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    Thread: A Peep into the World of Digital Audio Formats

    1. #1
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      A Peep into the World of Digital Audio Formats

      So, finally your dream has come true. After the exhaustive research, relentless queries, oscillating mindset, you have finally managed to setup a nice Audio Setup for your car. It’s time for your friends and peers to know you’ve got a superb ICE setup. You put in your favorite track in USB, Hit the play button and to your horror you realize that all those mp3’s that were so good in your computer speaker is no longer good. You understand that ICE is not as forgiving as your Home Audio and good source is a definite must to achieve your perceived SQ. And you start again, this time in pursuit to get so called ‘High Quality’ Tracks so that you do justice to your spend on ICE.

      Typical questions that come to you mind;
      • Is Audio CD the only source to Sound Nirvana?
      • Why aren’t .mp3 files as good as CD?
      • What’s this ACC ? how better is it when compared to my .mp3 ?
      • What the hell are .Wav, .FLAC, .ALAC files?
      • etc…


      Digital Audio Format:

      A Digital audio format is a file format for storing digital audio data on a computer system. Unlike Analog Formats like magnetic tapes, and discs, the Digital format stores information / Data as 0’s and 1’s.

      Classifying the Digital Audio Format:

      There are three major ways in which digital audio file formats are classified:
      1. Uncompressed audio format
      2. Formats with lossless compression
      3. Formats with lossy compression


      Uncompressed audio formats, as the name says are raw files. They do not have any compression and as such their file size is quite large. Since they don’t have to undergo any kind of compression, they retain the exact quality of sound that is recorded. Examples such as WAV, AIFF, PCM represent uncompressed Audio Format.

      • WAV: Waveform Audio File Format, commonly known as WAV due to its filename extension, is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs. It is the main format used on Windows systems for raw and typically uncompressed audio.
      • AIFF: Audio Interchange File Format (AIFF) is an audio file format standard used for storing sound data for personal computers and other electronic audio devices. The format was co-developedby Apple Computer in 1988 based on Electronic Arts' Interchange File Format. Standard AIFF is a leading format (along with WAV) used by professional-level audio and video applications. Like any non-compressed, lossless format, it uses much more disk space than MP3—about 10MB for one minute of stereo audio at a sample rate of 44.1 kHz and a sample size of 16 bits.
      • PCM: Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals, which was invented by Alec Reeves in 1937. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems. They occupy enormous amount of space, even greater than WAV’s.
      Formats with lossless compression, are those which undergo compression, however the impact on Sound Quality is nearly negligible. In fact there have been instances where few users claim FLAC to be even superior to Audio CD. However, it basically boils down to ‘level’ of detail your ear can perceive. Mild Compression enables slightly better usage of space when compared to uncompressed file formats.
      • FLAC: Free Lossless Audio Codec (FLAC) is an audio compression codec primarily authored by Josh Coalson. FLAC employs a lossless data compression algorithm. A digital audio recording compressed by FLAC can be decompressed into an identical copy of the original audio data. Audio sources encoded to FLAC are typically reduced to 50–60% of their original size. FLAC is supported by more hardware devices than competing lossless formats like WavPack.
      • WavPack: WavPack compression (.WV files) can compress (and restore) 8-, 16-, 24-, and 32-bit fixed-point, and 32-bit floating point audio files in the .WAV file format. It also supports surround sound streams and high frequency sampling rates. Like other lossless compression schemes, the data reduction rate varies with the source, but it is generally between 30% and 60% for typical music.
      • ALAC: Apple Lossless (also known as Apple Lossless Encoder, ALE, or Apple Lossless Audio Codec, ALAC) is an audio codec developed by Apple Inc. for lossless data compression of digital music. Apple Lossless data is stored within an MP4 container with the filename extension .m4a. All current iPods and iPhones can play Apple Lossless-encoded files. Apple claims that audio files compressed with its lossless codec will use up "about half the storage space" that the uncompressed data would require. Testers using a selection of music have found that compressed files are about 40% to 60% the size of the originals depending on the kind of music, similar to other lossless formats. Furthermore, the speed at which it can be decoded makes it useful for a limited-power device such as the iPod.
      • Monkey's Audio(.APE): A digital recording (such as a CD) encoded to the Monkey's Audio format can be decompressed into an identical copy of the original audio data. As with the FLAC and ALAC format, files encoded to Monkey's Audio are typically reduced to about half of the original size, with data transfer rates and bandwidth requirements being reduced accordingly. Monkey's Audio's advantages are slightly better compression rates compared to FLAC and WavPack, as well as multithreading/multicore support. However the main drawback is the fact that it employs a symmetric algorithm, meaning the decoding takes comparable resources to encoding, which makes it unsuitable for all but the fastest portable players / system
      Formats with lossy compression, are more focused on reduction in file size through advanced / multiple compression techniques than retaining the original Quality of the recording. A variety of techniques are used, mainly by exploiting psychoacoustics, to remove data with minimal reduction in the quality of reproduction. For many everyday listening situations, the loss in data (and thus quality) is imperceptible. The popular MP3 format is probably the best-known example, but Apple's AAC format is another common one. Most formats offer a range of degrees of compression, generally measured in bit rate. The lower the rate, the smaller the file and the greater the quality loss.

