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https://github.com/xenia-project/FFmpeg.git
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new implementation of exponent decoding
Originally committed as revision 9749 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles
parent
d699d38393
commit
4415076f55
@ -46,9 +46,8 @@ static const int nfchans_tbl[8] = { 2, 1, 2, 3, 3, 4, 4, 5 };
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*/
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static float scale_factors[25];
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static int8_t exp_1[128];
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static int8_t exp_2[128];
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static int8_t exp_3[128];
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/** table for grouping exponents */
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static uint8_t exp_ungroup_tbl[128][3];
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static int16_t l3_quantizers_1[32];
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static int16_t l3_quantizers_2[32];
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@ -267,30 +266,7 @@ static void generate_quantizers_table_3(int16_t quantizers[], int level, int len
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*/
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static void ac3_tables_init(void)
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{
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int i, j, v;
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/* Exponent Decoding Tables */
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for (i = 0; i < 5; i++) {
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v = i - 2;
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for (j = 0; j < 25; j++)
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exp_1[i * 25 + j] = v;
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}
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for (i = 0; i < 25; i++) {
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v = (i % 5) - 2;
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for (j = 0; j < 5; j++)
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exp_2[i * 5 + j] = v;
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}
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for (i = 0; i < 25; i++) {
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v = -2;
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for (j = 0; j < 5; j++)
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exp_3[i * 5 + j] = v++;
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}
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for (i = 125; i < 128; i++)
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exp_1[i] = exp_2[i] = exp_3[i] = 25;
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/* End Exponent Decoding Tables */
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int i;
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/* Quantizer ungrouping tables. */
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// for level-3 quantizers
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@ -317,6 +293,14 @@ static void ac3_tables_init(void)
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//generate scale factors
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for (i = 0; i < 25; i++)
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scale_factors[i] = pow(2.0, -(i + 15));
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/* generate exponent tables
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reference: Section 7.1.3 Exponent Decoding */
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for(i=0; i<128; i++) {
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exp_ungroup_tbl[i][0] = i / 25;
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exp_ungroup_tbl[i][1] = (i % 25) / 5;
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exp_ungroup_tbl[i][2] = (i % 25) % 5;
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}
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}
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@ -472,60 +456,30 @@ static void ac3_parse_bsi(AC3DecodeContext *ctx)
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* @param dexps Decoded exponents are stored in dexps
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* @return Returns 0 if exponents are decoded successfully, -1 if error occurs
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*/
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static int decode_exponents(GetBitContext *gb, int expstr, int ngrps, uint8_t absexp, uint8_t *dexps)
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static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
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uint8_t absexp, uint8_t *dexps)
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{
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int exps;
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int i, j, grp, grpsize;
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int dexp[256];
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int expacc, prevexp;
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while (ngrps--) {
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exps = get_bits(gb, 7);
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absexp += exp_1[exps];
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if (absexp > 24) {
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av_log(NULL, AV_LOG_ERROR, "Absolute Exponent > 24, ngrp = %d\n", ngrps);
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return -ngrps;
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}
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switch (expstr) {
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case EXP_D45:
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*(dexps++) = absexp;
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*(dexps++) = absexp;
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case EXP_D25:
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*(dexps++) = absexp;
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case EXP_D15:
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*(dexps++) = absexp;
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/* unpack groups */
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grpsize = expstr + (expstr == EXP_D45);
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for(grp=0,i=0; grp<ngrps; grp++) {
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expacc = get_bits(gb, 7);
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dexp[i++] = exp_ungroup_tbl[expacc][0];
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dexp[i++] = exp_ungroup_tbl[expacc][1];
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dexp[i++] = exp_ungroup_tbl[expacc][2];
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}
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absexp += exp_2[exps];
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if (absexp > 24) {
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av_log(NULL, AV_LOG_ERROR, "Absolute Exponent > 24, ngrp = %d\n", ngrps);
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return -ngrps;
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}
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switch (expstr) {
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case EXP_D45:
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*(dexps++) = absexp;
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*(dexps++) = absexp;
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case EXP_D25:
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*(dexps++) = absexp;
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case EXP_D15:
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*(dexps++) = absexp;
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}
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absexp += exp_3[exps];
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if (absexp > 24) {
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av_log(NULL, AV_LOG_ERROR, "Absolute Exponent > 24, ngrp = %d\n", ngrps);
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return -ngrps;
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}
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switch (expstr) {
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case EXP_D45:
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*(dexps++) = absexp;
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*(dexps++) = absexp;
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case EXP_D25:
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*(dexps++) = absexp;
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case EXP_D15:
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*(dexps++) = absexp;
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/* convert to absolute exps and expand groups */
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prevexp = absexp;
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for(i=0; i<ngrps*3; i++) {
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prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
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for(j=0; j<grpsize; j++) {
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dexps[(i*grpsize)+j] = prevexp;
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}
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}
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return 0;
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}
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/* Performs bit allocation.
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@ -1536,10 +1490,7 @@ static int ac3_parse_audio_block(AC3DecodeContext * ctx)
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bit_alloc_flags = 64;
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cplabsexp = get_bits(gb, 4) << 1;
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ngrps = (ctx->cplendmant - ctx->cplstrtmant) / (3 << (ctx->cplexpstr - 1));
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if (decode_exponents(gb, ctx->cplexpstr, ngrps, cplabsexp, ctx->dcplexps + ctx->cplstrtmant)) {
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av_log(NULL, AV_LOG_ERROR, "error decoding coupling exponents\n");
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return -1;
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}
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decode_exponents(gb, ctx->cplexpstr, ngrps, cplabsexp, ctx->dcplexps + ctx->cplstrtmant);
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}
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for (i = 0; i < nfchans; i++) /* fbw channel exponents */
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@ -1549,20 +1500,14 @@ static int ac3_parse_audio_block(AC3DecodeContext * ctx)
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ngrps = (ctx->endmant[i] + grpsize - 4) / grpsize;
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dexps = ctx->dexps[i];
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dexps[0] = get_bits(gb, 4);
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if (decode_exponents(gb, ctx->chexpstr[i], ngrps, dexps[0], dexps + 1)) {
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av_log(NULL, AV_LOG_ERROR, "error decoding channel %d exponents\n", i);
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return -1;
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}
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decode_exponents(gb, ctx->chexpstr[i], ngrps, dexps[0], dexps + 1);
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skip_bits(gb, 2); /* skip gainrng */
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}
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if (ctx->lfeexpstr != EXP_REUSE) { /* lfe exponents */
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bit_alloc_flags |= 32;
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ctx->dlfeexps[0] = get_bits(gb, 4);
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if (decode_exponents(gb, ctx->lfeexpstr, 2, ctx->dlfeexps[0], ctx->dlfeexps + 1)) {
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av_log(NULL, AV_LOG_ERROR, "error decoding lfe exponents\n");
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return -1;
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}
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decode_exponents(gb, ctx->lfeexpstr, 2, ctx->dlfeexps[0], ctx->dlfeexps + 1);
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}
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if (get_bits1(gb)) { /* bit allocation information */
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