[FFmpeg-user] How to output real frame number instead of sequentially added image numbers

[Stefano Sabatini]

On date Wednesday 2013-01-23 13:22:57 +0100, Bernard wrote:
> Hi Tracey,
> 
> in the mean time I've found one link with old code, seems not
> working in newer FFMPEG release as still a lot work should be done
> to adopt code to newest release.
> 
> the code was provide from Yuval Adam
> 
> http://ffmpeg.org/pipermail/ffmpeg-devel/2011-December/117830.html
> 
> The idea behind Yuval work is to replace %d parameter with  %t
> parameter, but this parameter is already now in use %T  or %t for
> log file creation and will probably be in collision with our
> intention for labeling Keyframes.
> 
> 
> My idea here is to introduce descriptive names instead.
> 
> Example:
> 
> %frames   will output    12345.jpg
> 
> complete command line will be:
> 
> ffmpeg -i "C:\myfilename.avi"  -vf select="eq(pict_type\,I)" -vsync 2 -s 200x112  -f image2  "D:\myoutput_file\%frames.jpeg"
> 
> 
> when the FFMPEG is in debug mode  (  - loglevel debug  ) all this
> information is already there:
> 
> ffmpeg   - loglevel debug  -i "C:\myfilename.avi"  -vf select="eq(pict_type\,I)" -vsync 2
> -s 200x112  -f image2  "D:\myoutput_frames\%d.jpeg"
> 
> above command line produces  file named   "ffmpeg-20130123-005308.log"  (generated today) and a part of file is:
> 
> frame=    3 fps=0.0 q=0.0 size=N/A time=00:00:00.52 bitrate=N/A n:34
> pts:122400 t:1.360000 pos:180224 key:0 interlace_type:P pict_type:P
> scene:nan -> select:0.000000
> frame=  319 fps=1.5 q=0.0 size=N/A time=00:02:31.80 bitrate=N/A
> n:3811 pts:13719600 t:152.440000 pos:17766412 key:0 interlace_type:P
> pict_type:P scene:nan -> select:0.000000
> 
> You can find that the "frame"  is the name of  the Generated
> outgoing images  and the corresponding frame number is n: (keyframe)
> 
> D:\myoutput_frames\3.jpg and D:\myoutput_frames\319.jpg in this case.  and there is also n: parameter which is in fact the correct frame number from input file
> 
> So:
> frame=  3 = n:34
> frame=  319  = n:3811
> 
> interpreting n: you can produce time code image name or in your case
> the time offset from start of the input video clip.
> 
> I think this is also the solution of your problem..
> 
> What we must do is to selectively link what is generated from  -
> loglevel debug parameter and then with this information (n:)
> renaming outgoing (generated)  images.
> 
> Regards,
> 
> Bernard
> 
> On 22.1.2013 23:55, tracey jaquith wrote:
> >Hi Bernard,
> >
> >This kind of was a maddeningly needed/wanted feature for me, too 8-)
> >and actually one step further -- I wanted the actual seconds as close as
> >possible from the start for each frame extracted.  (If this works for you, you
> >could tailor it to taste for either frame# (easier) or seconds-from-start like
> >it will do by default).  I'm nearly certain there is no option to do what you suggest
> >but OTOH I love to be wrong so I don't need to code 8-)
> >
> >This isn't really ready for primetime (I'm hacking around by stashing some new globals to
> >get information in the detection/identify part of the code) but it seems
> >to work pretty nicely.  Very recently, I was using avidemux to make an .idx
> >(index) file for MPEG1/MPEG2/MPEG-TS and then parsing it to find
> >the timestamp of GOP for a given frame number to go from
> >    "frame number" => "seconds from start"
> >(but now with the updated/current patch, I get very close to the number of seconds
> >  directly with the patched ffmpeg).
> >
> >http://archive.org/~tracey/downloads/patches/ffmpeg-thumbnails.patch
> >
> >
> >I would second an option (and would be happy to work on a more robust unhacky
> >solution/patch for consideration?) to output the #seconds or frame number
> >of each output frame
> >
> >(My build and patch applying scripts, overall, is here, given the kinds of things
> >  we do at my work (h.264 and ogv theora creation, vpx/WebM possible)):
> >
> >http://archive.org/~tracey/downloads/ffmpeg-README.txt

This is ticket #1452:
https://ffmpeg.org/trac/ffmpeg/ticket/1452

Also see the recent thread:
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/158092

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