@@ -68,6 +68,7 @@ version <next>:

 - HTTP Digest authentication

 - RTMP/RTMPT/RTMPS/RTMPE/RTMPTE protocol support via librtmp

 - Psygnosis YOP demuxer and video decoder

+- spectral extension support in the E-AC-3 decoder

@@ -815,14 +815,105 @@ 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 = get_bits1(gbc);

+        if (s->spx_in_use) {

+            int dst_start_freq, dst_end_freq, src_start_freq,

+                start_subband, end_subband;

+

+            /* determine which channels use spx */

+            if (s->channel_mode == AC3_CHMODE_MONO) {

+                s->channel_uses_spx[1] = 1;

+            } else {

+                for (ch = 1; ch <= fbw_channels; ch++)

+                    s->channel_uses_spx[ch] = get_bits1(gbc);

+            }

+

+            /* get the frequency bins of the spx copy region and the spx start

+               and end subbands */

+            dst_start_freq = get_bits(gbc, 2);

+            start_subband  = get_bits(gbc, 3) + 2;

+            if (start_subband > 7)

+                start_subband += start_subband - 7;

+            end_subband    = get_bits(gbc, 3) + 5;

+            if (end_subband   > 7)

+                end_subband   += end_subband   - 7;

+            dst_start_freq = dst_start_freq * 12 + 25;

+            src_start_freq = start_subband  * 12 + 25;

+            dst_end_freq   = end_subband    * 12 + 25;

+

+            /* check validity of spx ranges */

+            if (start_subband >= end_subband) {

+                av_log(s->avctx, AV_LOG_ERROR, "invalid spectral extension "

+                       "range (%d >= %d)\n", start_subband, end_subband);

+                return -1;

+            }

+            if (dst_start_freq >= src_start_freq) {

+                av_log(s->avctx, AV_LOG_ERROR, "invalid spectral extension "

+                       "copy start bin (%d >= %d)\n", dst_start_freq, src_start_freq);

+                return -1;

+            }

+

+            s->spx_dst_start_freq = dst_start_freq;

+            s->spx_src_start_freq = src_start_freq;

+            s->spx_dst_end_freq   = dst_end_freq;

+

+            decode_band_structure(gbc, blk, s->eac3, 0,

+                                  start_subband, end_subband,

+                                  ff_eac3_default_spx_band_struct,

+                                  &s->num_spx_bands,

+                                  s->spx_band_sizes);

+        } else {

+            for (ch = 1; ch <= fbw_channels; ch++) {

+                s->channel_uses_spx[ch] = 0;

+                s->first_spx_coords[ch] = 1;

+            }

         }

-        /* TODO: parse spectral extension strategy info */

     }

-    /* TODO: spectral extension coordinates */

+    /* spectral extension coordinates */

+    if (s->spx_in_use) {

+        for (ch = 1; ch <= fbw_channels; ch++) {

+            if (s->channel_uses_spx[ch]) {

+                if (s->first_spx_coords[ch] || get_bits1(gbc)) {

+                    float spx_blend;

+                    int bin, master_spx_coord;

+

+                    s->first_spx_coords[ch] = 0;

+                    spx_blend = get_bits(gbc, 5) * (1.0f/32);

+                    master_spx_coord = get_bits(gbc, 2) * 3;

+

+                    bin = s->spx_src_start_freq;

+                    for (bnd = 0; bnd < s->num_spx_bands; bnd++) {

+                        int bandsize;

+                        int spx_coord_exp, spx_coord_mant;

+                        float nratio, sblend, nblend, spx_coord;

+

+                        /* calculate blending factors */

+                        bandsize = s->spx_band_sizes[bnd];

+                        nratio = ((float)((bin + (bandsize >> 1))) / s->spx_dst_end_freq) - spx_blend;

+                        nratio = av_clipf(nratio, 0.0f, 1.0f);

+                        nblend = sqrtf(3.0f * nratio); // noise is scaled by sqrt(3) to give unity variance

+                        sblend = sqrtf(1.0f - nratio);

+                        bin += bandsize;

+

+                        /* decode spx coordinates */

+                        spx_coord_exp  = get_bits(gbc, 4);

+                        spx_coord_mant = get_bits(gbc, 2);

+                        if (spx_coord_exp == 15) spx_coord_mant <<= 1;

+                        else                     spx_coord_mant += 4;

+                        spx_coord_mant <<= (25 - spx_coord_exp - master_spx_coord);

+                        spx_coord = spx_coord_mant * (1.0f/(1<<23));

+

+                        /* multiply noise and signal blending factors by spx coordinate */

+                        s->spx_noise_blend [ch][bnd] = nblend * spx_coord;

+                        s->spx_signal_blend[ch][bnd] = sblend * spx_coord;

+                    }

+                }

+            } else {

+                s->first_spx_coords[ch] = 1;

+            }

+        }

+    }

     /* coupling strategy */

     if (s->eac3 ? s->cpl_strategy_exists[blk] : get_bits1(gbc)) {

@@ -859,9 +950,9 @@ 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);

-            cpl_end_subband   = get_bits(gbc, 4) + 3;

+            cpl_end_subband = s->spx_in_use ? (s->spx_src_start_freq - 37) / 12 :

+                                              get_bits(gbc, 4) + 3;

             if (cpl_start_subband >= cpl_end_subband) {

                 av_log(s->avctx, AV_LOG_ERROR, "invalid coupling range (%d >= %d)\n",

                        cpl_start_subband, cpl_end_subband);

@@ -934,8 +1025,11 @@ 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 && s->start_freq[CPL_CH] <= 61) {

                 s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);

+            } else if (s->spx_in_use && s->spx_src_start_freq <= 61) {

+                s->num_rematrixing_bands--;

+            }

             for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)

                 s->rematrixing_flags[bnd] = get_bits1(gbc);

         } else if (!blk) {

@@ -960,6 +1054,8 @@ 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_uses_spx[ch])

+                s->end_freq[ch] = s->spx_src_start_freq;

             else {

                 int bandwidth_code = get_bits(gbc, 6);

                 if (bandwidth_code > 60) {

@@ -1156,8 +1252,6 @@ 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);

@@ -1173,6 +1267,11 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)

         s->dsp.int32_to_float_fmul_scalar(s->transform_coeffs[ch], s->fixed_coeffs[ch], gain, 256);

     }

+    /* apply spectral extension to high frequency bins */

+    if (s->spx_in_use) {

+        ff_eac3_apply_spectral_extension(s);

+    }

+

     /* downmix and MDCT. order depends on whether block switching is used for

        any channel in this block. this is because coefficients for the long

        and short transforms cannot be mixed. */

@@ -22,6 +22,29 @@

 /**

  * @file libavcodec/ac3.h

  * Common code between the AC-3 and E-AC-3 decoders.

+ *

+ * Summary of MDCT Coefficient Grouping:

+ * The individual MDCT coefficient indices are often referred to in the

+ * (E-)AC-3 specification as frequency bins.  These bins are grouped together

+ * into subbands of 12 coefficients each.  The subbands are grouped together

+ * into bands as defined in the bitstream by the band structures, which

+ * determine the number of bands and the size of each band.  The full spectrum

+ * of 256 frequency bins is divided into 1 DC bin + 21 subbands = 253 bins.

+ * This system of grouping coefficients is used for channel bandwidth, stereo

+ * rematrixing, channel coupling, enhanced coupling, and spectral extension.

+ *

+ * +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+

+ * |1|  |12|  |  [12|12|12|12]  |  |  |  |  |  |  |  |  |  |  |  |  |3|

+ * +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+

+ * ~~~  ~~~~     ~~~~~~~~~~~~~                                      ~~~

+ *  |     |            |                                             |

+ *  |     |            |                    3 unused frequency bins--+

+ *  |     |            |

+ *  |     |            +--1 band containing 4 subbands

+ *  |     |

+ *  |     +--1 subband of 12 frequency bins

+ *  |

+ *  +--DC frequency bin

  */

 #ifndef AVCODEC_AC3DEC_H

@@ -43,6 +66,7 @@

 #define AC3_MAX_COEFS   256

 #define AC3_BLOCK_SIZE  256

 #define MAX_BLOCKS        6

+#define SPX_MAX_BANDS    17

 typedef struct {

     AVCodecContext *avctx;                  ///< parent context

@@ -89,6 +113,22 @@ typedef struct {

     int cpl_coords[AC3_MAX_CHANNELS][18];   ///< coupling coordinates                   (cplco)

 ///@}

+///@defgroup spx spectral extension

+///@{

+    int spx_in_use;                             ///< spectral extension in use              (spxinu)

+    uint8_t channel_uses_spx[AC3_MAX_CHANNELS]; ///< channel uses spectral extension        (chinspx)

+    int8_t spx_atten_code[AC3_MAX_CHANNELS];    ///< spx attenuation code                   (spxattencod)

+    int spx_src_start_freq;                     ///< spx start frequency bin

+    int spx_dst_end_freq;                       ///< spx end frequency bin

+    int spx_dst_start_freq;                     ///< spx starting frequency bin for copying (copystartmant)

+                                                ///< the copy region ends at the start of the spx region.

