--- /dev/null
+/*
+ * bit reservoir source file
+ *
+ * Copyright (c) 1999 Mark Taylor
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/* $Id: reservoir.c,v 1.1 2002/04/28 17:30:27 kramm Exp $ */
+
+#include "config_static.h"
+
+#include <assert.h>
+#include "util.h"
+#include "reservoir.h"
+
+#ifdef WITH_DMALLOC
+#include <dmalloc.h>
+#endif
+
+/*
+ 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].
+ */
+
+int
+ResvFrameBegin(lame_global_flags *gfp,III_side_info_t *l3_side, int mean_bits, int frameLength )
+{
+ lame_internal_flags *gfc=gfp->internal_flags;
+ int fullFrameBits;
+ int resvLimit;
+ int maxmp3buf;
+
+/*
+ * Meaning of the variables:
+ * resvLimit: (0, 8, ..., 8*255 (MPEG-2), 8*511 (MPEG-1))
+ * Number of bits can be stored in previous frame(s) due to
+ * counter size constaints
+ * maxmp3buf: ( ??? ... 8*1951 (MPEG-1 and 2), 8*2047 (MPEG-2.5))
+ * Number of bits allowed to encode one frame (you can take 8*511 bit
+ * from the bit reservoir and at most 8*1440 bit from the current
+ * frame (320 kbps, 32 kHz), so 8*1951 bit is the largest possible
+ * value for MPEG-1 and -2)
+ *
+ * maximum allowed granule/channel size times 4 = 8*2047 bits.,
+ * so this is the absolute maximum supported by the format.
+ *
+ *
+ * fullFrameBits: maximum number of bits available for encoding
+ * the current frame.
+ *
+ * mean_bits: target number of bits per granule.
+ *
+ * frameLength:
+ *
+ * gfc->ResvMax: maximum allowed reservoir
+ *
+ * gfc->ResvSize: current reservoir size
+ *
+ * l3_side->resvDrain_pre:
+ * ancillary data to be added to previous frame:
+ * (only usefull in VBR modes if it is possible to have
+ * maxmp3buf < fullFrameBits)). Currently disabled,
+ * see #define NEW_DRAIN
+ *
+ * l3_side->resvDrain_post:
+ * ancillary data to be added to this frame:
+ *
+ */
+
+ /* main_data_begin has 9 bits in MPEG-1, 8 bits MPEG-2 */
+ resvLimit = (gfp->version==1) ? 8*511 : 8*255 ;
+
+
+ /* maximum allowed frame size. dont use more than this number of
+ bits, even if the frame has the space for them: */
+ /* Bouvigne suggests this more lax interpretation of the ISO doc
+ instead of using 8*960. */
+ if (gfp->strict_ISO) {
+ if (gfp->version==1)
+ maxmp3buf=8*((int)(320000/(gfp->out_samplerate / (FLOAT8)1152)/8 +.5));
+ else
+ maxmp3buf=8*((int)(160000/(gfp->out_samplerate / (FLOAT8)576)/8 +.5));
+ } else
+ /*all mp3 decoders should have enough buffer to handle this value: size of a 320kbps 32kHz frame*/
+ maxmp3buf = 8*1440;
+
+
+ if ( frameLength > maxmp3buf || gfp->disable_reservoir ) {
+ gfc->ResvMax = 0;
+ } else {
+ gfc->ResvMax = maxmp3buf - frameLength;
+ if ( gfc->ResvMax > resvLimit )
+ gfc->ResvMax = resvLimit;
+ }
+
+ fullFrameBits = mean_bits * gfc->mode_gr + Min ( gfc->ResvSize, gfc->ResvMax );
+
+ if ( fullFrameBits > maxmp3buf )
+ fullFrameBits = maxmp3buf;
+
+ assert ( 0 == gfc->ResvMax % 8 );
+ assert ( gfc->ResvMax >= 0 );
+
+ l3_side->resvDrain_pre = 0;
+
+ if ( gfc->pinfo != NULL ) {
+ gfc->pinfo->mean_bits = mean_bits / 2; /* expected bits per channel per granule [is this also right for mono/stereo, MPEG-1/2 ?] */
+ gfc->pinfo->resvsize = gfc->ResvSize;
+ }
+
+ return fullFrameBits;
+}
+
+
+/*
+ ResvMaxBits
+ returns targ_bits: target number of bits to use for 1 granule
+ extra_bits: amount extra available from reservoir
+ Mark Taylor 4/99
+*/
+void ResvMaxBits(lame_global_flags *gfp, int mean_bits, int *targ_bits, int *extra_bits)
+{
+ lame_internal_flags *gfc=gfp->internal_flags;
+ int add_bits;
+ int full_fac;
+
+ *targ_bits = mean_bits ;
+
+ /* extra bits if the reservoir is almost full */
+ full_fac=9;
+ if (gfc->ResvSize > ((gfc->ResvMax * full_fac) / 10)) {
+ add_bits= gfc->ResvSize-((gfc->ResvMax * full_fac) / 10);
+ *targ_bits += add_bits;
+ }else {
+ add_bits =0 ;
+ /* build up reservoir. this builds the reservoir a little slower
+ * than FhG. It could simple be mean_bits/15, but this was rigged
+ * to always produce 100 (the old value) at 128kbs */
+ /* *targ_bits -= (int) (mean_bits/15.2);*/
+ if (!gfp->disable_reservoir)
+ *targ_bits -= .1*mean_bits;
+ }
+
+
+ /* amount from the reservoir we are allowed to use. ISO says 6/10 */
+ *extra_bits =
+ (gfc->ResvSize < (gfc->ResvMax*6)/10 ? gfc->ResvSize : (gfc->ResvMax*6)/10);
+ *extra_bits -= add_bits;
+
+ if (*extra_bits < 0) *extra_bits=0;
+
+
+}
+
+/*
+ ResvAdjust:
+ Called after a granule's bit allocation. Readjusts the size of
+ the reservoir to reflect the granule's usage.
+*/
+void
+ResvAdjust(lame_internal_flags *gfc,gr_info *gi, III_side_info_t *l3_side, int mean_bits )
+{
+ gfc->ResvSize += (mean_bits / gfc->channels_out) - gi->part2_3_length;
+#if 0
+ printf("part2_3_length: %i avg=%i incres: %i resvsize=%i\n",gi->part2_3_length,
+ mean_bits/gfc->channels_out,
+mean_bits/gfc->channels_out-gi->part2_3_length,gfc->ResvSize);
+#endif
+}
+
+
+/*
+ ResvFrameEnd:
+ Called after all granules in a frame have been allocated. Makes sure
+ that the reservoir size is within limits, possibly by adding stuffing
+ bits.
+*/
+void
+ResvFrameEnd(lame_internal_flags *gfc, III_side_info_t *l3_side, int mean_bits)
+{
+ int stuffingBits;
+ int over_bits;
+
+
+ /* just in case mean_bits is odd, this is necessary... */
+ if ( gfc->channels_out == 2 && (mean_bits & 1) )
+ gfc->ResvSize += 1;
+
+ stuffingBits=0;
+ l3_side->resvDrain_post = 0;
+ l3_side->resvDrain_pre = 0;
+
+ /* we must be byte aligned */
+ if ( (over_bits = gfc->ResvSize % 8) != 0 )
+ stuffingBits += over_bits;
+
+
+ over_bits = (gfc->ResvSize - stuffingBits) - gfc->ResvMax;
+ if (over_bits > 0) {
+ assert ( 0 == over_bits % 8 );
+ assert ( over_bits >= 0 );
+ stuffingBits += over_bits;
+ }
+
+
+#undef NEW_DRAIN
+#ifdef NEW_DRAIN
+ /* drain as many bits as possible into previous frame ancillary data
+ * In particular, in VBR mode ResvMax may have changed, and we have
+ * to make sure main_data_begin does not create a reservoir bigger
+ * than ResvMax mt 4/00*/
+ {
+ int mdb_bytes = Min(l3_side->main_data_begin*8,stuffingBits)/8;
+ l3_side->resvDrain_pre += 8*mdb_bytes;
+ stuffingBits -= 8*mdb_bytes;
+ gfc->ResvSize -= 8*mdb_bytes;
+ l3_side->main_data_begin -= mdb_bytes;
+
+
+ /* drain just enough to be byte aligned. The remaining bits will
+ * be added to the reservoir, and we will deal with them next frame.
+ * If the next frame is at a lower bitrate, it may have a larger ResvMax,
+ * and we will not have to waste these bits! mt 4/00 */
+ assert ( stuffingBits >= 0 );
+ l3_side->resvDrain_post += (stuffingBits % 8);
+ gfc->ResvSize -= stuffingBits % 8;
+ }
+#else
+ /* drain the rest into this frames ancillary data*/
+ l3_side->resvDrain_post += stuffingBits;
+ gfc->ResvSize -= stuffingBits;
+#endif
+
+ return;
+}
+
+
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