Chiebot-Mirror
/
FFmpeg
mirror of https://github.com/FFmpeg/FFmpeg.git
8
0
Fork 0
Code Issues Projects Releases Wiki Activity

AC-3 decoder, soc revision 71, Sep 4 09:47:12 2006 UTC by cloud9

Browse Source 
Redundant code cleanup.
Optimized dither generation.
Minor optimization in bit allocation.
Comments.

Originally committed as revision 9669 to svn://svn.ffmpeg.org/ffmpeg/trunk
pull/126/head
Justin Ruggles 18 years ago
parent 860fe8c908
commit c7cfc48f37
1 changed files with 151 additions and 89 deletions
Whitespace
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. 240
      libavcodec/ac3dec.c

240
libavcodec/ac3dec.c
Unescape View File

@ -13,8 +13,6 @@
*
* Thanks Makoto Matsumoto and Takuji Nishimura for the Mersenne Twister.
*
* Kaiser-Bessel derived window by Justin Ruggles.
*
* Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com).
* Something is wrong up on cloud # 9!
*
@ -95,7 +93,6 @@ typedef struct {
/* Mersenne Twister */
typedef struct {
uint32_t flags;
uint16_t crc1;
uint8_t fscod;
@ -148,74 +145,81 @@ typedef struct {
int bit_rate;
int frame_size;
int nfchans;
int lfeon;
float dynrng;
float dynrng2;
float chcoeffs[6];
float cplco[5][18];
int ncplbnd;
int ncplsubnd;
int cplstrtmant;
int cplendmant;
int endmant[5];
uint8_t dcplexps[256];
uint8_t dexps[5][256];
uint8_t dlfeexps[256];
uint8_t cplbap[256];
uint8_t bap[5][256];
uint8_t lfebap[256];
int blkoutput;
DECLARE_ALIGNED_16(float, transform_coeffs[MAX_CHANNELS][BLOCK_SIZE]);
int nfchans; //number of channels
int lfeon; //lfe channel in use
float dynrng; //dynamic range gain
float dynrng2; //dynamic range gain for 1+1 mode
float chcoeffs[6]; //normalized channel coefficients
float cplco[5][18]; //coupling coordinates
int ncplbnd; //number of coupling bands
int ncplsubnd; //number of coupling sub bands
int cplstrtmant; //coupling start mantissa
int cplendmant; //coupling end mantissa
int endmant[5]; //channel end mantissas
uint8_t dcplexps[256]; //decoded coupling exponents
uint8_t dexps[5][256]; //decoded fbw channel exponents
uint8_t dlfeexps[256]; //decoded lfe channel exponents
uint8_t cplbap[256]; //coupling bit allocation pointers
uint8_t bap[5][256]; //fbw channel bit allocation pointers
uint8_t lfebap[256]; //lfe channel bit allocation pointers
int blkoutput; //output configuration for block
DECLARE_ALIGNED_16(float, transform_coeffs[MAX_CHANNELS][BLOCK_SIZE]); //transform coefficients
/* For IMDCT. */
MDCTContext imdct_512; //N/8 point IFFT context
MDCTContext imdct_256; //N/4 point IFFT context
MDCTContext imdct_512; //for 512 sample imdct transform
MDCTContext imdct_256; //for 256 sample imdct transform
DSPContext dsp; //for optimization
DECLARE_ALIGNED_16(float, output[MAX_CHANNELS][BLOCK_SIZE]);
DECLARE_ALIGNED_16(float, delay[MAX_CHANNELS][BLOCK_SIZE]);
DECLARE_ALIGNED_16(float, tmp_imdct[BLOCK_SIZE]);
DECLARE_ALIGNED_16(float, tmp_output[BLOCK_SIZE * 2]);
DECLARE_ALIGNED_16(float, window[BLOCK_SIZE]);
DECLARE_ALIGNED_16(float, output[MAX_CHANNELS][BLOCK_SIZE]); //output after imdct transform and windowing
DECLARE_ALIGNED_16(float, delay[MAX_CHANNELS][BLOCK_SIZE]); //delay - added to the next block
DECLARE_ALIGNED_16(float, tmp_imdct[BLOCK_SIZE]); //temporary storage for imdct transform
DECLARE_ALIGNED_16(float, tmp_output[BLOCK_SIZE * 2]); //temporary storage for output before windowing
DECLARE_ALIGNED_16(float, window[BLOCK_SIZE]); //window coefficients
/* Miscellaneous. */
GetBitContext gb;
dither_state dith_state;
dither_state dith_state; //for dither generation
} AC3DecodeContext;
/* BEGIN Mersenne Twister Code. */
static void dither_seed(dither_state *state, uint32_t seed)
{
if (seed == 0) seed = 0x1f2e3d4c;
static const uint32_t mag01[2] = { 0x00, MATRIX_A };
uint32_t y;
int kk;
if (seed == 0)
seed = 0x7ba05e; //default seed to my birthday!
