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auto bit depth foobar

post #1 of 6
Thread Starter 

What does the auto bit depth setting mean? I can also choose 16 - 24 bit and so on. What bit depth is chosen when set to auto in foobar? In this case for converting a cd to flac files.

 

With kind regards,

 

Theun Spaans

post #2 of 6

The bit depth is the number of bits per sample. In audio, that corresponds to the SNR and maximum dynamic range of the music. When reading a digital file, a DAC has to approximate the ~infinite values of the analog sine wave. The fewer bits there are per sample, the more rounding is necessary. This creates "quantization noise", junk that's not in the original signal. Each bit per sample decreases the amount of rounding, and decreases the volume of the quantization noise by about 6 dB. So a 16 bit depth file will generate quantization noise about 96 dB below the maximum volume. This is enough for all recordings in 95% of all situations (only very loud playback of quiet recordings, or extensive use of digital volume control, will make it audible). 24 bit audio gives 144 dB of SNR, which is more than any DAC can manage (the inherent noise added by the electronics is higher than this, usually SNR is ~120 dB or 20 effective bits at most).

 

When converting from CD to FLAC, you want to convert it at 16 bits. That's what the CD is, and increasing it will just pad the files with extra zeroes and waste space.

 

However, if your DAC supports it, there's no reason not to set playback to 24 bits, even if your audio is 16 bits. This will automatically add the extra zeroes, requires no wasted space, and allows for a lot of digital volume attenuation without making the quantization noise audible.

 

Presumably "Auto" will set it to 16 bits for ripping CDs. As in, it sets it to whatever the source file is. So if you were converting 24 bit WAV files, it would set it to 24 bits.


Edited by Head Injury - 3/15/12 at 11:45am
post #3 of 6
Thread Starter 

thanks!

post #4 of 6
Quote from here:

Personally, I use this for a column: 

CODE
$if($strcmp(%__encoding%,lossy),%bitrate% kbps,%__bitspersample% bit)



Then I can get rid of the bitrate column, since bitrate is not really important for lossless files, and bitdepth doesn't exist for lossy files.

 

 

 

I'd like to know the bits per sample info of every file foobar plays, be it flac, mp3 etc. 

 

__bitspersample not always return that info, sometimes it's "?".

 

But I believe every music file, be it loss less or lossy, has a fixed, obtainable number of bits per sample, isn't that so?

How could I get that with foobar?

 

Thanks in advance,

 

xezi.

post #5 of 6
Quote:
Originally Posted by xezi View Post
 

 

I'd like to know the bits per sample info of every file foobar plays, be it flac, mp3 etc. 

 

__bitspersample not always return that info, sometimes it's "?".

 

But I believe every music file, be it loss less or lossy, has a fixed, obtainable number of bits per sample, isn't that so?

How could I get that with foobar?

 

Thanks in advance,

 

xezi.

 

I don't use foobar, but I imagine that the "?" is for VBR files. Lossy files like mp3 and AAC can have variable bitrates so that you can have smaller files while still having high bitrates on complex segments where it is most needed. For VBR, players vary in how they handle displaying it.

post #6 of 6

Well, thanks. I think you addressed bit rate, I was talking about bit depth.

 

I went educate myself a bit about the matter, and it seems lossy files are in general frequency based

compression algorithms, which make bit depth not only unavailable (mp3 header doesn't even hold that information)

but meaningless.

 

That is a partial answer however, because at some point the samples should stream into a DAC. 

If one sends a 320kbps mp3 song through usb for a Fiio E17 at 16bit/96kHz, for example, at some point

the mp3 got to be converted to 16 bit samples at a 96kHz (fixed, I think) sampling frequency. 

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