Banner: The Hope for brass band, organ, choir, and percussion

Page 2 of 3 FirstFirst 123 LastLast
Results 16 to 30 of 39

Thread: Cd Formats

  1. #16
    Senior Member Kuhlau's Avatar
    Join Date
    Oct 2008
    Location
    Hampshire, UK
    Posts
    258
    Post Thanks / Like

    Default

    Things are as Mr. Terrible says. Even though we've become accustomed to thinking of CDs as the best sound we can get, formats like SACD, DVD-Audio and others have shown what more there is to hear. And with some sites like Linn Records and Gimell Records now selling downloads in studio master quality, we're almost into an age where we can expect everything that's possible from digital sound reproduction.

    FK
    An everyman for himself ~ Classical music reviews & resources
    --
    Follow me on Twitter

  2. #17
    Andante
    Guest

    Default

    Where I have been going wrong is thinking that the employment of format converters I.e. Media Monkey Foobar etc to convert mp3 to FLAC and EAC would restore mp3 to an acceptable audio format whereas if I have understood you correctly it will make not a scrap of difference.
    Now if I rip from a CD and convert to FLAC or EAC then burn, the result will be much better than a normal Window Media Player copy or WAV.
    How’s that?

    Is SACD popular I just do not come across it over hear

  3. #18
    Senior Member Kuhlau's Avatar
    Join Date
    Oct 2008
    Location
    Hampshire, UK
    Posts
    258
    Post Thanks / Like

    Default

    You're almost there, Andante.

    Let's break this down into some simple (and rather too simplistic) equations:


    WAV = Good as it gets / CD quality

    FLAC = Same as WAV, but smaller filesizes

    EAC = Not a format, but a program to accurately extract data from CDs

    SACD = Super Audo CD / Better than CD quality


    Does this help at all?


    And yes, burning MP3s to CD does diddly squat to the sound quality. Once digital information is lost, it can't be recovered.

    FK
    An everyman for himself ~ Classical music reviews & resources
    --
    Follow me on Twitter

  4. #19
    Andante
    Guest

    Default

    OK, one other thing, mp3 is a small file due to both compression and removal of digi information, what is the digi info that is removed?? and would it be too inconvenient with to days tech advances to stop removing info
    I have yet to hear a SACD they are dual layer I believe, are they better than Audio DVD?
    I reckon its about time the d/l quality of Classical in particular was improved,

  5. #20
    Senior Member Kuhlau's Avatar
    Join Date
    Oct 2008
    Location
    Hampshire, UK
    Posts
    258
    Post Thanks / Like

    Default

    MP3 files are compressed precisely because digital information has been removed - although this is only one form of compression, as I'll explain in a minute. The information removed relates to the frequencies which the human ear can't actually hear at either end of the sound spectrum; and the lower the bitrate used for encoding, the more data is removed from either end until the sound becomes very poor indeed.

    When you use good-quality hifi equipment and compare the playback of an MP3 file to that of an SACD, you can hear clearly what's happened as a result of that compression. What you perceive when listening to SACD is much greater dynamic range, and consequently, a real sense of 'space' or presence in the recording. Some SACDs are so good that, depending on how advanced your equipment is, you can experience the music almost exactly the way the conductor would've heard it.

    No compressed - or 'lossy' - format such as MP3 can ever give you what SACD can. This is the limitation of MP3: the technlogy is already very old (in techie terms), and can't be redesigned to remove less data. That's why we have WMA, OGG Vorbis, AAC, M4A, ATRAC3Plus and a myriad of other lossy formats, most of them better at compression of sound without such severve quality loss. But now that digital storage media is so cheap and plentiful, and broadband speeds are making larger files quicker to download, compression should slowly become a thing of the past.

    Now, to complicate and confuse matters a little, there's another kind of compression. The FLAC encoding technology is very different to that of MP3, because digital data isn't 'thrown away' during compression. With FLAC, the compression works just like it does with a zip file. So, let's say that in our digitally ripped music track, we have the following binary sequence:

    00000011110000111111

    FLAC technology will look at this sequence and instead of seeing it in such a linear fashion, will effectively 'rewrite' the sequence thus:

    6 x 0 4 x 1 4 x 0 6 x 1

    Do you see the difference? The technology isn't trying to write great long strings of binary data, but instead 'compressing' these by writing them more intelligently and efficiently. This means that when FLAC files are decoded for playback, a 'reversal' of this intelligent compression results in sound quality IDENTICAL to that of the source CD; no information was discarded, remember, it was just written differently.

    As for DVD-A, the sound is comparable to that of SACD, although my preference is for the latter. I just think SACD has the edge, but I'm not sure there's a great deal in it.

    I agree that classical downloads should be lossless (like FLAC), and I'm pleased to say that it's starting to happen. If you look at a site called Passionato, you'll see they sell classical music in FLAC format ... though only to UK customers at the moment, I believe. For historical recordings, Pristine Classical is another site offering FLAC (though one wonders why, given how poor some of the aged transfers were to begin with).

