Author: thilo.borgmann
Date: Tue Oct 13 21:35:21 2009
New Revision: 5408
Log:
Added long-term prediction.
Modified:
als/als_data.h
als/alsdec.c
Modified: als/als_data.h
==============================================================================
--- als/als_data.h Tue Oct 13 21:29:01 2009 (r5407)
+++ als/als_data.h Tue Oct 13 21:35:21 2009 (r5408)
@@ -92,4 +92,11 @@ static const int16_t parcor_scaled_value
};
+/** Gain values of p(0) for long-term prediction.
+ * To be indexed by the Rice coded indices.
+ */
+static const int ltp_gain [] = {
+ 0, 8, 16, 24, 32, 40, 48, 56, 64, 70, 76, 82, 88, 92, 96, 100
+};
+
#endif /* AVCODEC_ALS_DATA_H */
Modified: als/alsdec.c
==============================================================================
--- als/alsdec.c Tue Oct 13 21:29:01 2009 (r5407)
+++ als/alsdec.c Tue Oct 13 21:35:21 2009 (r5408)
@@ -79,6 +79,7 @@ typedef struct {
unsigned int frame_id; ///< the frame ID / number of the current
frame
unsigned int js_switch; ///< if true, joint-stereo decoding is
enforced
unsigned int num_blocks; ///< number of blocks used in the current
frame
+ int ltp_lag_length; ///< number of bits used for ltp lag value
int32_t *quant_cof; ///< quantized parcor coefficients
int32_t *lpc_cof; ///< coefficients of the direct form
prediction filter
int32_t *prev_raw_samples; ///< contains unshifted raw samples from
the previous block
@@ -290,7 +291,6 @@ static int check_specific_config(ALSDecC
}
MISSING_ERR(sconf->floating, "Floating point decoding",
-1);
- MISSING_ERR(sconf->long_term_prediction, "Long-term prediction",
-1);
MISSING_ERR(sconf->bgmc, "BGMC entropy decoding",
-1);
MISSING_ERR(sconf->mc_coding, "Multi-channel correlation",
-1);
MISSING_ERR(sconf->rlslms, "Adaptive RLS-LMS prediction",
-1);
@@ -470,6 +470,9 @@ static int read_var_block(ALSDecContext
int smp = 0;
int sb, store_prev_samples;
int64_t y;
+ int use_ltp = 0;
+ int lag = 0;
+ int gain[5];
*js_blocks = get_bits1(gb);
@@ -568,7 +571,26 @@ static int read_var_block(ALSDecContext
}
}
- // TODO: LTP mode
+ // read LTP gain and lag values
+ if (sconf->long_term_prediction) {
+ use_ltp = get_bits1(gb);
+
+ if (use_ltp) {
+ gain[0] = decode_rice(gb, 1) << 3;
+ gain[1] = decode_rice(gb, 2) << 3;
+
+ gain[2] = get_unary(gb, 0, 4);
+ gain[2] <<= 2;
+ gain[2] += get_bits(gb, 2);
+ gain[2] = ltp_gain[gain[2]];
+
+ gain[3] = decode_rice(gb, 2) << 3;
+ gain[4] = decode_rice(gb, 1) << 3;
+
+ lag = get_bits(gb, ctx->ltp_lag_length);
+ lag += FFMAX(4, opt_order + 1);
+ }
+ }
// read first value and residuals in case of a random access block
if (ra_block) {
@@ -593,6 +615,26 @@ static int read_var_block(ALSDecContext
*current_res++ = decode_rice(gb, s[sb]);
}
+ // revert long-term prediction
+ if (use_ltp) {
+ int ltp_smp;
+
+ for (ltp_smp = 0; ltp_smp < block_length; ltp_smp++) {
+ int center = ltp_smp - lag;
+ int begin = FFMAX(0, center - 2);
+ int end = center + 3;
+ int tab = 5 - (end - begin);
+ int base;
+
+ y = 1 << 6;
+
+ for (base = begin; base < end; base++, tab++)
+ y += MUL64(gain[tab], raw_samples[base]);
+
+ raw_samples[ltp_smp] += y >> 7;
+ }
+ }
+
// reconstruct all samples from residuals
if (ra_block) {
for (smp = 0; smp < opt_order; smp++) {
@@ -974,6 +1016,14 @@ static av_cold int decode_init(AVCodecCo
avctx->bits_per_raw_sample = (sconf->resolution + 1) * 8;
}
+ // set lag value for long-term prediction
+ if (avctx->sample_rate >= 192000)
+ ctx->ltp_lag_length = 10;
+ else if (avctx->sample_rate >= 96000)
+ ctx->ltp_lag_length = 9;
+ else
+ ctx->ltp_lag_length = 8;
+
avctx->frame_size = sconf->frame_length;
channel_size = sconf->frame_length + sconf->max_order;
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