original 24/48 wav file: 264,904,968 bytes flac level 8: 105,992,780 bytes dithered 16/48 wav file:173,885,996 bytes flac level 8: 108,700,948 bytes
truncated 16/48 wav file: 173,885,996 bytes flac level 8: 105,224,448 bytes RMS level of original 24 bit: -15.3dB with peaks at -0.3dB if I normalize the original file to a max of 0.0, the resulting flac file is 192,798,482 bytes. weird.... Scott On Thu, Dec 2, 2010 at 4:36 PM, Brian Willoughby <[email protected]>wrote: > > On Dec 2, 2010, at 07:55, scott brown wrote: > >> My first thought was that the file had low levels (before he sent me the >> file), but that's definitely not the case with this file. There are many >> peaks that reach 0dBFS. >> > Live, uncompressed music often has peaks that are 4 dB higher, or more, > than a typical commercial CD. Such peaks are brief, and would not really > affect the total size of the FLAC file. Really, the average level is what > determines whether the FLAC file ends up being smaller than 50% as it is in > this case. > > > > He sent me the original wav this morning and I loaded it into Wave Editor >> on OS X. I dithered to 16 bit using MBIT+ (high/ultra setting) and saved >> the 16 bit file. I did nothing else (no normalizing or any other >> processing). I can't give you the 16 bit size right now since I'm at work >> and the file is on my Mac at home, but I can report back tonight. >> > > Impressive! I have read many comments that MBIT+ is the best. I've only > recently licensed it myself, so I have not yet had time to form a personal > opinion as to whether it is better than the dither that I have been using > for years. > > No matter how good the dither is, though, it's still noise. The human ear > and brain system cannot hear MBIT+, but FLAC is just a mathematical process. > Dithering from 24-bit to 16-bit is equivalent to increasing the > quantization noise by about 48 dB! It's actually quite impressive that you > can add 48 dB of noise and the FLAC file only increases in size by less than > 2%. > > Thanks for the details. I'm curious about the file size, but uncompressed > WAV should be exactly as I predicted. > > > > Whatever my process is, though, the guy who originally recorded the file >> gets the same results with whatever method he uses to convert to 16 bit on >> Windows. I can ask him what his 24 > 16 bit process is. I can also just >> truncate the file down to 16 bit and report back on the resulting flac file >> size. Would you expect that flac file to be around the same size as the 24 >> bit? In my experience, my 24/48 flac files are always substantialy bigger >> than my 16 bit flac files, which is why this case confuses me... >> > Personally, I rarely pay close attention to the exact compression. I'm > happy just that FLAC is smaller and lossless. But I am still curious about > the various reasons why some files turn out bigger or smaller than others. > I tend to do everything in 24-bit, even final mastering, so I have not > looked at 16-bit in a long while. > > I can say that DTS surround music disc, which is 14-bit data in 16-bit CD > format, does end up with a FLAC that is almost exactly 87.5% of the WAV. > This makes perfect sense, because the DTS data looks like random white > noise to FLAC, and the only thing FLAC can do is compress those 2 unused > bits. > > It's tempting to look at the 24-bit to 16-bit conversion as simply dropping > 1/3 of the data, since files are based on 8-bit bytes. But one way to look > at this is that FLAC deals with audio samples as if they were all 32-bit. > The 16-bit samples simply have more noise. It will be interesting to see > what happens with your 16-bit truncation test. I would expect that the FLAC > would only get smaller, not increase in size, if all you do is truncate. > > Fortunately, FLAC is quite smart about bit utilization, and can even detect > 16-bit samples in a 24-bit file. I don't think that's happening with your > files, though, because I would expect the 24-bit FLAC to be around 33% of > the 24-bit WAV if it actually only had 16-bit samples, instead of the 40% > that you're seeing. But I suppose that's always possible. > > Brian Willoughby > Sound Consulting > > P.S. I'm still curious where Nicholas came up with the 14% value. Is that > based on decibels, bits, or some other metric I haven't thought of? > >
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