state->mt[0] = seed;
for (state->mti = 1; state->mti < NMT; state->mti++)
state->mt[state->mti] = ((69069 * state->mt[state->mti - 1]) + 1);
for (kk = 0; kk < NMT - MMT; kk++) {
y = (state->mt[kk] & UPPER_MASK) | (state->mt[kk + 1] & LOWER_MASK);
state->mt[kk] = state->mt[kk + MMT] ^ (y >> 1) ^ mag01[y & 0x01];
}
for (;kk < NMT - 1; kk++) {
y = (state->mt[kk] & UPPER_MASK) | (state->mt[kk + 1] & LOWER_MASK);
state->mt[kk] = state->mt[kk + (MMT - NMT)] ^ (y >> 1) ^ mag01[y & 0x01];
}
y = (state->mt[NMT - 1] & UPPER_MASK) | (state->mt[0] & LOWER_MASK);
state->mt[NMT - 1] = state->mt[MMT - 1] ^ (y >> 1) ^ mag01[y & 0x01];
state->mti = 0;
}
static uint32_t dither_uint32(dither_state *state)
static int16_t dither_int16(dither_state *state)
{
uint32_t y;
static const uint32_t mag01[2] = { 0x00, MATRIX_A };
int kk;
if (state->mti >= NMT) {
for (kk = 0; kk < NMT - MMT; kk++) {
y = (state->mt[kk] & UPPER_MASK) | (state->mt[kk + 1] & LOWER_MASK);
state->mt[kk] = state->mt[kk + MMT] ^ (y >> 1) ^ mag01[y & 0x01];
}
for (;kk < NMT - 1; kk++) {
y = (state->mt[kk] & UPPER_MASK) | (state->mt[kk + 1] & LOWER_MASK);
state->mt[kk] = state->mt[kk + (MMT - NMT)] ^ (y >> 1) ^ mag01[y & 0x01];
}
y = (state->mt[NMT - 1] & UPPER_MASK) | (state->mt[0] & LOWER_MASK);
state->mt[NMT - 1] = state->mt[MMT - 1] ^ (y >> 1) ^ mag01[y & 0x01];
if (state->mti >= NMT)
state->mti = 0;
}
y = state->mt[state->mti++];
y ^= (y >> 11);
@ -223,16 +227,11 @@ static uint32_t dither_uint32(dither_state *state)
y ^= ((y << 15) & 0xefc60000);
y ^= (y >> 18);
return y;
}
static inline int16_t dither_int16(dither_state *state)
{
return ((dither_uint32(state) << 16) >> 16);
return ((y << 16) >> 16);
}
/* END Mersenne Twister */
/*********** BEGIN INIT HELPER FUNCTIONS ***********/
/**
* Generate a Kaiser-Bessel Derived Window.
*/
@ -257,6 +256,9 @@ static void ac3_window_init(float *window)
window[i] = sqrt(local_window[i] / sum);
}
/*
* Generate quantizer tables.
*/
static void generate_quantizers_table(int16_t quantizers[], int level, int length)
{
int i;
@ -308,6 +310,9 @@ static void generate_quantizers_table_3(int16_t quantizers[], int level, int len
quantizers[i] = 0;
}
/*
* Initialize tables at runtime.
*/
static void ac3_tables_init(void)
{
int i, j, k, l, v;
@ -323,6 +328,10 @@ static void ac3_tables_init(void)
masktab[253] = masktab[254] = masktab[255] = 0;
bndtab[50] = 0;
/* PSD Table For Mapping Exponents To PSD. */
for (i = 0; i < 25; i++)
psdtab[i] = 3072 - (i << 7);
/* Exponent Decoding Tables */
for (i = 0; i < 5; i++) {
v = i - 2;
@ -366,6 +375,11 @@ static void ac3_tables_init(void)
//for level-15 quantizers
generate_quantizers_table(l15_quantizers, 15, 15);
/* End Quantizer ungrouping tables. */
//generate scale factors
for (i = 0; i < 25; i++)
scale_factors[i] = pow(2.0, -(i + 15));
}
@ -376,14 +390,21 @@ static int ac3_decode_init(AVCodecContext *avctx)
ac3_tables_init();
ff_mdct_init(&ctx->imdct_256, 8, 1);
ff_mdct_init(&ctx->imdct_512, 9, 1);
/* Kaiser-Bessel derived window. */
ac3_window_init(ctx->window);
dsputil_init(&ctx->dsp, avctx);
dither_seed(&ctx->dith_state, 0);
return 0;
}
/*********** END INIT FUNCTIONS ***********/
/* Synchronize to ac3 bitstream.
* This function searches for the syncword '0xb77'.
*
* @param buf Pointer to "probable" ac3 bitstream buffer
* @param buf_size Size of buffer
* @return Returns the position where syncword is found, -1 if no syncword is found
*/
static int ac3_synchronize(uint8_t *buf, int buf_size)
{
int i;
@ -395,7 +416,14 @@ static int ac3_synchronize(uint8_t *buf, int buf_size)
return -1;
}
//Returns -1 when 'fscod' is not valid;
/* Parse the 'sync_info' from the ac3 bitstream.
* This function extracts the sync_info from ac3 bitstream.
* GetBitContext within AC3DecodeContext must point to
* start of the synchronized ac3 bitstream.
*
* @param ctx AC3DecodeContext
* @return Returns framesize, returns 0 if fscod, frmsizecod or bsid is not valid
*/
static int ac3_parse_sync_info(AC3DecodeContext *ctx)
{
GetBitContext *gb = &ctx->gb;
@ -434,6 +462,11 @@ static int ac3_parse_sync_info(AC3DecodeContext *ctx)
return 0;
}
/* Parse bsi from ac3 bitstream.
* This function extracts the bitstream information (bsi) from ac3 bitstream.
*
* @param ctx AC3DecodeContext after processed by ac3_parse_sync_info
*/
static void ac3_parse_bsi(AC3DecodeContext *ctx)
{
GetBitContext *gb = &ctx->gb;
@ -490,10 +523,16 @@ static void ac3_parse_bsi(AC3DecodeContext *ctx)
}
}
/* Decodes the grouped exponents and stores them
* in decoded exponents (dexps).
* The code is derived from liba52.
* Uses liba52 tables.
/* Decodes the grouped exponents.
* This function decodes the coded exponents according to exponent strategy
* and stores them in the decoded exponents buffer.
*
* @param gb GetBitContext which points to start of coded exponents
* @param expstr Exponent coding strategy
* @param ngrps Number of grouped exponetns
* @param absexp Absolute exponent
* @param dexps Decoded exponents are stored in dexps
* @return Returns 0 if exponents are decoded successfully, -1 if error occurs
*/
static int decode_exponents(GetBitContext *gb, int expstr, int ngrps, uint8_t absexp, uint8_t *dexps)
{
@ -551,6 +590,7 @@ static int decode_exponents(GetBitContext *gb, int expstr, int ngrps, uint8_t ab
return 0;
}
/*********** HELPER FUNCTIONS FOR BIT ALLOCATION ***********/
static inline int logadd(int a, int b)
{
int c = a - b;
@ -583,11 +623,10 @@ static inline int calc_lowcomp(int a, int b0, int b1, int bin)
return a;
}
/*********** END HELPER FUNCTIONS FOR BIT ALLOCATION ***********/
/* do the bit allocation for chnl.
* chnl = 0 to 4 - fbw channel
* chnl = 5 coupling channel
* chnl = 6 lfe channel
/* Performs bit allocation.
* This function performs bit allocation for the requested chanenl.
*/
static void do_bit_allocation(AC3DecodeContext *ctx, int chnl)
{
@ -655,7 +694,7 @@ static void do_bit_allocation(AC3DecodeContext *ctx, int chnl)
}
for (bin = start; bin < end; bin++) /* exponent mapping into psd */
psd[bin] = (3072 - (exps[bin] << 7));
psd[bin] = psdtab[exps[bin]];
/* psd integration */
j = start;
@ -972,6 +1011,10 @@ static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_gro
return 0;
}
/* Get the transform coefficients.
* This function extracts the tranform coefficients form the ac3 bitstream.
* This function is called after bit allocation is performed.
*/
static int get_transform_coeffs(AC3DecodeContext * ctx)
{
int i, end;
@ -1011,6 +1054,7 @@ static int get_transform_coeffs(AC3DecodeContext * ctx)
return 0;
}
/* Rematrixing routines. */
static void do_rematrixing1(AC3DecodeContext *ctx, int start, int end)
{
float tmp0, tmp1;
@ -1050,6 +1094,10 @@ static void do_rematrixing(AC3DecodeContext *ctx)
}
}
/* This function sets the normalized channel coefficients.
* Transform coefficients are multipllied by the channel
* coefficients to get normalized transform coefficients.
*/
static void get_downmix_coeffs(AC3DecodeContext *ctx)
{
int from = ctx->acmod;
@ -1217,6 +1265,7 @@ static void get_downmix_coeffs(AC3DecodeContext *ctx)
}
}
/*********** BEGIN DOWNMIX FUNCTIONS ***********/
static inline void mix_dualmono_to_mono(AC3DecodeContext *ctx)
{
int i;
@ -1433,12 +1482,20 @@ static inline void mix_3f_2r_to_dolby(AC3DecodeContext *ctx)
memset(output[4], 0, sizeof(output[4]));
memset(output[5], 0, sizeof(output[5]));
}
/*********** END DOWNMIX FUNCTIONS ***********/
/* Downmix the output.
* This function downmixes the output when the number of input
* channels is not equal to the number of output channels requested.
*/
static void do_downmix(AC3DecodeContext *ctx)
{
int from = ctx->acmod;
int to = ctx->blkoutput;
if (to == AC3_OUTPUT_UNMODIFIED)
return;
switch (from) {
case AC3_INPUT_DUALMONO:
switch (to) {
@ -1545,16 +1602,9 @@ static void dump_floats(const char *name, int prec, const float *tab, int n)
av_log(NULL, AV_LOG_INFO, "\n");
}
#define CMUL(pre, pim, are, aim, bre, bim) \
{\
float _are = (are);\
float _aim = (aim);\
float _bre = (bre);\
float _bim = (bim);\
(pre) = _are * _bre - _aim * _bim;\
(pim) = _are * _bim + _aim * _bre;\
}
/* This function performs the imdct on 256 sample transform
* coefficients.
*/
static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
{
int k;
@ -1575,6 +1625,9 @@ static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
ctx->dsp.vector_fmul_reverse(ptr, ctx->tmp_output + 256, ctx->window, BLOCK_SIZE);
}
/* This function performs the imdct on 512 sample transform
* coefficients.
*/
static void do_imdct_512(AC3DecodeContext *ctx, int chindex)
{
float *ptr;
@ -1587,6 +1640,7 @@ static void do_imdct_512(AC3DecodeContext *ctx, int chindex)
ctx->dsp.vector_fmul_reverse(ptr, ctx->tmp_output + 256, ctx->window, BLOCK_SIZE);
}
/* IMDCT Transform. */
static inline void do_imdct(AC3DecodeContext *ctx)
{
int i;
@ -1602,6 +1656,11 @@ static inline void do_imdct(AC3DecodeContext *ctx)
}
}
/* Parse the audio block from ac3 bitstream.
* This function extract the audio block from the ac3 bitstream
* and produces the output for the block. This function must
* be called for each of the six audio block in the ac3 bitstream.
*/
static int ac3_parse_audio_block(AC3DecodeContext * ctx)
{
int nfchans = ctx->nfchans;
@ -1609,7 +1668,6 @@ static int ac3_parse_audio_block(AC3DecodeContext * ctx)
int i, bnd, rbnd, seg, grpsize;
GetBitContext *gb = &ctx->gb;
int bit_alloc_flags = 0;
float drange;
uint8_t *dexps;
int mstrcplco, cplcoexp, cplcomant;
int dynrng, chbwcod, ngrps, cplabsexp, skipl;
@ -1879,16 +1937,6 @@ static int ac3_parse_audio_block(AC3DecodeContext * ctx)
return 0;
}
/*static inline int16_t convert(float f)
{
if (f >= 1.0)
return 32767;
else if (f <= -1.0)
return -32768;
else
return (lrintf(f * 32767.0));
}*/
static inline int16_t convert(int32_t i)
{
if (i > 0x43c07fff)
@ -1901,6 +1949,14 @@ static inline int16_t convert(int32_t i)
static int frame_count = 0;
/* Decode ac3 frame.
*
* @param avctx Pointer to AVCodecContext
* @param data Pointer to pcm smaples
* @param data_size Set to number of pcm samples produced by decoding
* @param buf Data to be decoded
* @param buf_size Size of the buffer
*/
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
{
AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
@ -1981,8 +2037,14 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
return ctx->frame_size;
}
static int ac3_decode_end(AVCodecContext *ctx)
/* Uninitialize ac3 decoder.
*/
static int ac3_decode_end(AVCodecContext *avctx)
{
AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
ff_mdct_end(&ctx->imdct_512);
ff_mdct_end(&ctx->imdct_256);
return 0;
}

Write Preview
Loading…
Cancel
Save