• Main Page
  • Related Pages
  • Modules
  • Data Structures
  • Files
  • File List
  • Globals

libavcodec/atrac1.c

Go to the documentation of this file.
00001 /*
00002  * Atrac 1 compatible decoder
00003  * Copyright (c) 2009 Maxim Poliakovski
00004  * Copyright (c) 2009 Benjamin Larsson
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * FFmpeg is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00029 /* Many thanks to Tim Craig for all the help! */
00030 
00031 #include <math.h>
00032 #include <stddef.h>
00033 #include <stdio.h>
00034 
00035 #include "avcodec.h"
00036 #include "get_bits.h"
00037 #include "dsputil.h"
00038 #include "fft.h"
00039 
00040 #include "atrac.h"
00041 #include "atrac1data.h"
00042 
00043 #define AT1_MAX_BFU      52                 ///< max number of block floating units in a sound unit
00044 #define AT1_SU_SIZE      212                ///< number of bytes in a sound unit
00045 #define AT1_SU_SAMPLES   512                ///< number of samples in a sound unit
00046 #define AT1_FRAME_SIZE   AT1_SU_SIZE * 2
00047 #define AT1_SU_MAX_BITS  AT1_SU_SIZE * 8
00048 #define AT1_MAX_CHANNELS 2
00049 
00050 #define AT1_QMF_BANDS    3
00051 #define IDX_LOW_BAND     0
00052 #define IDX_MID_BAND     1
00053 #define IDX_HIGH_BAND    2
00054 
00058 typedef struct {
00059     int                 log2_block_count[AT1_QMF_BANDS];    
00060     int                 num_bfus;                           
00061     float*              spectrum[2];
00062     DECLARE_ALIGNED(16, float, spec1)[AT1_SU_SAMPLES];     
00063     DECLARE_ALIGNED(16, float, spec2)[AT1_SU_SAMPLES];     
00064     DECLARE_ALIGNED(16, float, fst_qmf_delay)[46];         
00065     DECLARE_ALIGNED(16, float, snd_qmf_delay)[46];         
00066     DECLARE_ALIGNED(16, float, last_qmf_delay)[256+23];    
00067 } AT1SUCtx;
00068 
00072 typedef struct {
00073     AT1SUCtx            SUs[AT1_MAX_CHANNELS];              
00074     DECLARE_ALIGNED(16, float, spec)[AT1_SU_SAMPLES];      
00075 
00076     DECLARE_ALIGNED(16, float,  low)[256];
00077     DECLARE_ALIGNED(16, float,  mid)[256];
00078     DECLARE_ALIGNED(16, float, high)[512];
00079     float*              bands[3];
00080     DECLARE_ALIGNED(16, float, out_samples)[AT1_MAX_CHANNELS][AT1_SU_SAMPLES];
00081     FFTContext          mdct_ctx[3];
00082     int                 channels;
00083     DSPContext          dsp;
00084 } AT1Ctx;
00085 
00087 static const uint16_t samples_per_band[3] = {128, 128, 256};
00088 static const uint8_t   mdct_long_nbits[3] = {7, 7, 8};
00089 
00090 
00091 static void at1_imdct(AT1Ctx *q, float *spec, float *out, int nbits,
00092                       int rev_spec)
00093 {
00094     FFTContext* mdct_context = &q->mdct_ctx[nbits - 5 - (nbits > 6)];
00095     int transf_size = 1 << nbits;
00096 
00097     if (rev_spec) {
00098         int i;
00099         for (i = 0; i < transf_size / 2; i++)
00100             FFSWAP(float, spec[i], spec[transf_size - 1 - i]);
00101     }
00102     ff_imdct_half(mdct_context, out, spec);
00103 }
00104 
00105 
00106 static int at1_imdct_block(AT1SUCtx* su, AT1Ctx *q)
00107 {
00108     int          band_num, band_samples, log2_block_count, nbits, num_blocks, block_size;
00109     unsigned int start_pos, ref_pos = 0, pos = 0;
00110 
00111     for (band_num = 0; band_num < AT1_QMF_BANDS; band_num++) {