    FK
    Last edited by Kuhlau; Nov-13-2008 at 23:26. Reason: Additional information needed adding.
    An everyman for himself ~ Classical music reviews & resources
    --
    Follow me on Twitter

  6. #21
    Senior Member purple99's Avatar
    Join Date
    Apr 2008
    Location
    London, UK
    Posts
    176
    Post Thanks / Like

    Default

    Great post. It's not really that complicated, but few who understand it are willing to explain it in non-nerd language. The key thing is to transfer as much original material from the recording session to listeners' ears as possible. As Kuhlau says, with HD space so cheap and fast broadband connections becoming the norm in First World countries, there's increasingly little excuse to use the old lossy MP3 format.

  7. #22
    Andante
    Guest

    Default

    Quote Originally Posted by purple99 View Post
    As Kuhlau says, with HD space so cheap and fast broadband connections becoming the norm in First World countries, there's increasingly little excuse to use the old lossy MP3 format.
    Hi 99, this is what I was trying to say in my non nerdy way

    Kuhlau, thanks I am at last beginning to understand, it is something that puzzled me but being old and doddery I am easily confused
    I suppose mp4 is not a great improvement, so all in all a case to be had for purchasing your music from your local dealer, at least for the present.

  8. #23
    Senior Member purple99's Avatar
    Join Date
    Apr 2008
    Location
    London, UK
    Posts
    176
    Post Thanks / Like

    Default

    Quote Originally Posted by Andante View Post
    Hi 99, this is what I was trying to say in my non nerdy way
    Thanks to you, Kuhlau and Mr Terrible I now understand how the various formats relate to each other. Page bookmarked.

  9. #24
    Senior Member Kuhlau's Avatar
    Join Date
    Oct 2008
    Location
    Hampshire, UK
    Posts
    258
    Post Thanks / Like

    Default

    Glad I could share in being of some assistance.

    FK
    An everyman for himself ~ Classical music reviews & resources
    --
    Follow me on Twitter

  10. #25
    Andante
    Guest

    Default

    Ha Ha dont think that's the end to it, I still have to wade through all the info that you have given. e,g the binary system is yesterdays technology ??

  11. #26
    Senior Member Kuhlau's Avatar
    Join Date
    Oct 2008
    Location
    Hampshire, UK
    Posts
    258
    Post Thanks / Like

    Default

    All computing still reduces to binary at its most basic level, Andante.

    Interestingly, there was a response to an article in the letters pages of International Record Review earlier this year which basically gave the same technical 'advice' as I gave here ... yet I only read that back issue today. Nice to have my understanding independently confirmed.

    FK
    An everyman for himself ~ Classical music reviews & resources
    --
    Follow me on Twitter

  12. #27
    Junior Member
    Join Date
    Oct 2008
    Posts
    26
    Post Thanks / Like

    Default Confusing terms

    I think part of the problem with this subject is the use of comfusing terms that have different meanings in different contexts -- the worst culprit being 'compression'

    Compression is most often used to mean the control of dynamic range -- specifically the reduction of dynamic range, so that loud sounds aren't as loud as they were, while quieter sounds are louder. The idea being to let you hear the quite stuff above the background noise of the listening room while the loud bits don't annoy the neighbours.

    However, in the context of digital audio codecs, 'compression' refers to the amount of data reduction being applied -- or how much the file size is reduced.

    There are four basic ways to achieve a reduction in the data file size. The first is to use a lower sample rate. For example, instead of using the 44.1kHz rate of CD, the telephone system uses an 8kHz sample rate. The advantage is that you imediately have only about one fifth of the data to worry about... but the disadvantage is that the audio bandwidth is reduced to just 3.5kHz instead of 20kHz. Lousy for quality music, but adequate for intelligible speech... which is why it is used.

    The second technique is to reduce the wordlength -- how many bits are used to describe the audio amplitude. Studio quality recordings are made with 24 bits per sample which gives a potential dynamic range in excess of 130dB. CDs are made with 16 bits per sample giving a potential dynamic range of over 90dB -- but that reduction in wordlength removes more than 30% of the data. Telephone systems use only 8 bits, reducing the data even more. But clearly, the disadvantage with this approach is a higher and more obvious noise floor, and a lower potential dynamic range.

    The third option is to remove what is referred to as 'redundant data' and this is the scheme used by loss-less codecs like FLAC and MLP (amongst many others). If you consider the digital encoding of a photograph, each pixel must be described in terms of its colour and brightness, and in a high resolution picture that results in a huge amount of information. A loss-less codec reduces much of that information by avoiding repetition of identical data -- doing away with the 'redundant' information.

    So if the sky is a uniform blue, say, rather than saying this is a bright blue pixel, this is a bright blue pixel, this is a bright blue pixel, this is a bright blue pixel... The codec notes it as this is a bright blue pixel, and so are the next 327, this is a less bright blue pixel and so are the next 28... and so on.

