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I'm a music lover. I have lot of songs stored on my laptop, but the problem is I'm running out of space on my hard disk, because of the different audio formats which occupy lots of space.

Now I want to convert all those different audio formats into one.

Which is the best in terms of space it occupies on hard disk, but with good or fair audible quality? what's the best format available which occupies low space with good quality?

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AAC and its successor HE-AAC provide very good audio quality, even at low bitrates. In that respect, MP3 isn't that bad either, given that you can use Variable Bitrate Encoding (VBR) at bitrates from 198 to 320 kBit/s. Variable bitrate ensures that bits are allocated to those parts that need it, and it conserves bits for passages that are easy to encode. Don't use Constant Bit Rate encoding unless you are in a streaming scenario – it'll hurt quality.

Note that you should check which encoder you are using. FAAC and LAME are typically considered good (and free) encoders, but that doesn't stop you from trying others, as @Lèse majesté pointed out. For example the Fraunhofer MP3 encoder, which is commercial.

This is a subjective thing – and if you're passionate about music, just trust your ears and try for yourself.

If you're unsure, this figure compares some recent audio codecs at 48 kBit/s – thus, a really low bitrate. It's taken from an EBU technical paper.

However, what you never want to do is reencode audio files from another compressed format. Say you already have tons of 128 kBit/s MP3s, they won't sound better in AAC. They'll even sound worse because you're throwing away information from a file that already lost most of its quality.

So, if you transcode, then only do it from WAV files, CDs, or other lossless media such as FLAC files.

Trust me, I was so stupid as to rip some CDs to Windows Media Audio back in the days. I later had to convert those to MP3 again, and you could definitely hear that they were really bad in quality after that process.

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  • Excellent answer. In answer to your question regarding the trade off between quality and disk space, I always find that 128kbps - 320kbps mp3's offer a good balance of sound (for my portable mp3 player) and space for storage on my hdd. I have a lot of music and find 128kbps mp3's an acceptable size. The styles of music I listen to really don't improve all that much with higher bit-rates IMO. Then again there could be something wrong with my hearing, or my music :)
    – hardlywired
    May 9, 2012 at 8:11
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    Voted you up, but I still want to point out that different codecs for the same format (e.g. LAME vs. FrH vs. tooLAME, etc.) as well as different versions of the same codec can produce very different results. Likewise, different codecs can produce optimal results at different bitrates, and the actual compression settings you choose for each codec can also make a huge impact, as with the type of audio you're compressing. Furthermore, these perceptual tests are somewhat subjective, and different people may prefer different codecs.
    – Lèse majesté
    May 9, 2012 at 8:17
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    @Lèsemajesté You're correct pointing that out, thank you! Perceptual tests are subjective, but they're averaged over a number of participants, so if you're an average listener, the results might apply to you. I agree that if you're really passionate about music, you should think more carefully about which encoder to use. It's up to the OP to try different implementations.
    – slhck
    May 9, 2012 at 8:24
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    Also, this comparison seems to have left out Ogg/Vorbis, which a lot of people prefer for both its quality and open source status. Though the two most popular PMPs don't support it--which brings up another point. You should also consider what formats are most suited to your playback methods. At the end of the day, the difference between AAC/Vorbis/MP3 are likely to matter less than what your car MP3 player or PMP supports.
    – Lèse majesté
    May 9, 2012 at 8:24
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    @slhck: Yea, unless you're an audiophile, then results from perceptual tests from a large sample population are probably a decent (and convenient) indicator of which codecs currently provide the best quality. But if you're really anal about this sorta thing, here are some other public perceptual tests: Hydrogen Audio June 2011 and SoundExperts.org. There used to be a site where you can perform the test yourself online, but I can't find it ATM.
    – Lèse majesté
    May 9, 2012 at 8:32
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What's the best audio format available when I want to convert my files?

The format it is already in (no conversion).

As @slhck said, converting from one compressed format to another compressed format always results in poorer audio quality. To produce better or equal quality in smaller files you have to start with the original uncompressed audio material.

@slhck answered a different and slightly more interesting question "which audio file format gives the best subjective results at 48kbps" :-)

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the only way to save disk space on your hard drive is to delete unused files, recode files do not help much, if you ask me I always prefer high quality (256, 320) to my favorite music files, and 128 is enough for music files that do not matter much, do not be afraid to delete files that you want after all you can not have all the music in the world

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  • Double confusion here. First, bitrates are not formats. Second, changing bitrates obviousy does change file sizes, so how can you claim "the only way to save disk space on your hard drive is to delete unused files"?
    – Isaac Rabinovitch
    Oct 25, 2012 at 21:58
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The best target audio format may be "the best" by certain criteria:

  • sound quality,
  • device/software compatibility,
  • file size.

Lossless formats

To achieve maximal sound quality lossless formats are recommended.

These formats support PCM (*.wav, *.flac, *.aiff, .alac,...) and DSD (.dsf, *.dff, *.iso [sacd iso]) audio stuff.

Lossless formats store audio stuff without altering.

File size compression

To reduce file size, compressed formats are used.

Compressed formats are:

  • lossless: *.flac, *.ape, *.m4a(ALAC), MLP,... lossy: *.mp3,
  • lossy: *.m4a(AAC), *.ogg, ...

Lossy formats

Lossy formats lose part of audio information, but have significant file size reducing.

As rule, very popular mp3 have high sound quality at high bitrates 256...320 kbps.

AAC format developers, promise better sound quality of AAC than mp3. But, I suppose, it should be checked individually for each of your audio systems.

AAC supports multichannel configuration. Though it is not so important for mobile devices, that have stereo outputs (headphones) rather.

As rule, mp3 and AAC formats have no metadata support issues.

Audiophile formats

For audiophile applications FLAC and ALAC may be recommended.

If you have DSD capable audio device, DSF file may be better choise, because it supports metadata (text and artworks).

Some of digital audio players support *.iso [sacd iso] images. However these files can contains 2 versions of single album: stereo and multichannel. It consume additional hard disk space. And it may be important for stereo mobile audio device with limited hard disk space. The issue may be solved via extracting stereo tracks to DSF or FLAC. Also multichannel music files may be downmixed to stereo.

Read details about audio formats and look at sound quality researching links here.

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