de.sciss.jump3r.mp3

Class Reservoir

java.lang.Object

de.sciss.jump3r.mp3.Reservoir

public class Reservoir
extends java.lang.Object

ResvFrameBegin:
Called (repeatedly) at the beginning of a frame. Updates the maximum size of the reservoir, and checks to make sure main_data_begin was set properly by the formatter
Background information: This is the original text from the ISO standard. Because of sooo many bugs and irritations correcting comments are added in brackets []. A '^W' means you should remove the last word.

  1. The following rule can be used to calculate the maximum
     number of bits used for one granule [^W frame]:

     At the highest possible bitrate of Layer III (320 kbps
     per stereo signal [^W^W^W], 48 kHz) the frames must be of
     [^W^W^W are designed to have] constant length, i.e.
     one buffer [^W^W the frame] length is:

 
         320 kbps * 1152/48 kHz = 7680 bit = 960 byte
 
     This value is used as the maximum buffer per channel [^W^W] at
     lower bitrates [than 320 kbps]. At 64 kbps mono or 128 kbps
     stereo the main granule length is 64 kbps * 576/48 kHz = 768 bit
     [per granule and channel] at 48 kHz sampling frequency.
     This means that there is a maximum deviation (short time buffer
     [= reservoir]) of 7680 - 2*2*768 = 4608 bits is allowed at 64 kbps.
     The actual deviation is equal to the number of bytes [with the
     meaning of octets] denoted by the main_data_end offset pointer.
     The actual maximum deviation is (2^9-1)*8 bit = 4088 bits
     [for MPEG-1 and (2^8-1)*8 bit for MPEG-2, both are hard limits].
     ... The xchange of buffer bits between the left and right channel
     is allowed without restrictions [exception: dual channel].
     Because of the [constructed] constraint on the buffer size
     main_data_end is always set to 0 in the case of bit_rate_index==14,
     i.e. data rate 320 kbps per stereo signal [^W^W^W]. In this case
     all data are allocated between adjacent header [^W sync] words
     [, i.e. there is no buffering at all].
 

Constructor Summary

Constructors

Constructor and Description
Reservoir()

Method Summary

Modifier and Type	Method and Description
void	ResvAdjust(LameInternalFlags gfc, GrInfo gi) Called after a granule's bit allocation.
int	ResvFrameBegin(LameGlobalFlags gfp, MeanBits mean_bits)
void	ResvFrameEnd(LameInternalFlags gfc, int mean_bits) Called after all granules in a frame have been allocated.
int	ResvMaxBits(LameGlobalFlags gfp, int mean_bits, MeanBits targ_bits, int cbr) returns targ_bits: target number of bits to use for 1 granule extra_bits: amount extra available from reservoir Mark Taylor 4/99
void	setModules(BitStream bs)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Reservoir

public Reservoir()

Method Detail

setModules

public final void setModules(BitStream bs)

ResvFrameBegin

public final int ResvFrameBegin(LameGlobalFlags gfp,
                                MeanBits mean_bits)

ResvMaxBits

public final int ResvMaxBits(LameGlobalFlags gfp,
                             int mean_bits,
                             MeanBits targ_bits,
                             int cbr)

returns targ_bits: target number of bits to use for 1 granule
extra_bits: amount extra available from reservoir
Mark Taylor 4/99

ResvAdjust

public final void ResvAdjust(LameInternalFlags gfc,
                             GrInfo gi)

Called after a granule's bit allocation. Readjusts the size of the reservoir to reflect the granule's usage.

ResvFrameEnd

public final void ResvFrameEnd(LameInternalFlags gfc,
                               int mean_bits)

Called after all granules in a frame have been allocated. Makes sure that the reservoir size is within limits, possibly by adding stuffing bits.