Golang : Save webcamera frames to video file

This tutorial will show you how to save image frames captured by a web camera and store the images into a video file. The code below is a simple command line program that will activate the web camera with Go-OpenCV, grab the image frame one at a time, store the image into a video file continuously in a for loop. The loop will only be broken after the ESC key is pressed.

To build the code below, first install the OpenCV library.

On MacOSX, use homebrew to:

>brew install homebrew/science/opencv

and follow by

go get github.com/lazywei/go-opencv

Build the code and execute it with a target file name.

Here you go!

saveWebCam2File.go

---

 package main

 /*
 #include <stdio.h>
 #include <unistd.h>
 #include <termios.h>
 char getch(){
 char ch = 0;
 struct termios old = {0};
 fflush(stdout);
 if( tcgetattr(0, &old) < 0 ) perror("tcsetattr()");
 old.c_lflag &= ~ICANON;
 old.c_lflag &= ~ECHO;
 old.c_cc[VMIN] = 1;
 old.c_cc[VTIME] = 0;
 if( tcsetattr(0, TCSANOW, &old) < 0 ) perror("tcsetattr ICANON");
 if( read(0, &ch,1) < 0 ) perror("read()");
 old.c_lflag |= ICANON;
 old.c_lflag |= ECHO;
 if(tcsetattr(0, TCSADRAIN, &old) < 0) perror("tcsetattr ~ICANON");
 return ch;
 }
 */
 import "C"
 // stackoverflow.com/questions/14094190/golang-function-similar-to-getchar

 import (
 "fmt"
 "github.com/lazywei/go-opencv/opencv"
 "math/rand"
 "os"
 "time"
 )

 func main() {

 if len(os.Args) != 2 {
 fmt.Printf("Usage : %s <save to filename>\n", os.Args[0])
 os.Exit(0)
 }

 videoFileName := os.Args[1]

 // activate webCamera
 webCamera := opencv.NewCameraCapture(opencv.CV_CAP_ANY) // autodetect

 if webCamera == nil {
 panic("Unable to open camera")
 }

 // !! NEED TO CHECK IF YOUR OS HAS THE CODECS INSTALLED BEFORE SELECTING THE CODEC !!
 // !! OTHERWISE, YOU WILL GET A VERY SMALL & CORRUPT VIDEO FILE !!

 // see http://www.fourcc.org/codecs.php for other possible combinations
 // opencv.FOURCC('p', 'i', 'm', '1') // MPEG-1 codec
 // opencv.FOURCC('m', 'j', 'p', 'g') // motion-jpeg codec
 // opencv.FOURCC('m', 'p', '4', '2') // MPEG-4.2 codec
 // opencv.FOURCC('d', 'i', 'v', '3') // MPEG-4.3 codec
 // opencv.FOURCC('m', 'p', '4', 'v') // MPEG-4 codec
 // opencv.FOURCC('u', '2', '6', '3') // H263 codec
 // opencv.FOURCC('i', '2', '6', '3') // H263I codec
 // opencv.FOURCC('f', 'l', 'v', '1') // FLV1 codec

 // codec := opencv.CV_FOURCC_PROMPT // Windows only. Prompt for codec selection
 // codec := int(webCamera.GetProperty(opencv.CV_CAP_PROP_FOURCC)) -- won't work on my Mac

 codec := int(opencv.FOURCC('m', 'p', '4', 'v')) // must be lower case, upper case will screw the file...

 fps := float32(30) // 30 frames per second
 //fps := float32(webCamera.GetProperty(opencv.CV_CAP_PROP_POS_FRAMES))
 frameWidth := int(webCamera.GetProperty(opencv.CV_CAP_PROP_FRAME_WIDTH))
 frameHeight := int(webCamera.GetProperty(opencv.CV_CAP_PROP_FRAME_HEIGHT))
 isColor := 1 // 0 = false(grayscale), 1 = true -- for Windows only I think

 // !! IMPORTANT : Remember to set the type to frameWidth and frameHeight for
 // for both input(src) and output(destination) as the same
 // otherwise, you gonna get this error message -
 // [OpenCV Error: Assertion failed (dst.data == dst0.data) in cvCvtColor,]

 // Just a note, you still can resize the frames before writing to file if you want

 // for more info, read http://docs.opencv.org/trunk/dd/d9e/classcv_1_1VideoWriter.html
 videoFileWriter := opencv.NewVideoWriter(videoFileName, codec, fps, frameWidth, frameHeight, isColor)

 // uncomment to see your own recording
 // win := opencv.NewWindow("Go-OpenCV record webcam to file")

 fmt.Println("Press ESC key to to quit")

 // go rountine to intercept ESC key
 // since opencv.WaitKey does not work on my Mac :(

 go func() {
 key := C.getch()
 fmt.Println()
 fmt.Println("Cleaning up ...")
 if key == 27 {
 //videoFileWriter.Release()  -- optional
 webCamera.Release()
 //win.Destroy() -- uncomment to see your own recording
 fmt.Println("Play", videoFileName, "with a video player to see the result. Remember, no audio!")
 os.Exit(0)
 }
 }()

 // recording in progress ticker. From good old DOS days.
 ticker := []string{
 "-",
 "\\",
 "/",
 "|",
 }
 rand.Seed(time.Now().UnixNano())

 for {

 if webCamera.GrabFrame() {

 imgFrame := webCamera.RetrieveFrame(1)

 if imgFrame != nil {
 //win.ShowImage(imgFrame) -- uncomment to see your own recording

 // save frame to video
 frameNum := videoFileWriter.WriteFrame(imgFrame)

 if frameNum > 0 {
 fmt.Printf("\rRecording is live now. Wave to your webcamera! [%v]", ticker[rand.Intn(len(ticker)-1)])
 }

 //if opencv.WaitKey(1) >= 0 {  -- won't work on Mac! :(
 // os.Exit(0)
 //}

 }

 }

 }

 }

---

Sample output:

>./saveWebCam2File test.mp4

Press ESC key to to quit

Recording now. Wave to your webcamera! [/]

Cleaning up ...

Cleaned up camera.

Play test.mp4 to see the result. Remember, no audio!

Happy cam whoring!

References:

https://www.socketloop.com/tutorials/golang-overwrite-previous-output-with-count-down-timer

http://www.fourcc.org/codecs.php

https://socketloop.com/tutorials/golang-randomly-pick-an-item-from-a-slice-array-example

http://stackoverflow.com/questions/14094190/golang-function-similar-to-getchar