add concurrency to cli and readme

lib/cli.js

@@ -15,7 +15,7 @@ module.exports = async (argv) => {
     .option('-d, --transition-duration <duration>', 'duration of transition to use in ms', parseInt, 500)
     .option('-T, --transitions <file>', 'json file to load transitions from')
     .option('-f, --frame-format <format>', 'format to use for temp frame images', /^(raw|png|jpg)$/i, 'raw')
-    .option('-c, --concurrency <number>', 'concurrency to process videos', parseInt, 4)
+    .option('-c, --concurrency <number>', 'number of videos to process in parallel', parseInt, 4)
     .option('-C, --no-cleanup-frames', 'disables cleaning up temp frame images')
     .parse(argv)
 
@@ -35,6 +35,7 @@ module.exports = async (argv) => {
 
     await concat({
       log: console.log,
+      concurrency: program.concurrency,
 
       videos,
       output: program.output,

readme.md

@@ -45,6 +45,7 @@ npm install -g ffmpeg-concat
     -d, --transition-duration <duration>  duration of transition to use in ms (default: 500)
     -T, --transitions <file>              json file to load transitions from
     -f, --frame-format <format>           format to use for temp frame images (default: raw)
+    -c, --concurrency <number>            number of videos to process in parallel (default: 4)
     -C, --no-cleanup-frames               disables cleaning up temp frame images
     -h, --help                            output usage information
 
@@ -189,6 +190,13 @@ Default: `true`
 
 By default, we cleanup temporary frame images. Set this to `false` if you need to debug intermediate results.
 
+##### concurrency
+
+Type: `Number`
+Default: `4`
+
+Max number of videos to process in parallel.
+
 ##### log
 
 Type: `Function`