Skip to content

GitLab

E
ESP32-audioI2S
Commit cbc9e1b9 authored by schreibfaul1's avatar schreibfaul1
Browse files
Options

add comments

parent 3d733b3f
Show whitespace changes
Inline Side-by-side
Showing with 46 additions and 31 deletions
src/flac_decoder/flac_decoder.cpp
View file @ cbc9e1b9
......@@ -933,31 +933,39 @@ int8_t decodeSubframes(int* bytesLeft){
//----------------------------------------------------------------------------------------------------------------------
int8_t decodeSubframe(uint8_t sampleDepth, uint8_t ch, int* bytesLeft) {
int8_t ret = 0;
readUint(1, bytesLeft);
uint8_t type = readUint(6, bytesLeft);
int shift = readUint(1, bytesLeft);
readUint(1, bytesLeft); // Zero bit padding, to prevent sync-fooling string of 1s
uint8_t type = readUint(6, bytesLeft); // Subframe type: 000000 : SUBFRAME_CONSTANT
// 000001 : SUBFRAME_VERBATIM
// 00001x : reserved
// 0001xx : reserved
// 001xxx : if(xxx <= 4) SUBFRAME_FIXED, xxx=order ; else reserved
// 01xxxx : reserved
// 1xxxxx : SUBFRAME_LPC, xxxxx=order-1
int shift = readUint(1, bytesLeft); // Wasted bits-per-sample' flag:
// 0 : no wasted bits-per-sample in source subblock, k=0
// 1 : k wasted bits-per-sample in source subblock, k-1 follows, unary coded; e.g. k=3 => 001 follows, k=7 => 0000001 follows.
if (shift == 1) {
while (readUint(1, bytesLeft) == 0)
shift++;
while (readUint(1, bytesLeft) == 0) { shift++;}
}
sampleDepth -= shift;
if(type == 0){ // Constant coding
int16_t s= readSignedInt(sampleDepth, bytesLeft);
int32_t s= readSignedInt(sampleDepth, bytesLeft); // SUBFRAME_CONSTANT
for(int i=0; i < s_blockSize; i++){
s_samplesBuffer[ch][i] = s;
}
}
else if (type == 1) { // Verbatim coding
for (int i = 0; i < s_blockSize; i++)
s_samplesBuffer[ch][i] = readSignedInt(sampleDepth, bytesLeft);
s_samplesBuffer[ch][i] = readSignedInt(sampleDepth, bytesLeft); // SUBFRAME_VERBATIM
}
else if (8 <= type && type <= 12){
ret = decodeFixedPredictionSubframe(type - 8, sampleDepth, ch, bytesLeft);
ret = decodeFixedPredictionSubframe(type - 8, sampleDepth, ch, bytesLeft); // SUBFRAME_FIXED
if(ret) return ret;
}
else if (32 <= type && type <= 63){
ret = decodeLinearPredictiveCodingSubframe(type - 31, sampleDepth, ch, bytesLeft);
ret = decodeLinearPredictiveCodingSubframe(type - 31, sampleDepth, ch, bytesLeft); // SUBFRAME_LPC
if(ret) return ret;
}
else{
......@@ -970,14 +978,15 @@ int8_t decodeSubframe(uint8_t sampleDepth, uint8_t ch, int* bytesLeft) {
}
return ERR_FLAC_NONE;
}
//----------------------------------------------------------------------------------------------------------------------
int8_t decodeFixedPredictionSubframe(uint8_t predOrder, uint8_t sampleDepth, uint8_t ch, int* bytesLeft) {
//----------------------------------------------------------------------------------------------------------------------------------------------------
int8_t decodeFixedPredictionSubframe(uint8_t predOrder, uint8_t sampleDepth, uint8_t ch, int* bytesLeft) { // SUBFRAME_FIXED
uint8_t ret = 0;
for(uint8_t i = 0; i < predOrder; i++)
s_samplesBuffer[ch][i] = readSignedInt(sampleDepth, bytesLeft);
s_samplesBuffer[ch][i] = readSignedInt(sampleDepth, bytesLeft); // Unencoded warm-up samples (n = frame's bits-per-sample * predictor order).
ret = decodeResiduals(predOrder, ch, bytesLeft);
if(ret) return ret;
coefs.clear();
coefs.clear(); coefs.shrink_to_fit();
if(predOrder == 0) coefs.resize(0);
if(predOrder == 1) coefs.push_back(1); // FIXED_PREDICTION_COEFFICIENTS
if(predOrder == 2){coefs.push_back(2); coefs.push_back(-1);}
