BitPerfect 3.0

4.5MB | 11/25/15

英文简介：

vandal-4-all

What is BitPerfect?
BitPerfect is an App that runs alongside iTunes and provides capabilities to improve its playback of high quality audio files. When you use BitPerfect, iTunes is still your main interface to your music collection. You still use iTunes to create, store, and manage your music collection, to build playlists, and to decide what you want to play and when you want to play it. BitPerfect just sits in the background, doing nothing, until you ask iTunes to play a track; then BitPerfect steps in and takes over the playback. However, you won’t see anything to visually indicate that anything is different, because iTunes still thinks it is playing the music – the track position indicator moves along as normal, and the volume control slider ramps the volume up and down. But all of your instructions to iTunes are intercepted by BitPerfect, which implements any playback actions you have just initiated.

So why use BitPerfect? There are three primary reasons. First, and foremost, BitPerfect is designed to squeeze the best possible audio quality from your sound system using your Mac as a music server. Second, BitPerfect supports playback in the native file format, even if that format changes from track to track. Third, from version 2.0 onwards, BitPerfect can seamlessly play back DSD files, through the use of Hybrid-DSD files which you can import into your iTunes Library. You will need to purchase DSD Master from the App Store to create Hybrid-DSD files.

Audiophile Sound Quality

The driving force behind BitPerfect, and the core attribute of the BitPerfect philosophy, is a desire to extract the best possible sound quality from your Mac when used as a music server for an audiophile-grade sound system.

We began by examining how a computer manages audio playback, and focused on the concept of ‘bit perfect’ playback. This term refers to the idea that all a computer has to do is deliver the exact data contained in the audio file to the DAC (Digital-to-Analog Converter), a device which turns the data into actual music. Many Audio Player applications exist which ensure that ‘bit perfect’ data is indeed delivered to the DAC, but it was a surprise to us to find that despite this, they all sounded different. Our research showed us that there are two contributors to these audible differences – the server software and the operating system. And we found that Mac’s OS X operating system consistently provided superior results when compared to Windows – even when we ran both OS X and Windows on the same piece of Mac hardware (dual-booting into one or other operating system).

We then chose to focus on the server software’s contribution to sound quality, and established, by trial and error, a number of basic principles. How and why these principles can affect what is always ‘bit perfect’ audio playback remains a matter of speculation and, in some quarters, outright skepticism. Be that as it may, we created BitPerfect as a vehicle that encapsulates nearly everything we know about optimizing the sound quality of audio playback on the Mac platform. Of course, iTunes itself is also capable of delivering ‘bit perfect’ audio playback. But it is our contention that BitPerfect provides a significant improvement in sound quality over native iTunes. So, cue up your favorite tracks, get comfortable in your favorite listening chair, and find out for yourself.

Back in 2012, we put our money where our mouth is. We paid out over $3,000 in order to exhibit at Montreal’s SSI, a high-end audio show. We prevailed upon our friends in the industry to lend us the most sophisticated, cutting-edge, audiophile-grade playback gear we could get hold of, in order to demonstrate as convincingly as possible the capabilities of BitPerfect. Our DAC was the Da Vinci, by Light Harmonic, an incredible device which alone retails for $20,000! Our amplifiers were the CP-800 and CA-2300 models from Classe Audio, which together retail for $12,000. The loudspeakers were Wilson Audio Sophia 3, which, although they retail for $16,900, are the “entry level” model in the Wilson range. Speaker cables were Cardas Golden Cross, which alone retail for $5,800. Quite an impressive collection! Read what Michael Lavorgna of AudioStream had to say about it:

http://www.audiostream.com/content/bitperfect

Seamless playback of different audio formats

Not to be confused with different file formats, which are merely different ways of storing the same digital music data, the music itself can be represented digitally in fundamentally different ways. Here we shall concern ourselves only with so-called ‘PCM’ formats.

The music signal we want to store and subsequently re-create is an electrical waveform whose oscillations represent the actual sound waves. In PCM (Pulse Code Modulation), the analog music signal is sampled at a regular fixed rate, which is called the Sample Rate. Each time the music signal is sampled, the magnitude of the signal at that particular instant is stored as a digital value. The precision with which this digital value is stored is called the Bit Depth. The first wide-spread digital music format, the Compact Disc, adopted a PCM format which has become a standard to this day, and is often referred to as ‘Red Book’. The CD format uses a Sample Rate of 44.1kHz and a bit depth of 16 bits.

However, many experts in both the recording and playback fields acknowledge that superior sound quality can be obtained by increasing the bit depth, and also by increasing the sampling rate. 24-bit bit depth is now an acknowledged standard for ‘high-resolution’ files, as well as various sample rates based on multiples of either CD’s 44.1kHz or DVD’s 48kHz. These different formats include ‘24/96’ (which means 24-bit 96kHz), and include sample rates up to 384kHz and even beyond. Many music sources now offer downloads of “Studio Master” quality music in one or other of the high resolution formats, and equipment for amateur recording enthusiasts is cheaply available which can produce high-resolution recordings (your everyday Mac laptop can do this). As a result, many music collectors now include tracks in various high-resolution formats in their music collections.

Under Apple's OS/X operating system, when iTunes plays back a music track, it looks at the format of the track itself, and then looks at the settings of the output device. If the settings do not match, iTunes will automatically convert the file from its own ‘native’ format to the format which the output device has been set to. Most audio experts agree that this process inevitably results in some degradation of the sound quality. Your only recourse, if your music collection contains tracks with different music formats, is to go into the Audio Midi utility and manually change the output settings each time the format of the music file changes. Most users find this to be an annoyance.

When BitPerfect handles the playback, it automatically re-configures the output device to the format of the music track being played. It does this instantly, so that tracks of different formats can be played seamlessly, one after the other. You no longer need to keep track of what the music format is, BitPerfect handles all of that in the background. For the modern computer-based music collector, this is a critical advantage.

BitPerfect can Play DSD files

DSD is the name of the music format used by SACDs. DSD represents music in a radically different way to PCM, and many audiophiles have come to the opinion that DSD sounds more "musical" - more like analog - than does PCM. Although SACD as a format never caught on, the DSD format itself is making a dramatic comeback, and downloadable DSD files can now be purchased from several sources.

Starting with version 2.0, BitPerfect can play back DSD files. However, you cannot import DSD files directly into iTunes. BitPerfect has developed a solution for this, which we call the "Hybrid-DSD" file. A Hybrid-DSD file looks and behaves like an ordinary Apple Lossless file, but also contains the original DSD content which BitPerfect can play back, provided your audio output device supports DSD. At the time of writing, only a limited number of highly specialized devices support DSD playback, but new products are appearing on the market at an accelerating pace, and at ever lower price points. It is necessary to purchase DSD Master from the App Store in order to convert ordinary DSD files into Hybrid-DSD files.

官网: http://bitperfectsound.blogspot.com/p/what-is-bitperfect.html