[FFmpeg-user] Unresolved concatenation and subtitle problems

[Mark Filipak]

   Investigation of unresolved concatenation and subtitle problems.

   Two scripts, one running '-vf showinfo', the other, '-show_streams'.

echo 1.1 00305 M2TS SHOWINFO - h:\BDMV\STREAM\00305.m2ts
set SOURCE=h:\BDMV\STREAM\00305.m2ts
set PREP=-report -analyzeduration 5772725000 -probesize 15091101696
set ARGS=-map 0 -vf showinfo -c:v rawvideo -sn -an -f null c:\void.mkv
set TARGET=e:\00305.m2ts_showinfo.txt
ffmpeg %PREP% -i %SOURCE% %ARGS% 2>%TARGET%

echo 1.2 00305 M2TS SHOW STREAMS - h:\BDMV\STREAM\00305.m2ts
set SOURCE=h:\BDMV\STREAM\00305.m2ts
set PREP=-analyzeduration 5772725000 -probesize 15091101696
set ARGS=-show_streams
set TARGET=e:\00305.m2ts_streams.txt
ffprobe %PREP% -i %SOURCE% %ARGS% >%TARGET%

   Both of them provoke
   "Failed to allocate buffers for seekback" message, and
   165 "DTS discontinuity in stream 2" (the subs) messages.
       packet   12 with DTS  12859568, packet   13 with DTS  12970433
       packet   20 with DTS  13302507, packet   21 with DTS  13417133
       packet   28 with DTS  14965402, packet   29 with DTS  15080059
       :
       packet 6026 with DTS 495381711, packet 6027 with DTS 495687565

   COMPARING WHAT MPV SHOWS VERSUS 'showinfo' VERSUS 'show_streams'
   MPV first = 0
   MPV total = 1:36:12.725291[6..] = 5772.725291[6..] seconds
   MPV final = 5772.725291[6..]-1.001/24 = 5772.68358[3..] seconds
   MPV              0..519541522.4[9..] ticks --> 0..138405.[9..] frames
                    :                             :
   showinfo [note1] 0..519541522                  0..138406
   show_streams     1048560 = video start_pts
                    1048560 = audio start_pts
                    7685190 = subs  start_pts [note2] (PREP shown above)
                    1048560 = subs  start_pts [note3] (no PREP)
   [note1] First & final '-vf showinfo' listings:
     [Parsed_showinfo_0 @ 00000000d91a1f00] n:     0 pts:        0 -snip-
     [Parsed_showinfo_0 @ 00000000d91a1f00] n:138406 pts:519541522 -snip-
   [note2] 7685190 ticks 'says' 1st subtitle is at 1:13.740 - confirmed.
   [note3] 1048560 ticks 'says' 1st subtitle is at 0:00.000 - incorrect.


Q1: Why do 'ffmpeg -vf showinfo' and 'ffprobe -show_streams' differ?
Q2: Is '-analyzeduration 5772725000 -probesize 15091101696' catching all?
Q3: What is the effect of 'no PREP' on concatination?


If you have questions, kindly ask.
I have the results saved, and I can explain the "COMPARING" section.

Thank you -- Mark.
(stopping now to get some sleep).