Vr

LabTalk Object Type:

External Object

The vr object reads a video file and imports frame (or frames) of video to matrix object/matrixbook.

 

Methods:

Method Description
vr.Open(fname) Open a video with the specified file name (include the complete file path)

Return value:

  • 0: successful.
  • Other values: failure and the value is the standard error code.
vr.SeekFrame(frameOffset, nOrigin) Move the pointer associated with the video to a new location that is framesOffset frames from nOrigin.

nOrigin values:

  • -1: the first frame of the video
  • 0: default value. The current frame
  • 1: the last frame of the video
vr.SeekTime(msecOffset, nOrigin) Move the pointer associated with the video to a frame that locates msecOffset milliseconds after nOrigin.

nOrigin values

  • -1: the beginning of the video
  • 0: default value. The current time
  • 1: the end of the video
vr.ReadFrame([dataset]) Import a frame to the specified dataset. If the dataset is not given then the active one is used.
vr.ReadFrame(MBookName, layerIndex, objectIndex) Import a frame to the specified matrix object [MBookName]LayerIndex!"ojectIndex".
vr.ReadFrames(MBookName, frameCount, skipFrames) Import frameCount frames to the first matrixsheet of MBookName, skipping every skipFrames frames. Each frame is imported into a matrix object.
vr.Close( ) Close the video.

Return value:

  • 0: successful.
  • 1: failure.

Properties:

All Vr properties are read-only.

Property Access Description
Vr.FourCC Read only

numeric

 A number corresponding to the video's four character code.
Vr.FourCC$ Read only

string

 Four character code used to identify the video codec.
Vr.Format Read only

numeric

 OpenCV format code. See below Channel properties for extracted info:

Channels: number of channels per frame

ChannelBits: bits per channel

ChannelInt: channel data integer values

ChannelSigned: channel data signed values

Note: the format and channel properties are based on the lastly read frame.
Vr.Channels Read only

numeric

 Number of channels per frame
Vr.ChannelBits Read only

numeric

 Bits per channel
Vr.ChannelInt Read only

numeric

 Channel data integer values
Vr.ChannelSigned Read only

numeric

 Channel data signed values
Vr.FPS Read only

numeric

 Frames per second
Vr.FrameCount Read only

numeric

 Number of frames in the video file
Vr.Width Read only

numeric

 Video width in pixels
Vr.Height Read only

numeric

 Video height in pixels
Vr.PosFrames Read only

numeric

 Current position in frame
Vr.PosMSec Read only

numeric

 Current position in millisecond

Examples:

This script shows how to import 1 out of every 15 frames into the active matrixbook, each frame to a matrix object.

string vfilename$ = "C:\test.mp4";
int StepSize = 15; // skip every 15 frames

int err = vr.Open(%(vfilename$));// Open the video file.
if( 0 == err )
{
        int TotalFrames = vr.FrameCount/StepSize;
 
        // Read from beginning to the end of the file into matrix.
        vr.ReadFrames(%h, TotalFrames, StepSize);
        vr.Close();// Close the video file.
};

There is also a full example of how to import 100 frames from a video into a new matrixbook.
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