CBR Versus VBR?

Do a web search for "cbr vs vbr". You'll find lots of opinions.

Regards.

GARTH wrote:
I want to know if one was better than the other. Something more cut & dried. No gray areas. Kinda like cigarette smoking. It is what it is..

CBR is better.

ed2345 - What actually makes CBR better, technically speaking? Thanks! 🙂

Fiddle Freak, In this particular thread we have been asked to avoid "gray areas," but look here.

Also See THIS POST

Best of Luck

As per Apple's own tech notes describing the various modes in its AAC encoder, VBR is best for quality: http://developer.apple.com/technotes/tn2008/tn2237.html

{quote}Constant Bit Rate (CBR) - Recommended for live streaming.

This mode achieves a constant target bit rate and is completely compliant to the CBR mode specified in the MPEG-4 standard. This mode is suitable for constant-bit-rate network transmission when decoding in real-time with a fixed end-to-end audio delay. However, due to the strict constant bit rate constraint, this mode offers the lowest audio quality and highest complexity among all the encoding modes offered.

Average Bit Rate (ABR) - Default Mode, recommended for controlling file size.

A target bit rate is achieved over a long term average (typically after the first few seconds of encoding). Unlike the CBR mode, this mode does not provide constant delay when using constant bit rate transmission, but provides best overall quality while still being able to strictly control the resulting file size with less complexity than the CBR mode.

Variable Bit Rate (VBR) - Recommended for controlling audio quality.

The audio signal is encoded with constant (and settable) quality and virtually no bit rate constraints. This is the best mode to achieve consistent audio quality across many files and the smallest file size to achieve that quality. It also has the lowest complexity of all the encoding modes.

Variable Bit Rate But Constrained (VBR Constrained) - Recommended as a compromise between VBR and ABR.

This mode is similar to VBR but limits the average bit rate variation. The lower limit is the user-selected bit rate. Higher bit rate is adapted for difficult tracks and can generate larger files than the ABR mode.{quote}

iTunes uses the CBR and VBR Constrained modes.

Haberdasher2000, Good info, thanks. But be aware that VBR (like AAC itself) was designed to improve compression performance at the bitrates that were popular several years ago. The examples in the article all use 160, which is a bit dated.

At the bitrates used today, e.g. 256, the difference among schemes is minimal. You can see this by clicking through the links provided above by Buegie, and following the story from 96 through to 320!

There's an error in my first post, the standard mode in iTunes is actually ABR now, not CBR. When you check the VBR box, it will still use VBR Constrained.

I guess you could argue that at a high bitrate like 256kbps any setting will be transparent most of the time for most people, but the beauty of VBR is that the bitrate can go much higher on hard-to-encode music. Therefore it's safe to say that VBR should always be used if quality is of main concern. Even at high bitrates there might still be sounds where the encoder struggles to maintain transparency.

With the true VBR mode, which is not available in iTunes, you don't even specify a bitrate, you just set a quality level and let the encoder work its magic. On the highest setting, some files will be just <100kbps, whereas others will be >260kbps depending on the complexity of the music. In other words, you get the highest quality possible using as little space possible.

That is a good assessment. There is also a minor disadvantage of VBR in that many players, occasionally including iTunes, are subject to getting confused by it and displaying wrong track times. Then you have to clean the files up using VBRfix.

Like most people, I tend to work at 256 nowadays, so the differences are hardly noticeable. But in the end, it is a matter of preference.

Anyway, we did not follow the OP's instruction to avoid gray areas, but hopefully we have put all the facts on the table. (-:

After some early investigation, I've been using 256VBR since I started w/iTunes 4.x or 5.x

Actually, my preferred method is to rip/save all audio "masters" in a Lossless audio format such as Apple Lossless, WAV, AIFF or FLAC (from the original CD), and then transcode directly from the Lossless source file to your preferred Lossy format such as MP3 or AAC.

This procedure preserves as much of the original audio signal as possible and prevents the compound loss of audio details from the file (by transcoding one Lossy codec to another Lossy codec).

I use the Apple Lossless codec. It may have some risk if ever Apple leaves the music biz, or goes belly-up.

Should I need to move to a higher Lossy codec (supported by iTunes) I can mass convert all my Lossless files without going back to the original CDs.

Lossless to use on the home system via a PC - Lossy on my Laptop, iPhone and Work PCs. Not too difficult to administer and somewhat 'future-proof'.

FYI - Never had a Track-Time error on my VBR files. Or at least that I noticed...

Best of Luck