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add support for spectral extension 

Originally committed as revision 15812 to svn://svn.ffmpeg.org/ffmpeg/trunk
tags/v0.5
Justin Ruggles 16 years ago
parent
0c5d750df9
commit
0cc51734b2
5 changed files with 272 additions and 17 deletions
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  1. +92
    -9
      libavcodec/ac3dec.c
  2. +27
    -0
      libavcodec/ac3dec.h
  3. +46
    -0
      libavcodec/ac3dec_data.c
  4. +2
    -0
      libavcodec/ac3dec_data.h
  5. +105
    -8
      libavcodec/eac3dec.c

+ 92
- 9
libavcodec/ac3dec.c View File

@@ -818,14 +818,86 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)

/* spectral extension strategy */
if (s->eac3 && (!blk || get_bits1(gbc))) {
if (get_bits1(gbc)) {
av_log_missing_feature(s->avctx, "Spectral extension", 1);
return -1;
s->spx_in_use[blk] = get_bits1(gbc);
if (s->spx_in_use[blk]) {
int begf, endf;
int spx_end_subband;

/* determine which channels use spx */
if (s->channel_mode == AC3_CHMODE_MONO) {
s->channel_in_spx[1] = 1;
s->spx_coords_exist[1] = 0;
} else {
for (ch = 1; ch <= fbw_channels; ch++) {
s->channel_in_spx[ch] = get_bits1(gbc);
s->spx_coords_exist[ch] = 0;
}
}

s->spx_copy_start_freq = get_bits(gbc, 2) * 12 + 25;
begf = get_bits(gbc, 3);
endf = get_bits(gbc, 3);
s->spx_start_subband = begf < 6 ? begf+2 : 2*begf-3;
spx_end_subband = endf < 4 ? endf+5 : 2*endf+3;
s->num_spx_subbands = spx_end_subband - s->spx_start_subband;
s->spx_start_freq = s->spx_start_subband * 12 + 25;
s->spx_end_freq = spx_end_subband * 12 + 25;

decode_band_structure(gbc, blk, s->eac3, 0,
s->spx_start_subband, spx_end_subband,
ff_eac3_default_spx_band_struct,
s->spx_band_struct, NULL, &s->num_spx_bands,
s->spx_band_sizes);
} else {
for (ch = 1; ch <= fbw_channels; ch++) {
s->channel_in_spx[ch] = 0;
s->first_spx_coords[ch] = 1;
}
}
/* TODO: parse spectral extension strategy info */
} else {
s->spx_in_use[blk] = blk ? s->spx_in_use[blk-1] : 0;
}

/* TODO: spectral extension coordinates */
/* spectral extension coordinates */
if (s->spx_in_use[blk]) {
for (ch = 1; ch <= fbw_channels; ch++) {
if (s->channel_in_spx[ch]) {
if (s->first_spx_coords[ch] || get_bits1(gbc)) {
int bin, spx_blend;
int master_spx_coord;
s->first_spx_coords[ch] = 0;
s->spx_coords_exist[ch] = 1;
spx_blend = get_bits(gbc, 5) << 18;
master_spx_coord = get_bits(gbc, 2) * 3;
bin = s->spx_start_freq;
for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
int spx_coord_exp, spx_coord_mant;

/* calculate blending factors */
int bandsize = s->spx_band_sizes[bnd];
int nratio = (((bin + (bandsize >> 1)) << 23) / s->spx_end_freq) - spx_blend;
nratio = av_clip(nratio, 0, INT24_MAX);
s->spx_noise_blend [ch][bnd] = ff_sqrt(( nratio) << 8) * M_SQRT_POW2_15;
s->spx_signal_blend[ch][bnd] = ff_sqrt((INT24_MAX - nratio) << 8) * M_SQRT_POW2_15;
bin += bandsize;

/* decode spx coordinates */
spx_coord_exp = get_bits(gbc, 4);
spx_coord_mant = get_bits(gbc, 2);
if (spx_coord_exp == 15)
s->spx_coords[ch][bnd] = spx_coord_mant << 26;
else
s->spx_coords[ch][bnd] = (spx_coord_mant + 4) << 25;
s->spx_coords[ch][bnd] >>= (spx_coord_exp + master_spx_coord);
}
} else {
s->spx_coords_exist[ch] = 0;
}
} else {
s->first_spx_coords[ch] = 1;
}
}
}

