/* stream reading */
/* supports reading 1 to 16 bits, in big endian format */
static int readbits_16(AlacFile alac, int bits)
{
int result = 0;
int new_accumulator = 0;
int part1 = 0;
int part2 = 0;
int part3 = 0;
part1 = (alac.input_buffer[alac.ibIdx] & 0xff);
part2 = (alac.input_buffer[alac.ibIdx + 1] & 0xff);
part3 = (alac.input_buffer[alac.ibIdx + 2] & 0xff);
result = ((part1 << 16) | (part2 << 8) | part3);
/* shift left by the number of bits we've already read,
* so that the top 'n' bits of the 24 bits we read will
* be the return bits */
result = result << alac.input_buffer_bitaccumulator;
result = result & 0x00ffffff;
/* and then only want the top 'n' bits from that, where
* n is 'bits' */
result = result >> (24 - bits);
new_accumulator = (alac.input_buffer_bitaccumulator + bits);
/* increase the buffer pointer if we've read over n bytes. */
alac.ibIdx += (new_accumulator >> 3);
/* and the remainder goes back into the bit accumulator */
alac.input_buffer_bitaccumulator = (new_accumulator & 7);
return(result);
}
public static AlacFile create_alac(int samplesize, int numchannels)
{
AlacFile newfile = new AlacFile();
newfile.samplesize = samplesize;
newfile.numchannels = numchannels;
newfile.bytespersample = (samplesize / 8) * numchannels;
return(newfile);
}
static void unreadbits(AlacFile alac, int bits)
{
int new_accumulator = (alac.input_buffer_bitaccumulator - bits);
alac.ibIdx += (new_accumulator >> 3);
alac.input_buffer_bitaccumulator = (new_accumulator & 7);
if (alac.input_buffer_bitaccumulator < 0)
{
alac.input_buffer_bitaccumulator *= -1;
}
}
/* supports reading 1 to 32 bits, in big endian format */
static int readbits(AlacFile alac, int bits)
{
int result = 0;
if (bits > 16)
{
bits -= 16;
result = readbits_16(alac, 16) << bits;
}
result |= readbits_16(alac, bits);
return(result);
}
public static int entropy_decode_value(AlacFile alac, int readSampleSize, int k, uint rice_kmodifier_mask)
{
int x = 0; // decoded value
// read x, number of 1s before 0 represent the rice value.
while (x <= Consts.RICE_THRESHOLD && readbit(alac) != 0)
{
x++;
}
if (x > Consts.RICE_THRESHOLD)
{
// read the number from the bit stream (raw value)
int value = 0;
value = readbits(alac, readSampleSize);
// mask value
value &= (int)((0xffffffff) >> (32 - readSampleSize));
x = value;
}
else
{
if (k != 1)
{
int extraBits = readbits(alac, k);
x *= (int)(((1 << k) - 1) & rice_kmodifier_mask);
if (extraBits > 1)
{
x += extraBits - 1;
}
else
{
unreadbits(alac, 1);
}
}
}
return(x);
}
/* reads a single bit */
static int readbit(AlacFile alac)
{
int result = 0;
int new_accumulator = 0;
int part1 = 0;
part1 = (alac.input_buffer[alac.ibIdx] & 0xff);
result = part1;
result = result << alac.input_buffer_bitaccumulator;
result = result >> 7 & 1;
new_accumulator = (alac.input_buffer_bitaccumulator + 1);
alac.ibIdx += new_accumulator / 8;
alac.input_buffer_bitaccumulator = (new_accumulator % 8);
return(result);
}
public static int DecodeFrame(AlacFile alac, byte[] inbuffer, int[] outbuffer)
{
int channels;
int outputsamples = alac.setinfo_max_samples_per_frame;
/* setup the stream */
alac.input_buffer = inbuffer;
alac.input_buffer_bitaccumulator = 0;
alac.ibIdx = 0;
channels = readbits(alac, 3);
int outputsize = outputsamples * alac.bytespersample;
if (channels == 0) // 1 channel
{
int hassize;
int isnotcompressed;
int readsamplesize;
int uncompressed_bytes;
int ricemodifier;
int tempPred = 0;
/* 2^result = something to do with output waiting.
* perhaps matters if we read > 1 frame in a pass?
