Linear Predictive Coding

EditDate	2025-2-13

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This is the heart of both fLaC compression and predicting the next sound, I think

Going to decode here and see how easily it can be introduced into my playAlong code.Web References https://en.wikipedia.org/wiki/Linear prediction

• w:Linear prediction
• w:Linear predictive coding

Linear Predictive Coding

Frame Header 2

Line Number	Code Package	LOC purpose	Operation Description
2987	SDC	read_residual_partitioned_rice	sample += u; Key parameters sample = 4088 for partition 0 4096 thereafter
2883	SDC	read_subframe_lpc	break
2889	SDC	Do Full Decode
2892	SDC	Get Warm-up values	8 previously stored warm-up values based on order=8
2894	SDC	call FLAC lpc max bps
960	LPC	FLAC__lpc_max_residual_bps	Variables uint32_t subframe_bps = 24 const FLAC__int32 * flac_restrict qlp_coeff : 0x555555859EFC <Hex> Address 0 - 3 4 - 7 8 - B C - F 0000555555859EF0 08000000 0F000000 0D000000 E51D0000 0000555555859F00 282E0000 E0E2FFFF F4CFFFFF 170C0000 0000555555859F10 17210000 72010000 6EF2FFFF uint32_t order = 8 int lp_quantization = 13 0xD
948	LPC	FLAC__lpc_max_prediction_before_shift_bps	FLAC__int32 abs_sum_of_qlp_coeff = 0;
951	LPC	FLAC__lpc_max_prediction_before_shift_bps	iterative based on i < order = 8 abs_sum_of_qlp_coeff += abs(qlp_coeff[i]); abs_sum_of_qlp_coeff = 0xd56b = 54635 if abs_sum_of_qlp_coeff = 0 = 1
2898	SDC	read_subframe_lpc_	FLAC__lpc_restore_signal_wide

Next Edit

Pertinent Code

960 LPC FLAC__int32 predictor_sum_bps = FLAC__lpc_max_prediction_before_shift_bps(subframe_bps, qlp_coeff, order) - lp_quantization; 1264 LPC *(data++) = (FLAC__int32)(*(r++) + (sum >> lp_quantization)); First result:

• Little Endian in Memory C670FFFF
• Big Endian as read FFFF70C6
• testBigEndian.raw 0030 FF70C6

Notes for code analysis

4 bytes / int 32 Bits.

little endian memory dump of in storage buffer

19 7F D1 4F 19 7F D1 4F 19 7F D1 4F FD 44 01 37  56 26 0A 25 B2 EE F6 7F 9D 10 5D 79 62 33 5B 9F B4 0E 65 24 15 7A 35 13 370144FD4FD17F19 at 2380 in test.flac.

File

3701 44FD 4FD1 4FD1 7F19 7FF6 EEB2 250A 2656 does not line up with contiguous memory location.  Only 64 bit word valid in memory (if reversed) 
loc 2380 in file

word