How can I extract audio from video with ffmpeg?

Question

I tried the following command to extract audio from video:

ffmpeg -i Sample.avi -vn -ar 44100 -ac 2 -ab 192k -f mp3 Sample.mp3

but I get the following output

libavutil     50.15. 1 / 50.15. 1
libavcodec    52.72. 2 / 52.72. 2
libavformat   52.64. 2 / 52.64. 2
libavdevice   52. 2. 0 / 52. 2. 0
libavfilter    1.19. 0 /  1.19. 0
libswscale     0.11. 0 /  0.11. 0
libpostproc   51. 2. 0 / 51. 2. 0
SamplE.avi: Invalid data found when processing input

Can anyone help, please?

Answer 1

To extract the audio stream without re-encoding:

ffmpeg -i input-video.avi -vn -acodec copy output-audio.aac

• -vn is no video.
• -acodec copy says use the same audio stream that's already in there.

Read the output to see what codec it is, to set the right filename extension.

Answer 2

To encode a high quality MP3 or MP4 audio from a movie file (eg AVI, MP4, MOV, etc) or audio file (eg WAV), I find it's best to use -q:a 0 for variable bit rate and it's good practice to specify -map a to exclude video/subtitles and only grab audio:

ffmpeg -i sample.avi -q:a 0 -map a sample.mp3

If you want to extract a portion of audio from a video use the -ss option to specify the starting timestamp, and the -t option to specify the encoding duration, eg from 3 minutes and 5 seconds in for 45 seconds:

ffmpeg -i sample.avi -ss 00:03:05 -t 00:00:45.0 -q:a 0 -map a sample.mp3

• The timestamps need to be in HH:MM:SS.xxx format or in seconds.

• If you don't specify the -t option it will go to the end.

• You can use the -to option instead of the -t option, if you want to specify the range, eg for 45 seconds: 00:03:05 + 45 = 00:03:50

Working example:

1. Download ffmpeg
2. Open a Command Prompt (Start > Run > CMD) or on a Mac/Linux open a Terminal
3. cd (the change directory command) to the directory with the ffmeg.exe, as depicted.
4. Issue your command and wait for the output file (or troubleshoot any errors)

Windows

Mac/Linux