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VBR vs CBR, Better or just different?
RockGtrSeattle
post Nov 20 2002, 02:18
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I've done rips in both VBR and CBR. It *seems* to me that, overall, VBR rips have the best playback sound quality. The rip level I do with CBR is usually around 256k.

So this makes me wonder, why would someone use VBR over CBR? Compatibility with older players? Portability to other playback systems?

Thanks for any insights you can provide (or any links you can point me to).

- RGS
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gnoshi
post Nov 20 2002, 02:38
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I assume that you mean why would someone use CBR over VBR?

Pretty much all playback systems I can think of now support VBR; I would say probably the only reason people would use CBR now is because
a) that is all their crappy encoder can do
B) they don't know better
c) they were fooled by someone else who didn't know better

Of course, this may vary from codec to codec (eg. mp3pro only does CBR doesn't it?)
But yes, VBR is better (makes sense, use less bits when you need less, use more when you need more).
Of course, I may be wrong, and not infrequently am.

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jmvalin
post Nov 20 2002, 03:11
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QUOTE (RockGtrSeattle @ Nov 19 2002 - 08:18 PM)
So this makes me wonder, why would someone use VBR over CBR?  Compatibility with older players?  Portability to other playback systems?

While VBR is probably best for files, where it's the total size that counts, there are applications (e.g. streaming in real-time) where you need CBR because the limit is the maximum bandwidth, not the total size.
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guruboolez
post Nov 20 2002, 03:13
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QUOTE (gnoshi @ Nov 20 2002 - 02:38 AM)
Of course, this may vary from codec to codec (eg. mp3pro only does CBR doesn't it?)

Mp3pro is VBR since april. CoolEdit2 and MusicMatch paid for the new codec.
WMA is VBR too now.
One of the last modern codec totally CBR is Atrac3 (minidisc and Real)
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kennedyb4
post Nov 20 2002, 04:41
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CBR is easier to edit too. If you capture audio from TV, Video, or frequently radio, cutting out glitches and commercials etc, CBR is a lot easier to work with.

I am pretty impressed with people that can detect differences between 256 files and good VBR files, at least on "regular" music.

This post has been edited by kennedyb4: Nov 20 2002, 04:43
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Garf
post Nov 20 2002, 09:43
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QUOTE (jmvalin @ Nov 20 2002 - 04:11 AM)
QUOTE (RockGtrSeattle @ Nov 19 2002 - 08:18 PM)
So this makes me wonder, why would someone use VBR over CBR?  Compatibility with older players?  Portability to other playback systems?

While VBR is probably best for files, where it's the total size that counts, there are applications (e.g. streaming in real-time) where you need CBR because the limit is the maximum bandwidth, not the total size.

You can use VBR here as well, just limit the maximum bitrate. Perfectly possible with Vorbis.
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Dibrom
post Nov 20 2002, 10:12
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QUOTE (Garf @ Nov 20 2002 - 01:43 AM)
QUOTE (jmvalin @ Nov 20 2002 - 04:11 AM)
QUOTE (RockGtrSeattle @ Nov 19 2002 - 08:18 PM)
So this makes me wonder, why would someone use VBR over CBR?  Compatibility with older players?  Portability to other playback systems?

While VBR is probably best for files, where it's the total size that counts, there are applications (e.g. streaming in real-time) where you need CBR because the limit is the maximum bandwidth, not the total size.

You can use VBR here as well, just limit the maximum bitrate. Perfectly possible with Vorbis.

Would this really be that useful though? In streaming applications, you're not limited by a finite file size, only by the bandwidth of your connection. Given that (and that it's usually low bandwidth, relatively), wouldn't it make more sense to use CBR at the maximum bitrate your connection can stream at? Seems to me this would allow for a maximization of quality in such a situation. VBR is really only useful when you want higher quality than you'd often be able to get at a given constant bitrate.. this works because you can go over that bitrate for critical short periods, but this won't work with streaming.
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Kblood
post Nov 20 2002, 10:21
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Well, if you take into account that pretty much every streaming solution has some kind of buffer, then VBR will certainly help to maximize the profits of the buffer space, won't it? I can think of, for example, streaming spoken word situations, in which the silence between the sentences would require less bandwidth to be received, thus allowing your machine to start buffering the stream further ahead in time...

Am I right? smile.gif
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Garf
post Nov 20 2002, 10:28
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QUOTE (Kblood @ Nov 20 2002 - 11:21 AM)
Well, if you take into account that pretty much every streaming solution has some kind of buffer, then VBR will certainly help to maximize the profits of the buffer space, won't it? I can think of, for example, streaming spoken word situations, in which the silence between the sentences would require less bandwidth to be received, thus allowing your machine to start buffering the stream further ahead in time...

Am I right? smile.gif

You are. VBR is definetely better than CBR even for streaming. The only thing you need to make sure is that the buffer of the receiver isn't overrun. This means that for very short periods higher bitrates are possible. Vorbis for example assumes a 2 or 4 second buffer in the receiving application.
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Dibrom
post Nov 20 2002, 10:35
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QUOTE (Garf @ Nov 20 2002 - 02:28 AM)
You are. VBR is definetely better than CBR even for streaming. The only thing you need to make sure is that the buffer of the receiver isn't overrun. This means that for very short periods higher bitrates are possible. Vorbis for example assumes a 2 or 4 second buffer in the receiving application.

Yes, this works if you have good buffering system in place, and the stream actually does go up to higher bitrates for short periods.

With the example you gave, I was assuming that in both cases, the maximum bitrate of the stream was the same (say, streaming at 64kbps cbr, or vbr with a 64kbps ceiling). I guess I should have realized that's not what you meant though, because that wouldn't provide any quality benefits. If you have something like 64kbps average though, with dips to 48kbps (where you could buffer ahead) and peaks say at 80kbps (using some of the extra buffer profits), and a good buffer, then that would probably work well for some applications.
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ErikS
post Nov 20 2002, 11:16
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QUOTE (Dibrom @ Nov 20 2002 - 10:35 AM)
With the example you gave, I was assuming that in both cases, the maximum bitrate of the stream was the same (say, streaming at 64kbps cbr, or vbr with a 64kbps ceiling).

To give a fair match the ceiling bitrate of the vbr codec of course has to be set to the same as the bitrate of the cbr codec. But the trick is that you should calculate the bitrate over a time window of the same size as the buffer has. This will lead to an averaging of the bitrate and cut off momentary high bitrate peaks.
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