VBR v. CBR?
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Thread: VBR v. CBR?

  1. #1
    Tech Student L0BED's Avatar
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    Default VBR v. CBR?

    Combed thru about 10 pages of search results for terms "audio", "quality", etc. and found little discussion about this so I figured I'd chance a new thread.

    Is there any significant difference or risk of a drop in quality between VBR and CBR encoding for an MP3? I often have the choice of downloading a 320CBR MP3 vs. the same song encoded VBR in the mid-200s or so. Basically, I'm wondering if (since VBR bitrates are the 'average'...I think) VBR actually produces a better sound quality, or if I should just be grabbing 320CBR's of every track. Space isn't an issue for me - I am aware that CBR 'fills in' songs to keep them at a constant bitrate.

    Am I just splitting hairs here? Sorry to make another 'audio quality' thread, but there do seem to be some knowledgeable audiophiles around (which I am certainly not).

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    DJTT Administrator del Ritmo padi_04's Avatar
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    CBR doesn't fill in anything, it takes away less stuff than VBR. Since both are lossy conversions, always aim for the less destructive.

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    Tech Student L0BED's Avatar
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    Never thought of it that way, but obviously you're right...I guess with VBR there's only a chance that you inadvertently lose part of the signal.

    Sold! thanks much.

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    Tech Mentor DJSigma's Avatar
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    CBR is kinda pointless IMO, unless you are using DJ gear that doesn't play nicely with it. While the "it takes less away" argument would appear to make sense if you don't look into it that deeply, in terms of transparent encodes that argument doesn't really hold up.

    If a track contains a period of silence, or a period where just hi-hats are playing, for example, with 320 Kbps CBR that would be encoded at 320 Kbps along with the "busier" parts of the track and that gives you no benefit whatsoever. All it does is make the file bigger. VBR encoding adjusts the bitrate of an MP3 constantly within a given range depending on the qualities of the song at any given time, so if there's silence in a track the bitrate would drop to the minimum, while at busy points it would push up towards the maximum.

    From the HydrogenAudio Wiki: -

    The rule of thumb when considering encoding options: at a given bitrate, VBR is higher quality than ABR, which is higher quality than CBR (VBR > ABR > CBR in terms of quality). However, ABX tests demonstrate that as bitrate increases, the perceptual differences diminish, with all modes generally reaching transparency well before their maximum settings; when you can't tell the difference, the modes are qualitatively the same.
    http://wiki.hydrogenaudio.org/index.php?title=LAME

    But if space isn't an issue, I would suggest going for lossless files instead of lossy ones.

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    Tech Student L0BED's Avatar
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    Quote Originally Posted by DJSigma View Post
    If a track contains a period of silence, or a period where just hi-hats are playing, for example, with 320 Kbps CBR that would be encoded at 320 Kbps along with the "busier" parts of the track and that gives you no benefit whatsoever. All it does is make the file bigger.
    This is what I meant by 'filling'. I think padi is saying that it's better to have a bigger file than to risk VBR actually cutting out part of the signal (if that can even happen).

    Quote Originally Posted by DJSigma View Post
    But if space isn't an issue, I would suggest going for lossless files instead of lossy ones.
    The only lossless format I know of is FLAC (although apparently there are lossless WMAs?) which doesn't seem to play nicely with a fair bit of software (including Traktor, according to some posts elsewhere). Plus, I am an OCD metadata user.

    Edit: apparently FLAC supports metadata! I guess FLAC shall be my #1 option then, followed by CBR320 MP3. Helpful.
    Last edited by L0BED; 11-22-2012 at 10:13 AM.

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    RGAS Guru Xonetacular's Avatar
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    Quote Originally Posted by padi_04 View Post
    CBR doesn't fill in anything, it takes away less stuff than VBR. Since both are lossy conversions, always aim for the less destructive.

    Not necessarily true.

    A well encoded VBR file will have the exact same quality as a 320 CBR file with less space.

    LAME V0 (alt preset extreme- highest setting for LAME mp3 encoding) is identical sound quality to 320 CBR and goes as high as 320 but only where necessary, so if encoding your own .mp3s V0 is a smarter choice and there is no reason to choose 320 CBR unless you just want the bitrate field to look consistent to stuff downloaded from beatport and the like, but the quality is identical...

    As an analogy- V0 is to 320 as FLAC is to wav. Flac is also lossless but much smaller file size than wav because of variable bitrate, just like a V0 encoded .mp3 contains the exact same information bit fot bit as a 320 CBR file at lower filesize since it is a more efficient and smarter format.
    Last edited by Xonetacular; 11-22-2012 at 10:22 AM.


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    Tech Mentor DJSigma's Avatar
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    VBR doesn't lead to an encode that is perceivably different from CBR at high settings. That's why CBR is pointless really. As mentioned above, the V0 preset can go as high as 320 Kbps, but only when it's deemed necessary. The MP3 codec (LAME specifically) has been tweaked and fine tuned over many years and is designed with VBR encoding in mind, primarily.

    There are various lossless codecs you can use - FLAC, Apple Lossless, WMA Lossless, APE, WavPack etc. - and all of the commonly used ones support metadata, which I am also OCD about. I use FLAC with Traktor (and for listening in general) and it works fine.

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    Tech Student L0BED's Avatar
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    Quote Originally Posted by Xonetacular View Post
    As an analogy- V0 is to 320 as FLAC is to wav. Flac is also lossless but much smaller file size than wav because of variable bitrate, just like a V0 encoded .mp3 contains the exact same information bit fot bit as a 320 CBR file at lower filesize since it is a more efficient and smarter format.
    This makes sense, thanks! If I ever end up making anything worth encoding to mp3 I'll keep it in mind.

    FLAC also seems to be annoyingly hard to find, but I'll keep a lookout for it.

  9. #9
    Tech Mentor DJSigma's Avatar
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    Quote Originally Posted by L0BED View Post
    This makes sense, thanks! If I ever end up making anything worth encoding to mp3 I'll keep it in mind.

    FLAC also seems to be annoyingly hard to find, but I'll keep a lookout for it.
    Bear in mind that encoding/transcoding works like this with lossless files, whether compressed or uncompressed: -

    Uncompressed lossless ---> Compressed lossless = no quality loss (e.g. WAV to FLAC)
    Compressed lossless ---> Uncompressed lossless = no quality loss (e.g. FLAC to WAV)
    Compressed lossless ---> Compressed lossless = no quality loss (e.g. Apple Lossless to FLAC)

    So it doesn't really matter what format the file is in when you buy it as long as it's lossless. Encoding/transcoding to FLAC takes seconds with dBpoweramp, Switch, or your software of choice, and good encoding software will retain all of the metadata across the transcode too.

    BTW, I'm not saying that you will definitely notice a difference in sound quality if you purchase a FLAC file over an MP3, but if you want the best quality (even if it's usually theoretical, rather than actually perceived) and space is not an issue, then lossless is the way to go over lossy.

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