*/
readbits(alac, 4);
readbits(alac, 12); // unknown, skip 12 bits
hassize = readbits(alac, 1); // the output sample size is stored soon
uncompressed_bytes = readbits(alac, 2); // number of bytes in the (compressed) stream that are not compressed
isnotcompressed = readbits(alac, 1); // whether the frame is compressed
if (hassize != 0)
{
/* now read the number of samples,
* as a 32bit integer */
outputsamples = readbits(alac, 32);
outputsize = outputsamples * alac.bytespersample;
}
readsamplesize = alac.setinfo_sample_size - (uncompressed_bytes * 8);
if (isnotcompressed == 0)
{ // so it is compressed
int[] predictor_coef_table = alac.predictor_coef_table;
int predictor_coef_num;
int prediction_type;
int prediction_quantitization;
int i;
/* skip 16 bits, not sure what they are. seem to be used in
* two channel case */
readbits(alac, 8);
readbits(alac, 8);
prediction_type = readbits(alac, 4);
prediction_quantitization = readbits(alac, 4);
ricemodifier = readbits(alac, 3);
predictor_coef_num = readbits(alac, 5);
/* read the predictor table */
for (i = 0; i < predictor_coef_num; i++)
{
tempPred = readbits(alac, 16);
if (tempPred > 32767)
{
// the predictor coef table values are only 16 bit signed
tempPred = tempPred - 65536;
}
predictor_coef_table[i] = tempPred;
}
if (uncompressed_bytes != 0)
{
for (i = 0; i < outputsamples; i++)
{
alac.uncompressed_bytes_buffer_a[i] = readbits(alac, uncompressed_bytes * 8);
}
}
entropy_rice_decode(alac, alac.predicterror_buffer_a, outputsamples, readsamplesize, alac.setinfo_rice_initialhistory, alac.setinfo_rice_kmodifier, ricemodifier * (alac.setinfo_rice_historymult / 4), (uint)(1 << alac.setinfo_rice_kmodifier) - 1);
if (prediction_type == 0)
{ // adaptive fir
alac.outputsamples_buffer_a = predictor_decompress_fir_adapt(alac.predicterror_buffer_a, outputsamples, readsamplesize, predictor_coef_table, predictor_coef_num, prediction_quantitization);
}
else
{
//System.err.println("FIXME: unhandled predicition type: " + prediction_type);
/* i think the only other prediction type (or perhaps this is just a
* boolean?) runs adaptive fir twice.. like:
* predictor_decompress_fir_adapt(predictor_error, tempout, ...)
* predictor_decompress_fir_adapt(predictor_error, outputsamples ...)
* little strange..
*/
}
}
else
{ // not compressed, easy case
if (alac.setinfo_sample_size <= 16)
{
int bitsmove = 0;
for (int i = 0; i < outputsamples; i++)
{
int audiobits = readbits(alac, alac.setinfo_sample_size);
bitsmove = 32 - alac.setinfo_sample_size;
audiobits = ((audiobits << bitsmove) >> bitsmove);
alac.outputsamples_buffer_a[i] = audiobits;
}
}
else
{
int x;
int m = 1 << (24 - 1);
for (int i = 0; i < outputsamples; i++)
{
int audiobits;
audiobits = readbits(alac, 16);
/* special case of sign extension..
* as we'll be ORing the low 16bits into this */
audiobits = audiobits << (alac.setinfo_sample_size - 16);
audiobits = audiobits | readbits(alac, alac.setinfo_sample_size - 16);
x = audiobits & ((1 << 24) - 1);
audiobits = (x ^ m) - m; // sign extend 24 bits
alac.outputsamples_buffer_a[i] = audiobits;
}
}
uncompressed_bytes = 0; // always 0 for uncompressed
}
switch (alac.setinfo_sample_size)
{
case 16:
{
for (int i = 0; i < outputsamples; i++)
{
int sample = alac.outputsamples_buffer_a[i];
outbuffer[i * alac.numchannels] = sample;
/*
** We have to handle the case where the data is actually mono, but the stsd atom says it has 2 channels
** in this case we create a stereo file where one of the channels is silent. If mono and 1 channel this value
** will be overwritten in the next iteration
*/
outbuffer[(i * alac.numchannels) + 1] = 0;
}
break;
}
case 24:
{
for (int i = 0; i < outputsamples; i++)
{
int sample = alac.outputsamples_buffer_a[i];
if (uncompressed_bytes != 0)
{
int mask = 0;
sample = sample << (uncompressed_bytes * 8);
mask = (int)~(0xFFFFFFFF << (uncompressed_bytes * 8));
sample = sample | (alac.uncompressed_bytes_buffer_a[i] & mask);
}
outbuffer[i * alac.numchannels * 3] = ((sample) & 0xFF);
outbuffer[i * alac.numchannels * 3 + 1] = ((sample >> 8) & 0xFF);
outbuffer[i * alac.numchannels * 3 + 2] = ((sample >> 16) & 0xFF);
/*
** We have to handle the case where the data is actually mono, but the stsd atom says it has 2 channels
** in this case we create a stereo file where one of the channels is silent. If mono and 1 channel this value
** will be overwritten in the next iteration
*/
outbuffer[i * alac.numchannels * 3 + 3] = 0;
outbuffer[i * alac.numchannels * 3 + 4] = 0;
outbuffer[i * alac.numchannels * 3 + 5] = 0;
}
break;
}
case 20:
case 32:
//System.err.println("FIXME: unimplemented sample size " + alac.setinfo_sample_size);
break;
default:
break;
}
}
else if (channels == 1) // 2 channels
{
int hassize;
int isnotcompressed;
int readsamplesize;
int uncompressed_bytes;
int interlacing_shift;
int interlacing_leftweight;
/* 2^result = something to do with output waiting.