+    int num_spx_bands;                          ///< number of spx bands                    (nspxbnds)

+    uint8_t spx_band_sizes[SPX_MAX_BANDS];      ///< number of bins in each spx band

+    uint8_t first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states           (firstspxcos)

+    float spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor  (nblendfact)

+    float spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS];///< spx signal blending factor (sblendfact)

+///@}

+

 ///@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

@@ -182,4 +222,11 @@ void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch);

 void ff_ac3_downmix_c(float (*samples)[256], float (*matrix)[2],

                       int out_ch, int in_ch, int len);

+/**

+ * Apply spectral extension to each channel by copying lower frequency

+ * coefficients to higher frequency bins and applying side information to

+ * approximate the original high frequency signal.

+ */

+void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);

+

 #endif /* AVCODEC_AC3DEC_H */

@@ -64,3 +64,9 @@ const uint8_t ff_eac3_hebap_tab[64] = {

  */

 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 };

@@ -29,5 +29,6 @@ extern const uint8_t ff_ac3_rematrix_band_tab[5];

 extern const uint8_t ff_eac3_hebap_tab[64];

 extern const uint8_t ff_eac3_default_cpl_band_struct[18];

+extern const uint8_t ff_eac3_default_spx_band_struct[17];

 #endif /* AVCODEC_AC3DEC_DATA_H */

@@ -30,7 +30,7 @@

 #include "libavutil/avutil.h"

 #define LIBAVCODEC_VERSION_MAJOR 52

-#define LIBAVCODEC_VERSION_MINOR 62

+#define LIBAVCODEC_VERSION_MINOR 63

 #define LIBAVCODEC_VERSION_MICRO  0

 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \

@@ -23,10 +23,6 @@

 /*

  * There are several features of E-AC-3 that this decoder does not yet support.

  *

- * Spectral Extension

- *     There is a patch to get this working for the two samples we have that

- *     use it, but it needs some minor changes in order to be accepted.

- *

  * Enhanced Coupling

  *     No known samples exist.  If any ever surface, this feature should not be

  *     too difficult to implement.

@@ -67,6 +63,95 @@ typedef enum {

 #define EAC3_SR_CODE_REDUCED  3

+void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)

+{

+    int bin, bnd, ch, i;

+    uint8_t wrapflag[SPX_MAX_BANDS]={1,0,}, num_copy_sections, copy_sizes[SPX_MAX_BANDS];

+    float 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_dst_start_freq;

+    num_copy_sections = 0;

+    for (bnd = 0; bnd < s->num_spx_bands; bnd++) {

+        int copysize;

+        int bandsize = s->spx_band_sizes[bnd];

+        if (bin + bandsize > s->spx_src_start_freq) {

+            copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;

+            bin = s->spx_dst_start_freq;

+            wrapflag[bnd] = 1;

+        }

+        for (i = 0; i < bandsize; i += copysize) {

+            if (bin == s->spx_src_start_freq) {

+                copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;

+                bin = s->spx_dst_start_freq;

+            }

+            copysize = FFMIN(bandsize - i, s->spx_src_start_freq - bin);

+            bin += copysize;

+        }

+    }

+    copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;

+

+    for (ch = 1; ch <= s->fbw_channels; ch++) {

+        if (!s->channel_uses_spx[ch])

+            continue;

+

+        /* Copy coeffs from normal bands to extension bands */

+        bin = s->spx_src_start_freq;

+        for (i = 0; i < num_copy_sections; i++) {

+            memcpy(&s->transform_coeffs[ch][bin],

+                   &s->transform_coeffs[ch][s->spx_dst_start_freq],

+                   copy_sizes[i]*sizeof(float));

+            bin += copy_sizes[i];

+        }

+

+        /* Calculate RMS energy for each SPX band. */

+        bin = s->spx_src_start_freq;

+        for (bnd = 0; bnd < s->num_spx_bands; bnd++) {

+            int bandsize = s->spx_band_sizes[bnd];

+            float accum = 0.0f;

+            for (i = 0; i < bandsize; i++) {

+                float coeff = s->transform_coeffs[ch][bin++];

+                accum += coeff * coeff;

+            }

+            rms_energy[bnd] = sqrtf(accum / bandsize);

+        }

+

+        /* Apply a notch filter at transitions between normal and extension

+           bands and at all wrap points. */

+        if (s->spx_atten_code[ch] >= 0) {

+            const float *atten_tab = ff_eac3_spx_atten_tab[s->spx_atten_code[ch]];

+            bin = s->spx_src_start_freq - 2;

+            for (bnd = 0; bnd < s->num_spx_bands; bnd++) {

+                if (wrapflag[bnd]) {

+                    float *coeffs = &s->transform_coeffs[ch][bin];

+                    coeffs[0] *= atten_tab[0];

+                    coeffs[1] *= atten_tab[1];

+                    coeffs[2] *= atten_tab[2];

+                    coeffs[3] *= atten_tab[1];

