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add dialogue normalization 

Originally committed as revision 9948 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2007-08-05 19:36:35 +00:00
parent 8767b80f5f
commit 01f354531d
1 changed files with 16 additions and 4 deletions
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20
libavcodec/ac3dec.c
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@ -72,6 +72,9 @@ static const uint8_t qntztab[16] = {
/** dynamic range table. converts codes to scale factors. */
static float dynrng_tbl[256];
/** dialogue normalization table */
static float dialnorm_tbl[32];
/* Adjustmens in dB gain */
#define LEVEL_MINUS_3DB 0.7071067811865476
#define LEVEL_MINUS_4POINT5DB 0.5946035575013605
@ -159,6 +162,7 @@ typedef struct {
int out_channels; ///< number of output channels
float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
float dialnorm[2]; ///< dialogue normalization
float dynrng; //dynamic range gain
float dynrng2; //dynamic range gain for 1+1 mode
float cplco[AC3_MAX_CHANNELS][18]; //coupling coordinates
@ -269,6 +273,14 @@ static void ac3_tables_init(void)
dynrng_tbl[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
}
/* generate dialogue normalization table
references: Section 5.4.2.8 dialnorm
Section 7.6 Dialogue Normalization */
for(i=1; i<32; i++) {
dialnorm_tbl[i] = expf((i-31) * M_LN10 / 20.0f);
}
dialnorm_tbl[0] = dialnorm_tbl[31];
//generate scale factors
for (i = 0; i < 25; i++)
scale_factors[i] = pow(2.0, -i);
@ -362,7 +374,7 @@ static int ac3_parse_header(AC3DecodeContext *ctx)
/* read the rest of the bsi. read twice for dual mono mode. */
i = !(ctx->acmod);
do {
skip_bits(gb, 5); //skip dialog normalization
ctx->dialnorm[i] = dialnorm_tbl[get_bits(gb, 5)]; // dialogue normalization
if (get_bits1(gb))
skip_bits(gb, 8); //skip compression
if (get_bits1(gb))
@ -1007,13 +1019,13 @@ static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
if(ctx->acmod == AC3_ACMOD_STEREO)
do_rematrixing(ctx);
/* apply scaling to coefficients (headroom, dynrng) */
/* apply scaling to coefficients (headroom, dialnorm, dynrng) */
for(ch=1; ch<=ctx->nchans; ch++) {
float gain = 2.0f * ctx->mul_bias;
if(ctx->acmod == AC3_ACMOD_DUALMONO && ch == 2) {
gain *= ctx->dynrng2;
gain *= ctx->dialnorm[ch-1] * ctx->dynrng2;
} else {
gain *= ctx->dynrng;
gain *= ctx->dialnorm[0] * ctx->dynrng;
}
for(i=0; i<ctx->endmant[ch]; i++) {
ctx->transform_coeffs[ch][i] *= gain;