      • MP3: MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression. MP3 is an audio-specific format that was designed by the Moving Picture Experts Group as part of its MPEG-1 standard and later extended in MPEG-2 standard. The use in MP3 of a lossy compression algorithm is designed to greatly reduce the amount of data required to represent the audio recording and still sound like a faithful reproduction of the original uncompressed audio for most listeners. An MP3 file that is created using the setting of 128 kbit/s will result in a file that is about 11 times smaller than the CD file created from the original audio source. An MP3 file can also be constructed at higher or lower bit rates, with higher or lower resulting quality. Although bit rates for mp3 start from 32 kbit/s, typical reproduction bit rate is 128 kbps and upward. A sample rate of 44.1 kHz is almost always used, because this is also used for CD audio, the main source used for creating MP3 files. The rate of 128 kbit/s has a Compression ratio of 11:1, offering adequate audio quality in a relatively small space. As Internet bandwidth availability and hard drive sizes have increased, higher bit rates up to 320 kbps are widespread. Uncompressed audio as stored on an audio-CD has a bit rate of 1,411.2 kbit/s, so the bitrates 128, 160 and 192 kbit/s represent compression ratios of approximately 11:1, 9:1 and 7:1 respectively.
      • AAC: Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates. Blind tests show that AAC demonstrates greater sound quality and transparency than MP3 for files coded at the same bit rate. Few Improvements include:
        • More sample frequencies (from 8 to 96 kHz) than MP3 (16 to 48 kHz)
        • Up to 48 channels (MP3 supports up to two channels in MPEG-1 mode and up to 5.1 channels in MPEG-2 mode)
        • Higher coding efficiency for stationary signals
        • Higher coding accuracy for transient signals
        • Much better handling of audio frequencies above 16 kHz
        • More flexible joint stereo (different methods can be used in different frequency ranges)
      • Windows Media Audio: Windows Media Audio (WMA) is an audio data compression technology developed by Microsoft. WMA consists of four distinct codecs. Like AAC, WMA was intended to address perceived deficiencies in the MP3 standard.


      Summing up:
      The Decision on the format is sadly not wholly your choice. Your Head Unit’s ability to take in different formats is the key here. Although compressed lossy formats sacrifice on SQ, they take the cake for practicality and functionality grounds. Mp3 is no doubt the Common man’s most preferred format to play music. Normally most HU’s that come with an USB interface can play mp3 and wma directly. Few play AAC as well. Whenever you play these files, keep in mind the Bitrate of the songs. Ensure you rip your music to 192 kbps or more.

      Very Few Head Units that can play WAV directly. Other Formats like FLAC, APE etc.. are not supported directly by Head units. The best way to play a lossless format is the ipod way. If your HU is ipod compatible then your best bet is to use ALAC.

      For the Current crop of CD based HU’s Audio CD is the way to go if you want uncompromising Sound Quality. However, .mp3 and ACC encoded at 320 kbps is not far behind. Although the specs show quite a lot of difference, Human ear is not fine enough for these differences to be noticed.