+                    coeffs[4] *= atten_tab[0];

+                }

+                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_src_start_freq;

+        for (bnd = 0; bnd < s->num_spx_bands; bnd++) {

+            float nscale = s->spx_noise_blend[ch][bnd] * rms_energy[bnd] * (1.0f/(1<<31));

+            float sscale = s->spx_signal_blend[ch][bnd];

+            for (i = 0; i < s->spx_band_sizes[bnd]; i++) {

+                float noise  = nscale * (int32_t)av_lfg_get(&s->dith_state);

+                s->transform_coeffs[ch][bin]   *= sscale;

+                s->transform_coeffs[ch][bin++] += noise;

+            }

+        }

+    }

+}

+

+

 /** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */

 #define COEFF_0 10273905LL

@@ -492,12 +577,11 @@ 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;

         }

     }

@@ -514,6 +598,7 @@ 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;

@@ -1093,3 +1093,42 @@ const uint8_t ff_eac3_frm_expstr[32][6] = {

 {    EXP_D45,    EXP_D45,    EXP_D45,    EXP_D45,    EXP_D25,  EXP_REUSE},

 {    EXP_D45,    EXP_D45,    EXP_D45,    EXP_D45,    EXP_D45,    EXP_D45},

 };

+

+/**

+ * Table E.25: Spectral Extension Attenuation Table

+ * ff_eac3_spx_atten_tab[code][bin]=pow(2.0,(bin+1)*(code+1)/-15.0);

+ */

+const float ff_eac3_spx_atten_tab[32][3] = {

+    { 0.954841603910416503f, 0.911722488558216804f, 0.870550563296124125f },

+    { 0.911722488558216804f, 0.831237896142787758f, 0.757858283255198995f },

+    { 0.870550563296124125f, 0.757858283255198995f, 0.659753955386447100f },

+    { 0.831237896142787758f, 0.690956439983888004f, 0.574349177498517438f },

+    { 0.793700525984099792f, 0.629960524947436595f, 0.500000000000000000f },

+    { 0.757858283255198995f, 0.574349177498517438f, 0.435275281648062062f },

+    { 0.723634618720189082f, 0.523647061410313364f, 0.378929141627599553f },

+    { 0.690956439983888004f, 0.477420801955208307f, 0.329876977693223550f },

+    { 0.659753955386447100f, 0.435275281648062062f, 0.287174588749258719f },

+    { 0.629960524947436595f, 0.396850262992049896f, 0.250000000000000000f },

+    { 0.601512518041058319f, 0.361817309360094541f, 0.217637640824031003f },

+    { 0.574349177498517438f, 0.329876977693223550f, 0.189464570813799776f },

+    { 0.548412489847312945f, 0.300756259020529160f, 0.164938488846611775f },

+    { 0.523647061410313364f, 0.274206244923656473f, 0.143587294374629387f },

+    { 0.500000000000000000f, 0.250000000000000000f, 0.125000000000000000f },

+    { 0.477420801955208307f, 0.227930622139554201f, 0.108818820412015502f },

+    { 0.455861244279108402f, 0.207809474035696939f, 0.094732285406899888f },

+    { 0.435275281648062062f, 0.189464570813799776f, 0.082469244423305887f },

+    { 0.415618948071393879f, 0.172739109995972029f, 0.071793647187314694f },

+    { 0.396850262992049896f, 0.157490131236859149f, 0.062500000000000000f },

+    { 0.378929141627599553f, 0.143587294374629387f, 0.054409410206007751f },

+    { 0.361817309360094541f, 0.130911765352578369f, 0.047366142703449930f },

+    { 0.345478219991944002f, 0.119355200488802049f, 0.041234622211652958f },

+    { 0.329876977693223550f, 0.108818820412015502f, 0.035896823593657347f },

+    { 0.314980262473718298f, 0.099212565748012460f, 0.031250000000000000f },

+    { 0.300756259020529160f, 0.090454327340023621f, 0.027204705103003875f },

+    { 0.287174588749258719f, 0.082469244423305887f, 0.023683071351724965f },

+    { 0.274206244923656473f, 0.075189064755132290f, 0.020617311105826479f },

+    { 0.261823530705156682f, 0.068551561230914118f, 0.017948411796828673f },

+    { 0.250000000000000000f, 0.062500000000000000f, 0.015625000000000000f },

+    { 0.238710400977604098f, 0.056982655534888536f, 0.013602352551501938f },

+    { 0.227930622139554201f, 0.051952368508924235f, 0.011841535675862483f }

+};

@@ -31,5 +31,6 @@ extern const int16_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 float   ff_eac3_spx_atten_tab[32][3];

 #endif /* AVCODEC_EAC3DEC_DATA_H */