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FFmpeg/libavcodec/flacenc.c

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/**
* FLAC audio encoder
* Copyright (c) 2006 Justin Ruggles <jruggle@earthlink.net>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "avcodec.h"
#include "bitstream.h"
#include "crc.h"
#include "golomb.h"
#define FLAC_MAX_CH 8
#define FLAC_MIN_BLOCKSIZE 16
#define FLAC_MAX_BLOCKSIZE 65535
#define FLAC_SUBFRAME_CONSTANT 0
#define FLAC_SUBFRAME_VERBATIM 1
#define FLAC_SUBFRAME_FIXED 8
#define FLAC_SUBFRAME_LPC 32
#define FLAC_CHMODE_NOT_STEREO 0
#define FLAC_CHMODE_LEFT_RIGHT 1
#define FLAC_CHMODE_LEFT_SIDE 8
#define FLAC_CHMODE_RIGHT_SIDE 9
#define FLAC_CHMODE_MID_SIDE 10
#define ORDER_METHOD_EST 0
#define ORDER_METHOD_2LEVEL 1
#define ORDER_METHOD_4LEVEL 2
#define ORDER_METHOD_8LEVEL 3
#define ORDER_METHOD_SEARCH 4
#define FLAC_STREAMINFO_SIZE 34
#define MIN_LPC_ORDER 1
#define MAX_LPC_ORDER 32
#define MAX_FIXED_ORDER 4
#define MAX_PARTITION_ORDER 8
#define MAX_PARTITIONS (1 << MAX_PARTITION_ORDER)
#define MAX_LPC_PRECISION 15
#define MAX_LPC_SHIFT 15
#define MAX_RICE_PARAM 14
typedef struct CompressionOptions {
int compression_level;
int block_time_ms;
int use_lpc;
int lpc_coeff_precision;
int min_prediction_order;
int max_prediction_order;
int prediction_order_method;
int min_partition_order;
int max_partition_order;
} CompressionOptions;
typedef struct RiceContext {
int porder;
int params[MAX_PARTITIONS];
} RiceContext;
typedef struct FlacSubframe {
int type;
int type_code;
int obits;
int order;
int32_t coefs[MAX_LPC_ORDER];
int shift;
RiceContext rc;
int32_t samples[FLAC_MAX_BLOCKSIZE];
int32_t residual[FLAC_MAX_BLOCKSIZE];
} FlacSubframe;
typedef struct FlacFrame {
FlacSubframe subframes[FLAC_MAX_CH];
int blocksize;
int bs_code[2];
uint8_t crc8;
int ch_mode;
} FlacFrame;
typedef struct FlacEncodeContext {
PutBitContext pb;
int channels;
int ch_code;
int samplerate;
int sr_code[2];
int blocksize;
int max_framesize;
uint32_t frame_count;
FlacFrame frame;
CompressionOptions options;
AVCodecContext *avctx;
} FlacEncodeContext;
static const int flac_samplerates[16] = {
0, 0, 0, 0,
8000, 16000, 22050, 24000, 32000, 44100, 48000, 96000,
0, 0, 0, 0
};
static const int flac_blocksizes[16] = {
0,
192,
576, 1152, 2304, 4608,
0, 0,
256, 512, 1024, 2048, 4096, 8192, 16384, 32768
};
/**
* Writes streaminfo metadata block to byte array
*/
static void write_streaminfo(FlacEncodeContext *s, uint8_t *header)
{
PutBitContext pb;
memset(header, 0, FLAC_STREAMINFO_SIZE);
init_put_bits(&pb, header, FLAC_STREAMINFO_SIZE);
/* streaminfo metadata block */
put_bits(&pb, 16, s->blocksize);
put_bits(&pb, 16, s->blocksize);
put_bits(&pb, 24, 0);
put_bits(&pb, 24, s->max_framesize);
put_bits(&pb, 20, s->samplerate);
put_bits(&pb, 3, s->channels-1);
put_bits(&pb, 5, 15); /* bits per sample - 1 */
flush_put_bits(&pb);
/* total samples = 0 */
/* MD5 signature = 0 */
}
/**
* Sets blocksize based on samplerate
* Chooses the closest predefined blocksize >= BLOCK_TIME_MS milliseconds
*/
static int select_blocksize(int samplerate, int block_time_ms)
{
int i;
int target;
int blocksize;
assert(samplerate > 0);
blocksize = flac_blocksizes[1];
target = (samplerate * block_time_ms) / 1000;
for(i=0; i<16; i++) {
if(target >= flac_blocksizes[i] && flac_blocksizes[i] > blocksize) {
blocksize = flac_blocksizes[i];
}
}
return blocksize;
}
static int flac_encode_init(AVCodecContext *avctx)
{
int freq = avctx->sample_rate;
int channels = avctx->channels;
FlacEncodeContext *s = avctx->priv_data;
int i, level;
uint8_t *streaminfo;
s->avctx = avctx;
if(avctx->sample_fmt != SAMPLE_FMT_S16) {
return -1;
}
