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I have a small video file which ffprobe describes as:- 

Input #0, avi, from 'sample.avi': 
Metadata: 
encoder : Lavf55.12.100 
Duration: 00:00:35.00, start: 0.000000, bitrate: 546 kb/s 
Stream #0:0: Video: msmpeg4v3 (MP43 / 0x3334504D), yuv420p, 320x240, 
             506 kb/s, 200 fps, 200 tbr, 200 tbn, 200 tbc

As the video is 35 sec. long, and with 200 fps frame rate, I expect there would be (35 x 200) = 7000 frames in the video.

If I use ffmpeg to actually extract frame images from the video, I actually get 6999 images (near enough, I suppose). The command I use for this is:-

c:\> ffmpeg -i sample.avi  -f image2 -c:v png Img%%04d.png

Note: the '%%' is required when the command is run from the WinXP CLI

However, using the command:-

c:\> ffprobe -select_streams v -show_frames sample.avi > frames.lis

and counting how many [FRAME] items are in frames.lis gives a frame count of 1023 frames and not 7000.

Any explanation?

Here's a link to a very similar file that behaves in the same way (~7MB):

http://www.filedropper.com/sample_65

Left-click on the "Download This File" image on the page.

I'm using 17APR2014 static Win32 build of ffmpeg 'ffprobe' under WinXP-SP3.

If there's another way to do it, I'm primarily trying to build a table of "frame number" versus "time" for a series of video files for use in another application.

Thanks.

Skeeve
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1 Answers1

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Is there a reason 1023 cannot be correct? The fps you are referring to is header info and so it can easily be incorrect.

In the output of the png's, are there a lot of duplicate frames? Ffmpeg may be doing you a favor and outputting copied frames to match the reported fps and duration.

Using ffprobe is my recommended solution. It's difficult to be certain 100% of the time unless you are actually decoding the frames and counting. So using -count_frames or -show_frames should give you the number you are looking for.

Note: There is no guarantee that the duration listed is accurate.

dstob
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