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Hi,
A few very quick questions to help me clarify what I think I know about lossless music….

Currently, most of my music is stored on my computer for use on my iPod at a high MP3 bit rate.

As I will soon be purchasing a good hi-fi system I am going to start importing my CDs again using lossless compression. These digital files will be my main source of music and I want the information in these files to be EXACTLY the same as is on the CD. Ie. There should be no difference between playing the CD or the imported digital file through the same DAC.

Is this achieved with lossless compression?
Does the computer/sound card affect the imported file?
Does the importing software affect the resulting imported lossless file?
Is there a difference in apple lossless or wav? Are there any other options I should consider?
Does converting between lossless files affect the data ie. ( if I convert a wav file to flac, convert this flac to apple lossless and then convert this apple lossless to wav, will the two wav files be exactly the same?)

Thanks for the advice,
Conor

On a related note, I read this on the Squeezebox Classic website...

 

Supported Audio formats

• 
  
  Lossless Formats (Apple Lossless, FLAC, WMA Lossless)
  
  
  • "Bit-perfect" CD audio streaming, with reduced storage and bandwidth usage
  • Approximately 2:1 compression ratio
• 
  
  Uncompressed formats (AIFF, WAV, PCM)
  
  
  • Supports raw pass-through of uncompressed PCM audio formats
  • Digital passthrough to S/PDIF for DTS
• 
  
  Compressed formats (MP3, AAC, Ogg Vorbis, MP2, MusePack, WMA)
  
  
  • MPEG decoding uses MAD software, widely regarded as the most accurate, most compatible MP3 decoder
  • Supports all MP3 data rates and sample rates, including VBR

What does it mean by "Digital passthrough to S/PDIF for DTS" for uncompressed formats?

 

Thanks

These digital files will be my main source of music and I want the information in these files to be EXACTLY the same as is on the CD. Ie. There should be no difference between playing the CD or the imported digital file through the same DAC. Is this achieved with lossless compression?

Lossless compression is a necessary but not sufficient condition. If you want an exact copy then you need either some way of verifying that it's exact, or if that's not possible take all reasonable steps to try to ensure that it is. On windows the approach is generally to use EAC (exact audio copy), which is a plugin for some media players (dpPoweramp is one I think), which creates a checksum of your rip and compares it to other people's, giving you a level of confidence that your rip is exact. On a Mac, EAC is tricky to implement and your best bet is to use iTunes with error correction turned on - this is the approach I use and it's served me well, but I can't be 100% sure that my copies are 'exact'.

Does the computer/sound card affect the imported file?

No, if you take one of the the approaches listed above. If you do not, you can be at the mercy of lesser quality CD drives producing poor quality rips. The soundcard is not involved.

Does the importing software affect the resulting imported lossless file?

In my opinion, no, though only iTunes uses a licensed version of the apple lossless codec - any other is using a reverse-engineered one. And if you extrapolate that, it's possible that different players may implement different WMA or FLAC codecs...

Is there a difference in apple lossless or wav?

In my experience, no.

Are there any other options I should consider?

Depends on both your OS and what you want to stream it with. If you're on windows, FLAC and WMA lossless are alternatives to apple lossless, both of which support tagging, as are AIFF and WAV, which don't (or at least I know WAV doesn't, less sure about AIFF), and neither of the latter are compressed so you need a lot of disc space. Which option is best depends on what you want to play it with, since some formats are supported by some clients and not others. Got any ideas about whether you might use airport express, uniti, squeezebox, windows media extender etc etc?

Does converting between lossless files affect the data ie. (if I convert a wav file to flac, convert this flac to apple lossless and then convert this apple lossless to wav, will the two wav files be exactly the same?)

That's the theory, yes, and there's plenty of evidence out there of people having done this conversion and comparing file versions before and after and ending up with the same result down at a binary level, but I'm kind of going to take everybody's word for it on that one as the results I'm getting are pretty damn good and life's too short.

On the bit-perfect rip point.....on a Mac, you can use XLD to rip your music, this has an option to "query AccurateRip database" to check for bit perfect rips, as EAC does in windows. It also has an option to add files to iTunes automatically.

Very handy program for converting between different audio formats as well as CD ripping. The web site may be quite confusing, but the program is fine to use, just download the GUI version to avoid all the command line stuff!

 

jon

lambconor:

On a related note, I read this on the Squeezebox Classic website...

