@mux/ai

Whether you're localizing

for global audiences or

just playing around with

multi-language content,

ffmpeg makes it super

seamless to swap or add an

audio track to your video.

In this quick guide, I'll

show you how to add a foreign

language audio track to your

videos using only command line

and no video editor required.

Let's get into it.

We're gonna have a couple use

cases here, but the first one

is going to completely replace

the English with the French.

So I have our terminal

loaded up here as well

as our two files here.

So our first one is going to

be the original video file.

Darius, you talked earlier,

and as you hear it's in

English and web component

players can be dropped

right into your application.

Perfect.

Another tutorial, did you

know that you can also,

and then we're gonna, uh,

take a look at the, the

French Dub diversion or

translated version here.

Great.

First things first

is ffmpeg, right?

And then I stands for input.

So we're gonna do our first

input, which is video mp4,

and then we're gonna do our

second input of French mp4.

Next thing, is gonna be

"-c:v" So C stands for codec

and V stands for video.

That's how we select the

video codec and we're gonna

stream copy that because

we don't need to encode it.

Next thing we're gonna map

both the streams into the

locations that we want.

So first thing is gonna

be the video stream.

So we're just gonna take

the stream index zero,

which is video mp4.

We're gonna take the

video stream of that V

and the destination index

is going to also be zero.

So the first stream, right?

Our second map, uh, parameter

here is gonna be one, which

is the one is index, one of

inputs, which is French .m4a.

The audio of that, there's

only audio, and then we're

gonna have that be in the

index zero destination.

So going along to this and

for the audio, we are just

going to also stream copy.

So if we wanted to, I

could have just done

dash C and just copy.

But for learning purposes

it's a little easier this way.

Um, replaced time .mp4,

that's gonna be our, our

output command ,right?

We're gonna run it.

Hit enter.

All right.

We'll see it here.

Done.

Let's take a listen.

Perfect.

And if we wanted to see

that it was just one.

I wanna audio stream.

You can see here there's

just one, this is the, the

video here and then the,

the audio here as well.

That's the first use case,

which is just replacing

the original audio track.

Now we're onto use case

two, which is just to add an

additional audio track and

embed that, um, in the .mp4.

So we have a replace

one here, but again,

same two assets here.

And we are going to do

something very similar.

So if ffmpeg, of course

video .mp4 is our first

and then French .m4a.

And then we are gonna map

both of the audio streams as

well as the video stream here.

"0:v" is just selecting

all video streams

or the video stream.

Um, and then we're gonna

map all audio streams on

the first input, and then

we're gonna map all audio

streams on the second input.

And then in this case,

we are just gonna stream

copy, both or all.

And we're gonna call

this "multilang," right?

So first input, second

input are selecting the

video stream, selecting the

auto stream on the first

input, selecting the audio

stream on the second input.

And we're gonna copy

all of them together.

Okay?

We're gonna run it.

Um, when we play it, it will

likely, yeah, you won't be

able to, it will kind of

merge them both together.

But for this purpose, if we

wanted to probe it and see,

you see you have both.

So in some players they

might play 'em together

like QuickTime here.

Um, but.

These have both embedded here.

Now, let's see, let's

see if we wanted to

use like something

like VLC and play it.

Darius, you talked

earlier this week

about how our iframe.

All right, you can

just hear the English.

Perfect.

But if I wanted to

select a different

audio track, hit two.

And we hear the French,

and that's use case two,

and that's how you add

foreign language audio

tracks to your videos.

Great for localization,

accessibility, AI workflows,

or just giving your

content a broader reach.