/* coupling strategy */
if (s->eac3 ? s->cpl_strategy_exists[blk] : get_bits1(gbc)) {
@@ -862,9 +934,12 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)
s->phase_flags_in_use = get_bits1(gbc);

/* coupling frequency range */
/* TODO: modify coupling end freq if spectral extension is used */
cpl_start_subband = get_bits(gbc, 4);
if (s->spx_in_use[blk]) {
cpl_end_subband = s->spx_start_subband - 1;
} else {
cpl_end_subband = get_bits(gbc, 4) + 3;
}
s->num_cpl_subbands = cpl_end_subband - cpl_start_subband;
if (s->num_cpl_subbands < 0) {
av_log(s->avctx, AV_LOG_ERROR, "invalid coupling range (%d > %d)\n",
@@ -939,8 +1014,14 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)
if (channel_mode == AC3_CHMODE_STEREO) {
if ((s->eac3 && !blk) || get_bits1(gbc)) {
s->num_rematrixing_bands = 4;
if(cpl_in_use && s->start_freq[CPL_CH] <= 61)
if (cpl_in_use) {
if (s->start_freq[CPL_CH] <= 61)
s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
} else if (s->spx_in_use[blk]) {
if (s->spx_start_freq <= 61)
s->num_rematrixing_bands -= 1 + (s->spx_start_freq <= 37) +
(s->spx_start_freq <= 25);
}
for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
s->rematrixing_flags[bnd] = get_bits1(gbc);
} else if (!blk) {
@@ -965,6 +1046,8 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)
int prev = s->end_freq[ch];
if (s->channel_in_cpl[ch])
s->end_freq[ch] = s->start_freq[CPL_CH];
else if (s->channel_in_spx[ch])
s->end_freq[ch] = s->spx_start_freq;
else {
int bandwidth_code = get_bits(gbc, 6);
if (bandwidth_code > 60) {
@@ -1155,12 +1238,12 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)

/* TODO: generate enhanced coupling coordinates and uncouple */

/* TODO: apply spectral extension */

/* recover coefficients if rematrixing is in use */
if(s->channel_mode == AC3_CHMODE_STEREO)
do_rematrixing(s);

ff_eac3_apply_spectral_extension(s);

/* apply scaling to coefficients (headroom, dynrng) */
for(ch=1; ch<=s->channels; ch++) {
float gain = s->mul_bias / 4194304.0f;


+ 27
- 0
libavcodec/ac3dec.h View File

@@ -42,6 +42,11 @@
#define AC3_MAX_COEFS 256
#define AC3_BLOCK_SIZE 256
#define MAX_BLOCKS 6
#define SPX_MAX_BANDS 17

#define INT24_MIN -8388608
#define INT24_MAX 8388607
#define M_SQRT_POW2_15 181

typedef struct {
AVCodecContext *avctx; ///< parent context
@@ -88,6 +93,26 @@ typedef struct {
int cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates (cplco)
///@}

///@defgroup spx spectral extension
///@{
int spx_in_use[MAX_BLOCKS]; ///< spectral extension in use (spxinu)
int channel_in_spx[AC3_MAX_CHANNELS]; ///< channel in spectral extension (chinspx)
int spx_atten_code[AC3_MAX_CHANNELS]; ///< spx attenuation code (spxattencod)
int spx_coords_exist[AC3_MAX_CHANNELS]; ///< indicates if a channel has spx coords (spxcoe)
int spx_start_subband; ///< spx beginning frequency band (spxbegf)
int spx_start_freq; ///< spx start frequency bin
int spx_end_freq; ///< spx end frequency bin
int spx_copy_start_freq; ///< spx starting frequency for copying (copystartmant)
int num_spx_subbands; ///< number of spectral extension subbands
int num_spx_bands; ///< number of spectral extension bands (nspxbnds)
uint8_t spx_band_struct[SPX_MAX_BANDS]; ///< spectral extension band structure (spxbndstrc)
int spx_band_sizes[SPX_MAX_BANDS]; ///< number of bins in each band (spxbndsztab)
int first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states (firstspxcos)
int spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor (nblendfact)
int spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx signal blending factor (sblendfact)
int spx_coords[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spectral extension coordinates (spxco)
///@}

