>
> CBR VBR ABR
>
> Can use different frame sizes no yes yes
>
> File size depends also on
> complexity of source no yes no
>
CBR and ABR adjust bits based on the PE. VBR adjusts the bits
based on the quantization noise. So both depend on the complexity
of the source material.
> Can adapted bit demand by
> * different frame sizes no yes yes
> * use of bits from the pool yes ? no
>
VBR and ABR use bits from the bit reservoir, but the
reservoir is intentionally kept as small as possible.
With VBR and ABR, there is no reason to try to build
up a large reservoir.
>
> What would be done in VBR/ABR if the needed frame size is between two
> allowed sizes? Emitting frames with wobbling effective frame size or also
> using a (small) bit pool and a more constant effective frame size?
>
VBR/ABR would have to use the larger size. The unused bits
are added to the reservoir, so for the next frame it may
use the smaller frame size + reservoir, and so the
bitrate will wobble as you suggest.
VBR/ABR only uses the reservoir to avoid wasting bits,
since the number of bits needed is never exactly equal
to the number available.
Mark
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