if(channels < 1 || channels > FLAC_MAX_CH) {
return -1;
}
s->channels = channels;
s->ch_code = s->channels-1;
/* find samplerate in table */
if(freq < 1)
return -1;
for(i=4; i<12; i++) {
if(freq == flac_samplerates[i]) {
s->samplerate = flac_samplerates[i];
s->sr_code[0] = i;
s->sr_code[1] = 0;
break;
}
}
/* if not in table, samplerate is non-standard */
if(i == 12) {
if(freq % 1000 == 0 && freq < 255000) {
s->sr_code[0] = 12;
s->sr_code[1] = freq / 1000;
} else if(freq % 10 == 0 && freq < 655350) {
s->sr_code[0] = 14;
s->sr_code[1] = freq / 10;
} else if(freq < 65535) {
s->sr_code[0] = 13;
s->sr_code[1] = freq;
} else {
return -1;
}
s->samplerate = freq;
}
/* set compression option defaults based on avctx->compression_level */
if(avctx->compression_level < 0) {
s->options.compression_level = 5;
} else {
s->options.compression_level = avctx->compression_level;
}
av_log(avctx, AV_LOG_DEBUG, " compression: %d\n", s->options.compression_level);
level= s->options.compression_level;
if(level > 5) {
av_log(avctx, AV_LOG_ERROR, "invalid compression level: %d\n",
s->options.compression_level);
return -1;
}
s->options.block_time_ms = ((int[]){ 27, 27, 27,105,105,105})[level];
s->options.use_lpc = ((int[]){ 0, 0, 0, 1, 1, 1})[level];
s->options.min_prediction_order= ((int[]){ 2, 0, 0, 1, 1, 1})[level];
s->options.max_prediction_order= ((int[]){ 3, 4, 4, 6, 8, 8})[level];
s->options.prediction_order_method = ORDER_METHOD_EST;
s->options.min_partition_order = ((int[]){ 2, 2, 0, 0, 0, 0})[level];
s->options.max_partition_order = ((int[]){ 2, 2, 3, 3, 3, 8})[level];
/* set compression option overrides from AVCodecContext */
if(avctx->use_lpc >= 0) {
s->options.use_lpc = !!avctx->use_lpc;
}
av_log(avctx, AV_LOG_DEBUG, " use lpc: %s\n",
s->options.use_lpc? "yes" : "no");
if(avctx->min_prediction_order >= 0) {
if(s->options.use_lpc) {
if(avctx->min_prediction_order < MIN_LPC_ORDER ||
avctx->min_prediction_order > MAX_LPC_ORDER) {
av_log(avctx, AV_LOG_ERROR, "invalid min prediction order: %d\n",
avctx->min_prediction_order);
return -1;
}
} else {
if(avctx->min_prediction_order > MAX_FIXED_ORDER) {
av_log(avctx, AV_LOG_ERROR, "invalid min prediction order: %d\n",
avctx->min_prediction_order);
return -1;
}
}
s->options.min_prediction_order = avctx->min_prediction_order;
}
if(avctx->max_prediction_order >= 0) {
if(s->options.use_lpc) {
if(avctx->max_prediction_order < MIN_LPC_ORDER ||
avctx->max_prediction_order > MAX_LPC_ORDER) {
av_log(avctx, AV_LOG_ERROR, "invalid max prediction order: %d\n",
avctx->max_prediction_order);
return -1;
}
} else {
if(avctx->max_prediction_order > MAX_FIXED_ORDER) {
av_log(avctx, AV_LOG_ERROR, "invalid max prediction order: %d\n",
avctx->max_prediction_order);
return -1;
}
}
s->options.max_prediction_order = avctx->max_prediction_order;
}
if(s->options.max_prediction_order < s->options.min_prediction_order) {
av_log(avctx, AV_LOG_ERROR, "invalid prediction orders: min=%d max=%d\n",
s->options.min_prediction_order, s->options.max_prediction_order);
return -1;
}
av_log(avctx, AV_LOG_DEBUG, " prediction order: %d, %d\n",
s->options.min_prediction_order, s->options.max_prediction_order);
if(avctx->prediction_order_method >= 0) {
if(avctx->prediction_order_method > ORDER_METHOD_SEARCH) {
av_log(avctx, AV_LOG_ERROR, "invalid prediction order method: %d\n",
avctx->prediction_order_method);
return -1;
}
s->options.prediction_order_method = avctx->prediction_order_method;
}
switch(avctx->prediction_order_method) {
case ORDER_METHOD_EST: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
"estimate"); break;
case ORDER_METHOD_2LEVEL: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
"2-level"); break;
case ORDER_METHOD_4LEVEL: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
"4-level"); break;
case ORDER_METHOD_8LEVEL: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
"8-level"); break;
case ORDER_METHOD_SEARCH: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
"full search"); break;
}
if(avctx->min_partition_order >= 0) {
if(avctx->min_partition_order > MAX_PARTITION_ORDER) {
av_log(avctx, AV_LOG_ERROR, "invalid min partition order: %d\n",
avctx->min_partition_order);
return -1;
}
s->options.min_partition_order = avctx->min_partition_order;
}
if(avctx->max_partition_order >= 0) {
if(avctx->max_partition_order > MAX_PARTITION_ORDER) {
av_log(avctx, AV_LOG_ERROR, "invalid max partition order: %d\n",
avctx->max_partition_order);
return -1;
}
s->options.max_partition_order = avctx->max_partition_order;
}
if(s->options.max_partition_order < s->options.min_partition_order) {
av_log(avctx, AV_LOG_ERROR, "invalid partition orders: min=%d max=%d\n",
s->options.min_partition_order, s->options.max_partition_order);
return -1;
}
av_log(avctx, AV_LOG_DEBUG, " partition order: %d, %d\n",
s->options.min_partition_order, s->options.max_partition_order);
if(avctx->frame_size > 0) {
if(avctx->frame_size < FLAC_MIN_BLOCKSIZE ||
avctx->frame_size > FLAC_MAX_BLOCKSIZE) {
av_log(avctx, AV_LOG_ERROR, "invalid block size: %d\n",
avctx->frame_size);
return -1;
}
s->blocksize = avctx->frame_size;
} else {
s->blocksize = select_blocksize(s->samplerate, s->options.block_time_ms);
avctx->frame_size = s->blocksize;
}
av_log(avctx, AV_LOG_DEBUG, " block size: %d\n", s->blocksize);
/* set LPC precision */
if(avctx->lpc_coeff_precision > 0) {
if(avctx->lpc_coeff_precision > MAX_LPC_PRECISION) {
av_log(avctx, AV_LOG_ERROR, "invalid lpc coeff precision: %d\n",
avctx->lpc_coeff_precision);
return -1;
}
s->options.lpc_coeff_precision = avctx->lpc_coeff_precision;
} else {
/* select LPC precision based on block size */
if( s->blocksize <= 192) s->options.lpc_coeff_precision = 7;
else if(s->blocksize <= 384) s->options.lpc_coeff_precision = 8;
else if(s->blocksize <= 576) s->options.lpc_coeff_precision = 9;
else if(s->blocksize <= 1152) s->options.lpc_coeff_precision = 10;
else if(s->blocksize <= 2304) s->options.lpc_coeff_precision = 11;
else if(s->blocksize <= 4608) s->options.lpc_coeff_precision = 12;
else if(s->blocksize <= 8192) s->options.lpc_coeff_precision = 13;
else if(s->blocksize <= 16384) s->options.lpc_coeff_precision = 14;
else s->options.lpc_coeff_precision = 15;
}
av_log(avctx, AV_LOG_DEBUG, " lpc precision: %d\n",
s->options.lpc_coeff_precision);
/* set maximum encoded frame size in verbatim mode */
if(s->channels == 2) {
s->max_framesize = 14 + ((s->blocksize * 33 + 7) >> 3);
} else {
s->max_framesize = 14 + (s->blocksize * s->channels * 2);
}
streaminfo = av_malloc(FLAC_STREAMINFO_SIZE);
write_streaminfo(s, streaminfo);
avctx->extradata = streaminfo;
avctx->extradata_size = FLAC_STREAMINFO_SIZE;
s->frame_count = 0;
avctx->coded_frame = avcodec_alloc_frame();
avctx->coded_frame->key_frame = 1;
return 0;
}
static void init_frame(FlacEncodeContext *s)
{
int i, ch;
FlacFrame *frame;
frame = &s->frame;
for(i=0; i<16; i++) {
if(s->blocksize == flac_blocksizes[i]) {
frame->blocksize = flac_blocksizes[i];
frame->bs_code[0] = i;
frame->bs_code[1] = 0;
break;
}
}
if(i == 16) {
frame->blocksize = s->blocksize;
if(frame->blocksize <= 256) {
frame->bs_code[0] = 6;
frame->bs_code[1] = frame->blocksize-1;
} else {
frame->bs_code[0] = 7;
frame->bs_code[1] = frame->blocksize-1;
}
}
for(ch=0; ch<s->channels; ch++) {
frame->subframes[ch].obits = 16;
}
}
/**
* Copy channel-interleaved input samples into separate subframes
*/
static void copy_samples(FlacEncodeContext *s, int16_t *samples)