    In this way, the amount of data required to describe the picture is reduced significantly, but the information and accuracy is preserved absolutely -- which is why it's called Loss-less. Audio signals tend to be very cyclical in nature much of the time, and this is largely predictable. The loss-less codecs simple take advantage of this 'predictability' to remove the redundant data and this reduce the file size. There are obvious limits to how far this can be taken, and that's why loss-loess audio codecs typically only reduce file sizes by about 60%.

    The final option is where it all gets very contentious, and that's to remove 'irrelevant data' -- the elements of a complex sound recording that the human hearing system can not resolve and detect. Formats like Dolby Digital (AC3), DTS (apt-x), MiniDisc (ATRAC), DAB radio, MP3, MP4 and all the rest are lossy codecs and they all work (albeit in slightly different details) by trying to throw away parts of the sound that their designers' think we can't hear and won't notice.

    The premise is that the human ear/brain is not a linear sound analysing system, but it actually a highly reactive and non-linear system whcih suffers from an effect called 'frequency masking'. Essentially, if I played you a quiet single-pitch tone at, say, 3kHz you would be able to perceive it quite happily. If I then add in a very much louder tone, starting at 100Hz, and gradually increase its frequency, you'll be able to hear and distinguish the two separate tones. But as the louder tone starts to approach about 2kHz the 3kHz tone will seem to disappear, and it won't come back until the loud tone has carried on up to something like 5kHz or more. It's quite a sobering demonstration, actually! But this 'frequency-masking' effect occurs throughout the hearing range and is the underlying principle of the old analogue tape noise-reduction systems like Dolby B and C.

    In the case of the ever-popular MP3 format, the basic scheme is to divide the original audio signal into a large number of narrow frequency bands. The signal in each band is then analysed to determine which frequency components can and can't be heard in the presence of all the rest. Those that the systems thinks can't be heard are immediately discarded, never to be heard again! Obviously, this process immediately removes quite a lot of data from the signal.

    The next stage is to analyse the signals elements that are left to determine how much louder they are than the system noise floor in each frequency band. The wordlength used to describe their amplitudes is then reduced to the minimum possible consistent with retaining a reasonable signal-noise ratio. This removes a whole load more data... and that's basically how the stereo signal from a CD player can be reduced from 1411kb/s (2x16x44100) down to a puny 128kb/s for MP3.

    To trained ears, the quality loss is obvious, but the majority of the iPod listeners seem quite happy with the result, even though over 90% of the original information has been discarded.Clearly, using a higher data rate -- such as 320kb/s -- means that less data has to be thrown away and so the quality loss (and file size reduction) is not as great.

    MP3 is a very clever system, but this is an area of technology that is advancing rapidly as the way the ear/brain works becomes better understood, and data processing power and speed improves. So MP3 is already old-hat, and there are better codecs around now (AAC being one of many) -- but the familiarity or MP3 is such that it will remain popular for a long time to come.

    If you start with an MP3 file, a large proportion of data has been thrown away, as I've explained, and that can't be recovered in any way. However, if you convert the MP3 file to some other format (eg a wav file to burn onto an audio CD), the data has to be 'recompiled' into the appropriate format. Which means that instead of describing the data in terms of a series of narrow frequency ranges with variable wordlengths, the signal has to be rebuilt into conventional samples with a fixed wordlength... and in doing that considerably more data is required to describe the remaining audio.

    But if you were to analyse that rebuilt signal carefully, you would see narrow frequency bands disappearing and reappearing as the signal changed, and the noise floor would be bouncing up and down in the different bands -- all as a result of the MP3 processing. So the quality remains at the MP3 level, even though the actual file size has increased.

    Sorry for the long post -- but hopefully that's helped to explain what is going on in these systems and why they work in the way they do.

    Hugh

  13. #28
    Senior Member Kuhlau's Avatar
    Join Date
    Oct 2008
    Location
    Hampshire, UK
    Posts
    258
    Post Thanks / Like

    Default

    Outstanding!

    Hugh, my thanks to you. An excellent explanation that should now bring this discussion to its natural end.

    FK
    An everyman for himself ~ Classical music reviews & resources
    --
    Follow me on Twitter

  14. #29
    Andante
    Guest

    Default

    Hugerr
    Thank you for taking the time and effort to make such an informative post, I have a greater understanding now of the issues involved, it is to be hoped that this will be perused by our members.
    Thanks again Kahlau for being so patient with me.

  15. #30
    Senior Member Kuhlau's Avatar
    Join Date
    Oct 2008
    Location
    Hampshire, UK
    Posts
    258
    Post Thanks / Like

    Default

    Always happy to be patient with those who genuinely want to understand something.

    FK
    An everyman for himself ~ Classical music reviews & resources
    --
    Follow me on Twitter

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •