IPB

Welcome Guest ( Log In | Register )

MP3 Bit Reservoir, Did I understand it right ?
krafty
post Aug 30 2012, 02:53
Post #1





Group: Members
Posts: 280
Joined: 20-March 10
Member No.: 79175



Ok, so I've read some posts and learned a bit about the principles, but, something is still not clear...

- In V0, there is room for frames to go higher than 320kbps while sparing these bits on the low bitrate frames? (It can go a bit higher than 320 kbps limit)

- In 320 CBR, that doesn't happen, because the frame is literally stuck and can't got higher than 320 kbps, and thus it wastes on the frames that were with low bitrate. (It cannot go higher the 320kbps limit)

Is it still true that VBR would not be so consistent/precise as 320 in terms of choosing the right bitrate for a particular frame: eg: a frame needs 256 k but it "guesses" and calculates 250 k and then it was not truly consistent?

Thanks for answers.

This post has been edited by krafty: Aug 30 2012, 02:55
Go to the top of the page
+Quote Post
 
Start new topic
Replies
halb27
post Aug 30 2012, 09:04
Post #2





Group: Members
Posts: 2439
Joined: 9-October 05
From: Dormagen, Germany
Member No.: 25015



Bit reservoir is used with CBR (especially CBR 320), ABR, VBR.
Bit reservoir is the data space within a frame which is not used for audio data of the current frame. It can be used for audio data storage of the subsequent frame(s) - within specific limitations. This way bitrate can locally be roughly 50% higher than 320 kbps. It's all about frame data usage and is not restricted by CBR 320 or any other encoding mode.

As for choosing the "right" bitrate: The encoding machinery doesn't know the "right" bitrate, it just tries to do it right. The quality measurement of VBR and CBR is different, and for low to moderate quality levels VBR should be better in the overall view as long as the machinery doesn't have major flaws. For high to very high quality demands it's hard to say whether VBR or CBR is better overall. Opinion of most people probably is in favor of CBR 320 over -V0, but it was shown on HA already that -V0 can give better results than CBR 320.
And when it come to special solutions like my 3.99.5y -V0+ variant which maximizes bit reservoir, use extremely high audio data bitrate for impulses, and prevents audio data bitrate from going low (as CBR does) - and nonetheless is a VBR method -, things are becoming even more unclear as for which very high bitrate method is best in terms of quality.

This post has been edited by halb27: Aug 30 2012, 09:25


--------------------
lame3100m -V1 --insane-factor 0.75
Go to the top of the page
+Quote Post

Posts in this topic


Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



RSS Lo-Fi Version Time is now: 24th October 2014 - 08:31