00112         float *prev_buf;
00113         int j;
00114 
00115         band_samples = samples_per_band[band_num];
00116         log2_block_count = su->log2_block_count[band_num];
00117 
00118         /* number of mdct blocks in the current QMF band: 1 - for long mode */
00119         /* 4 for short mode(low/middle bands) and 8 for short mode(high band)*/
00120         num_blocks = 1 << log2_block_count;
00121 
00122         if (num_blocks == 1) {
00123             /* mdct block size in samples: 128 (long mode, low & mid bands), */
00124             /* 256 (long mode, high band) and 32 (short mode, all bands) */
00125             block_size = band_samples >> log2_block_count;
00126 
00127             /* calc transform size in bits according to the block_size_mode */
00128             nbits = mdct_long_nbits[band_num] - log2_block_count;
00129 
00130             if (nbits != 5 && nbits != 7 && nbits != 8)
00131                 return -1;
00132         } else {
00133             block_size = 32;
00134             nbits = 5;
00135         }
00136 
00137         start_pos = 0;
00138         prev_buf = &su->spectrum[1][ref_pos + band_samples - 16];
00139         for (j=0; j < num_blocks; j++) {
00140             at1_imdct(q, &q->spec[pos], &su->spectrum[0][ref_pos + start_pos], nbits, band_num);
00141 
00142             /* overlap and window */
00143             q->dsp.vector_fmul_window(&q->bands[band_num][start_pos], prev_buf,
00144                                       &su->spectrum[0][ref_pos + start_pos], ff_sine_32, 0, 16);
00145 
00146             prev_buf = &su->spectrum[0][ref_pos+start_pos + 16];
00147             start_pos += block_size;
00148             pos += block_size;
00149         }
00150 
00151         if (num_blocks == 1)
00152             memcpy(q->bands[band_num] + 32, &su->spectrum[0][ref_pos + 16], 240 * sizeof(float));
00153 
00154         ref_pos += band_samples;
00155     }
00156 
00157     /* Swap buffers so the mdct overlap works */
00158     FFSWAP(float*, su->spectrum[0], su->spectrum[1]);
00159 
00160     return 0;
00161 }
00162 
00167 static int at1_parse_bsm(GetBitContext* gb, int log2_block_cnt[AT1_QMF_BANDS])
00168 {
00169     int log2_block_count_tmp, i;
00170 
00171     for (i = 0; i < 2; i++) {
00172         /* low and mid band */
00173         log2_block_count_tmp = get_bits(gb, 2);
00174         if (log2_block_count_tmp & 1)
00175             return -1;
00176         log2_block_cnt[i] = 2 - log2_block_count_tmp;
00177     }
00178 
00179     /* high band */
00180     log2_block_count_tmp = get_bits(gb, 2);
00181     if (log2_block_count_tmp != 0 && log2_block_count_tmp != 3)
00182         return -1;
00183     log2_block_cnt[IDX_HIGH_BAND] = 3 - log2_block_count_tmp;
00184 
00185     skip_bits(gb, 2);
00186     return 0;
00187 }
00188 
00189 
00190 static int at1_unpack_dequant(GetBitContext* gb, AT1SUCtx* su,
00191                               float spec[AT1_SU_SAMPLES])
00192 {
00193     int bits_used, band_num, bfu_num, i;
00194     uint8_t idwls[AT1_MAX_BFU];                 
00195     uint8_t idsfs[AT1_MAX_BFU];                 
00196 
00197     /* parse the info byte (2nd byte) telling how much BFUs were coded */
00198     su->num_bfus = bfu_amount_tab1[get_bits(gb, 3)];
00199 
00200     /* calc number of consumed bits:
00201         num_BFUs * (idwl(4bits) + idsf(6bits)) + log2_block_count(8bits) + info_byte(8bits)
00202         + info_byte_copy(8bits) + log2_block_count_copy(8bits) */
00203     bits_used = su->num_bfus * 10 + 32 +
00204                 bfu_amount_tab2[get_bits(gb, 2)] +
00205                 (bfu_amount_tab3[get_bits(gb, 3)] << 1);
00206 
00207     /* get word length index (idwl) for each BFU */
00208     for (i = 0; i < su->num_bfus; i++)
00209         idwls[i] = get_bits(gb, 4);
00210 
00211     /* get scalefactor index (idsf) for each BFU */
00212     for (i = 0; i < su->num_bfus; i++)
00213         idsfs[i] = get_bits(gb, 6);
00214 
00215     /* zero idwl/idsf for empty BFUs */
00216     for (i = su->num_bfus; i < AT1_MAX_BFU; i++)
00217         idwls[i] = idsfs[i] = 0;
00218 
00219     /* read in the spectral data and reconstruct MDCT spectrum of this channel */
00220     for (band_num = 0; band_num < AT1_QMF_BANDS; band_num++) {
00221         for (bfu_num = bfu_bands_t[band_num]; bfu_num < bfu_bands_t[band_num+1]; bfu_num++) {
00222             int pos;
00223 
00224             int num_specs = specs_per_bfu[bfu_num];
00225             int word_len  = !!idwls[bfu_num] + idwls[bfu_num];
00226             float scale_factor = sf_table[idsfs[bfu_num]];
00227             bits_used += word_len * num_specs; /* add number of bits consumed by current BFU */
00228 
00229             /* check for bitstream overflow */
00230             if (bits_used > AT1_SU_MAX_BITS)
00231                 return -1;
00232 
00233             /* get the position of the 1st spec according to the block size mode */
00234             pos = su->log2_block_count[band_num] ? bfu_start_short[bfu_num] : bfu_start_long[bfu_num];
00235 
00236             if (word_len) {
00237                 float   max_quant = 1.0 / (float)((1 << (word_len - 1)) - 1);
00238 
00239                 for (i = 0; i < num_specs; i++) {
00240                     /* read in a quantized spec and convert it to
00241                      * signed int and then inverse quantization
00242                      */
00243                     spec[pos+i] = get_sbits(gb, word_len) * scale_factor * max_quant;
00244                 }
00245             } else { /* word_len = 0 -> empty BFU, zero all specs in the emty BFU */
00246                 memset(&spec[pos], 0, num_specs * sizeof(float));
00247             }
00248         }
00249     }
00250 
00251     return 0;
00252 }
00253 
00254 
00255 static void at1_subband_synthesis(AT1Ctx *q, AT1SUCtx* su, float *pOut)
00256 {
00257     float temp[256];
00258     float iqmf_temp[512 + 46];
00259 
00260     /* combine low and middle bands */
00261     atrac_iqmf(q->bands[0], q->bands[1], 128, temp, su->fst_qmf_delay, iqmf_temp);
00262 
00263     /* delay the signal of the high band by 23 samples */
00264     memcpy( su->last_qmf_delay,    &su->last_qmf_delay[256], sizeof(float) *  23);
00265     memcpy(&su->last_qmf_delay[23], q->bands[2],             sizeof(float) * 256);
00266 
00267     /* combine (low + middle) and high bands */
00268     atrac_iqmf(temp, su->last_qmf_delay, 256, pOut, su->snd_qmf_delay, iqmf_temp);
00269 }
00270 
00271 
00272 static int atrac1_decode_frame(AVCodecContext *avctx, void *data,
00273                                int *data_size, AVPacket *avpkt)
00274 {
00275     const uint8_t *buf = avpkt->data;
