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?

Solution 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.

Solution 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

Solution 3

Extract all audio tracks / streams

This puts all audio into one file:

ffmpeg -i input.mov -map 0:a -c copy output.mov

• -map 0:a selects all audio streams only. Video and subtitles will be excluded.
• -c copy enables stream copy mode. This copies the audio and does not re-encode it. Remove -c copy if you want the audio to be re-encoded.
• Choose an output format that supports your audio format. See comparison of container formats.

---

Extract a specific audio track / stream

Example to extract audio stream #4:

ffmpeg -i input.mkv -map 0:a:3 -c copy output.m4a

• -map 0:a:3 selects audio stream #4 only (ffmpeg starts counting from 0).
• -c copy enables stream copy mode. This copies the audio and does not re-encode it. Remove -c copy if you want the audio to be re-encoded.
• Choose an output format that supports your audio format. See comparison of container formats.

---

Extract and re-encode audio / change format

Similar to the examples above, but without -c copy. Various examples:

ffmpeg -i input.mp4 -map 0:a output.mp3
ffmpeg -i input.mkv -map 0:a output.m4a
ffmpeg -i input.avi -map 0:a -c:a aac output.mka
ffmpeg -i input.mp4 output.wav

---

Extract all audio streams individually

This input in this example has 4 audio streams. Each audio stream will be output as single, individual files.

ffmpeg -i input.mov -map 0:a:0 output0.wav -map 0:a:1 output1.wav -map 0:a:2 output2.wav -map 0:a:3 output3.wav

Optionally add -c copy before each output file name to enable stream copy mode.

---

Extract a certain channel

Use the channelsplit filter. Example to get the Front Right (FR) channel from a stereo input:

ffmpeg -i stereo.wav -filter_complex "[0:a]channelsplit=channel_layout=stereo:channels=FR[right]" -map "[right]" front_right.wav

• channel_layout is the channel layout of the input. It is not automatically detected so you must provide the layout name.
• channels lists the channel(s) you want to extract.
• See ffmpeg -layouts for audio channel layout names (for channel_layout) and channel names (for channels).
• Using stream copy mode (-c copy) is not possible to use when filtering, so the audio must be re-encoded.
• See FFmpeg Wiki: Audio Channels for more examples.

---

What's the difference between -map and -vn?

ffmpeg has a default stream selection behavior that will select 1 stream per stream type (1 video, 1 audio, 1 subtitle, 1 data).

-vn is an old, legacy option. It excludes video from the default stream selection behavior. So audio, subtitles, and data are still automatically selected unless told not to with -an, -sn, or -dn.

-map is more complicated but more flexible and useful. -map disables the default stream selection behavior and ffmpeg will only include what you tell it to with -map option(s). -map can also be used to exclude certain streams or stream types. For example, -map 0 -map -0:v would include all streams except all video.

See FFmpeg Wiki: Map for more examples.

---

Errors

Invalid audio stream. Exactly one MP3 audio stream is required.

MP3 only supports 1 audio stream. The error means you are trying to put more than 1 audio stream into MP3. It can also mean you are trying to put non-MP3 audio into MP3.

WAVE files have exactly one stream

Similar to above.

Could not find tag for codec in stream #0, codec not currently supported in container

You are trying to put an audio format into an output that does not support it, such as PCM (WAV) into MP4.

Remove -c copy, choose a different output format (change the file name extension), or manually choose the encoder (such as -c:a aac).

See comparison of container formats.

Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument

This is a useless, generic error. The actual, informative error should immediately precede this generic error message.

Solution 4

Seems like you're extracting audio from a video file & downmixing to stereo channel.
To just extract audio (without re-encoding):

ffmpeg.exe -i in.mp4 -vn -c:a copy out.m4a

To extract audio & downmix to stereo (without re-encoding):

ffmpeg.exe -i in.mp4 -vn -c:a copy -ac 2 out.m4a

To generate an mp3 file, you'd re-encode audio:

ffmpeg.exe -i in.mp4 -vn -ac 2 out.mp3

Solution 5

The command line is correct and works on a valid video file. I would make sure that you have installed the correct library to work with mp3, install lame o probe with another audio codec.

Usually

ffmpeg -formats

or

ffmpeg -codecs

would give sufficient information so that you know more.

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