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authorJai Menon <jmenon86@gmail.com>2008-08-19 17:20:41 +0000
committerJai Menon <jmenon86@gmail.com>2008-08-19 17:20:41 +0000
commite13894e80e25ecfda73fce3fbf1e206642c695a9 (patch)
tree8018173c2087f0868526cc83985b332bcb5150f5 /libavcodec/alacenc.c
parentcc940caf4d98bce64defc48e33ff51a5cc9e985f (diff)
downloadffmpeg-e13894e80e25ecfda73fce3fbf1e206642c695a9.tar.gz
alacenc: last few hunks approved by michael
Originally committed as revision 14845 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/alacenc.c')
-rw-r--r--libavcodec/alacenc.c110
1 files changed, 110 insertions, 0 deletions
diff --git a/libavcodec/alacenc.c b/libavcodec/alacenc.c
index d6332bff28..a1fb66f9e2 100644
--- a/libavcodec/alacenc.c
+++ b/libavcodec/alacenc.c
@@ -217,6 +217,114 @@ static void alac_stereo_decorrelation(AlacEncodeContext *s)
}
}
+static void alac_linear_predictor(AlacEncodeContext *s, int ch)
+{
+ int i;
+ LPCContext lpc = s->lpc[ch];
+
+ if(lpc.lpc_order == 31) {
+ s->predictor_buf[0] = s->sample_buf[ch][0];
+
+ for(i=1; i<s->avctx->frame_size; i++)
+ s->predictor_buf[i] = s->sample_buf[ch][i] - s->sample_buf[ch][i-1];
+
+ return;
+ }
+
+ // generalised linear predictor
+
+ if(lpc.lpc_order > 0) {
+ int32_t *samples = s->sample_buf[ch];
+ int32_t *residual = s->predictor_buf;
+
+ // generate warm-up samples
+ residual[0] = samples[0];
+ for(i=1;i<=lpc.lpc_order;i++)
+ residual[i] = samples[i] - samples[i-1];
+
+ // perform lpc on remaining samples
+ for(i = lpc.lpc_order + 1; i < s->avctx->frame_size; i++) {
+ int sum = 1 << (lpc.lpc_quant - 1), res_val, j;
+
+ for (j = 0; j < lpc.lpc_order; j++) {
+ sum += (samples[lpc.lpc_order-j] - samples[0]) *
+ lpc.lpc_coeff[j];
+ }
+
+ sum >>= lpc.lpc_quant;
+ sum += samples[0];
+ residual[i] = samples[lpc.lpc_order+1] - sum;
+ res_val = residual[i];
+
+ if(res_val) {
+ int index = lpc.lpc_order - 1;
+ int neg = (res_val < 0);
+
+ while(index >= 0 && (neg ? (res_val < 0):(res_val > 0))) {
+ int val = samples[0] - samples[lpc.lpc_order - index];
+ int sign = (val ? FFSIGN(val) : 0);
+
+ if(neg)
+ sign*=-1;
+
+ lpc.lpc_coeff[index] -= sign;
+ val *= sign;
+ res_val -= ((val >> lpc.lpc_quant) *
+ (lpc.lpc_order - index));
+ index--;
+ }
+ }
+ samples++;
+ }
+ }
+}
+
+static void alac_entropy_coder(AlacEncodeContext *s)
+{
+ unsigned int history = s->rc.initial_history;
+ int sign_modifier = 0, i, k;
+ int32_t *samples = s->predictor_buf;
+
+ for(i=0;i < s->avctx->frame_size;) {
+ int x;
+
+ k = av_log2((history >> 9) + 3);
+
+ x = -2*(*samples)-1;
+ x ^= (x>>31);
+
+ samples++;
+ i++;
+
+ encode_scalar(s, x - sign_modifier, k, s->write_sample_size);
+
+ history += x * s->rc.history_mult
+ - ((history * s->rc.history_mult) >> 9);
+
+ sign_modifier = 0;
+ if(x > 0xFFFF)
+ history = 0xFFFF;
+
+ if((history < 128) && (i < s->avctx->frame_size)) {
+ unsigned int block_size = 0;
+
+ k = 7 - av_log2(history) + ((history + 16) >> 6);
+
+ while((*samples == 0) && (i < s->avctx->frame_size)) {
+ samples++;
+ i++;
+ block_size++;
+ }
+ encode_scalar(s, block_size, k, 16);
+
+ sign_modifier = (block_size <= 0xFFFF);
+
+ history = 0;
+ }
+
+ }
+}
+
static void write_compressed_frame(AlacEncodeContext *s)
{
int i, j;
@@ -295,6 +403,7 @@ static av_cold int alac_encode_init(AVCodecContext *avctx)
AV_WB8(alac_extradata+20, s->rc.k_modifier);
}
+ s->min_prediction_order = DEFAULT_MIN_PRED_ORDER;
if(avctx->min_prediction_order >= 0) {
if(avctx->min_prediction_order < MIN_LPC_ORDER ||
avctx->min_prediction_order > MAX_LPC_ORDER) {
@@ -305,6 +414,7 @@ static av_cold int alac_encode_init(AVCodecContext *avctx)
s->min_prediction_order = avctx->min_prediction_order;
}
+ s->max_prediction_order = DEFAULT_MAX_PRED_ORDER;
if(avctx->max_prediction_order >= 0) {
if(avctx->max_prediction_order < MIN_LPC_ORDER ||
avctx->max_prediction_order > MAX_LPC_ORDER) {