readme and comments

index.js

@@ -280,15 +280,15 @@ const fileType = input => {
 	}
 
 	// File Type Box (https://en.wikipedia.org/wiki/ISO_base_media_file_format)
-	// It is not required to be first, but is recommended to, almost all mpeg4 files start with ftyp box
-	// `ftyp` box must contain brand identifier, which must consist of ISO 8859-1 printable characters
-	// Here we check for 8859-1 printable characters + 1 unprintable for check simplicity
-	// They all can have mime video/mp4 except application/mp4 special case which is hard to detect.
-	// For some cases we're specific, everything else falls to video/mp4 with mp4 extension.
+	// It is not required to be first, but is recommended to, almost all ISO base media files start with ftyp box
+	// `ftyp` box must contain brand major identifier, which must consist of ISO 8859-1 printable characters
+	// Here we check for 8859-1 printable characters(for check simplicity, it is a mask which also catches one non-printable character).
 	if (
 		check([0x66, 0x74, 0x79, 0x70], {offset: 4}) && // `ftyp`
 		(buf[8] & 0x60) !== 0x00 && (buf[9] & 0x60) !== 0x00 && (buf[10] & 0x60) !== 0x00 && (buf[11] & 0x60) !== 0x00 // Brand major
 	) {
+		// They all can have mime video/mp4 except application/mp4 special case which is hard to detect.
+		// For some cases we're specific, everything else falls to video/mp4 with mp4 extension.
 		const brandMajor = buf.toString('utf8', 8, 12);
 		switch (brandMajor) {
 			case 'mif1':

readme.md

@@ -142,7 +142,6 @@ Type: [`stream.Readable`](https://nodejs.org/api/stream.html#stream_class_stream
 - [`7z`](https://en.wikipedia.org/wiki/7z)
 - [`dmg`](https://en.wikipedia.org/wiki/Apple_Disk_Image)
 - [`mp4`](https://en.wikipedia.org/wiki/MPEG-4_Part_14#Filename_extensions)
-- [`m4v`](https://en.wikipedia.org/wiki/M4V)
 - [`mid`](https://en.wikipedia.org/wiki/MIDI)
 - [`mkv`](https://en.wikipedia.org/wiki/Matroska)
 - [`webm`](https://en.wikipedia.org/wiki/WebM)
@@ -222,6 +221,15 @@ Type: [`stream.Readable`](https://nodejs.org/api/stream.html#stream_class_stream
 - [`alias`](https://en.wikipedia.org/wiki/Alias_%28Mac_OS%29) - macOS Alias file
 - [`voc`](https://wiki.multimedia.cx/index.php/Creative_Voice) - Creative Voice File
 - [`ac3`](https://www.atsc.org/standard/a522012-digital-audio-compression-ac-3-e-ac-3-standard-12172012/) - ATSC A/52 Audio File
+- [`3g2`](https://en.wikipedia.org/wiki/3GP_and_3G2#3G2) - Multimedia container format defined by the 3GPP2 for 3G CDMA2000 multimedia services
+- [`m4a`](https://en.wikipedia.org/wiki/M4A) - Audio-only MPEG-4 files
+- [`m4b`](https://en.wikipedia.org/wiki/M4B) - Audiobook and podcast MPEG-4 files, which also contain metadata including chapter markers, images, and hyperlinks
+- [`m4p`](https://en.wikipedia.org/wiki/MPEG-4_Part_14#Filename_extensions) - MPEG-4 files with audio streams encrypted by FairPlay Digital Rights Management as were sold through the iTunes Store
+- [`m4v`](https://en.wikipedia.org/wiki/M4V) -  MPEG-4 Visual bitstreams
+- [`f4a`](https://en.wikipedia.org/wiki/Flash_Video) - Audio-only ISO base media file format used by Adobe Flash Player
+- [`f4b`](https://en.wikipedia.org/wiki/Flash_Video) - Audiobook and podcast ISO base media file format used by Adobe Flash Player
+- [`f4p`](https://en.wikipedia.org/wiki/Flash_Video) - ISO base media file format protected by Adobe Access DRM used by Adobe Flash Player
+- [`f4v`](https://en.wikipedia.org/wiki/Flash_Video) - ISO base media file format used by Adobe Flash Player
 
 *SVG isn't included as it requires the whole file to be read, but you can get it [here](https://github.com/sindresorhus/is-svg).*