Add InputTrack.number

docs/guide/converting-media-files.md

@@ -306,8 +306,8 @@ const conversion = await Conversion.init({
 	output,
 
 	// Function gets invoked for each video track:
-	video: (videoTrack, n) => {
-		if (n > 1) {
+	video: (videoTrack) => {
+		if (videoTrack.number > 1) {
 			// Keep only the first video track
 			return { discard: true };
 		}
@@ -319,7 +319,7 @@ const conversion = await Conversion.init({
 	},
 
 	// Async functions work too:
-	audio: async (audioTrack, n) => {
+	audio: async (audioTrack) => {
 		if (audioTrack.languageCode !== 'rus') {
 			// Keep only Russian audio tracks
 			return { discard: true };

docs/guide/quick-start.md

@@ -556,14 +556,16 @@ const output = new Output(...);
 const conversion = await Conversion.init({
 	input,
 	output,
-	video: {
+	video: track => ({
 		width: 480,
 		bitrate: QUALITY_LOW,
-	},
-	audio: {
+		discard: track.number > 1, // Keep only the first video track
+	}),
+	audio: track => ({
 		numberOfChannels: 1,
 		bitrate: QUALITY_LOW,
-	},
+		discard: track.number > 1, // Keep only the first audio track
+	}),
 	trim: {
 		// Let's keep only the first 60 seconds
 		start: 0,

docs/guide/reading-media-files.md

@@ -98,6 +98,10 @@ Once you have an `InputTrack`, you can start extracting metadata from it.
 // Get a unique ID for this track in the input file:
 track.id; // => number
 
+// Get the 1-based index of this track among all tracks of the same type
+// (e.g., first video track is 1, second video track is 2, etc.):
+track.number; // => number
+
 // Check the track's type:
 track.type; // => 'video' | 'audio' | 'subtitle';