Raw audio: Difference between revisions

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RAW Audio is an audio file format for storing uncompressed audio in raw form. Comparable to WAV or AIFF in size, RAW Audio file does not include any header information (sampling rate, bit depth, endian, or number of channels)
RAW Audio is an audio file format for storing uncompressed audio in raw form. Comparable to WAV or AIFF in size, RAW Audio file does not include any header information (sampling rate, bit depth, endian, or number of channels)


==convert an mp3 to raw==
Using
* [http://ffmpeg.org/ ffmpeg]: " A complete, cross-platform solution to record, convert and stream audio and video." 
* [http://sox.sourceforge.net/ Sox]: the Swiss Army knife of sound processing programs


cat img.png > audio.raw
aplay -f S8 -c 1 -r 4000 audio.raw


<code>-f</code> sample format / bit rate:  
Find out the properties of the audio file with ffmpeg
* 8bit: S8 U8
ffmpeg -i file.mp3
* 16bit: S16_LE S16_BE U16_LE U16_BE
  sox -V file.wav
* 24bit: S24_LE S24_BE U24_LE U24_BE
* 32bit: S32_LE S32_BE U32_LE U32_BE


<code>-c</code>: channel number
Sox has no handler for mp3 formate, hence you have need to convert from mp3 to wav, ffmpeg does it quickly and well
ffmpeg -i file.mp3 -acodec pcm_s16le -ar 44100 file.wav


<code>-r</code>: sample rate. 4000 Hz is the minimum allowed by aplay. 44100Hz is the default sample rate for CDs
* <code>-acodec pcm_s16le</code>: audio codec is PCM signed 16bit
* <code>-ar 44100</code>: audio rate 44.1kHz


Sox: display information on the wav file
sox -V file.wav


Sox: convert the wav file to raw
sox file.wav -b 16 -c 1 -r 44100 -t raw file.raw
* <code>-b 16</code> bit-rate
* <code>-c 1</code> number of channels
* <code>-r 44100</code>sampling rate
* <code>-t raw</code>target raw


If we want to '''write the result of playing the raw file into an audio file with a head''', like a wav we can use [http://sox.sourceforge.net/ Sox] for the job
play (sox): play back the raw file at same bit-rate and sample-rate
play -b 16 --endian little -e signed -r 44100 -c 1 Zong3.raw
* <code>--endian little</code>: "specify whether the byte-order of the audio data is, respectively, `little endian'... Endianness  applies only to data encoded as floating-point, or as signed  or unsigned  integers of 16 or more bits.  It is often necessary to specify one of these options for headerless files"
* <code>-e signed</code> encoding. Signed is commonly used with a 16 or  24  -bit  encoding  size.


sox -r 4000 -b 8 -c 1 -e signed-integer pg_0018.raw pg_0018.wav


Notice that I have to indicate the same audio parameters:
Same thing but with aplay:
aplay -f S16_LE -c 1 -r 44100 Zong3.raw
* <code>-f</code> sample forma+bit rate+endian: 
** 8bit: S8 U8
** 16bit: S16_LE S16_BE U16_LE U16_BE
** 24bit: S24_LE S24_BE U24_LE U24_BE
** 32bit: S32_LE S32_BE U32_LE U32_BE
*<code>-c</code>: channel number
*<code>-r</code>: sample rate. 4000 Hz is the minimum allowed by aplay. 44100Hz is the default sample rate for CDs


<code>-r 4000</code> sample sate
== convert image to raw audio==


<code>-b 8</code> bit rate
copy the image to another file, with the extension raw 
cp img.png  img.raw
 
play: use sox previously use command to play that audio
play -b 16 --endian big -e signed -r 44100 -c 1 img.raw
* lowering the sampling rate <code>-r</code> will ''slow-down'' the playback
 
 
Save the result of playing the raw file into audio file with a head (wav)
sox -r 44100 -b 16 -c 1 -e signed img.raw img.wav
 
Notice that the same audio parameters need to be declared: sample-rate, bit-rate, channel number, encoding
 
play: without having to declare any parameters
play img.wav


<code>-e signed-integer</code> encoding




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=Links=
=Links=
* [https://web.archive.org/web/20160525083851/http://www.fmtz.com:80/misc/raw-audio-file-formats Raw Audio File Formats Information] (at the [[Wayback Machine]])
* [https://web.archive.org/web/20160525083851/http://www.fmtz.com:80/misc/raw-audio-file-formats Raw Audio File Formats Information] (at the [[Wayback Machine]])
* [https://www.nesono.com/node/275 SOX Conversions, Raw Files, Splitting And Merging Channels]
* [http://stefaanlippens.net/audio_conversion_cheat_sheet/ Audio Conversion Cheat Sheet]
* [SoX] in the Cookbook

Latest revision as of 15:26, 29 January 2018

RAW Audio is an audio file format for storing uncompressed audio in raw form. Comparable to WAV or AIFF in size, RAW Audio file does not include any header information (sampling rate, bit depth, endian, or number of channels)

convert an mp3 to raw

Using

  • ffmpeg: " A complete, cross-platform solution to record, convert and stream audio and video."
  • Sox: the Swiss Army knife of sound processing programs


Find out the properties of the audio file with ffmpeg 

ffmpeg -i file.mp3
sox -V file.wav

Sox has no handler for mp3 formate, hence you have need to convert from mp3 to wav, ffmpeg does it quickly and well 

ffmpeg -i file.mp3 -acodec pcm_s16le -ar 44100 file.wav
  • -acodec pcm_s16le: audio codec is PCM signed 16bit
  • -ar 44100: audio rate 44.1kHz

Sox: display information on the wav file 

sox -V file.wav

Sox: convert the wav file to raw 

sox file.wav -b 16 -c 1 -r 44100 -t raw file.raw
  • -b 16 bit-rate
  • -c 1 number of channels
  • -r 44100sampling rate
  • -t rawtarget raw

play (sox): play back the raw file at same bit-rate and sample-rate 

play -b 16 --endian little -e signed -r 44100 -c 1 Zong3.raw
  • --endian little: "specify whether the byte-order of the audio data is, respectively, `little endian'... Endianness applies only to data encoded as floating-point, or as signed or unsigned integers of 16 or more bits. It is often necessary to specify one of these options for headerless files"
  • -e signed encoding. Signed is commonly used with a 16 or 24 -bit encoding size.


Same thing but with aplay: 

aplay -f S16_LE -c 1 -r 44100 Zong3.raw
  • -f sample forma+bit rate+endian:
    • 8bit: S8 U8
    • 16bit: S16_LE S16_BE U16_LE U16_BE
    • 24bit: S24_LE S24_BE U24_LE U24_BE
    • 32bit: S32_LE S32_BE U32_LE U32_BE
  • -c: channel number
  • -r: sample rate. 4000 Hz is the minimum allowed by aplay. 44100Hz is the default sample rate for CDs

convert image to raw audio

copy the image to another file, with the extension raw 

cp img.png  img.raw

play: use sox previously use command to play that audio 

play -b 16 --endian big -e signed -r 44100 -c 1 img.raw
  • lowering the sampling rate -r will slow-down the playback


Save the result of playing the raw file into audio file with a head (wav) 

sox -r 44100 -b 16 -c 1 -e signed img.raw img.wav

Notice that the same audio parameters need to be declared: sample-rate, bit-rate, channel number, encoding

play: without having to declare any parameters 

play img.wav



Links

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