment's starting timestamp to @code{baseMediaDecodeTime} from the @code{tfdt} box.
+Default is disabled, which will preferentially use the @code{earliest_presentation_time} from the @code{sidx} box.
+In either case, the timestamp from the @code{mfra} box will be used if it's available and @code{use_mfra_for} is
+set to pts or dts.
+
 @item export_all
 Export unrecognized boxes within the @var{udta} box as metadata entries. The first four
 characters of the box type are set as the key. Default is false.

libavformat/isom.h

@@ -277,6 +277,7 @@ typedef struct MOVContext {
     int moov_retry;
     int use_mfra_for;
     int has_looked_for_mfra;
+    int use_tfdt;
     MOVFragmentIndex frag_index;
     int atom_depth;
     unsigned int aax_mode;  ///< 'aax' file has been detected

libavformat/mov.c

@@ -4803,7 +4803,7 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
             dts = frag_stream_info->first_tfra_pts;
             av_log(c->fc, AV_LOG_DEBUG, "found mfra time %"PRId64
                     ", using it for dts\n", pts);
-        } else if (frag_stream_info->sidx_pts != AV_NOPTS_VALUE) {
+        } else if (frag_stream_info->sidx_pts != AV_NOPTS_VALUE && !c->use_tfdt) {
             // FIXME: sidx earliest_presentation_time is *PTS*, s.b.
             // pts = frag_stream_info->sidx_pts;
             dts = frag_stream_info->sidx_pts - sc->time_offset;
@@ -8169,6 +8169,8 @@ static const AVOption mov_options[] = {
         FLAGS, "use_mfra_for" },
     {"pts", "pts", 0, AV_OPT_TYPE_CONST, {.i64 = FF_MOV_FLAG_MFRA_PTS}, 0, 0,
         FLAGS, "use_mfra_for" },
+    {"use_tfdt", "use tfdt for fragment timestamps", OFFSET(use_tfdt), AV_OPT_TYPE_BOOL, {.i64 = 0},
+        0, 1, FLAGS},
     { "export_all", "Export unrecognized metadata entries", OFFSET(export_all),
         AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, .flags = FLAGS },
     { "export_xmp", "Export full XMP metadata", OFFSET(export_xmp),