{
int i, j, ch;
FlacFrame *frame;
frame = &s->frame;
for(i=0,j=0; i<frame->blocksize; i++) {
for(ch=0; ch<s->channels; ch++,j++) {
frame->subframes[ch].samples[i] = samples[j];
}
}
}
#define rice_encode_count(sum, n, k) (((n)*((k)+1))+((sum-(n>>1))>>(k)))
static int find_optimal_param(uint32_t sum, int n)
{
int k, k_opt;
uint32_t nbits[MAX_RICE_PARAM+1];
k_opt = 0;
nbits[0] = UINT32_MAX;
for(k=0; k<=MAX_RICE_PARAM; k++) {
nbits[k] = rice_encode_count(sum, n, k);
if(nbits[k] < nbits[k_opt]) {
k_opt = k;
}
}
return k_opt;
}
static uint32_t calc_optimal_rice_params(RiceContext *rc, int porder,
uint32_t *sums, int n, int pred_order)
{
int i;
int k, cnt, part;
uint32_t all_bits;
part = (1 << porder);
all_bits = 0;
cnt = (n >> porder) - pred_order;
for(i=0; i<part; i++) {
if(i == 1) cnt = (n >> porder);
k = find_optimal_param(sums[i], cnt);
rc->params[i] = k;
all_bits += rice_encode_count(sums[i], cnt, k);
}
all_bits += (4 * part);
rc->porder = porder;
return all_bits;
}
static void calc_sums(int pmin, int pmax, uint32_t *data, int n, int pred_order,
uint32_t sums[][MAX_PARTITIONS])
{
int i, j;
int parts;
uint32_t *res, *res_end;
/* sums for highest level */
parts = (1 << pmax);
res = &data[pred_order];
res_end = &data[n >> pmax];
for(i=0; i<parts; i++) {
sums[pmax][i] = 0;
while(res < res_end){
sums[pmax][i] += *(res++);
}
res_end+= n >> pmax;
}
/* sums for lower levels */
for(i=pmax-1; i>=pmin; i--) {
parts = (1 << i);
for(j=0; j<parts; j++) {
sums[i][j] = sums[i+1][2*j] + sums[i+1][2*j+1];
}
}
}
static uint32_t calc_rice_params(RiceContext *rc, int pmin, int pmax,
int32_t *data, int n, int pred_order)
{
int i;
uint32_t bits[MAX_PARTITION_ORDER+1];
int opt_porder;
RiceContext tmp_rc;
uint32_t *udata;
uint32_t sums[MAX_PARTITION_ORDER+1][MAX_PARTITIONS];
assert(pmin >= 0 && pmin <= MAX_PARTITION_ORDER);
assert(pmax >= 0 && pmax <= MAX_PARTITION_ORDER);
assert(pmin <= pmax);
udata = av_malloc(n * sizeof(uint32_t));
for(i=0; i<n; i++) {
udata[i] = (2*data[i]) ^ (data[i]>>31);
}
calc_sums(pmin, pmax, udata, n, pred_order, sums);
opt_porder = pmin;
bits[pmin] = UINT32_MAX;
for(i=pmin; i<=pmax; i++) {
bits[i] = calc_optimal_rice_params(&tmp_rc, i, sums[i], n, pred_order);
if(bits[i] <= bits[opt_porder]) {
opt_porder = i;
*rc= tmp_rc;
}
}
av_freep(&udata);
return bits[opt_porder];
}
static int get_max_p_order(int max_porder, int n, int order)
{
int porder = FFMIN(max_porder, av_log2(n^(n-1)));
if(order > 0)
porder = FFMIN(porder, av_log2(n/order));
return porder;
}
static uint32_t calc_rice_params_fixed(RiceContext *rc, int pmin, int pmax,
int32_t *data, int n, int pred_order,
int bps)
{
uint32_t bits;
pmin = get_max_p_order(pmin, n, pred_order);
pmax = get_max_p_order(pmax, n, pred_order);
bits = pred_order*bps + 6;
bits += calc_rice_params(rc, pmin, pmax, data, n, pred_order);
return bits;
}
static uint32_t calc_rice_params_lpc(RiceContext *rc, int pmin, int pmax,
int32_t *data, int n, int pred_order,
int bps, int precision)
{
uint32_t bits;
pmin = get_max_p_order(pmin, n, pred_order);
pmax = get_max_p_order(pmax, n, pred_order);
bits = pred_order*bps + 4 + 5 + pred_order*precision + 6;
bits += calc_rice_params(rc, pmin, pmax, data, n, pred_order);
return bits;
}
/**
* Apply Welch window function to audio block
*/
static void apply_welch_window(const int32_t *data, int len, double *w_data)
{
int i, n2;
double w;
double c;
n2 = (len >> 1);
c = 2.0 / (len - 1.0);
for(i=0; i<n2; i++) {
w = c - i - 1.0;
w = 1.0 - (w * w);
w_data[i] = data[i] * w;
w_data[len-1-i] = data[len-1-i] * w;
}
}
/**
* Calculates autocorrelation data from audio samples
* A Welch window function is applied before calculation.
*/
static void compute_autocorr(const int32_t *data, int len, int lag,
double *autoc)
{
int i, lag_ptr;
double tmp[len + lag];
double *data1= tmp + lag;
apply_welch_window(data, len, data1);
for(i=0; i<lag; i++){
autoc[i] = 1.0;
data1[i-lag]= 0.0;
}
for(i=0; i<len; i++){
for(lag_ptr= i-lag; lag_ptr<=i; lag_ptr++){
autoc[i-lag_ptr] += data1[i] * data1[lag_ptr];
}
}
}
/**
* Levinson-Durbin recursion.
* Produces LPC coefficients from autocorrelation data.
*/
static void compute_lpc_coefs(const double *autoc, int max_order,
double lpc[][MAX_LPC_ORDER], double *ref)
{
int i, j, i2;
double r, err, tmp;
double lpc_tmp[MAX_LPC_ORDER];
for(i=0; i<max_order; i++) lpc_tmp[i] = 0;
err = autoc[0];
for(i=0; i<max_order; i++) {
r = -autoc[i+1];
for(j=0; j<i; j++) {
r -= lpc_tmp[j] * autoc[i-j];
}
r /= err;
ref[i] = fabs(r);
err *= 1.0 - (r * r);
i2 = (i >> 1);
lpc_tmp[i] = r;
for(j=0; j<i2; j++) {
tmp = lpc_tmp[j];
lpc_tmp[j] += r * lpc_tmp[i-1-j];
lpc_tmp[i-1-j] += r * tmp;
}
if(i & 1) {
lpc_tmp[j] += lpc_tmp[j] * r;
}
for(j=0; j<=i; j++) {
lpc[i][j] = -lpc_tmp[j];
}
}
}
/**
* Quantize LPC coefficients
*/
static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
int32_t *lpc_out, int *shift)
{
int i;
double cmax, error;
int32_t qmax;
int sh;
/* define maximum levels */
qmax = (1 << (precision - 1)) - 1;
/* find maximum coefficient value */
cmax = 0.0;
for(i=0; i<order; i++) {
cmax= FFMAX(cmax, fabs(lpc_in[i]));
}
/* if maximum value quantizes to zero, return all zeros */
if(cmax * (1 << MAX_LPC_SHIFT) < 1.0) {
*shift = 0;
memset(lpc_out, 0, sizeof(int32_t) * order);
return;
}
/* calculate level shift which scales max coeff to available bits */
sh = MAX_LPC_SHIFT;
while((cmax * (1 << sh) > qmax) && (sh > 0)) {
sh--;
}
/* since negative shift values are unsupported in decoder, scale down
coefficients instead */
if(sh == 0 && cmax > qmax) {
double scale = ((double)qmax) / cmax;
for(i=0; i<order; i++) {
lpc_in[i] *= scale;
}
}
/* output quantized coefficients and level shift */
error=0;
for(i=0; i<order; i++) {
error += lpc_in[i] * (1 << sh);
lpc_out[i] = clip(lrintf(error), -qmax, qmax);
error -= lpc_out[i];
}
*shift = sh;
}
static int estimate_best_order(double *ref, int max_order)
{
int i, est;
est = 1;
for(i=max_order-1; i>=0; i--) {
if(ref[i] > 0.10) {
est = i+1;
break;
}
}
return est;
}
/**
* Calculate LPC coefficients for multiple orders
*/
static int lpc_calc_coefs(const int32_t *samples, int blocksize, int max_order,
int precision, int32_t coefs[][MAX_LPC_ORDER],
int *shift)
{
double autoc[MAX_LPC_ORDER+1];
double ref[MAX_LPC_ORDER];
double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
int i;
int opt_order;
assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER);
compute_autocorr(samples, blocksize, max_order+1, autoc);
compute_lpc_coefs(autoc, max_order, lpc, ref);
opt_order = estimate_best_order(ref, max_order);
i = opt_order-1;
quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i]);
return opt_order;
}
static void encode_residual_verbatim(int32_t *res, int32_t *smp, int n)
{
assert(n > 0);
memcpy(res, smp, n * sizeof(int32_t));
}
static void encode_residual_fixed(int32_t *res, const int32_t *smp, int n,
int order)
{
int i;
for(i=0; i<order; i++) {
res[i] = smp[i];
}
if(order==0){
for(i=order; i<n; i++)
res[i]= smp[i];
}else if(order==1){
for(i=order; i<n; i++)
res[i]= smp[i] - smp[i-1];
}else if(order==2){
for(i=order; i<n; i++)
res[i]= smp[i] - 2*smp[i-1] + smp[i-2];
}else if(order==3){
for(i=order; i<n; i++)
res[i]= smp[i] - 3*smp[i-1] + 3*smp[i-2] - smp[i-3];
}else{
for(i=order; i<n; i++)
res[i]= smp[i] - 4*smp[i-1] + 6*smp[i-2] - 4*smp[i-3] + smp[i-4];
}
}
static void encode_residual_lpc(int32_t *res, const int32_t *smp, int n,
int order, const int32_t *coefs, int shift)
{
int i, j;
int32_t pred;
for(i=0; i<order; i++) {
res[i] = smp[i];
}
for(i=order; i<n; i++) {
pred = 0;
for(j=0; j<order; j++) {
pred += coefs[j] * smp[i-j-1];
}
res[i] = smp[i] - (pred >> shift);
}
}
static int encode_residual(FlacEncodeContext *ctx, int ch)
{
int i, n;
int min_order, max_order, opt_order, precision;
int min_porder, max_porder;
FlacFrame *frame;
FlacSubframe *sub;
int32_t coefs[MAX_LPC_ORDER][MAX_LPC_ORDER];
int shift[MAX_LPC_ORDER];
int32_t *res, *smp;
frame = &ctx->frame;
sub = &frame->subframes[ch];
res = sub->residual;
smp = sub->samples;
n = frame->blocksize;
/* CONSTANT */
for(i=1; i<n; i++) {
if(smp[i] != smp[0]) break;
}
if(i == n) {
sub->type = sub->type_code = FLAC_SUBFRAME_CONSTANT;
res[0] = smp[0];
return sub->obits;
}
/* VERBATIM */
if(n < 5) {
sub->type = sub->type_code = FLAC_SUBFRAME_VERBATIM;
encode_residual_verbatim(res, smp, n);
return sub->obits * n;
}
min_order = ctx->options.min_prediction_order;
max_order = ctx->options.max_prediction_order;
min_porder = ctx->options.min_partition_order;
max_porder = ctx->options.max_partition_order;
precision = ctx->options.lpc_coeff_precision;
/* FIXED */
if(!ctx->options.use_lpc || max_order == 0 || (n <= max_order)) {
uint32_t bits[MAX_FIXED_ORDER+1];
if(max_order > MAX_FIXED_ORDER) max_order = MAX_FIXED_ORDER;
opt_order = 0;
bits[0] = UINT32_MAX;
for(i=min_order; i<=max_order; i++) {
encode_residual_fixed(res, smp, n, i);
bits[i] = calc_rice_params_fixed(&sub->rc, min_porder, max_porder, res,
n, i, sub->obits);
if(bits[i] < bits[opt_order]) {
opt_order = i;
}
}
sub->order = opt_order;
sub->type = FLAC_SUBFRAME_FIXED;
sub->type_code = sub->type | sub->order;
if(sub->order != max_order) {
encode_residual_fixed(res, smp, n, sub->order);
return calc_rice_params_fixed(&sub->rc, min_porder, max_porder, res, n,
sub->order, sub->obits);
}
return bits[sub->order];
}
/* LPC */
sub->order = lpc_calc_coefs(smp, n, max_order, precision, coefs, shift);
sub->type = FLAC_SUBFRAME_LPC;
sub->type_code = sub->type | (sub->order-1);
sub->shift = shift[sub->order-1];
for(i=0; i<sub->order; i++) {
sub->coefs[i] = coefs[sub->order-1][i];
}
encode_residual_lpc(res, smp, n, sub->order, sub->coefs, sub->shift);
return calc_rice_params_lpc(&sub->rc, min_porder, max_porder, res, n, sub->order,
sub->obits, precision);
}
static int encode_residual_v(FlacEncodeContext *ctx, int ch)
{
int i, n;
FlacFrame *frame;
FlacSubframe *sub;
int32_t *res, *smp;
frame = &ctx->frame;
sub = &frame->subframes[ch];
res = sub->residual;
smp = sub->samples;
n = frame->blocksize;
/* CONSTANT */
for(i=1; i<n; i++) {
if(smp[i] != smp[0]) break;
}
if(i == n) {
sub->type = sub->type_code = FLAC_SUBFRAME_CONSTANT;
res[0] = smp[0];
return sub->obits;
}
/* VERBATIM */
sub->type = sub->type_code = FLAC_SUBFRAME_VERBATIM;
encode_residual_verbatim(res, smp, n);
return sub->obits * n;
}
static int estimate_stereo_mode(int32_t *left_ch, int32_t *right_ch, int n)
{
int i, best;
int32_t lt, rt;
uint64_t sum[4];
uint64_t score[4];
int k;
/* calculate sum of 2nd order residual for each channel */
sum[0] = sum[1] = sum[2] = sum[3] = 0;
for(i=2; i<n; i++) {
lt = left_ch[i] - 2*left_ch[i-1] + left_ch[i-2];
rt = right_ch[i] - 2*right_ch[i-1] + right_ch[i-2];
sum[2] += ABS((lt + rt) >> 1);
sum[3] += ABS(lt - rt);
sum[0] += ABS(lt);
sum[1] += ABS(rt);
}
/* estimate bit counts */
for(i=0; i<4; i++) {
k = find_optimal_param(2*sum[i], n);
sum[i] = rice_encode_count(2*sum[i], n, k);
}
/* calculate score for each mode */
score[0] = sum[0] + sum[1];
score[1] = sum[0] + sum[3];
score[2] = sum[1] + sum[3];
score[3] = sum[2] + sum[3];
/* return mode with lowest score */
best = 0;
for(i=1; i<4; i++) {
if(score[i] < score[best]) {
best = i;
}
}
if(best == 0) {
return FLAC_CHMODE_LEFT_RIGHT;
} else if(best == 1) {
return FLAC_CHMODE_LEFT_SIDE;
} else if(best == 2) {
return FLAC_CHMODE_RIGHT_SIDE;
} else {
return FLAC_CHMODE_MID_SIDE;
}
}
/**
* Perform stereo channel decorrelation
*/
static void channel_decorrelation(FlacEncodeContext *ctx)
{
FlacFrame *frame;
int32_t *left, *right;
int i, n;
frame = &ctx->frame;
n = frame->blocksize;
left = frame->subframes[0].samples;
right = frame->subframes[1].samples;
if(ctx->channels != 2) {
frame->ch_mode = FLAC_CHMODE_NOT_STEREO;
return;
}
frame->ch_mode = estimate_stereo_mode(left, right, n);
/* perform decorrelation and adjust bits-per-sample */
if(frame->ch_mode == FLAC_CHMODE_LEFT_RIGHT) {
return;
}
if(frame->ch_mode == FLAC_CHMODE_MID_SIDE) {
int32_t tmp;
for(i=0; i<n; i++) {
tmp = left[i];
left[i] = (tmp + right[i]) >> 1;
right[i] = tmp - right[i];
}
frame->subframes[1].obits++;
} else if(frame->ch_mode == FLAC_CHMODE_LEFT_SIDE) {
for(i=0; i<n; i++) {
right[i] = left[i] - right[i];
}
frame->subframes[1].obits++;
} else {
for(i=0; i<n; i++) {
left[i] -= right[i];
}
frame->subframes[0].obits++;
}
}
static void put_sbits(PutBitContext *pb, int bits, int32_t val)
{
assert(bits >= 0 && bits <= 31);
put_bits(pb, bits, val & ((1<<bits)-1));
}
static void write_utf8(PutBitContext *pb, uint32_t val)
{
int bytes, shift;
if(val < 0x80){
put_bits(pb, 8, val);
return;
}
bytes= (av_log2(val)+4) / 5;
shift = (bytes - 1) * 6;
put_bits(pb, 8, (256 - (256>>bytes)) | (val >> shift));
while(shift >= 6){
shift -= 6;
put_bits(pb, 8, 0x80 | ((val >> shift) & 0x3F));
}
}
static void output_frame_header(FlacEncodeContext *s)
{
FlacFrame *frame;
int crc;
frame = &s->frame;
put_bits(&s->pb, 16, 0xFFF8);
put_bits(&s->pb, 4, frame->bs_code[0]);
put_bits(&s->pb, 4, s->sr_code[0]);
if(frame->ch_mode == FLAC_CHMODE_NOT_STEREO) {
put_bits(&s->pb, 4, s->ch_code);
} else {
put_bits(&s->pb, 4, frame->ch_mode);
}
put_bits(&s->pb, 3, 4); /* bits-per-sample code */
put_bits(&s->pb, 1, 0);
write_utf8(&s->pb, s->frame_count);
if(frame->bs_code[0] == 6) {
put_bits(&s->pb, 8, frame->bs_code[1]);
} else if(frame->bs_code[0] == 7) {
put_bits(&s->pb, 16, frame->bs_code[1]);
}
if(s->sr_code[0] == 12) {
put_bits(&s->pb, 8, s->sr_code[1]);
} else if(s->sr_code[0] > 12) {
put_bits(&s->pb, 16, s->sr_code[1]);
}
flush_put_bits(&s->pb);
crc = av_crc(av_crc07, 0, s->pb.buf, put_bits_count(&s->pb)>>3);
put_bits(&s->pb, 8, crc);
}
static void output_subframe_constant(FlacEncodeContext *s, int ch)
{
FlacSubframe *sub;
int32_t res;
sub = &s->frame.subframes[ch];
res = sub->residual[0];
put_sbits(&s->pb, sub->obits, res);
}
static void output_subframe_verbatim(FlacEncodeContext *s, int ch)
{
int i;
FlacFrame *frame;
FlacSubframe *sub;
int32_t res;
frame = &s->frame;
sub = &frame->subframes[ch];
for(i=0; i<frame->blocksize; i++) {
res = sub->residual[i];
put_sbits(&s->pb, sub->obits, res);
}
}
static void output_residual(FlacEncodeContext *ctx, int ch)
{
int i, j, p, n, parts;
int k, porder, psize, res_cnt;
FlacFrame *frame;
FlacSubframe *sub;
int32_t *res;
frame = &ctx->frame;
sub = &frame->subframes[ch];
res = sub->residual;
