movenc: Indicate that negative timestamps are supported

The mov/mp4 muxer has support for handling negative timestamps
via edit lists (which customarily is used for handling the 1-frame
delay due to B-frames as well).

Using the muxer's native way of handling it is better than using
the generic offsetting. The generic offsetting is a bit too
crude when e.g. the timebase of one track is 1/fps, where the
edit lists can handle it accurately.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -3265,7 +3265,7 @@ AVOutputFormat ff_mov_muxer = {
     .write_header      = mov_write_header,
     .write_packet      = mov_write_packet,
     .write_trailer     = mov_write_trailer,
-    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH | AVFMT_TS_NEGATIVE,
     .codec_tag         = (const AVCodecTag* const []){
         ff_codec_movvideo_tags, ff_codec_movaudio_tags, 0
     },
@@ -3284,7 +3284,7 @@ AVOutputFormat ff_tgp_muxer = {
     .write_header      = mov_write_header,
     .write_packet      = mov_write_packet,
     .write_trailer     = mov_write_trailer,
-    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH | AVFMT_TS_NEGATIVE,
     .codec_tag         = (const AVCodecTag* const []){ codec_3gp_tags, 0 },
     .priv_class        = &tgp_muxer_class,
 };
@@ -3303,7 +3303,7 @@ AVOutputFormat ff_mp4_muxer = {
     .write_header      = mov_write_header,
     .write_packet      = mov_write_packet,
     .write_trailer     = mov_write_trailer,
-    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH | AVFMT_TS_NEGATIVE,
     .codec_tag         = (const AVCodecTag* const []){ ff_mp4_obj_type, 0 },
     .priv_class        = &mp4_muxer_class,
 };
@@ -3321,7 +3321,7 @@ AVOutputFormat ff_psp_muxer = {
     .write_header      = mov_write_header,
     .write_packet      = mov_write_packet,
     .write_trailer     = mov_write_trailer,
-    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH | AVFMT_TS_NEGATIVE,
     .codec_tag         = (const AVCodecTag* const []){ ff_mp4_obj_type, 0 },
     .priv_class        = &psp_muxer_class,
 };
@@ -3338,7 +3338,7 @@ AVOutputFormat ff_tg2_muxer = {
     .write_header      = mov_write_header,
     .write_packet      = mov_write_packet,
     .write_trailer     = mov_write_trailer,
-    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH | AVFMT_TS_NEGATIVE,
     .codec_tag         = (const AVCodecTag* const []){ codec_3gp_tags, 0 },
     .priv_class        = &tg2_muxer_class,
 };
@@ -3356,7 +3356,7 @@ AVOutputFormat ff_ipod_muxer = {
     .write_header      = mov_write_header,
     .write_packet      = mov_write_packet,
     .write_trailer     = mov_write_trailer,
-    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH | AVFMT_TS_NEGATIVE,
     .codec_tag         = (const AVCodecTag* const []){ codec_ipod_tags, 0 },
     .priv_class        = &ipod_muxer_class,
 };
@@ -3374,7 +3374,7 @@ AVOutputFormat ff_ismv_muxer = {
     .write_header      = mov_write_header,
     .write_packet      = mov_write_packet,
     .write_trailer     = mov_write_trailer,
-    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_ALLOW_FLUSH | AVFMT_TS_NEGATIVE,
     .codec_tag         = (const AVCodecTag* const []){ ff_mp4_obj_type, 0 },
     .priv_class        = &ismv_muxer_class,
 };