[FFmpeg-cvslog] r25991 - trunk/libavcodec/ac3enc.c
jbr
subversion
Tue Dec 14 15:53:02 CET 2010
Author: jbr
Date: Tue Dec 14 15:53:02 2010
New Revision: 25991
Log:
Split exponent processing into separate functions.
Modified:
trunk/libavcodec/ac3enc.c
Modified: trunk/libavcodec/ac3enc.c
==============================================================================
--- trunk/libavcodec/ac3enc.c Tue Dec 14 15:52:59 2010 (r25990)
+++ trunk/libavcodec/ac3enc.c Tue Dec 14 15:53:02 2010 (r25991)
@@ -412,6 +412,41 @@ static void apply_mdct(AC3EncodeContext
/**
+ * Extract exponents from the MDCT coefficients.
+ * This takes into account the normalization that was done to the input samples
+ * by adjusting the exponents by the exponent shift values.
+ */
+static void extract_exponents(AC3EncodeContext *s,
+ int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
+ int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
+ uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
+{
+ int blk, ch, i;
+
+ /* extract exponents */
+ for (ch = 0; ch < s->channels; ch++) {
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ /* compute "exponents". We take into account the normalization there */
+ for (i = 0; i < AC3_MAX_COEFS; i++) {
+ int e;
+ int v = abs(mdct_coef[blk][ch][i]);
+ if (v == 0)
+ e = 24;
+ else {
+ e = 23 - av_log2(v) + exp_shift[blk][ch];
+ if (e >= 24) {
+ e = 24;
+ mdct_coef[blk][ch][i] = 0;
+ }
+ }
+ exp[blk][ch][i] = e;
+ }
+ }
+ }
+}
+
+
+/**
* Calculate the sum of absolute differences (SAD) between 2 sets of exponents.
*/
static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
@@ -473,6 +508,21 @@ static void compute_exp_strategy_ch(uint
/**
+ * Calculate exponent strategies for all channels.
+ */
+static void compute_exp_strategy(AC3EncodeContext *s,
+ uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
+ uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
+{
+ int ch;
+
+ for (ch = 0; ch < s->channels; ch++) {
+ compute_exp_strategy_ch(exp_strategy, exp, ch, ch == s->lfe_channel);
+ }
+}
+
+
+/**
* Set each encoded exponent in a block to the minimum of itself and the
* exponent in the same frequency bin of a following block.
* exp[i] = min(exp[i], exp1[i]
@@ -540,6 +590,68 @@ static int encode_exponents_blk_ch(uint8
/**
+ * Encode exponents from original extracted form to what the decoder will see.
+ * This copies and groups exponents based on exponent strategy and reduces
+ * deltas between adjacent exponent groups so that they can be differentially
+ * encoded.
+ * @return bits needed to encode the exponents
+ */
+static int encode_exponents(AC3EncodeContext *s,
+ uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
+ uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
+ uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
+{
+ int blk, blk1, blk2, ch;
+ int frame_bits;
+
+ frame_bits = 0;
+ for (ch = 0; ch < s->channels; ch++) {
+ /* for the EXP_REUSE case we select the min of the exponents */
+ blk = 0;
+ while (blk < AC3_MAX_BLOCKS) {
+ blk1 = blk + 1;
+ while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1][ch] == EXP_REUSE) {
+ exponent_min(exp[blk][ch], exp[blk1][ch], s->nb_coefs[ch]);
+ blk1++;
+ }
+ frame_bits += encode_exponents_blk_ch(encoded_exp[blk][ch],
+ exp[blk][ch], s->nb_coefs[ch],
+ exp_strategy[blk][ch]);
+ /* copy encoded exponents for reuse case */
+ for (blk2 = blk+1; blk2 < blk1; blk2++) {
+ memcpy(encoded_exp[blk2][ch], encoded_exp[blk][ch],
+ s->nb_coefs[ch] * sizeof(uint8_t));
+ }
+ blk = blk1;
+ }
+ }
+
+ return frame_bits;
+}
+
+
+/**
+ * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
+ * Extract exponents from MDCT coefficients, calculate exponent strategies,
+ * and encode final exponents.
+ * @return bits needed to encode the exponents
+ */
+static int process_exponents(AC3EncodeContext *s,
+ int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
+ int8_t exp_shift[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
+ uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS],
+ uint8_t exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS],
+ uint8_t encoded_exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS])
+{
+ extract_exponents(s, mdct_coef, exp_shift, exp);
+
+ compute_exp_strategy(s, exp_strategy, exp);
+
+ return encode_exponents(s, exp, exp_strategy, encoded_exp);
+}
+
+
+/**
* Calculate the number of bits needed to encode a set of mantissas.
*/
static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
@@ -1174,8 +1286,7 @@ static int ac3_encode_frame(AVCodecConte
{
AC3EncodeContext *s = avctx->priv_data;
const int16_t *samples = data;
- int v;
- int blk, blk1, blk2, ch, i;
+ int blk;
int16_t planar_samples[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE+AC3_FRAME_SIZE];
int32_t mdct_coef[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
uint8_t exp[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][AC3_MAX_COEFS];
@@ -1189,56 +1300,7 @@ static int ac3_encode_frame(AVCodecConte
apply_mdct(s, planar_samples, exp_shift, mdct_coef);
- /* extract exponents */
- for (ch = 0; ch < s->channels; ch++) {
- for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
- /* compute "exponents". We take into account the normalization there */
- for (i = 0; i < AC3_MAX_COEFS; i++) {
- int e;
- v = abs(mdct_coef[blk][ch][i]);
- if (v == 0)
- e = 24;
- else {
- e = 23 - av_log2(v) + exp_shift[blk][ch];
- if (e >= 24) {
- e = 24;
- mdct_coef[blk][ch][i] = 0;
- }
- }
- exp[blk][ch][i] = e;
- }
- }
- }
-
- /* compute exponent strategies */
- for (ch = 0; ch < s->channels; ch++) {
- compute_exp_strategy_ch(exp_strategy, exp, ch, ch == s->lfe_channel);
- }
-
- /* encode exponents */
- frame_bits = 0;
- for (ch = 0; ch < s->channels; ch++) {
- /* compute the exponents as the decoder will see them. The
- EXP_REUSE case must be handled carefully : we select the
- min of the exponents */
- blk = 0;
- while (blk < AC3_MAX_BLOCKS) {
- blk1 = blk + 1;
- while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1][ch] == EXP_REUSE) {
- exponent_min(exp[blk][ch], exp[blk1][ch], s->nb_coefs[ch]);
- blk1++;
- }
- frame_bits += encode_exponents_blk_ch(encoded_exp[blk][ch],
- exp[blk][ch], s->nb_coefs[ch],
- exp_strategy[blk][ch]);
- /* copy encoded exponents for reuse case */
- for (blk2 = blk+1; blk2 < blk1; blk2++) {
- memcpy(encoded_exp[blk2][ch], encoded_exp[blk][ch],
- s->nb_coefs[ch] * sizeof(uint8_t));
- }
- blk = blk1;
- }
- }
+ frame_bits = process_exponents(s, mdct_coef, exp_shift, exp, exp_strategy, encoded_exp);
/* adjust for fractional frame sizes */
while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
More information about the ffmpeg-cvslog
mailing list