[jzhang1013]

So I think I have an idea of what VBR bitrate is but can someone explain it more in depth to me? For example what would 192k VBR mean? And whats the difference between that and normal 320k??

 

[Kicksonrt66]

VBR is variable bit rate. The encoder will use more or less bits depending on the nature of the music at that particular second, but generally target the rate you specified on average. This option gives the encoder the most flexibility to put bits where they are needed, so should give the best quality for a given rate.

CBR is constant bit rate. If you specify 192 kb/s, that is the number of bits it will use every second.

ABR (not so common) is Average bit rate. Sort of like VBR, but takes the specified number (ie 192k) as more of a mandate than a soft target.

 

[brandnewgame]

VBR = variable bit rate
CBR = constant bit rate

When in VBR mode a codec will cleverly increase the bit rate where more detail is required (complex passages) and decrease when the sound is easier to compress. Constant bit rate just remained fixed even in total silence. For MP3s I prefer VBR since it records amplitudes at variable timings which makes transients sound a little more natural than even 320kbps CBR. Ogg Vorbis is my favourite lossy VBR codec, though.

 

[jzhang1013]

So in a sense, 192k VBR is smarter and is save more space than say 320k. However CBR is a surer way.

 

[brandnewgame]

Quote:

Originally Posted by jzhang1013 /img/forum/go_quote.gif So in a sense, 192k VBR is smarter and is save more space than say 320k. However CBR is a surer way.

I wouldn't say surer since VBR is technically very well implemented on popular encoders. If you want archiving quality, lossless is the only way. To be honest, I would never use CBR as it doesn't appeal to me. It's almost like WAV vs lossless encoding (at least in my mind), wav includes a lot of redundant information, lossless tries to be as efficient as possible. Same for CBR vs VBR, CBR will include a lot of unnoticeable details whereas VBR tries to be as efficient as possible, the only difference is that now efficiency is smaller filesizes while retaining audible details. Ain't that the reason we use lossy compression?

 

[jzhang1013]

Quote:

Originally Posted by brandnewgame /img/forum/go_quote.gif I wouldn't say surer since VBR is technically very well implemented on popular encoders. If you want archiving quality, lossless is the only way. To be honest, I would never use CBR as it doesn't appeal to me. It's almost like WAV vs lossless encoding (at least in my mind), wav includes a lot of redundant information, lossless tries to be as efficient as possible. Same for CBR vs VBR, CBR will include a lot of unnoticeable details whereas VBR tries to be as efficient as possible, the only difference is that now efficiency is smaller filesizes while retaining audible details. Ain't that the reason we use lossy compression?

True, it does come down to the way it was first compressed and archived.

 

[Pio2001]

Quote:

Originally Posted by jzhang1013 /img/forum/go_quote.gif So in a sense, 192k VBR is smarter and is save more space than say 320k. However CBR is a surer way.

The question is biased by the 320 kbps limit of the mp3 format. Vorbis, for example, does not have this limitation. The quality being defined by the worst element of a chain, CBR is worse, because it features complex musical parts encoded with too few data, while VBR always uses enough data (at a given quality setting).

In mp3, VBR is limited to 320 kbps. So it is not as good as in other codecs, because there may be parts that, in real VBR, would need more than 320 kbps in order to keep the specified quality level.

CBR 320 kbps in mp3 is an exception. That's the maximum bitrate, all methods included. So it is always better than VBR.

However, in some given musical parts, a 256 CBR mp3 might be worse than a 192 kbps VBR one, because the 192 kbps VBR is allowed to use 320 kbps frames when needed, while the 256 kbps CBR is not.

 

[Aaron5604]

VBR streams frequencies deemed necessary for efficiency purposes.

So, songs that contain several instruments playing all at once will naturally output a higher bit-rate. The reason on why it's regarded as more "efficient" is because bit-rates (while the song is playing, decoding) instantaneously adapts by streaming JUST the right amount of memory necessary for instrumental playback. So, when there are NO frequencies, naturally you have NO memory streaming.

Basically... when you have (for example) 600 frequencies within a frame, VBR exerts X amount of memory to accomodate those 600 frequencies; no more, no less.

CBR is exactly as it sounds -- CONSTANT. Constantly streaming any set bit-rate for the duration of any given song, from start to finish.

So, even when you have no frequencies, NO sound -- you still have that set bit-rate streaming as if there were sound to be played. PCM/WAV uses this.

ABR (in essence) works the same as VBR. Only difference here, is they just went ahead and added, then divided for a mean avg. rather than streaming each frame live -- as the song is being played back. FLAC uses this.

 

[chinesekiwi]

Quote:

Originally Posted by Pio2001 /img/forum/go_quote.gif The question is biased by the 320 kbps limit of the mp3 format. Vorbis, for example, does not have this limitation. The quality being defined by the worst element of a chain, CBR is worse, because it features complex musical parts encoded with too few data, while VBR always uses enough data (at a given quality setting). In mp3, VBR is limited to 320 kbps. So it is not as good as in other codecs, because there may be parts that, in real VBR, would need more than 320 kbps in order to keep the specified quality level. CBR 320 kbps in mp3 is an exception. That's the maximum bitrate, all methods included. So it is always better than VBR. However, in some given musical parts, a 256 CBR mp3 might be worse than a 192 kbps VBR one, because the 192 kbps VBR is allowed to use 320 kbps frames when needed, while the 256 kbps CBR is not.

What I was about to say (so be in different words).
A spectrogram comparison shows the above pretty easily.

 

[JiPod]

Request clarification on iTunes 8 (and newer). Considering ripping CDs to AAC 256 VBR and uploading to my iPod Touch 1G.

Is it correct to assume the following:
1. minimum bit rate is 256 even during silence;
2. maximum bit rate is 320;
3. iTunes 8 (and newer) is a capable VBR encoder; and
4. the decoder on an iPod Touch 1G has limits, and anything above 192 is "indistinguishable"?

Thanks in advance.

 

[mbd2884]

Actually V0 VBR 245 is better than CBR 320. Other way around. As was said before, 320 adds a lot of junk to too keep it at 320.

 

[deadguy99]

in this day and age space should never be a problem ... most computers come with 500+gig drives and 1tb+ can be had for under 200 dollars. Portable players are also increasingly growing in size but not in price not to mention memory cards are dirt cheap right now... FLAC is the only way to go now

 

[Mayzei]

Let me just google that for you.

xx

 

[iriverdude]

Quote:

Originally Posted by deadguy99 /img/forum/go_quote.gif in this day and age space should never be a problem ... most computers come with 500+gig drives and 1tb+ can be had for under 200 dollars. Portable players are also increasingly growing in size but not in price not to mention memory cards are dirt cheap right now... FLAC is the only way to go now

Flac on home system, lossy on portable system. Until DAP's have 500GB+ HD I'll have to use lossy. It'll be great as I wouldn't need to convert flac-ogg for the DAP, I can just copy the entire lossless directory.

 

[i_don't_know]

If space is not an issue, would you guys say that high bitrate CBR > slightly lower bitrate VBR?