      The Other option is the Carputer – This the only one stop option to play all kinds of formats including uncompressed ones (provided you have sufficient disk space). From Analog Audio Tape to Digital Audio CD to 1000’s of Digital Audio Formats (that is ever increasing), it is inevitable that the future of Car Audio Head Unit is heading towards a CarPC.
      Last edited by Mi10; 15th Apr 2011 at 22:39.
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      Great thread Mi10! I knew bits of pieces of this but it's nice to have it all summed up here.

      Quote Originally Posted by Mi10 View Post
      The best way to play a lossless format is the ipod way. If your HU is ipod compatible then your best bet is to use ALAC.
      While this is true, you also need a HU that has the capability to bypass the iPod's onboard DAC to get the best out of the music file.
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      Very informative post Mi10...thanks for bringing this up.....
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      Thanks very much Praveen for a very informative post and also for tagging me. You have addressed the very issue I was totally at a loss to comprehend.

      Quote Originally Posted by Gilead View Post
      While this is true, you also need a HU that has the capability to bypass the iPod's onboard DAC to get the best out of the music file.
      I have experienced this. I find that for the very same recording, perfomance from HDD is much better than from iPod. I believe iPod adds its flavour to the music and my HU (Ken X7016) is perhaps unable to overide the iPod's onboard DAC.
      Last edited by Venkatesan; 15th Apr 2011 at 21:06.

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      Thats an excellent Article Mate. very informative and its gonna boost up the ICE with these high end formats
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      Id like to add another solution to play FLACs. I have a HTC HD2 running WM 6.5. there is a media player called Conduits Pocket Player that has a plugin to enable FLAC playback. this media player kicks serious ass. I dont have a head unit. my phone is connected directly to an amp through a cable that has a 3.5 mm stereo jack on one side and two RCA jacks on the other.
      Im pretty sure there will be FLAC playback solutions for Android too.

      so if you have a Windows / Android phone with a 3.5 mm audio jack, all you need to go fully solid state is an amp and a little cable or a head unit with Aux in.
      Last edited by 007; 15th Apr 2011 at 21:36.

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      Quote Originally Posted by Venkatesan View Post
      I believe iPod adds its flavour to the music and my HU (Ken X7016) is perhaps unable to overide the iPod's onboard DAC.
      The 7016 bypasses the iPod's DAC.

      Any HU that uses a digital USB cable to connect to the iPod will bypass the iPod's DAC. At the moment I can think of one famous HU that does not bypass the iPod's DAC and that is the Alpine 9887.
      Last edited by Gilead; 15th Apr 2011 at 22:46.
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      Quote Originally Posted by 007 View Post
      Id like to add another solution to play FLACs. I have a HTC HD2 running WM 6.5. there is a media player called Conduits Pocket Player that has a plugin to enable FLAC playback. this media player kicks serious ass. I dont have a head unit. my phone is connected directly to an amp through a cable that has a 3.5 mm stereo jack on one side and two RCA jacks on the other.
      Im pretty sure there will be FLAC playback solutions for Android too.

      so if you have a Windows / Android phone with a 3.5 mm audio jack, all you need to go fully solid state is an amp and a little cable or a head unit with Aux in.
      Agreed thats an option to play FLAC. That said a good source alone cannot make up an excellent Sound Quality. Since you are playing it off your Mobile Phone, its uses its DAC which i presume wont be at the level of a 10K HU (THats understandable too). Even when you connect via AUX, its the Mobile Phone (or whatever MEdia player thats connected)'s DAC is used.
      For Total SQ or better put as Quality Sound Reproduction you need Both a Good Source like FLAC as well as a Competent high quality DAC.
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      true. it does depend on the mobile phone's DAC and while it may not match the fidelity of a dedicated HU, it is still quite good. Im not talking about serious audiophile territory here. ever since I swapped my HU for the HD2, I havent missed it even once. so Im assuming any decent smartphone should be up to the task.

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      320kbps original track mp3 format is an "ok" for a average SQ setup and above average SQ setup

      Buy original CDs and play it. read the label on Cd about mixing and recording. .wav format is better than any other.
      Last edited by mclaren1885; 5th Jul 2011 at 00:03. Reason: Merged back to back posts.

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