///@defgroup aht adaptive hybrid transform
int channel_uses_aht[AC3_MAX_CHANNELS]; ///< channel AHT in use (chahtinu)
int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][MAX_BLOCKS]; ///< pre-IDCT mantissas
@@ -179,4 +204,6 @@ int ff_eac3_parse_header(AC3DecodeContext *s);
*/
void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch);

void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);

#endif /* AVCODEC_AC3DEC_H */

+ 46
- 0
libavcodec/ac3dec_data.c View File

@@ -1127,6 +1127,52 @@ const uint8_t ff_eac3_frm_expstr[32][6] = {
const uint8_t ff_eac3_default_cpl_band_struct[18] =
{ 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1 };

/**
* Table E2.15 Default Spectral Extension Banding Structure
*/
const uint8_t ff_eac3_default_spx_band_struct[17] =
{ 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1 };

/**
* Table E.25: Spectral Extension Attenuation Table
* 24-bit fixed-point version of the floating-point table in the specification.
* ff_eac3_spx_atten_tab[code][bin]=lrint(pow(1<<(bin+1),(code+1)/-15.0)*(1<<23));
*/
const int32_t ff_eac3_spx_atten_tab[32][3] = {
{ 8009792, 7648083, 7302707 },
{ 7648083, 6972929, 6357376 },
{ 7302707, 6357376, 5534417 },
{ 6972929, 5796163, 4817990 },
{ 6658043, 5284492, 4194304 },
{ 6357376, 4817990, 3651354 },
{ 6070287, 4392670, 3178688 },
{ 5796163, 4004896, 2767209 },
{ 5534417, 3651354, 2408995 },
{ 5284492, 3329021, 2097152 },
{ 5045853, 3035144, 1825677 },
{ 4817990, 2767209, 1589344 },
{ 4600417, 2522926, 1383604 },
{ 4392670, 2300209, 1204498 },
{ 4194304, 2097152, 1048576 },
{ 4004896, 1912021, 912838 },
{ 3824041, 1743232, 794672 },
{ 3651354, 1589344, 691802 },
{ 3486464, 1449041, 602249 },
{ 3329021, 1321123, 524288 },
{ 3178688, 1204498, 456419 },
{ 3035144, 1098167, 397336 },
{ 2898081, 1001224, 345901 },
{ 2767209, 912838, 301124 },
{ 2642246, 832255, 262144 },
{ 2522926, 758786, 228210 },
{ 2408995, 691802, 198668 },
{ 2300209, 630732, 172951 },
{ 2196335, 575052, 150562 },
{ 2097152, 524288, 131072 },
{ 2002448, 478005, 114105 },
{ 1912021, 435808, 99334 }
};

/**
* Table of bin locations for rematrixing bands
* reference: Section 7.5.2 Rematrixing : Frequency Band Definitions


+ 2
- 0
libavcodec/ac3dec_data.h View File

@@ -34,6 +34,8 @@ extern const int8_t ff_eac3_gaq_remap_2_4_b[9][2];
extern const int16_t (* const ff_eac3_mantissa_vq[8])[6];
extern const uint8_t ff_eac3_frm_expstr[32][6];
extern const uint8_t ff_eac3_default_cpl_band_struct[18];
extern const uint8_t ff_eac3_default_spx_band_struct[17];
extern const int32_t ff_eac3_spx_atten_tab[32][3];

extern const uint8_t ff_ac3_rematrix_band_tab[5];



+ 105
- 8
libavcodec/eac3dec.c View File

@@ -36,6 +36,104 @@ typedef enum {

#define EAC3_SR_CODE_REDUCED 3


void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)
{
int bin, bnd, ch, i;
int wrapflag[SPX_MAX_BANDS]={0,}, num_copy_sections, copy_sizes[SPX_MAX_BANDS];
int rms_energy[SPX_MAX_BANDS];

/* Set copy index mapping table. Set wrap flags to apply a notch filter at
wrap points later on. */
bin = s->spx_copy_start_freq;
num_copy_sections = 0;
for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
int bandsize = s->spx_band_sizes[bnd];
if ((bin + bandsize) > s->spx_start_freq) {
copy_sizes[num_copy_sections++] = bin - s->spx_copy_start_freq;
bin = s->spx_copy_start_freq;
wrapflag[bnd] = 1;
}
for (i = 0; i < bandsize; i++) {
if (bin == s->spx_start_freq) {
copy_sizes[num_copy_sections++] = bin - s->spx_copy_start_freq;
bin = s->spx_copy_start_freq;
}
bin++;
}
}
copy_sizes[num_copy_sections++] = bin - s->spx_copy_start_freq;

for (ch = 1; ch <= s->fbw_channels; ch++) {
if (!s->channel_in_spx[ch])
continue;

/* Copy coeffs from normal bands to extension bands */
bin = s->spx_start_freq;
for (bnd = 0; bnd < num_copy_sections; bnd++) {
memcpy(&s->fixed_coeffs[ch][bin],
&s->fixed_coeffs[ch][s->spx_copy_start_freq],
copy_sizes[bnd]*sizeof(int));
bin += copy_sizes[bnd];
}

/* Calculate RMS energy for each SPX band. */
bin = s->spx_start_freq;
for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
int bandsize = s->spx_band_sizes[bnd];
int64_t accum = 0;
for (i = 0; i < bandsize; i++) {
int64_t coeff = s->fixed_coeffs[ch][bin++];
accum += coeff * coeff;
}
rms_energy[bnd] = ff_sqrt((accum >> 15) / bandsize) * M_SQRT_POW2_15;
}

/* Apply a notch filter at transitions between normal and extension
bands and at all wrap points. */
if (s->spx_atten_code[ch] >= 0) {
const int32_t *atten_tab = ff_eac3_spx_atten_tab[s->spx_atten_code[ch]];
/* apply notch filter at baseband / extension region border */
bin = s->spx_start_freq - 2;
for (i = 0; i < 5; i++) {
s->fixed_coeffs[ch][bin] = ((int64_t)atten_tab[2-abs(i-2)] *
(int64_t)s->fixed_coeffs[ch][bin]) >> 23;
bin++;
}
/* apply notch at all other wrap points */
bin += s->spx_band_sizes[0];
for (bnd = 1; bnd < s->num_spx_bands; bnd++) {
if (wrapflag[bnd]) {
bin -= 5;
for (i = 0; i < 5; i++) {
s->fixed_coeffs[ch][bin] = (atten_tab[2-abs(i-2)] *
(int64_t)s->fixed_coeffs[ch][bin]) >> 23;
bin++;
}
}
bin += s->spx_band_sizes[bnd];
}
}

/* Apply noise-blended coefficient scaling based on previously
calculated RMS energy, blending factors, and SPX coordinates for
each band. */
bin = s->spx_start_freq;
for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
int64_t nscale, sscale, spxco;
nscale = (s->spx_noise_blend [ch][bnd] * rms_energy[bnd]) >> 23;
nscale = (nscale * 14529495) >> 23;
sscale = s->spx_signal_blend[ch][bnd];
spxco = s->spx_coords[ch][bnd];
for (i = 0; i < s->spx_band_sizes[bnd]; i++) {
int64_t noise = (nscale * (((int)av_lfg_get(&s->dith_state))>>8)) >> 23;
int64_t signal = (sscale * s->fixed_coeffs[ch][bin]) >> 23;
s->fixed_coeffs[ch][bin++] = ((noise + signal) * spxco) >> 23;
}
}
}
}

/** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */
#define COEFF_0 10273905LL

@@ -459,14 +557,12 @@ int ff_eac3_parse_header(AC3DecodeContext *s)
}

/* spectral extension attenuation data */
if (parse_spx_atten_data) {
av_log_missing_feature(s->avctx, "Spectral extension attenuation", 1);
for (ch = 1; ch <= s->fbw_channels; ch++) {
if (get_bits1(gbc)) { // channel has spx attenuation
skip_bits(gbc, 5); // skip spx attenuation code
}
}
}
for (ch = 1; ch <= s->fbw_channels; ch++) {
if (parse_spx_atten_data && get_bits1(gbc))
s->spx_atten_code[ch] = get_bits(gbc, 5);
else
s->spx_atten_code[ch] = -1;
}

/* block start information */
if (s->num_blocks > 1 && get_bits1(gbc)) {
@@ -480,6 +576,7 @@ int ff_eac3_parse_header(AC3DecodeContext *s)

/* syntax state initialization */
for (ch = 1; ch <= s->fbw_channels; ch++) {
s->first_spx_coords[ch] = 1;
s->first_cpl_coords[ch] = 1;
}
s->first_cpl_leak = 1;


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