[0:00] okay so this is how to extract audio
[0:01] from a video file and save it as an mp3
[0:04] using ffmpeg so I've got these two video
[0:07] files here and let's just play waves so
[0:10] MPV waves so you can see it's got a
[0:17] single audio track on it and let's just
[0:20] confirm that with ffmpeg so ffmpeg - I
[0:25] waves and you can see that it has one
[0:29] audio stream which is this one here so
[0:34] in order to extract that and save as an
[0:36] mp3 all we need to do is type in ffmpeg
[0:39] - I the name of our video files as waves
[0:43] and then our audio codec so - see code
[0:48] on a and we're going to use lib mp3 lame
[0:51] and now we need to decide whether we
[0:54] want a constant bitrate file or a
[0:56] variable bitrate file so in this case
[0:58] I'm just going to pick variable bitrate
[1:00] so - Q :
[1:03] a and let's go somewhere in the middle
[1:05] of the road so let's pick four and now
[1:09] all we need to do is provide an output
[1:11] file name so let's call it waves - sound
[1:14] dot mp3 and hit enter and we're done so
[1:18] if we just LS you can see that we now
[1:21] have an mp3 file and let's just play it
[1:23] with MPV
[1:31] so that's the audio extracted from our
[1:34] waves video file so what if we wanted to
[1:37] extract an audio track from a video file
[1:39] that's got multiple audio tracks so I've
[1:42] got this video cars here so let's play
[1:44] it so the first track is this weird tune
[1:52] and the second track is just another
[1:55] music track so let's quit that and let's
[1:59] just look at that with ffmpeg so ffmpeg
[2:02] - I cars so you can see that we have
[2:05] these two audio streams so all we need
[2:09] to do is modify our previous command a
[2:11] tiny bit so that we can select the audio
[2:14] track that we want to encode so let's
[2:17] just use ffmpeg to do that so ffmpeg - I
[2:22] cars and then same set up our audio
[2:25] codec so - C : a and it's going to be
[2:29] live mp3 lame and this time we're going
[2:33] to go for a constant bitrate so - B : a
[2:37] and let's set it to 320 K which is the
[2:39] highest that we can set so that's 32
[2:42] kilobytes per second so now what we need
[2:44] to do is select one of our audio tracks
[2:47] so we can do that using map so if we
[2:50] type in - map and for our second audio
[2:53] track it would be zero : - now let me
[2:57] just explain map for a second so this
[3:00] first number here and by the way all of
[3:02] these numbers start from zero in their
[3:04] scale so this first number here
[3:07] indicates the first file input - ffmpeg
[3:10] which is this file here if we had have
[3:12] actually put in another file in fact we
[3:16] can actually just do that so you can see
[3:17] so if we just use another - I waves dot
[3:26] mp4 so now we've got another input file
[3:29] so if we wanted to select an audio
[3:31] stream from this input file we would
[3:34] then set that to one so let's just go to
[3:37] the end so we'd set that to one and
[3:39] there is no second audio track within
[3:42] that file so this wouldn't work
[3:44] so we'd actually have to set it to one
[3:45] but let's just change it back to two and
[3:47] this back to zero so the first number
[3:50] indicates which file so we're selecting
[3:53] cars and the second number indicates
[3:56] which stream so zero in our caused or
[3:59] mp4 file is actually the video stream
[4:02] one is our first audio track and two is
[4:05] our second audio track so we're
[4:07] selecting the second audio track so all
[4:10] we need to do now is provide an output
[4:12] file name so let's just call it cars
[4:15] - second dot mp3 and let's hit enter
[4:20] and we're done so if we just LS and
[4:23] let's play it so NPV cars
[4:26] - second you can see that it's the
[4:31] second track play so what if we wanted
[4:36] to extract both of the audio tracks from
[4:38] that file and save them into separate
[4:40] mp3 files well we could actually do that
[4:43] in just one command line so let's just
[4:45] remove that file first so RM cars
[4:48] - second so that's gone now and if we
[4:53] just modify our previous command so
[4:55] let's just make some space and get rid
[4:56] of this because we don't need that
[4:58] anyway and all we need to do is another
[5:03] map so - map and it's the first file so
[5:07] 0 : and the first audio stream which is
[5:12] one in this particular case and just
[5:17] provide an output file name so let's
[5:19] call it cars and it's actually the first
[5:21] audio track so let's just call it first
[5:23] dot mp3
[5:29] and that's it so if we just LS now we've
[5:31] got two new mp3 files and if we play
[5:34] them so let's MPV cause - first
[5:39] [Music]
[5:41] there's the first audio track and let's
[5:44] just play the second there's the second
[5:50] audio track and that's all there is to
[5:54] it so I hope you found that useful if
[5:56] you did don't forget to subscribe and
[5:58] thanks for watching goodbye
[6:10] [Music]