Originally Posted by binky61 (Post 1728488)

When you rip a CD to FLAC format the result is always lossless the only variable is in the level of compression.

Originally Posted by Baph (Post 1728553)

I came to this thread not because I have a solution, but because I thought the below may happen instinctively. :)



That's a common misconception. Let me explain...

[geek mode]
In general, audio file formats use compression in order to reduce file size and aid portability. Again, in general this uses the ZIP compression algorithm.

Without loosing any data in the audio stream whatsoever, the ZIP algorithm can achieve compression of 10-20%, regardless of what it's compressing. That's loss-less compression right there, using "standard" algorithms.

That said, yet again, in general, 10-20% shaved off the file size of a CD (600-800Mb) isn't really that useful for most people. Therefore most converting tools actually strip audio out prior to compression. Further still, compressing the data looses some data too! This can achieve up to 80% compression, and still be reasonable quality.

FLAC is different.

FLAC uses linear prediction to convert the audio into a series of numbers, which is then passed through Golomb-Rice code and then run-length encodes the stream. This looses no data whatsoever from the stream (depending on implementation of Golomb-Rice - I could go on about fixed point vs floating point samples, but that's beyond the scope of discussion IMO).

In doing the above, FLAC can achieve 30-50% compression, without loosing any original data.

Right then, now that we've established FLAC will not loose any quality (depending on implementation), there is something else that needs consideration in producing exact reproductions.

If the disc is not PERFECTLY clean, along with the laser lens on the drive, you will loose quality (FLAC vs original CD). The reason for this is that the CRC's involved are just a failsafe.

CRC's only provide an approximation as to data accuracy. For example, if I know an MD5 CRC, I can provide completely wrong data, but that data will still provide the same CRC, therefore the routines will assume the data is correct, when it's actually 100% corrupt. I commonly do this with system passwords (any system admins reading this, safe yourself a headache & ditch MD5).

We have the same problem in work with CRC's. We have a setup that self-checks files on a computer before it starts, for legal reasons some files must NEVER be changed. We can doctor files happily so that they don't match the original, but the CRC is still valid so the machine boots & runs. But I digress...

So long as the data coming from the CD isn't dropping too many bits, the CRC's involved with reading the disc will tell the computer that the stream is fine. It's not an exact copy though, even if you store every single bit read successfully.

If you're after true audio quality, you may as well forget the CD completely though. There is a certain amount of data lost when recording in the studio, and then more yet when converting that audio to CD format.

If you want a true exact copy of audio, you need to spend a LOT of money on hardware (more than record companies do!!), and then record it to a format like FLAC.

Before anyone dies of a heart attack, 99.999% of all audio lost by recording, burning the original CD & then reading it back in a CD drive is outside the human hearing range.

[geek mode off]

Originally Posted by Nekkid (Post 1728734)

Baph, can you recomend any software (easy to use!) apart from the DBPoweramp already mentioned?

Thanks!!