......@@ -989,14 +998,17 @@ int8_t decodeFixedPredictionSubframe(uint8_t predOrder, uint8_t sampleDepth, uin
}
//----------------------------------------------------------------------------------------------------------------------
int8_t decodeLinearPredictiveCodingSubframe(int lpcOrder, int sampleDepth, uint8_t ch, int* bytesLeft){
int8_t ret = 0;
for (int i = 0; i < lpcOrder; i++)
s_samplesBuffer[ch][i] = readSignedInt(sampleDepth, bytesLeft);
int precision = readUint(4, bytesLeft) + 1;
int shift = readSignedInt(5, bytesLeft);
coefs.resize(0);
for (uint8_t i = 0; i < lpcOrder; i++)
coefs.push_back(readSignedInt(precision, bytesLeft));
for (int i = 0; i < lpcOrder; i++){
s_samplesBuffer[ch][i] = readSignedInt(sampleDepth, bytesLeft); // Unencoded warm-up samples (n = frame's bits-per-sample * lpc order).
}
int precision = readUint(4, bytesLeft) + 1; // (Quantized linear predictor coefficients' precision in bits)-1 (1111 = invalid).
int shift = readSignedInt(5, bytesLeft); // Quantized linear predictor coefficient shift needed in bits (NOTE: this number is signed two's-complement).
coefs.clear(); coefs.shrink_to_fit();
for (uint8_t i = 0; i < lpcOrder; i++){
coefs.push_back(readSignedInt(precision, bytesLeft)); // Unencoded predictor coefficients (n = qlp coeff precision * lpc order) (NOTE: the coefficients are signed two's-complement).
}
ret = decodeResiduals(lpcOrder, ch, bytesLeft);
if(ret) return ret;
restoreLinearPrediction(ch, shift);
......@@ -1005,16 +1017,19 @@ int8_t decodeLinearPredictiveCodingSubframe(int lpcOrder, int sampleDepth, uint8
//----------------------------------------------------------------------------------------------------------------------
int8_t decodeResiduals(uint8_t warmup, uint8_t ch, int* bytesLeft) {
int method = readUint(2, bytesLeft);
if (method >= 2)
return ERR_FLAC_RESERVED_RESIDUAL_CODING; // Reserved residual coding method
uint8_t paramBits = method == 0 ? 4 : 5;
int escapeParam = (method == 0 ? 0xF : 0x1F);
int partitionOrder = readUint(4, bytesLeft);
int numPartitions = 1 << partitionOrder;
if (s_blockSize % numPartitions != 0)
int method = readUint(2, bytesLeft); // Residual coding method:
// 00 : partitioned Rice coding with 4-bit Rice parameter; RESIDUAL_CODING_METHOD_PARTITIONED_RICE follows
// 01 : partitioned Rice coding with 5-bit Rice parameter; RESIDUAL_CODING_METHOD_PARTITIONED_RICE2 follows
// 10-11 : reserved
if (method >= 2) {return ERR_FLAC_RESERVED_RESIDUAL_CODING;}
uint8_t paramBits = method == 0 ? 4 : 5; // RESIDUAL_CODING_METHOD_PARTITIONED_RICE || RESIDUAL_CODING_METHOD_PARTITIONED_RICE2
int escapeParam = ( method == 0 ? 0xF : 0x1F);
int partitionOrder = readUint(4, bytesLeft); // Partition order
int numPartitions = 1 << partitionOrder; // There will be 2^order partitions.
if (s_blockSize % numPartitions != 0){
return ERR_FLAC_WRONG_RICE_PARTITION_NR; //Error: Block size not divisible by number of Rice partitions
}
int partitionSize = s_blockSize / numPartitions;
for (int i = 0; i < numPartitions; i++) {
......@@ -1029,7 +1044,7 @@ int8_t decodeResiduals(uint8_t warmup, uint8_t ch, int* bytesLeft) {
}
}
else {
int numBits = readUint(5, bytesLeft);
int numBits = readUint(5, bytesLeft); // Escape code, meaning the partition is in unencoded binary form using n bits per sample; n follows as a 5-bit number.
for (int j = start; j < end; j++){
if(s_f_bitReaderError) break;
s_samplesBuffer[ch][j] = readSignedInt(numBits, bytesLeft);
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment