[FFmpeg-user] 5 Questions about output listing for ffprobe (and ffmpeg, too)

[Mark Filipak]

5 Questions. Links to output listing documentation (which I have not 
found) would suffice.
Thanks! - Mark.

Source video:
=====
C:\CMD & tiny apps\ffmpeg>CMD /K ffprobe -i G:\VIDEO_TS\VTS_01_1.VOB 
-select_streams v:0 -show_frames -of flat -sexagesimal   ...followed by 
a very long pipe
   built with gcc 9.1.1 (GCC) 20190807
   configuration: --enable-gpl --enable-version3 --enable-sdl2 
--enable-fontconfig --enable-gnutls --enable-iconv --enable-libass 
--enable-libdav1d --enable-libbluray --enable-libfreetype 
--enable-libmp3lame --enable-libopencore-amrnb 
--enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus 
--enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora 
--enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp 
--enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg 
--enable-lzma --enable-zlib --enable-gmp --enable-libvidstab 
--enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa 
--enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx 
--enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va 
--enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth 
--enable-libopenmpt
   libavutil      56. 33.100 / 56. 33.100
   libavcodec     58. 55.101 / 58. 55.101
   libavformat    58. 31.104 / 58. 31.104
   libavdevice    58.  9.100 / 58.  9.100
   libavfilter     7. 58.101 /  7. 58.101
   libswscale      5.  6.100 /  5.  6.100
   libswresample   3.  6.100 /  3.  6.100
   libpostproc    55.  6.100 / 55.  6.100
Input #0, mpeg, from 'G:\VIDEO_TS\VTS_01_1.VOB':
     Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, top 
first), 720x480 [SAR 32:27 DAR 16:9], 29.97 fps, 59.94 tbr, 90k tbn, 
59.94 tbc
frames.frame.1800.interlaced_frame=0   ...pipe output
frames.frame.1800.top_field_first=1    ...pipe output
frames.frame.1800.repeat_pict=0        ...pipe output
frames.frame.1801.interlaced_frame=0   ...pipe output
frames.frame.1801.top_field_first=1    ...pipe output
frames.frame.1801.repeat_pict=1        ...pipe output
frames.frame.1802.interlaced_frame=0   ...pipe output
frames.frame.1802.top_field_first=0    ...pipe output
frames.frame.1802.repeat_pict=0        ...pipe output
frames.frame.1803.interlaced_frame=0   ...pipe output
frames.frame.1803.top_field_first=0    ...pipe output
frames.frame.1803.repeat_pict=1        ...pipe output
=====
As you can see, the source video is 29.97 FPS, soft telecine.

       Q1: So the MPEG source really is 720x480-24p, correct?
       Q2: I think I know that "90k tbn" relates to frame time accuracy, 
but what does "59.94 tbr" mean?
       Q3: What does "59.94 tbc" mean?
       ...Yeah, I know that Carl Eugen has answered that previously: 
"Different time bases, tbn is the container, tbc is codec iirc", but I 
just can't get my head around "time base". If the video is 29.97 fps, I 
just can't figure out what else there is.

I repackaged the video as MKV via 'mkvtoolnix-gui.exe' -- I'm trying to 
figure out what mkvtoolnix is doing.
=====
C:\CMD & tiny apps\ffmpeg>CMD /K ffprobe -i "M:\Movies1\xxxxxxx.mkv" 
-select_streams v:0 -show_frames -of flat -sexagesimal   ...followed by 
a very long pipe
...same banner as above of course...
Input #0, matroska,webm, from 'M:\Movies1\xxxxxxx.mkv':
     Stream #0:0: Video: mpeg2video (Main), yuv420p(tv, top first), 
720x480 [SAR 32:27 DAR 16:9], Closed Captions, SAR 186:157 DAR 279:157, 
59.94 fps, 59.94 tbr, 1k tbn, 59.94 tbc (default)
[mpeg2video @ 000002837731a8c0] ignoring pic cod ext after 0
frames.frame.1800.interlaced_frame=1   ...pipe output
frames.frame.1800.top_field_first=1    ...pipe output
frames.frame.1800.repeat_pict=0        ...pipe output
frames.frame.1801.interlaced_frame=1   ...pipe output
frames.frame.1801.top_field_first=1    ...pipe output
frames.frame.1801.repeat_pict=0        ...pipe output
frames.frame.1802.interlaced_frame=1   ...pipe output
frames.frame.1802.top_field_first=1    ...pipe output
frames.frame.1802.repeat_pict=0        ...pipe output
frames.frame.1803.interlaced_frame=1   ...pipe output
frames.frame.1803.top_field_first=1    ...pipe output
frames.frame.1803.repeat_pict=0        ...pipe output
=====
The MKV appears to be 720x480-60i (maybe -- as I don't know what "tbr" & 
"tbc" really mean).

       Q4: Is it actually 720x480-60i?
       Q5: I know what SAR & DAR are, but what does extra "SAR 186:157 
DAR 279:157" connote?

mkvtoolnix isn't supposed to change the video, just repackage it. But 
due to the speed at which mkvtoolnix repackages, it can't possibly be 
transcoding, yet the video seems changed. I have to be misinterpreting 
something. Help. (Note: I've examined the source video via 'VobEdit.exe' 
but I have no equivalent tool for MKVs.) ...All this is driving me to 
liquor.

BTW, I've tried asking at #ffmpeg-user but there's just too many moving 
parts to formulate terse questions. I sure wish someone knowledgeable 
would create an ffmpeg-glossary & a guide to command list outputs. 
ffmpeg seems to be using terminology that differs from MPEG standards.