Can't get video's number of frames before processing?

I used videoReader--> read but i get "[]" in the number of frames field. i have tried using vision.VideoFileReader but it gives a less informative header ( without that kind of information)

I need the frame number BEFORE processing , not after. I am uploading the video so you could try yourselves

Answer 1

[Dinesh Iyer]

Hi Lirian,

The vision.VideoFileReader system object allows reading only one frame at a time and does not allow random access.

I tried to open this file using Windows Media Player but was unable to do so. I believe I need some additional codecs as you mentioned.

Can you try to force VideoReader to read the last frame as below

if true
  vidObj = VideoReader('swipeCut.mp4');
  read(vidObj, Inf);
  vidObj.NumberOfFrames
end

This should display the last frame read. However, this operation might take time depending upon the size of the video.

I am curious however as to why you need the total number of frames?

Hope this helps.

Dinesh

[Liran]

i want the total number of frames in order to pre-allocate arrays at the right length . these arrays will contain all sorts of data i will get from the video. i believe pre-allocating will speed things up in my program.

[PRUDHVI RAJU]

%

% Read Video

video = VideoReader('fp.avi');
%video = VideoReader('sv.mp4');

%no.of frames

nframes=video.NumberOfFrames;

[Walter Roberson]

"Note: NumberOfFrames will be removed in a future release."

Answer 2

[Dima Lisin]

Thre maybe something wrong with the header of your video file. Can you try VideoReader on a different file?

[Liran]

i have used VideoReader on other videos and it was fine of course , but i really need to do it on this video (i attached it).

The video was recorded via "Rec." app on a Samsung Note 3 with android 4.4 (Kitkat) and this app records these videos the same way.

i don't know if it helps you figure out the problem but before i downloaded new codecs i couldn't even read the file at all.