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eac3dec: make GAQ dequantization 24-bit

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Originally committed as revision 18888 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2009-05-21 00:15:03 +00:00
parent ae04de316f
commit 9907c7804a
3 changed files with 18 additions and 17 deletions
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21
libavcodec/ac3dec_data.c
View File

@ -87,19 +87,18 @@ const int16_t ff_eac3_gaq_remap_2_4_a[9][2] = {
/**
* Table E3.6, Gk=2 & Gk=4, B
* Large mantissa inverse quantization, negative mantissa remapping offsets
* Table values from the spec are right-shifted by 8 to simplify calculations.
* ff_eac3_gaq_remap_3_4_b[hebap-8][Gk=2,4]
*/
const int8_t ff_eac3_gaq_remap_2_4_b[9][2] = {
{ -22, -5 },
{ -46, -20 },
{ -56, -26 },
{ -60, -29 },
{ -62, -31 },
{ -63, -32 },
{ -64, -32 },
{ -64, -32 },
{ -64, -32 },
const int16_t ff_eac3_gaq_remap_2_4_b[9][2] = {
{ -5461, -1170 },
{ -11703, -4915 },
{ -14199, -6606 },
{ -15327, -7412 },
{ -15864, -7805 },
{ -16126, -7999 },
{ -16255, -8096 },
{ -16320, -8144 },
{ -16352, -8168 }
};
static const int16_t vq_hebap1[4][6] = {

2
libavcodec/ac3dec_data.h
View File

@ -29,7 +29,7 @@ extern const uint8_t ff_eac3_hebap_tab[64];
extern const uint8_t ff_eac3_bits_vs_hebap[20];
extern const int16_t ff_eac3_gaq_remap_1[12];
extern const int16_t ff_eac3_gaq_remap_2_4_a[9][2];
extern const int8_t ff_eac3_gaq_remap_2_4_b[9][2];
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];

12
libavcodec/eac3dec.c
View File

@ -178,19 +178,21 @@ void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch)
if (mant == -(1 << (gbits-1))) {
/* large mantissa */
int b;
mant = get_sbits(gbc, bits-2+log_gain) << (26-log_gain-bits);
int mbits = bits - (2 - log_gain);
mant = get_sbits(gbc, mbits);
mant <<= (23 - (mbits - 1));
/* remap mantissa value to correct for asymmetric quantization */
if (mant >= 0)
b = 32768 >> (log_gain+8);
b = 1 << (23 - (mbits - 1));
else
b = ff_eac3_gaq_remap_2_4_b[hebap-8][log_gain-1];
mant += (ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] * (mant>>8) + b) >> 7;
b = ff_eac3_gaq_remap_2_4_b[hebap-8][log_gain-1] << 8;
mant += (((ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] << 8) * (int64_t)mant) >> 23) + b;
} else {
/* small mantissa, no GAQ, or Gk=1 */
mant <<= 24 - bits;
if (!log_gain) {
/* remap mantissa value for no GAQ or Gk=1 */
mant += (ff_eac3_gaq_remap_1[hebap-8] * (mant>>8)) >> 7;
mant += ((ff_eac3_gaq_remap_1[hebap-8] << 8) * (int64_t)mant) >> 23;
}
}
s->pre_mantissa[ch][bin][blk] = mant;