mp4 edts media time info is incorrect

[quink-black]

1. media_time is a signed value, either int(64) media_time or int(32) media_time. There is a special value -1. MediaInfoLib handled it as unsigned:

   name="Media time">4294967295

2. The unit of media_time and segment_duration is different:

   segment_duration is an integer that specifies the duration of this edit segment in units of the timescale in the Movie Header Box media_time is an integer containing the starting time within the media of this edit segment (in media time scale units, in composition time).

Current code use moov_mvhd_TimeScale for media_time, which should be Streams[moov_trak_tkhd_TrackID].mdhd_TimeScale. However, since mdhd comes after edts, we don't know mdhd_TimeScale yet when handle edts. The following patch doesn't work:

diff --git a/Source/MediaInfo/Multiple/File_Mpeg4_Elements.cpp b/Source/MediaInfo/Multiple/File_Mpeg4_Elements.cpp
index 89f6ae0d0..51ddf0e74 100644
--- a/Source/MediaInfo/Multiple/File_Mpeg4_Elements.cpp
+++ b/Source/MediaInfo/Multiple/File_Mpeg4_Elements.cpp
@@ -3856,7 +3856,7 @@ void File_Mpeg4::moov_trak_edts_elst()
         stream::edts_struct edts;
         Element_Begin1("Entry");
         Get_B_DEPENDOFVERSION(edts.Duration,                    "Track duration"); Param_Info2C(moov_mvhd_TimeScale, (int64u)edts.Duration*1000/moov_mvhd_TimeScale, " ms");
-        Get_B_DEPENDOFVERSION(edts.Delay,                       "Media time"); Param_Info2C(moov_mvhd_TimeScale && (edts.Delay!=(int32u)-1), (int64u)edts.Delay*1000/moov_mvhd_TimeScale, " ms");
+        Get_B_DEPENDOFVERSION(edts.Delay,                       "Media time"); Param_Info2C(Streams[moov_trak_tkhd_TrackID].mdhd_TimeScale && (edts.Delay!=(int32u)-1), (int64u)edts.Delay*1000/Streams[moov_trak_tkhd_TrackID].mdhd_TimeScale, " ms");^M
         Get_B4 (edts.Rate,                                      "Media rate"); Param_Info1(((float)edts.Rate)/0x10000);
         Element_End0();

[quink-black]

Yes, also editlist Media time can be in samples, not in ms.

media_time is still in media time scale units, and the media time scale is sample rate in this case, so media_time equals to sample_number / sample_rate.

[JeromeMartinez]

Looks like that it would be better to support sgpd at the same time for having coherent behavior, on my todo-list but this latter is long... :(.