* perhaps matters if we read > 1 frame in a pass?
*/
readbits(alac, 4);
readbits(alac, 12); // unknown, skip 12 bits
hassize = readbits(alac, 1); // the output sample size is stored soon
uncompressed_bytes = readbits(alac, 2); // the number of bytes in the (compressed) stream that are not compressed
isnotcompressed = readbits(alac, 1); // whether the frame is compressed
if (hassize != 0)
{
/* now read the number of samples,
* as a 32bit integer */
outputsamples = readbits(alac, 32);
outputsize = outputsamples * alac.bytespersample;
}
readsamplesize = alac.setinfo_sample_size - (uncompressed_bytes * 8) + 1;
if (isnotcompressed == 0)
{ // compressed
int[] predictor_coef_table_a = alac.predictor_coef_table_a;
int predictor_coef_num_a;
int prediction_type_a;
int prediction_quantitization_a;
int ricemodifier_a;
int[] predictor_coef_table_b = alac.predictor_coef_table_b;
int predictor_coef_num_b;
int prediction_type_b;
int prediction_quantitization_b;
int ricemodifier_b;
int tempPred = 0;
interlacing_shift = readbits(alac, 8);
interlacing_leftweight = readbits(alac, 8);
/******** channel 1 ***********/
prediction_type_a = readbits(alac, 4);
prediction_quantitization_a = readbits(alac, 4);
ricemodifier_a = readbits(alac, 3);
predictor_coef_num_a = readbits(alac, 5);
/* read the predictor table */
for (int i = 0; i < predictor_coef_num_a; i++)
{
tempPred = readbits(alac, 16);
if (tempPred > 32767)
{
// the predictor coef table values are only 16 bit signed
tempPred = tempPred - 65536;
}
predictor_coef_table_a[i] = tempPred;
}
/******** channel 2 *********/
prediction_type_b = readbits(alac, 4);
prediction_quantitization_b = readbits(alac, 4);
ricemodifier_b = readbits(alac, 3);
predictor_coef_num_b = readbits(alac, 5);
/* read the predictor table */
for (int i = 0; i < predictor_coef_num_b; i++)
{
tempPred = readbits(alac, 16);
if (tempPred > 32767)
{
// the predictor coef table values are only 16 bit signed
tempPred = tempPred - 65536;
}
predictor_coef_table_b[i] = tempPred;
}
/*********************/
if (uncompressed_bytes != 0)
{ // see mono case
for (int i = 0; i < outputsamples; i++)
{
alac.uncompressed_bytes_buffer_a[i] = readbits(alac, uncompressed_bytes * 8);
alac.uncompressed_bytes_buffer_b[i] = readbits(alac, uncompressed_bytes * 8);
}
}
/* channel 1 */
entropy_rice_decode(alac, alac.predicterror_buffer_a, outputsamples, readsamplesize, alac.setinfo_rice_initialhistory, alac.setinfo_rice_kmodifier, ricemodifier_a * (alac.setinfo_rice_historymult / 4), (uint)(1 << alac.setinfo_rice_kmodifier) - 1);
if (prediction_type_a == 0)
{ // adaptive fir
alac.outputsamples_buffer_a = predictor_decompress_fir_adapt(alac.predicterror_buffer_a, outputsamples, readsamplesize, predictor_coef_table_a, predictor_coef_num_a, prediction_quantitization_a);
}
else
{ // see mono case
//System.err.println("FIXME: unhandled predicition type: " + prediction_type_a);
}
/* channel 2 */
entropy_rice_decode(alac, alac.predicterror_buffer_b, outputsamples, readsamplesize, alac.setinfo_rice_initialhistory, alac.setinfo_rice_kmodifier, ricemodifier_b * (alac.setinfo_rice_historymult / 4), (uint)(1 << alac.setinfo_rice_kmodifier) - 1);
if (prediction_type_b == 0)
{ // adaptive fir
alac.outputsamples_buffer_b = predictor_decompress_fir_adapt(alac.predicterror_buffer_b, outputsamples, readsamplesize, predictor_coef_table_b, predictor_coef_num_b, prediction_quantitization_b);
}
else
{
//System.err.println("FIXME: unhandled predicition type: " + prediction_type_b);
}
}
else
{ // not compressed, easy case
if (alac.setinfo_sample_size <= 16)
