Audio Basis - articles about audio
Every day bulk of purchased and downloaded digital music in high resolution is growing. At our storage devices, huge musical libraries are accumulated.
And we convert music formats and resolutions to:
Read what is the best audio file converter, how audio file converters are distinguished. It helps you to choose the best audio converter software on Windows, Mac OS and other operating systems.
Also read How to Improve Sound Quality >
The first requirement for the best music conversion software is minimum quality losses during conversion.
Some formats may be transformed from one to another without losses:
Lossless conversion of these formats is possible when input and output sample rates and bit depths are identical.
Resampling (sample rate conversion) and bit depth conversion (in general), gain altering, and filtering are lossy processing.
The software has several classes of processing quality:
Home and professional audio converters
It is an approximate class definition. There are no standard definitions.
Professional conversion tools should provide a significant reserve of processing quality. It needs to conversion that is transparent for user.
Converting programs have many features (see list below). To choose the program, it needs to find the most useful one for your requirements. You can compare the different software according to personal demands. On the Internet, free audio converters are available. Commercial utilities also have free demo versions, as rule.
Resampling is altering of sampling rate to:
Digital filters, that are used to resample:
Dithering is a reducing method of sound distortions. It's used in audio bit-depth converters when resolution is truncated to 16 bits.
Read more about dithering >
CD ripping is copying CD audio content to sound files on hard disk of computer via CD-ripper software.
CD ripping may use different levels of access to audio data on CD:
Lower-level access allows detection of CD-reading errors with higher probability. Some CD rippers can attempt to recover audio data. Though there is no 100%-probability of error detection and correct recovery.
Read more about safe CD ripping >
Music loudness normalizing is used to maximize the loudness without overload.
Also, oversampling may cause overload of resampled stuff. Normalizing allows avoiding it.
Read more about loudness normalizing >
Seamless album conversion intended to continuous musical albums like operas, live concerts, musicals, etc. All tracks of these albums should be processed without pauses and artifacts between the tracks as continuous music stream.
Read more about seamless re-sampling >
Downmix 5.1 to stereo (multichannel to stereo) is multichannel stuff transformation to playback at stereo musical device/system.
Read more about downmix 5.1 to stereo >
Metadata (metatags) is information about a music file (song name, performer, album, year, artwork, etc.).
Group editing of several files is desirable.
Popular id3 standard metadata allows assignment of several types of artworks (album cover, performer/composer/etc. photo(s), other). As rule, players read only album cover artwork. Some metadata editors may allow assignment of artwork type and/or embed several artworks to a sound file.
Read more about metadata editing >
Management output stuff directory structure is an ability of music converting tool to create/copy directory structure, name for output file. As rule, file naming by metadata is used.
Precision of processing math does not matter to end user, as rule. Precision impact on noise/distortion level and anti-overload ability of signal processing. In general, the precision of math is higher, than recommended target bit depth.
Easy-to-use graphical user interface is an important thing, because transformation of musical stuff is repeatable operation. So minimum of actions is desirable.
Price is one of the most important features of any program. There are many free music converters. Some of these converting tools are command-line utilities. Some of these utilities may be managed via front-end programs with graphical user interface.
As rule, software development project should be funded for stable customer support and functionality expansion.
This funding may be provided via donations, advertising, selling of licenses or others.
Comparison of prices should be done inside a class of converting program: pro with pro, home with home.
Sound converter software quality may be compared by measured distortions and noise level.
Audio quality issues of conversion tools
Also you can compare converting software via ear tests:
This test don't guarantee minimal distortions for the best (in your opinion) audio converter software. But you can choose the program, that sound you like more.
Sample rate converter software quality is tested via sweep sine. Below we can view output of resampler program.
Hi-End re-sampling of sweep sine: no aliases, only sweep sine at output - output like to input
Mid-Fi re-sampling of sweep sine: low aliase level and sweep sine at output
Lo-Fi re-sampling of sweep sine: high aliase level and sweep sine at output
Sample rate converter comparison is performed by alias levels.
Different converters may not have audible difference. In this case you need check other features that are important for you.
Audio converter is not simple program, as look at first sight. Therefore, errors/bugs may be there.
Each modification of program may cause new bugs.
Programmers says that old bug fixing may generate new bugs.
So bug fixing is infinite process during lifetime of the project.
Also with time appear new demands to audio converters (formats, functionality or other).
No any demands may be released or released in nearest time. But software project, that aimed to the future, collect user's requests for future releases of developed program. Check frequency of releases.
Also pay attention to time of response of tech support of program vendor.
The best audio converter software on Mac OS or Windows may be choosen by minimum distortions level first. At first sight right choice between number of alternatives is tough thing.
Fortunately, you can try many free converters and free demo versions of some commercial programs.
Quality may compared by ears or via spectrum analyzing tools (converted file noise/aliases level).
Also to compare sound quality of different conversion tools you can check links below.
You can compare the quality of conversion by ears when playback converted stuff at your player.
A program may have some issues. Pay attention to quality of technical support.
Read common advice how to choose the best sample rate...
You record your DAW project at some sampling rate. The best decission is use the sampling rate for mixing.
Recording sampling rate may be taken as maximum sampling rate of your audio interface.
If your computer has issues with real-time work with such sampling rate, it's recommended increase sound-card driver's latency or reduce sampling rate.
From theoretical point of view, 24-bit give more abilities to solve distortion issues for quiet music fragments.
Practically, there are several factors does matter.
96-kHz sampling rate is preferable in common case by technical reasons.
There is no single question. It's defined by your equipment.
Depending on using audio system, 192 kHz may give advantages comparing 48 kHz.
Yes. You can convert sample rate of an audio files. Read how to do it...
For high-qualitative converter software, sample rate almost doesn't affect to sound quality.
It depends on algorithms, that the software uses.
In instance, AuI ConverteR is based on individually adjusted resampling filter for each combination input and output sampling rates.
It allows the best sound quality and time performance, that AuI's designers can, for each sample rate.
Also, for DAC, sampling rate may be matter for sound quality. Read more...