Problems obtaining the correct number of frames in video file

I am having trouble using VideoReader to determine the correct number of frames in a video file,

videoObj = VideoReader('2_1107.mpg') ; 
Warning: Unable to determine the number of frames in this file.

This workaround fails,

lastFrame = read(videoObj, inf)
Error using VideoReader/read (line 86)
The frame index requested is beyond the end of the file.

The following code returns a different number of frames each time it's run, e.g. 164, 263, 257.

videoObj = VideoReader('2_1107.mpg'); 
nFrame = 0 ;
isGood = true ;
while isGood
    nFrame = nFrame + 1 ;
    try
        thisFrame = read(videoObj, nFrame) ;
    catch
        isGood = false ;
        nFrame = nFrame - 1 ; % Don't include in the count if fails
    end
end

If VideoReader skipping or repeating frames on each pass through the file, how can I get the correct number of frames? More info: problem is present for both R2012a and R2012b run on Windows 7 (32-bit versions), video format is MPEG-2, size of the video is 65706 KB, and it's a variable frame rate file.

Answer 1

[Ryan G]

Have you tried something like this:

xyloObj = VideoReader('xylophone.mpg');
xylDat = read(xyloObj);
size(xylDat)

For this example, which is the mpg in the link provided, the final value in size is the number of frames. If this does not help, can you do a:

get(videoObj)

and post the results? I would be interested to see what data is missing.

[K E]

Your suggestion results in 10X as many frames as my counting code above! What does this mean?

videoDat = read(videoObj) ; 
Error using VideoReader/read (line 86)
Not enough memory available for 3089
 frames.

get(videoObj)
  General Settings:
    Duration = 103.08
    Name = 2_1107.mpg
    Path = G:\Test\Camera2
    Tag = 
    Type = VideoReader
    UserData = []

    Video Settings:
      BitsPerPixel = 24
      FrameRate = 0
      Height = 480
      NumberOfFrames = 3089
      VideoFormat = RGB24
      Width = 720

[Ryan G]

Are you using 64 or 32-bit MATLAB? How big is the video file? How much RAM do you have?

I have a feeling that the loop is running out of memory at different places and is thus returning different results.

EDIT: just noticed you said the file is ~65 MB. By comparison the xylo demo is 0.65 MB. However, reading in the xylo uses 32 MB! of ram. lets assume that your file uses 50X increase in memory vs file size. That would mean it uses over 3 gigs of ram to read it. Now, that ratio is probably not consistent across files being read, but I think you get the idea.

[K E]

I am using 32-bit MATLAB because I don't have the 64-bit MPEG-2 codec installed, but sounds like I need 64-bit MATLAB due to the file size. I have 8GB RAM.

[Ryan G]

32-bit will limit what you can do for video processing due to size. Technically 32-bit should be able to process that script you wrote since it's not storing anything, however, if you've already pushed your memory towards the limit (with the read command) it can quickly crap out.

Although you have 8gigs, I think you may already be aware that 32-bit will limit the amount you can access. I can't remember the exact number but it's somewhere between maybe 2-3gigs.

[K E]

Thanks so much Ryan. I really appreciate it since I am inching toward being able to use Matlab for the video analysis. An unfair follow-up: Do you happen to know about where to get a 64-bit MPEG-2 codec? Everything I found via web search & installed hasn't worked, probably because I don't know what I am doing. If this should be properly be posted as new question on Stack Overflow, please don't hesitate to say so.

[Ryan G]

I think you really have 2 options.

1) If you have access to the Computer Vision System Toolbox, this supports mpeg-2 using the command:

videoFReader = vision.VideoFileReader(FILENAME)

2) You can find a free converter to change the file from mpeg-2 to mpeg-1

see here

Depending on what you're looking to do this might be ok.

[K E]

Thanks again Ryan. You really helped me. I ended up using another free converter, ffmpeg, to convert from MPEG-2 to MPEG-1 using the following command which I could incorporate into a MATLAB script,

ffmpeg -i myMpeg2File.mpg -target ntsc-vcd -y myMpeg1File.mpg

64-bit VideoReader has no problems reading the MPEG-1 file and counts the same number of frames each time my code snippet runs. It takes a lot longer to count the frames now, so I think before it failed part way through the file.