 

Supported Audio formats

• 
  
  Lossless Formats (Apple Lossless, FLAC, WMA Lossless)
  
  
  • "Bit-perfect" CD audio streaming, with reduced storage and bandwidth usage
  • Approximately 2:1 compression ratio
• 
  
  Uncompressed formats (AIFF, WAV, PCM)
  
  
  • Supports raw pass-through of uncompressed PCM audio formats
  • Digital passthrough to S/PDIF for DTS
• 
  
  Compressed formats (MP3, AAC, Ogg Vorbis, MP2, MusePack, WMA)
  
  
  • MPEG decoding uses MAD software, widely regarded as the most accurate, most compatible MP3 decoder
  • Supports all MP3 data rates and sample rates, including VBR

What does it mean by "Digital passthrough to S/PDIF for DTS" for uncompressed formats?

 

Thanks

Your last question is relating to surround sound.

Hi,
Thanks very much for the replies. Some very interesting points.

 I have used itunes for years on my windows pc... so I will probably stick with this and use apple lossless with error correction turned on.

I am using a Squeezebox 3 classic and will eventually connect this to a DAC. Is there any real advantage to using uncompressed music (e.g wav) over something like apple lossless? 

 

Thanks,

Conor

 

There are a few people on here who have said they prefer the sound of AIFF (for example) over Apple Lossless, but I don't see it personally. One advantage of most of the lossless compressed formats though is that they have the facility to store metadata within the files themselves (as opposed to WAV, which uses the iTunes library file, and therefore doesn't take its info with it when you move it).

Last point - you may find that on Windows turning error correction on slows down your rip speed rather badly - not a problem on Mac for some reason, but that doesn't help you much.

One more question. CD quality is 1,411kbps. However, when I rip a CD in apple lossless on iTunes it ranges from 800kbps - over 1,000kpbs. In some cases on the same album the bit will vary on each track.

Why is this? 

In very simple terms, lossless compression works like this. Say I have a binary code which is 01010101 - I could compress this using an algorithm which says 014 - the algorithm knows that the 4 means 01 is repeated four times, so I've compressed 8 bits of information (8 numbers) down to 3 bits (3 numbers) for storage. When I want to read the data, I decode it using the algorithm and since it knows 014 means 01010101, I haven't lost any information.

On the other hand, if I have a binary code of 00111010, then I might compress this down to 0213010 - (i.e. 0 is repeated 2 times, 1 is repeated 3 times and 010 is left as is since there's no pattern). Since it's more complicated, I only managed to compress it down to 7 bits instead of 3 bits, but I used the same concept in the algorithm i.e. when the number is more than 1, it means the numbers in between are repeated that many times.

As I say, this is an incredibly simplified version, but it shows how you can get different bitrates depending on how clever the algorithm is and how complicated the data you are compressing is.

 

Generalising wildly:

A WAV file consists of 16 bits sampled 44,100 times per second, for each channel, irrespective of what the file contains = 16 x 44100 x 2 = 1,411,200 = 1411kbps.

Lossless files ignore stuff like silence, so the actual data rate is always less than this, and varies depending on complexity of music.

thanks. I understand the bit rate reason now. But is it technically not fully lossless? My friend is saying if its not 1,400kbps then its not truly lossless?

Shimminator:

thanks. I understand the bit rate reason now. But is it technically not fully lossless? My friend is saying if its not 1,400kbps then its not truly lossless?

It's not me, honest!

 

Shimminator:

thanks. I understand the bit rate reason now. But is it technically not fully lossless? My friend is saying if its not 1,400kbps then its not truly lossless?

The music is stored compressed but is restored to a 1,411kbps stream on the fly, losing nothing of the original track. If you can be bothered, take a wav file, compress it with a lossless codec, convert it back, compare the two...

Shimminator:

My friend is saying if its not 1,400kbps then its not truly lossless?

Lossless compression doesn't really have anything to do with bitrate. It's purely a term for audio codecs which have the ability to compress a file without losing any detail using certain compression algorithms (as explained above). FLAC and ALAC are two different codecs which come under the lossless banner.

This is in contrast to lossy compression formats like AAC and MP3. For these, the bitrate rules the roost. So if you want a song to have a bitrate of 128 Kbps, then these formats will throw away as much detail as is required to compress the song to that bitrate. The information that is thrown away basically depends on how "clever" that codec is and what it considers important information and what it doesn't.

Shimminator:

thanks. I understand the bit rate reason now. But is it technically not fully lossless? My friend is saying if its not 1,400kbps then its not truly lossless?

It is lossless because if you convert it back to a WAV file it's bit-identical to the WAV file you created the lossless file from in the first place. No information has been lost.

Think of it like this: If you ripped a wav file from a CD it's uncompressed lossless right (1400kbps to satisfy your mate)?

Now, take that WAV file and zip it in Winzip (other compression tools are available...). You now have a smaller file, right? So it's compressed. However when you unzip the zip file, you get your original WAV file back, ergo it's also lossless.

Basically that's how FLAC etc works, you could conceivably write a media player that could play the zip file directly, without having to unpack it first, in layman's terms that's sort of what's happening with compressed lossless audio.