From dbaf46b0be3549b0324dd804f86a52e4e829e1a8 Mon Sep 17 00:00:00 2001
From: Adam Hunter <arhunter@gmail.com>
Date: Fri, 8 Nov 2019 10:43:02 -0500
Subject: [PATCH 1/2] Adds forceSARRatio option to add 'scale=iw*sar:ih' to
 video-filter list.

---
 index.js  | 24 ++++++++++++++++++++++--
 readme.md |  7 +++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/index.js b/index.js
index 79c3a7e..591c509 100644
--- a/index.js
+++ b/index.js
@@ -6,6 +6,15 @@ const probe = require('ffmpeg-probe')
 
 const noop = () => { }
 
+const applyVFList = (cmd, list) => {
+  if (!Array.isArray(list) || list.length === 0) {
+    return
+  }
+  cmd.outputOptions([
+    '-vf', list.join(',')
+  ])
+}
+
 module.exports = async (opts) => {
   const {
     log = noop,
@@ -19,7 +28,8 @@ module.exports = async (opts) => {
     offsets,
     fps,
     numFrames,
-    ffmpegPath
+    ffmpegPath,
+    forceSARRatio
   } = opts
 
   if (!input) throw new Error('missing required input')
@@ -34,10 +44,18 @@ module.exports = async (opts) => {
   const cmd = ffmpeg(input)
     .on('start', (cmd) => log({ cmd }))
 
+  const vfList = []
+
+  if (Boolean(forceSARRatio)) {
+    vfList.push('scale=iw*sar:ih')
+  }
+
   if (timestamps || offsets) {
     const folder = outputPath.dir
     const filename = outputPath.base
 
+    applyVFList(cmd, vfList)
+
     return new Promise((resolve, reject) => {
       cmd
         .on('end', () => resolve(output))
@@ -60,8 +78,8 @@ module.exports = async (opts) => {
 
       cmd.outputOptions([
         '-vsync', 'vfr',
-        '-vf', `select=not(mod(n\\,${nthFrame}))`
       ])
+      vfList.push(`select=not(mod(n\\,${nthFrame}))`)
     }
 
     if (outputPath.ext === '.raw') {
@@ -70,6 +88,8 @@ module.exports = async (opts) => {
       ])
     }
 
+    applyVFList(cmd, vfList)
+
     return new Promise((resolve, reject) => {
       cmd
         .on('end', () => resolve(output))
diff --git a/readme.md b/readme.md
index ccbe5c3..6648dfa 100644
--- a/readme.md
+++ b/readme.md
@@ -113,6 +113,13 @@ Type: `String`
 
 Specify a path for the ffmpeg binary.
 
+##### forceSARRatio
+
+Type: `Boolean`
+Default: false
+
+Force ffmpeg to use `scale=iw*sar:ih` video filter to use SampleAspectRatio as aspect ratio for thumbnail images.
+
 ## Related
 
 - [ffmpeg-extract-frame](https://github.com/transitive-bullshit/ffmpeg-extract-frame) - Extracts a single frame from a video.

From 2c77d24fd63cc53be99ec6293b04472bc8292523 Mon Sep 17 00:00:00 2001
From: Adam Hunter <arhunter@gmail.com>
Date: Fri, 24 Apr 2020 09:41:57 -0400
Subject: [PATCH 2/2] Adds startOffset and duration options Updates README with
 new parameter intructions Fixes bug where probe may return undefined for
 number of frames Adds me as contributor to package.json

---
 index.js     | 18 ++++++++++++++++--
 package.json |  8 +++++++-
 readme.md    | 14 ++++++++++++++
 3 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/index.js b/index.js
index 591c509..2640dfc 100644
--- a/index.js
+++ b/index.js
@@ -29,7 +29,9 @@ module.exports = async (opts) => {
     fps,
     numFrames,
     ffmpegPath,
-    forceSARRatio
+    forceSARRatio,
+    startOffset,
+    duration,
   } = opts
 
   if (!input) throw new Error('missing required input')
@@ -49,6 +51,14 @@ module.exports = async (opts) => {
   if (Boolean(forceSARRatio)) {
     vfList.push('scale=iw*sar:ih')
   }
+  
+  if (startOffset) {
+    cmd.addInputOptions(["-ss", parseInt(startOffset, 10)]);
+  }
+
+  if (duration) {
+    cmd.addInputOptions(["-t", parseInt(duration, 10)]);
+  }
 
   if (timestamps || offsets) {
     const folder = outputPath.dir
@@ -73,7 +83,10 @@ module.exports = async (opts) => {
       ])
     } else if (numFrames) {
       const info = await probe(input)
-      const numFramesTotal = parseInt(info.streams[0].nb_frames)
+      let numFramesTotal = parseInt(info.streams[0].nb_frames)
+      if (isNaN(numFramesTotal)) {
+        numFramesTotal = Math.ceil((info.duration / 1000) * info.fps);
+      }
       const nthFrame = (numFramesTotal / numFrames) | 0
 
       cmd.outputOptions([
@@ -88,6 +101,7 @@ module.exports = async (opts) => {
       ])
     }
 
+
     applyVFList(cmd, vfList)
 
     return new Promise((resolve, reject) => {
diff --git a/package.json b/package.json
index 5fba57c..091b465 100644
--- a/package.json
+++ b/package.json
@@ -1,10 +1,16 @@
 {
   "name": "ffmpeg-extract-frames",
-  "version": "2.0.2",
+  "version": "2.0.3",
   "description": "Extracts frames from a video.",
   "main": "index.js",
   "repository": "transitive-bullshit/ffmpeg-extract-frames",
   "author": "Travis Fischer <travis@automagical.ai>",
+  "contributors": [
+    {
+      "name" : "Adam Hunter"
+      , "url" : "https://github.com/adamrhunter"
+    }
+  ],
   "license": "MIT",
   "reveal": true,
   "scripts": {
diff --git a/readme.md b/readme.md
index 6648dfa..b201dd5 100644
--- a/readme.md
+++ b/readme.md
@@ -4,6 +4,8 @@
 
 [![NPM](https://img.shields.io/npm/v/ffmpeg-extract-frames.svg)](https://www.npmjs.com/package/ffmpeg-extract-frames) [![Build Status](https://travis-ci.com/transitive-bullshit/ffmpeg-extract-frames.svg?branch=master)](https://travis-ci.com/transitive-bullshit/ffmpeg-extract-frames) [![JavaScript Style Guide](https://img.shields.io/badge/code_style-standard-brightgreen.svg)](https://standardjs.com)
 
+> This is a fork from the orginal (which seemed to have stopped accpeting PRs).  I've added some additional parameters/options to pass into the process (and fixed some bugs with frame offsets)
+
 ## Install
 
 ```bash
@@ -120,6 +122,18 @@ Default: false
 
 Force ffmpeg to use `scale=iw*sar:ih` video filter to use SampleAspectRatio as aspect ratio for thumbnail images.
 
+##### startOffset
+
+Type: `Number`
+
+Start the frame extraction from the given offset (in seconds)
+
+##### duration
+
+Type: `Number`
+
+Run the extraction for only the given duration (in seconds)
+
 ## Related
 
 - [ffmpeg-extract-frame](https://github.com/transitive-bullshit/ffmpeg-extract-frame) - Extracts a single frame from a video.