Extracting wav from mp4 while preserving the highest possible quality

I went through the documentation and I can extract a wav file from an mp4 file with the command:

ffmpeg -i my_video.mp4 output_audio.wav

However, how can I control the quality of the wav file? (e.g. say I want to preserve the quality of the original audio as much as I can)

Solution 1:

wav files typically contain uncompressed audio, and that is the default when producing a wav file using ffmpeg. So your command will already preserve the maximum quality, since there is no lossy compression (or compression of any kind) to reduce the quality.

Assuming that the original audio is compressed, you can keep the same quality without the large file size needed for uncompressed audio by just copying the original audio (without the video) to a new mp4 file:

ffmpeg -i my_video.mp4 -c copy -map 0:a output_audio.mp4

You could also re-encode it or convert it to a different audio codec, but if that codec uses lossy compression then quality will be lost.

Solution 2:

Extracting Lossless/ Lossy Audio from Videos (flv / mp4 to wav / flac / mp3) Using ffmpegversion 2.3.1 in Ubuntu 14.04

Visit: http://howto-pages.org/ffmpeg/

First of all find the basic data from the source. Open the video in VLC Player. Go to

> Tools > Codec Information 
> Stream 0 (Video/ Codec/ Resolution/ Frame rate) 
> Stream 1 (Audio/ Codec/ Channel/ Sample rate)

Consider an input file (-i), such as, input.mp4 or other files- flv, avi, ...). To remove the video (-vn) and take audio out uncompressed (output.wav) at a sample rate of 44100 Hz (-ar 44100) in pulse code modulated with signed, 16 bit, little endian (-acodec pcm_s16le) samples and 2 channels (stereo) (-ac 2) use the following command.

ffmpeg -i input.mp4 -vn -acodec pcm_s16le -ar 44100 -ac 2 output.wav

Other -acodec options are mp3 flac m4a.

-acode flac converts to 24 bit file. For 16 bit sampling it should be

ffmpeg -i input.mp4 -acodec flac -bits_per_raw_sample 16 -ar 44100 output.flac

wav and flac files are larger than the mp4 file

ac3 conversion works with -acodec 3F2R/LFE -ac 6 but creats 4 dummy tracks, as checked in Audacity.

For mp3 conversion, simply use

ffmpeg -i input.mp4 -vn -acodec mp3 -ab 320k -ar 44100 -ac 2 output.mp3

One could get more options for both input and output by trying from the list obtained from command line on the terminal

$ ffmpeg -help