TravisMullen/video-integrity.js

## video-integrity.js
const MODULE_NAME = 'Calculate positions offset value for each frame provided.'

/**
 * Convert time into seconds which is the smallest increment of time encoded into the video.
 * @param  {string} time Time in the format of HH:MM:SS using colons as the delimiter.
 * @return {number}      Time converted to seconds.
 */
const seconds = time => {
  const [hours,minutes,seconds] = time.split(':')
  return parseInt((((parseInt(hours) * 60) + parseInt(minutes)) * 60) + parseInt(seconds))
}
// const seconds = (minutes,seconds) => (minutes*60) + seconds

/**
 * Determine the difference between embedded timestamp and actually playback time from video display.
 * @param  {string} videoindex Time of video playback position indicated by the software streaming the video file.
 * @param  {string} timestamp  Time of video as indicated by the timestamp encoded into the visual frame.
 * @return {number}            Offset between the file's playback video time and the encoded time from the original video.
 */
const marker = (videoindex,timestamp) => timestamp - videoindex

/** Calculate position offset value from a single frame. */
const calculate = (videoindex,timestamp) => (
  marker(
    seconds(videoindex),
    seconds(timestamp)
  )
)

/** Calculate an series of positions offset values from an arrays of frames. */
const calculateAll = arr => {
  const offsets = []
  console.time(MODULE_NAME)
  for (item of arr) {
    console.count('calculate frame')
    const [videoindex,timestamp] = item
    console.log(`video tracking index: ${videoindex} s, encoded timestamp: ${timestamp} s`)
    console.log(calculate(videoindex,timestamp))
  }
  console.timeEnd(MODULE_NAME)
}

/**
 * @example
 *
 * The following data set is taken from body-worn camera of:
 * Deputy J. McClellan <8926> of the Orange County Sheriff's Office ("OCSO")
 * from an arrest made on April 1, 2019.
 *
 * The OCSO Records Identification Section ("Records Section") provided a video
 * which attempts to hide that the Deputy deactivated his body-worn camera.
 *
 * The Records Section attempts to obscure that two clips are pasted together
 * by claiming a necessary full-frame redaction, instead of redacting only a portion of the frame.
 * Generally, it is common practice to use a blur filter so that if a grouping of frames is removed
 * it can allows for the human eye can to detect any clipping or jumping. It's a good faith best practice.
 * In this case, the first section of full-frame redaction ("the point of compromise")
 * does not implement the blur filter, which is in fact used later on in the same video,
 * but instead said section implements a black box which additionally obscures the video's native encoded timestamp.
 *
 * This algorithm is designed to be easily reproducible by anyone whom
 * has a copy of the forged video record by stopping the playback window on any frame
 * before or after the point of compromise occurs, and making a relative comparison of the two value for each frame.
 *
 * The following array consists of eight (8) random frames before the point of compromise starts,
 * and ten (10) random frames after the point of compromise ends.
 *
 */

calculateAll([
  [ // frame 1
    '0:0:0',    // time of video playback of the file.
    '06:44:16'  // time as encoded into video stream.
  ],
  ['0:0:3', '06:44:19'],
  ['0:0:14', '06:44:30'],
  ['0:0:27', '06:44:43'],
  ['0:1:20', '06:45:36'],
  ['0:1:27', '06:45:44'],
  ['0:2:31', '06:46:48'],
  ['0:3:03', '06:47:19'],
  // ** redaction occurs masking encoded timestamps ** //
  ['0:15:54', '07:00:09'],
  ['0:17:13', '07:01:28'],
  ['0:18:42', '07:02:57'],
  ['0:19:26', '07:03:41'],
  ['0:21:36', '07:05:51'],
  ['0:23:29', '07:07:44'],
  ['0:25:05', '07:09:20'],
  ['0:26:27', '07:10:43'],
  ['0:30:17', '07:14:32'],
  ['0:31:02', '07:15:17'],
])
	const MODULE_NAME = 'Calculate positions offset value for each frame provided.'

	/**
	* Convert time into seconds which is the smallest increment of time encoded into the video.
	* @param {string} time Time in the format of HH:MM:SS using colons as the delimiter.
	* @return {number} Time converted to seconds.
	*/
	const seconds = time => {
	const [hours,minutes,seconds] = time.split(':')
	return parseInt((((parseInt(hours) * 60) + parseInt(minutes)) * 60) + parseInt(seconds))
	}
	// const seconds = (minutes,seconds) => (minutes*60) + seconds

	/**
	* Determine the difference between embedded timestamp and actually playback time from video display.
	* @param {string} videoindex Time of video playback position indicated by the software streaming the video file.
	* @param {string} timestamp Time of video as indicated by the timestamp encoded into the visual frame.
	* @return {number} Offset between the file's playback video time and the encoded time from the original video.
	*/
	const marker = (videoindex,timestamp) => timestamp - videoindex

	/** Calculate position offset value from a single frame. */
	const calculate = (videoindex,timestamp) => (
	marker(
	seconds(videoindex),
	seconds(timestamp)
	)
	)

	/** Calculate an series of positions offset values from an arrays of frames. */
	const calculateAll = arr => {
	const offsets = []
	console.time(MODULE_NAME)
	for (item of arr) {
	console.count('calculate frame')
	const [videoindex,timestamp] = item
	console.log(`video tracking index: ${videoindex} s, encoded timestamp: ${timestamp} s`)
	console.log(calculate(videoindex,timestamp))
	}
	console.timeEnd(MODULE_NAME)
	}

	/**
	* @example
	*
	* The following data set is taken from body-worn camera of:
	* Deputy J. McClellan <8926> of the Orange County Sheriff's Office ("OCSO")
	* from an arrest made on April 1, 2019.
	*
	* The OCSO Records Identification Section ("Records Section") provided a video
	* which attempts to hide that the Deputy deactivated his body-worn camera.
	*
	* The Records Section attempts to obscure that two clips are pasted together
	* by claiming a necessary full-frame redaction, instead of redacting only a portion of the frame.
	* Generally, it is common practice to use a blur filter so that if a grouping of frames is removed
	* it can allows for the human eye can to detect any clipping or jumping. It's a good faith best practice.
	* In this case, the first section of full-frame redaction ("the point of compromise")
	* does not implement the blur filter, which is in fact used later on in the same video,
	* but instead said section implements a black box which additionally obscures the video's native encoded timestamp.
	*
	* This algorithm is designed to be easily reproducible by anyone whom
	* has a copy of the forged video record by stopping the playback window on any frame
	* before or after the point of compromise occurs, and making a relative comparison of the two value for each frame.
	*
	* The following array consists of eight (8) random frames before the point of compromise starts,
	* and ten (10) random frames after the point of compromise ends.
	*
	*/

	calculateAll([
	[ // frame 1
	'0:0:0', // time of video playback of the file.
	'06:44:16' // time as encoded into video stream.
	],
	['0:0:3', '06:44:19'],
	['0:0:14', '06:44:30'],
	['0:0:27', '06:44:43'],
	['0:1:20', '06:45:36'],
	['0:1:27', '06:45:44'],
	['0:2:31', '06:46:48'],
	['0:3:03', '06:47:19'],
	// redaction occurs masking encoded timestamps //
	['0:15:54', '07:00:09'],
	['0:17:13', '07:01:28'],
	['0:18:42', '07:02:57'],
	['0:19:26', '07:03:41'],
	['0:21:36', '07:05:51'],
	['0:23:29', '07:07:44'],
	['0:25:05', '07:09:20'],
	['0:26:27', '07:10:43'],
	['0:30:17', '07:14:32'],
	['0:31:02', '07:15:17'],
	])