[FFmpeg-user] 55-Telecine, 2020-04-26 Status Report, Part 2

[Mark Filipak]

55-Telecine for Blu-ray Movies.

55-Telecine works wonderfully for transcoding M2TS movies (for superior display on 60Hz TVs) 
provided that the M2TS streams don't have subtitles and/or are short. I reckon that the limitations 
are due to mishandling of subtitle time stamps by the 'interleave' filter -- I remember reading that 
subtitle packets can span GOPs, and 'interleave' may be assigning bogus PTSs to fragments. The issue 
is under investigation (https://trac.ffmpeg.org/ticket/8626 -- the ticket's title, "pp=linblenddeint 
failure", is stale and no longer applies). The 'interleave' problem prevents me putting 55-telecine 
into general use for Blu-ray movies.

New Information:

As an experiment, to bypass the problem in https://trac.ffmpeg.org/ticket/8626, I tested whether 
extracting subtitles separately and then merging them back in would replicate the problem or do 
something different. It did something different.

Step 1: Transcode to 2001av.MKV.
Step 2: Extract subtitles to 2001s.MKV.
Step 3: Merge 2001s.MKV & 2001av.MKV to 2001.MKV.
Step 4: Merge 2001s.MKV & 2001av.MKV to 2001.MKVToolNix.MKV via MKVToolNix.

Step 3 did bypass the https://trac.ffmpeg.org/ticket/8626 problem (which I will report to the trac 
system). however, it did not entirely succeed. Any suggestions regarding the procedure below would 
be very welcome.

Regards,
Mark.


Step 1: Transcode to 2001av.MKV.
ffmpeg -report -ss 2:57 -analyzeduration 5000000000 -probesize 5000000000 -i 
"G:\BDMV\STREAM\00000.m2ts" -filter_complex 
"telecine=pattern=5,split[A][B],[A]select='not(eq(mod((n+1)\,5)\,3))'[C],[B]select='eq(mod((n+1)\,5)\,3)',pp=linblenddeint[D],[C][D]interleave" 
-map 0 -codec:v libx264 -crf 20 -codec:a copy -codec:a:1 pcm_s16be -sn -dn "2001av.MKV"

1 video stream
8 audio streams
349 instances of "[mpegts @ 000001e0e4df0080] DTS discontinuity in stream xx: packet xxx with DTS 
xxxxxxxx, packet 5 with DTS xxxxxxxx"


Step 2: Extract subtitles to 2001s.MKV.
ffmpeg -report -ss 2:57 -analyzeduration 5000000000 -probesize 5000000000 -i 
"G:\BDMV\STREAM\00000.m2ts" -map 0 -vn -an -codec:s copy -dn "2001s.MKV"

18 subtitle streams
349 instances of "[mpegts @ 000001e0e4df0080] DTS discontinuity in stream xx: packet xxx with DTS 
xxxxxxxx, packet 5 with DTS xxxxxxxx"


Step 3: Merge 2001s.MKV & 2001av.MKV to 2001.MKV.
ffmpeg -report -analyzeduration 5000000000 -probesize 5000000000 -i 2001av.MKV -i 2001s.MKV -map 0 
-codec:v copy -codec:a copy -map 1:s -codec:s copy 2001.2.MKV

Subtitles lead audio by 1:14.


Step 4: Merge 2001s.MKV & 2001av.MKV to 2001.MKVToolNix.MKV via MKVToolNix.

No errors or warnings.
Subtitles & audio are in sync.