{
int bitsmove;
for (int i = 0; i < outputsamples; i++)
{
int audiobits_a;
int audiobits_b;
audiobits_a = readbits(alac, alac.setinfo_sample_size);
audiobits_b = readbits(alac, alac.setinfo_sample_size);
bitsmove = 32 - alac.setinfo_sample_size;
audiobits_a = ((audiobits_a << bitsmove) >> bitsmove);
audiobits_b = ((audiobits_b << bitsmove) >> bitsmove);
alac.outputsamples_buffer_a[i] = audiobits_a;
alac.outputsamples_buffer_b[i] = audiobits_b;
}
}
else
{
int x;
int m = 1 << (24 - 1);
for (int i = 0; i < outputsamples; i++)
{
int audiobits_a;
int audiobits_b;
audiobits_a = readbits(alac, 16);
audiobits_a = audiobits_a << (alac.setinfo_sample_size - 16);
audiobits_a = audiobits_a | readbits(alac, alac.setinfo_sample_size - 16);
x = audiobits_a & ((1 << 24) - 1);
audiobits_a = (x ^ m) - m; // sign extend 24 bits
audiobits_b = readbits(alac, 16);
audiobits_b = audiobits_b << (alac.setinfo_sample_size - 16);
audiobits_b = audiobits_b | readbits(alac, alac.setinfo_sample_size - 16);
x = audiobits_b & ((1 << 24) - 1);
audiobits_b = (x ^ m) - m; // sign extend 24 bits
alac.outputsamples_buffer_a[i] = audiobits_a;
alac.outputsamples_buffer_b[i] = audiobits_b;
}
}
uncompressed_bytes = 0; // always 0 for uncompressed
interlacing_shift = 0;
interlacing_leftweight = 0;
}
switch (alac.setinfo_sample_size)
{
case 16:
{
deinterlace_16(alac.outputsamples_buffer_a, alac.outputsamples_buffer_b, outbuffer, alac.numchannels, outputsamples, interlacing_shift, interlacing_leftweight);
break;
}
case 24:
{
deinterlace_24(alac.outputsamples_buffer_a, alac.outputsamples_buffer_b, uncompressed_bytes, alac.uncompressed_bytes_buffer_a, alac.uncompressed_bytes_buffer_b, outbuffer, alac.numchannels, outputsamples, interlacing_shift, interlacing_leftweight);
break;
}
case 20:
case 32:
//System.err.println("FIXME: unimplemented sample size " + alac.setinfo_sample_size);
break;
default:
break;
}
}
return(outputsize);
}
public static void entropy_rice_decode(AlacFile alac, int[] outputBuffer, int outputSize, int readSampleSize, int rice_initialhistory, int rice_kmodifier, int rice_historymult, uint rice_kmodifier_mask)
{
int history = rice_initialhistory;
int outputCount = 0;
int signModifier = 0;
while (outputCount < outputSize)
{
int decodedValue = 0;
int finalValue = 0;
int k = 0;
k = 31 - rice_kmodifier - count_leading_zeros((history >> 9) + 3, alac.lz);
if (k < 0)
{
k += rice_kmodifier;
}
else
{
k = rice_kmodifier;
}
// note: don't use rice_kmodifier_mask here (set mask to 0xFFFFFFFF)
decodedValue = entropy_decode_value(alac, readSampleSize, k, 0xFFFFFFFF);
decodedValue += signModifier;
finalValue = ((decodedValue + 1) / 2); // inc by 1 and shift out sign bit
if ((decodedValue & 1) != 0) // the sign is stored in the low bit
{
finalValue *= -1;
}
outputBuffer[outputCount] = finalValue;
signModifier = 0;
// update history
history += (decodedValue * rice_historymult) - ((history * rice_historymult) >> 9);
if (decodedValue > 0xFFFF)
{
history = 0xFFFF;
}
// special case, for compressed blocks of 0
if ((history < 128) && (outputCount + 1 < outputSize))
{
int blockSize = 0;
signModifier = 1;
k = count_leading_zeros(history, alac.lz) + ((history + 16) / 64) - 24;
// note: blockSize is always 16bit
blockSize = entropy_decode_value(alac, 16, k, rice_kmodifier_mask);
// got blockSize 0s
if (blockSize > 0)
{
int countSize = 0;
countSize = blockSize;
for (int j = 0; j < countSize; j++)
{
outputBuffer[outputCount + 1 + j] = 0;
}
outputCount += blockSize;
}
if (blockSize > 0xFFFF)
{
signModifier = 0;
}
history = 0;
}
outputCount++;
}
}
