Storage is getting cheaper day by day but it is still limited in smart phones. This is especially true for low end phones with low internal memory. Most of the music we store on our phones is in MP3 format. This music encoding format was first released to public in 1995. Since then we have come a long way and many new codecs have been developed that provide superior quality to MP3 at same size or same quality in smaller file size. The most notable is AAC (AAC-LC).
AAC stands for Advanced Audio Coding. This format has been popularized by Apple’s Ipod (having .m4a or .m4b extension). This format is also used by Nokia Music service resulting in faster downloads. It achieves much better quality than MP3 at similar bit rates. The format we will use is enhanced version of AAC called eAAC+ or HE-AAC v2.
About the eAAC+
This audio compression scheme is optimized for very low bit rates. It is enhances the existing AAC-LC (Low Complexity). The eAAC+ uses to techniques for optimization – Spectral Band Replication and Parametric stereo. There is also AAC+ or HE-AAC v1 which is AAC-LC with only Spectral Band Replication. Here is a brief explanation of these terms:
Spectral Band Replication(SBR): This acts as a lowpass filter allowing lower frequency to pass. The higher frequencies are not encoded very accurately. These higher frequencies take a lot of space. This method takes advantage of the fact that higher frequencies are not very clearly distinguishable by human beings.
Parametric Stereo (PS): In traditional stereo left and right streams are stored separately. But in this case there is one main mono stream and the stereo information is stored in a separate parametric stream of 2-3 kb/s. This parametric stream is used to reconstruct the original stereo audio.
The three types of AAC files AAC-LC, AAC+ and eAAC+ have the following relation:
eAAC+ = AAC+ with PS = AAC-LC with SBR and PS
To convert to eAAC+ format we will use Nero AAC encoder. This is a command line tool. To make our task easier we will use TAudioConverter. Here is the procedure:
Converting from any format to eAAC+
Step 1: Download and install TAudioConverter.
Step 2: Download Nero AAC codec from Softpedia or Nero. Extract the zip file to the installation directory of TAudioConveter. This directory is C:\Program Files (x86)\TAudioConverter 32bit for 64-bit Windows and C:\Program Files\TAudioConverter for 32-bit Windows. After extraction the program directory will look like this:
Step 3: Launch TAudioConverter. To add an audio file just drag and drop on its windows or click add button. It is recommended that the source is in lossless format or highest possible quality available. The TAudioConverter is very versatile and accepts various formats as input (aac, mp3, wav, flac, ac3, ogg, etc.). It even accepts videos as input.
Step 4: Change the settings to the following:
- Format: AAC(NeroAACEnc) (Click the button on upper right side and select Lossy>AAC(NeroAACEnc))
- Encode Method: Quality
- Quality: 15
Step 5: Hit Start button and output file will be created in the TAC directory in Documents. Transfer it to your phone and enjoy extra space.
Testing and Results:
We used the song Big Yellow Taxi by Counting Crows for testing. It has sufficient variations to test the audio quality.
|MP3:||.mp3||128 kbps||2 min 49 sec||3.49 MB|
|eAAC+ (Output):||.m4a||34 Kbps||2 min 49 sec||0.96 MB|
The resulting file is roughly 1/4th the size the size of comparable mp3 file. Thus, you can store can store 3 times more music in this format.
To play the .m4a files on PC we recommend Foobar, a very high quality audio player. We played the resulting file on on Xperia M, a midrange android, using headphones provided in the box. The quality was good and there were no perceptible artifacts.
You can listen to output file yourself or Download it.
The phone does not recognizes the file as music.
Check the website of your phone manufacturer if it supports eAAC+ or HE-AAC v2. If you have any of the following then it will support eAAC+:
- All versions of Android. Link
- All version of iOS 4.3 and above.
- All Windows Phone 7 and Windows Phone 8
Even old Nokia phones like N72 and Sony Ericson phones like w595 support it.
Some phones may not recognize .m4a extension. In that case we have to change the output extension. Go to program’s setting. In the Encoding tab set the ‘AAC Extension’ as ‘AAC’. The output files will now have .aac extension.
The music sounds good on PC but bad on phone.
It may happen that your phone does not support eAAC+ but only AAC+ or AAC-LC. Try using quality value of 20 or 25 in the settings.
The music sounds bad on PC.
Use supported audio player like Foobar.
The music sounds bad on home Hi-Fi system or High quality headphones on Computer.
The settings above are intended for mobile devices which are used in noisy environment and do not have high quality components. For home system feel increase the quality value. A quality value of 50 should be good and is virtually transparent.