MP4: Sony Real Time Metadata — drop-frame flag no longer detected (regression since 24.11) #2656

Summary

On Sony Alpha MP4 files carrying the camera's RTMD (Real Time Metadata) track,
MediaInfo no longer reports the drop-frame flag. Version 24.04 reported it
correctly; 26.01 and 26.05 do not.

The change appears related to I2094, MXF: Sony Real Time Metadata: fix timecode drop frame flag in the 24.11 changelog. That entry refers to MXF, but the
regression shows up on MP4.

Sample file

W0292.MP4 — Sony A7S III, 119.88 fps, NTSC drop-frame.

Happy to upload the file wherever is most convenient.

Observed

$ mediainfo --Output='Other;%TimeCode_FirstFrame%|%TimeCode_DropFrame%' W0292.MP4

The full dump (mediainfo -f) on 26.05 also reports TimeCode_DropFrame : No,
so this is not a template or output-format issue.

Expected

The file is drop-frame. Two independent references agree:

• Sony Catalyst Browse (the camera manufacturer's own tool) shows
  02:34:28;012, with the drop-frame separator.
• DaVinci Resolve reports the clip as 119.880 DF.

MediaInfo 24.04 agreed with both. 26.x does not.

Environment

• macOS, Intel
• MediaInfo CLI 24.04 (correct) and 26.01 / 26.05 (incorrect)
• Also reproduced with MediaInfo 26.01 on Windows 10, so it does not look
  platform-specific.

Impact

Without the drop-frame flag the end timecode is computed with non-drop arithmetic,
whichat 119.88 fps drifts by 8 frames per minute — 80 frames on a ten-minute take.
The exported timecode then disagrees with what Catalyst Browse and Resolve
display for the same clip.

We have not downgraded to 24.04, because 26.05 is a clear improvement elsewhere
(HEVC profile reporting, Canon manufacturer capitalisation, bitrate accuracy),
and we would rather wait for a fix than lose those.

Notes

The timecode value itself is read correctly in every version — the frame field
matches Catalyst exactly. Only the drop-frame flag and its separator are
affected.

We could not recover the flag from any other source in the file: ffprobe reports
the same timecode without the separator from both the tmcd track and the
container, and ExifTool exposes no timecode tag at all (including with -ee).
The information does appear to survive in the file itself, since both Catalyst
and Resolve still read it.