[FFmpeg-user] Question about framecount

[Fabian Schmidt]

Dear Mailing list peers!

I am currently using ffmpeg in order to produce screenshots of each new scene in archival footage. The name of the screenshot is supposed to include the framcount and I want to make a screenshot 3 frames after the cut so my commandline looks like this:

ffmpeg -i WESTERBORK_2019_progres.mov -filter:v "select=if(gt(scene\,0.13)\,st(1\,n)-n\,if(ld(1)\,eq(n\,ld(1)+3))),showinfo" -vsync vfr  Westerbork_Film_%05d.jpg

Even though this worked the last two films with my current material I get a stange output. The timecode in the name is roughly 4% higher that the one I burnt in to the videofile (for orientation). Examples:


Westerbork_Film_6479.jpg:



Westerbork_Film_2157.jpg:


This happens with every version (I remuxed the file in mkv toolnix and speded it down to 16 fps and to 25fps) I made. So, even though I doubt it will help, here’s the media info of the file. It’s a silent film; the file is an export from Davinci resolve where I added the frame count:


 General
Complete name                            : WESTERBORK_2019_progres.mov
Format                                   : MPEG-4
Format profile                           : QuickTime
Codec ID                                 : qt   0000.02 (qt  )
File size                                : 8.90 GiB
Duration                                 : 1 h 12 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 17.6 Mb/s
Encoded date                             : UTC 2021-06-04 18:51:26
Tagged date                              : UTC 2021-06-04 18:51:26
Writing application                      : Blackmagic Design DaVinci Resolve

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High at L4
Format settings                          : CABAC / 2 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 2 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 1 h 12 min
Bit rate mode                            : Variable
Bit rate                                 : 17.3 Mb/s
Maximum bit rate                         : 768 kb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.333
Stream size                              : 8.74 GiB (98%)
Encoded date                             : UTC 2021-06-04 18:51:26
Tagged date                              : UTC 2021-06-04 18:51:26
Color range                              : Limited
Color primaries                          : BT.709
Matrix coefficients                      : BT.709
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 1 h 12 min
Bit rate mode                            : Constant
Bit rate                                 : 320 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 166 MiB (2%)
Default                                  : Yes
Alternate group                          : 1
Encoded date                             : UTC 2021-06-04 18:51:26
Tagged date                              : UTC 2021-06-04 18:51:26

Other
ID                                       : 3
Type                                     : Time code
Format                                   : QuickTime TC
Duration                                 : 1 h 12 min
Frame rate                               : 25.000 FPS
Time code of first frame                 : 01:00:00:00
Time code, striped                       : Yes
Language                                 : English
Default                                  : No
Encoded date                             : UTC 2021-06-04 18:51:26
Tagged date                              : UTC 2021-06-04 18:51:26


Looking forward to hear any tips or comments. Also one more question to the experts: Sometimes ffmepg puts out the frame count in the name with 000 in front and sometimes not. I guess it has something to do with the %05d or %d in the end. Where can I find an explanation how this works?

Kind regards
Fabian

__

PhD candidate at Filmuniversität Babelsberg, Germany

latest publication: http://www.apparatusjournal.net/index.php/apparatus/article/view/223/515

new research project: VHH - Visual History of the Holocaust: Rethinking Curation in the Digital Age <https://ef.huji.ac.il/book/vhh-visual-history-holocaust-rethinking-curation-digital-age>
currently working for Ludwig Boltzmann Institute for Digital History (LBIDH)  <https://geschichte.lbg.ac.at/team/fabian-schmidt>and Filmuniversität Babelsberg KONRAD WOLF
upcoming research project: DFG-Filmikonen  <https://www.filmuniversitaet.de/filmuni/aktuelles/news/artikel/detail/filmbilder-aus-der-nazizeit-im-fokus>
filmproject: Atrocity Film <http://blog.atrocityfilm.com/>
IMDB <https://www.imdb.com/name/nm1144289/>


Fabian Schmidt
Husemannstr. 12
10435 Berlin
0049 0172 3256513