VBR, ABR and CBR ??

[moiz]

What's the difference between them?

All I know through Wikipedia is, that in CBR the bitrate remains the same no matter whether the sound at a particular point is simple or complex, when simple, some bits will go unused. But, ABR gives more bits to complex sounds and less to simple ones and is better than CBR in tearms of quality.

But, I couldn't get the difference between VBR and ABR ??

Will the file size be same at a given bitrate say, 192/128/96/224 kbps in all three of them ??

[TJohns]

CBR allocates bits at a constant rate, as you've said. Thus you'll get a file of an easily determined size (bitrate * duration)

VBR is usually a multi-pass process...scan the whole file first, then you know EXACTLY which sections are more complex than others and so can allocate more bits in precisely the right places when you go thru the file a second time. In this case the AVERAGE bitrate * duration determines the filesize

ABR is more of a "blinkered" approach...it only scans the file once (allocating bits as it goes), but tries to work out complexity by comparing the current part of the file with the previous sections that were just finished. A reasonable approach if the complexity doesn't vary wildly from one part of the file to the next...Size here is harder to determine, since less complex areas get less bits, more complex gets more bits (but neither would be the optimal rates that VBR calculates) so overall you could be under or over your requested bitrate

Trevor

[guns1inger]

Worth noting :

Some hardware players and some video editors do not like ABR/VBR encoded MP3 audio. Results can be anything from crashes and lockups to unpredictable playback ro simple refusal to play. CBR is universally accepted.

[FulciLives]

If you are creating a DivX or XviD video file and want to use MP3 then as guns1inger says use CBR MP3 otherwise you are asking for trouble.

- John "FulciLives" Coleman

[moiz]

Thank you to all of you!

Does this only apply on MP3? I mean, AAC and AC3 don't have CBR/ABR/VBR thing?

[guns1inger]

AC3 is CBR. AAC may support VBR - I don't know enough about all the profiles - but I have only seen CBR encoded files.

[poisondeathray]

Nero's AAC implementation (free) supports all, but not all front-ends will give you access to all 3. LameXP, and MeGUI are some examples that support all 3 modes

I think CT-AAC's version is only CBR

[moiz]

For PC playback only, which of the 3 gives the best quality at a given bitrate?

[guns1inger]

AAC

[moiz]

I mean among VBR, CBR and ABR, which one would sound best on PC at a given bitrate?

[guns1inger]

At higher bitrates (256 and up) you will be hard pressed to find any difference. At lower bitrates VBR should sound better as the available bitrate should be allocated based on need.

[moiz]

OK, thank you very much for educating this newbie!