Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
> I will inform you about the results.
In short: ffmpeg and ffprobe perform very well on VFR video. The
presentation time stamp %{pts} is the right information to display by
drawtext if you need to know the exact time for a certain frame.
It's a pity that you cannot format the float number displayed; it seems
to be set to 6 decimal places.
In regard to the several mobile phone cameras we have tested, we found
that all of them (including an iPhone) recorded VFR video, but the
framerate was not very variable: It lies between 29-something and 30
fps. Only the iPhone dropped down to 28 fps every few seconds, obviously
being occupied by some other task.
In the case of the VFR video that started this discussion, the framerate
allegedly varied between 15 and 30 fps, but this was due to a single
frame drop at its very beginning, the rest of the time it behaved like
any other mobile phone.
The variations in the vehicle movement seem to have to be blamed on the
supervision cam.
Thank you for your support!
Wolfgang Hugemann
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Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
2018-09-18 22:25 GMT+02:00, Wolfgang Hugemann : >> Please tell us more about the properties of your actual >> input file to give us a chance to help you. > > I would supply it by link, but I can't: It shows a video taken by a > surveillance camera prior to a vehicular accident, and I am obliged to > keep it secret. What I asked for was ffmpeg -i output for the file. Carl Eugen ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
> Please tell us more about the properties of your actual > input file to give us a chance to help you. I would supply it by link, but I can't: It shows a video taken by a surveillance camera prior to a vehicular accident, and I am obliged to keep it secret. It shows the video running on a computer screen, filmed by a mobile phone camera and then transferred via WhatsApp. These people have ideas ... Nevertheless, I have just read that most mobile phone cameras record VFR video and I have just proven that to be correct for my mobile phone camera. I will produce some demo videos, showing a turntable or alike (i.e. something moving or turning at constant speed), which will let me allow to check how correctly ffmpeg deals with VFR video. These videos can then be easily provided, if necessary. I will inform you about the results. Thanks for your help so far! Wolfgang Hugemann ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
2018-09-18 18:34 GMT+02:00, Wolfgang Hugemann : > ffmpeg -y -vsync 2 -i "concat:25.avi|50.avi" test.mp4 This produces an invalid file as FFmpeg does not create fully compliant vfr mp4 files (that is at least what Baptiste, the author of the relevant code, claims). Please tell us more about the properties of your actual input file to give us a chance to help you. Carl Eugen ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
2018-09-17 15:19 GMT+02:00, Wolfgang Hugemann : > ffmpeg version 4.0.2 Copyright (c) 2000-2018 the FFmpeg developers (Apart from testing current FFmpeg) Please provide ffmpeg -i output for the stream you want to analyze. Carl Eugen ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
On Tue, Sep 18, 2018 at 2:35 PM Wolfgang Hugemann wrote: > > > I would like to display the exact time where the frame has to be placed > in the timeline, such that I can calculate the speed of the passenger > car, which ran into an accident. > If the input file has the correct timestamps, then the pts function is what you need - it is not a "frame counter". You can format the output like shown at https://video.stackexchange.com/a/21907/1871 Gyan ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
> Drawtext filter already have timecode you want, and its in all in documentation. Yes, there is a timecode option for the drawtext command, creating a SMPTE, but using it you have to supply an fixed framerate, which is then used to produce the SMPTE. This is not the right aprpoach for VFR video. I consciously used the word timestamp in the subject heading. As there seems to be confusion about the terminology: I would like to display the exact time where the frame has to be placed in the timeline, such that I can calculate the speed of the passenger car, which ran into an accident. Wolfgang Hugemann ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
On 9/17/18, Wolfgang Hugemann wrote:
>> You want timecode and not pts, look at
>> drawtext manual.
>
> You may assume that I already did that.
>
> IMHO, the main issue is not drawtext, but where to get the text from.
> There only a few ready-made options, all other information has to be
> drawn from metadata provided by some other source.
>
> For example, if you want to print the SMPTE derived from VITC, you use
> something like:
>
> -vf "readvitc:drawtext=text=%%{metadata\\:lavfi.readvitc.tc_str}"
>
> Thus if you want to write a timecode / timestamp on the video, you will
> probably have to use a certain filer that can provide this information.
>
> Any ideas?
Drawtext filter already have timecode you want, and its in all in documentation.
If you really want timecode and not something else.
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Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
> You want timecode and not pts, look at
> drawtext manual.
You may assume that I already did that.
IMHO, the main issue is not drawtext, but where to get the text from.
There only a few ready-made options, all other information has to be
drawn from metadata provided by some other source.
For example, if you want to print the SMPTE derived from VITC, you use
something like:
-vf "readvitc:drawtext=text=%%{metadata\\:lavfi.readvitc.tc_str}"
Thus if you want to write a timecode / timestamp on the video, you will
probably have to use a certain filer that can provide this information.
Any ideas?
Wolfgang Hugemann
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Re: [FFmpeg-user] Timestamp for variable frame rate (VFR ) video
On 9/17/18, Wolfgang Hugemann wrote:
> I have a WhatsApp video which is definitively VFR, as can be told from
> the content (a passenger car at constant speed) and is reported by the
> new vfrdet filter.
>
> I would like to display a timecode in each frame, derived from the frame
> metadata:
>
> "drawtext=text=%%{pts}"
> yields wrong results, as it not much more than a frame counter, I guess.
>
> So it should probably be something like
>
> "drawtext=%%{metadata\\:???}
>
> but what exactly?
vfrdet filtere uses frame pts. You want timecode and not pts, look at
drawtext manual.
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