wiki:audio types

Audio Types

FFmpeg can read various raw audio types (sample formats) and demux or mux them into different containers (formats). For example, you can read and write raw PCM audio into a WAV container. Or convert between raw types.

Sample Formats

Raw audio in FFmpeg can take several different "forms", i.e. sample formats. For instance:

  • s means "signed" (for the integer representations), u would mean "unsigned"
  • 16 means 16 Bits per sample
  • le means "little endian" coding for the samples

You can see a list of supported sample formats by inspecting the ffmpeg -formats output:

$ ffmpeg -formats | grep PCM
 DE alaw            PCM A-law
 DE f32be           PCM 32-bit floating-point big-endian
 DE f32le           PCM 32-bit floating-point little-endian
 DE f64be           PCM 64-bit floating-point big-endian
 DE f64le           PCM 64-bit floating-point little-endian
 DE mulaw           PCM mu-law
 DE s16be           PCM signed 16-bit big-endian
 DE s16le           PCM signed 16-bit little-endian
 DE s24be           PCM signed 24-bit big-endian
 DE s24le           PCM signed 24-bit little-endian
 DE s32be           PCM signed 32-bit big-endian
 DE s32le           PCM signed 32-bit little-endian
 DE s8              PCM signed 8-bit
 DE u16be           PCM unsigned 16-bit big-endian
 DE u16le           PCM unsigned 16-bit little-endian
 DE u24be           PCM unsigned 24-bit big-endian
 DE u24le           PCM unsigned 24-bit little-endian
 DE u32be           PCM unsigned 32-bit big-endian
 DE u32le           PCM unsigned 32-bit little-endian
 DE u8              PCM unsigned 8-bit

These represent all the built-in raw audio sample formats.

Reading and Writing Raw Audio

FFmpeg can take input of raw audio types by specifying the type on the command line. For instance, to convert a "raw" audio type to a ".wav" file:

ffmpeg -f s32le input_filename.raw output.wav

You can specify number of channels, etc. as well, ex:

ffmpeg -f u16le -ar 44100 -ac 1 -i input.raw output.wav

The default for muxing into WAV files is pcm_s16le. You can change it by specifying the audio codec and using the WAV file extension:

ffmpeg -i input -c:a pcm_s32le output.wav

which will create a WAV file containing audio with that codec (not a raw file). There are also other containers that can contain raw audio packets, like pcm_bluray.

If you want to create a raw file, don't use the WAV format, but the raw one (as seen in the table above), e.g. s16le, and the appropriate audio codec:

ffmpeg -i input -f s16le -c:a pcm_s16le output.raw

You can determine the format of a file, ex

$ ffmpeg -i Downloads/BabyElephantWalk60.wav 
ffmpeg version ...
Input #0, wav, from 'Downloads/BabyElephantWalk60.wav':
  Duration: 00:01:00.00, bitrate: 352 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 22050 Hz, mono, s16, 352 kb/s

The pcm_s16le tells you what format your audio is in. And that happens to be a common format.

Last modified 3 years ago Last modified on Mar 21, 2021, 3:19:04 AM
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