00276     int buf_size       = avpkt->size;
00277     AT1Ctx *q          = avctx->priv_data;
00278     int ch, ret, i;
00279     GetBitContext gb;
00280     float* samples = data;
00281 
00282 
00283     if (buf_size < 212 * q->channels) {
00284         av_log(q,AV_LOG_ERROR,"Not enought data to decode!\n");
00285         return -1;
00286     }
00287 
00288     for (ch = 0; ch < q->channels; ch++) {
00289         AT1SUCtx* su = &q->SUs[ch];
00290 
00291         init_get_bits(&gb, &buf[212 * ch], 212 * 8);
00292 
00293         /* parse block_size_mode, 1st byte */
00294         ret = at1_parse_bsm(&gb, su->log2_block_count);
00295         if (ret < 0)
00296             return ret;
00297 
00298         ret = at1_unpack_dequant(&gb, su, q->spec);
00299         if (ret < 0)
00300             return ret;
00301 
00302         ret = at1_imdct_block(su, q);
00303         if (ret < 0)
00304             return ret;
00305         at1_subband_synthesis(q, su, q->out_samples[ch]);
00306     }
00307 
00308     /* interleave; FIXME, should create/use a DSP function */
00309     if (q->channels == 1) {
00310         /* mono */
00311         memcpy(samples, q->out_samples[0], AT1_SU_SAMPLES * 4);
00312     } else {
00313         /* stereo */
00314         for (i = 0; i < AT1_SU_SAMPLES; i++) {
00315             samples[i * 2]     = q->out_samples[0][i];
00316             samples[i * 2 + 1] = q->out_samples[1][i];
00317         }
00318     }
00319 
00320     *data_size = q->channels * AT1_SU_SAMPLES * sizeof(*samples);
00321     return avctx->block_align;
00322 }
00323 
00324 
00325 static av_cold int atrac1_decode_init(AVCodecContext *avctx)
00326 {
00327     AT1Ctx *q = avctx->priv_data;
00328 
00329     avctx->sample_fmt = SAMPLE_FMT_FLT;
00330 
00331     q->channels = avctx->channels;
00332 
00333     /* Init the mdct transforms */
00334     ff_mdct_init(&q->mdct_ctx[0], 6, 1, -1.0/ (1 << 15));
00335     ff_mdct_init(&q->mdct_ctx[1], 8, 1, -1.0/ (1 << 15));
00336     ff_mdct_init(&q->mdct_ctx[2], 9, 1, -1.0/ (1 << 15));
00337 
00338     ff_init_ff_sine_windows(5);
00339 
00340     atrac_generate_tables();
00341 
00342     dsputil_init(&q->dsp, avctx);
00343 
00344     q->bands[0] = q->low;
00345     q->bands[1] = q->mid;
00346     q->bands[2] = q->high;
00347 
00348     /* Prepare the mdct overlap buffers */
00349     q->SUs[0].spectrum[0] = q->SUs[0].spec1;
00350     q->SUs[0].spectrum[1] = q->SUs[0].spec2;
00351     q->SUs[1].spectrum[0] = q->SUs[1].spec1;
00352     q->SUs[1].spectrum[1] = q->SUs[1].spec2;
00353 
00354     return 0;
00355 }
00356 
00357 
00358 static av_cold int atrac1_decode_end(AVCodecContext * avctx) {
00359     AT1Ctx *q = avctx->priv_data;
00360 
00361     ff_mdct_end(&q->mdct_ctx[0]);
00362     ff_mdct_end(&q->mdct_ctx[1]);
00363     ff_mdct_end(&q->mdct_ctx[2]);
00364     return 0;
00365 }
00366 
00367 
00368 AVCodec atrac1_decoder = {
00369     .name = "atrac1",
00370     .type = AVMEDIA_TYPE_AUDIO,
00371     .id = CODEC_ID_ATRAC1,
00372     .priv_data_size = sizeof(AT1Ctx),
00373     .init = atrac1_decode_init,
00374     .close = atrac1_decode_end,
00375     .decode = atrac1_decode_frame,
00376     .long_name = NULL_IF_CONFIG_SMALL("Atrac 1 (Adaptive TRansform Acoustic Coding)"),
00377 };

Generated on Fri Sep 16 2011 17:17:34 for FFmpeg by  doxygen 1.7.1