[FFmpeg-user] ffmpeg output list question

[Mark Filipak]

I run this command:
ffmpeg -ss 30.0 -i %1 -hide_banner -filter:v idet -frames:v 900 -an -f 
rawvideo -y NUL
to gather data on multimedia source files (passed in via %1).

I've run it against a wide mix -- close to a hundred -- sources:
- 24 FPS,
- 25 FPS,
- soft telecined,
- hard telecined, and
- NTSC with embedded hard telecined (e.g., "Making of" documentaries).
I've included a typical output (with added line #s) at the bottom of 
this message.

Question: Is the output listing documented anywhere?
Of particular interest are:
- the meaning of "tbr" (line 04),
- the meaning of "tbc" (line 04),
- the meaning of "dup" (line 18),
- why 'dup'+'drop'+'Neither'+'Top'+'Bottom' (lines 18 & 20) always 
equals 901, and
- why 'Neither'+'Top'+'Bottom' (line 20) totals 830 instead of 1660.

Any/all input/opinion welcome. Thanks.

01 Input #0, mpeg, from 'J:\VIDEO_TS\VTS_02_1.VOB':
02   Duration: 00:17:58.04, start: 0.233567, bitrate: 7966 kb/s
03     Stream #0:0[0x1bf]: Data: dvd_nav_packet
04     Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, top 
first), 720x480 [SAR 32:27 DAR 16:9], Closed Captions, 29.97 fps, 59.94 
tbr, 90k tbn, 59.94 tbc
05     Stream #0:2[0x89]: Audio: dts (DTS), 48000 Hz, 5.1(side), fltp, 
1536 kb/s
06     Stream #0:3[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s
07     Stream #0:4[0x82]: Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s
08 Stream mapping:
09   Stream #0:1 -> #0:0 (mpeg2video (native) -> rawvideo (native))
10 Press [q] to stop, [?] for help
11 Output #0, rawvideo, to 'NUL':
12   Metadata:
13     encoder         : Lavf58.31.104
14     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 
720x480 [SAR 32:27 DAR 16:9], q=2-31, 124291 kb/s, 29.97 fps, 29.97 tbn, 
29.97 tbc
15     Metadata:
16       encoder         : Lavc58.55.101 rawvideo
17 [mpeg @ 000001b42001a600] New subtitle stream 0:5 at pos:22458382 and 
DTS:42.7761s
18 frame=  900 fps=0.0 q=-0.0 Lsize=  455625kB time=00:00:30.03 
bitrate=124291.7kbits/s dup=71 drop=0 speed=44.6x
19 video:455625kB audio:0kB subtitle:0kB other streams:0kB global 
headers:0kB muxing overhead: 0.000000%
20 [Parsed_idet_0 @ 000001b4205d1c80] Repeated Fields: Neither:   799 
Top:    17 Bottom:    14
21 [Parsed_idet_0 @ 000001b4205d1c80] Single frame detection: TFF:   289 
BFF:     7 Progressive:   112 Undetermined:   422
22 [Parsed_idet_0 @ 000001b4205d1c80] Multi frame detection: TFF:   538 
BFF:     0 Progressive:   285 Undetermined:     7