n = frame->blocksize;
/* rice-encoded block */
put_bits(&ctx->pb, 2, 0);
/* partition order */
porder = sub->rc.porder;
psize = n >> porder;
parts = (1 << porder);
put_bits(&ctx->pb, 4, porder);
res_cnt = psize - sub->order;
/* residual */
j = sub->order;
for(p=0; p<parts; p++) {
k = sub->rc.params[p];
put_bits(&ctx->pb, 4, k);
if(p == 1) res_cnt = psize;
for(i=0; i<res_cnt && j<n; i++, j++) {
set_sr_golomb_flac(&ctx->pb, res[j], k, INT32_MAX, 0);
}
}
}
static void output_subframe_fixed(FlacEncodeContext *ctx, int ch)
{
int i;
FlacFrame *frame;
FlacSubframe *sub;
frame = &ctx->frame;
sub = &frame->subframes[ch];
/* warm-up samples */
for(i=0; i<sub->order; i++) {
put_sbits(&ctx->pb, sub->obits, sub->residual[i]);
}
/* residual */
output_residual(ctx, ch);
}
static void output_subframe_lpc(FlacEncodeContext *ctx, int ch)
{
int i, cbits;
FlacFrame *frame;
FlacSubframe *sub;
frame = &ctx->frame;
sub = &frame->subframes[ch];
/* warm-up samples */
for(i=0; i<sub->order; i++) {
put_sbits(&ctx->pb, sub->obits, sub->residual[i]);
}
/* LPC coefficients */
cbits = ctx->options.lpc_coeff_precision;
put_bits(&ctx->pb, 4, cbits-1);
put_sbits(&ctx->pb, 5, sub->shift);
for(i=0; i<sub->order; i++) {
put_sbits(&ctx->pb, cbits, sub->coefs[i]);
}
/* residual */
output_residual(ctx, ch);
}
static void output_subframes(FlacEncodeContext *s)
{
FlacFrame *frame;
FlacSubframe *sub;
int ch;
frame = &s->frame;
for(ch=0; ch<s->channels; ch++) {
sub = &frame->subframes[ch];
/* subframe header */
put_bits(&s->pb, 1, 0);
put_bits(&s->pb, 6, sub->type_code);
put_bits(&s->pb, 1, 0); /* no wasted bits */
/* subframe */
if(sub->type == FLAC_SUBFRAME_CONSTANT) {
output_subframe_constant(s, ch);
} else if(sub->type == FLAC_SUBFRAME_VERBATIM) {
output_subframe_verbatim(s, ch);
} else if(sub->type == FLAC_SUBFRAME_FIXED) {
output_subframe_fixed(s, ch);
} else if(sub->type == FLAC_SUBFRAME_LPC) {
output_subframe_lpc(s, ch);
}
}
}
static void output_frame_footer(FlacEncodeContext *s)
{
int crc;
flush_put_bits(&s->pb);
crc = bswap_16(av_crc(av_crc8005, 0, s->pb.buf, put_bits_count(&s->pb)>>3));
put_bits(&s->pb, 16, crc);
flush_put_bits(&s->pb);
}
static int flac_encode_frame(AVCodecContext *avctx, uint8_t *frame,
int buf_size, void *data)
{
int ch;
FlacEncodeContext *s;
int16_t *samples = data;
int out_bytes;
s = avctx->priv_data;
s->blocksize = avctx->frame_size;
init_frame(s);
copy_samples(s, samples);
channel_decorrelation(s);
for(ch=0; ch<s->channels; ch++) {
encode_residual(s, ch);
}
init_put_bits(&s->pb, frame, buf_size);
output_frame_header(s);
output_subframes(s);
output_frame_footer(s);
out_bytes = put_bits_count(&s->pb) >> 3;
if(out_bytes > s->max_framesize || out_bytes >= buf_size) {
/* frame too large. use verbatim mode */
for(ch=0; ch<s->channels; ch++) {
encode_residual_v(s, ch);
}
init_put_bits(&s->pb, frame, buf_size);
output_frame_header(s);
output_subframes(s);
output_frame_footer(s);
out_bytes = put_bits_count(&s->pb) >> 3;
if(out_bytes > s->max_framesize || out_bytes >= buf_size) {
/* still too large. must be an error. */
av_log(avctx, AV_LOG_ERROR, "error encoding frame\n");
return -1;
}
}
s->frame_count++;
return out_bytes;
}
static int flac_encode_close(AVCodecContext *avctx)
{
av_freep(&avctx->extradata);
avctx->extradata_size = 0;
av_freep(&avctx->coded_frame);
return 0;
}
AVCodec flac_encoder = {
"flac",
CODEC_TYPE_AUDIO,
CODEC_ID_FLAC,
sizeof(FlacEncodeContext),
flac_encode_init,
flac_encode_frame,
flac_encode_close,
NULL,
.capabilities = CODEC_CAP_SMALL_LAST_FRAME,
};