Module-private declarations shared across the software JPEGcodec translation units. More...

#include <stdint.h>
#include "ra8_attributes.h"
#include "ra8_err.h"

Include dependency graph for ra8_jpeg_sw_internal.h:

This graph shows which files directly or indirectly include this file:

Data Structures
struct	ra8_jpeg_bitreader_t
	Big-endian bit reader over an entropy-coded segment. More...
struct	ra8_jpeg_htab_t
	Decoded Huffman table – 256 entries indexed by symbol order. More...
struct	ra8_jpeg_dec_ctx_t
	Decoder state shared by the whole-buffer and streaming drivers. More...

Enumerations
enum	jpeg_misc_t : uint16_t { k_jpeg_byte_mask = 0xFFU , k_jpeg_nibble_mask = 0xFU , k_jpeg_reservoir_lo = 24U , k_jpeg_sof_dims_off = 5U , k_jpeg_mcu_align = 15U , k_jpeg_zrl_symbol = 0xF0U }
	Misc JPEG masks / offsets. More...
enum	jpeg_dsp_shift_t : uint8_t { k_jpeg_idct_p1_bias_sh = 27U , k_jpeg_idct_p1_sh = 28U , k_jpeg_idct_p2_bias_sh = 13U , k_jpeg_q14_shift = 14U , k_jpeg_ycc_q15_shift = 14U }
	Fixed-point IDCT / YCbCr shift amounts. More...
enum	jpeg_ycc_coeff_t : int16_t { k_cr_r_q15 = 22970 , k_cb_b_q15 = 29032 , k_cb_g_q15 = -5638 , k_cr_g_q15 = -11700 }
	Q15 BT.601 YCbCr->RGB coefficients (== Q16 / 2). More...
enum	jpeg_marker_range_t : uint16_t { k_jpeg_marker_sof_lo = 0xFFC0U , k_jpeg_marker_sof1 = 0xFFC1U , k_jpeg_marker_sof_hi = 0xFFCFU , k_jpeg_marker_jpg = 0xFFC8U , k_jpeg_marker_ff00 = 0xFF00U }
	JPEG SOF marker range and stuffing markers. More...
enum	jpeg_enc_t : uint16_t { k_jpeg_q_scale_low = 5000U , k_jpeg_q_scale_high = 200U , k_jpeg_q_round_bias = 50U , k_jpeg_q_percent = 100U , k_jpeg_sof_seg_len = 17U , k_jpeg_sos_seg_len = 12U , k_jpeg_spectral_end = 63U }
	JPEG encoder quality scaling and segment field values. More...
enum	jpeg_enc_field_t : uint8_t { k_jpeg_samp_2x2 = 0x22U , k_jpeg_samp_1x1 = 0x11U , k_jpeg_dht_ac_chroma = 0x11U , k_jpeg_sos_sel_chroma = 0x11U }
	JPEG component sampling / table-selector bytes (positional). More...
enum	ra8_jpeg_marker_t : uint16_t { k_ra8_jpeg_marker_soi = 0xFFD8U , k_ra8_jpeg_marker_eoi = 0xFFD9U , k_ra8_jpeg_marker_sos = 0xFFDAU , k_ra8_jpeg_marker_dqt = 0xFFDBU , k_ra8_jpeg_marker_dht = 0xFFC4U , k_ra8_jpeg_marker_dri = 0xFFDDU , k_ra8_jpeg_marker_sof0 = 0xFFC0U , k_ra8_jpeg_marker_sof1 = 0xFFC1U , k_ra8_jpeg_marker_sof2 = 0xFFC2U , k_ra8_jpeg_marker_sof3 = 0xFFC3U , k_ra8_jpeg_marker_app0 = 0xFFE0U , k_ra8_jpeg_marker_com = 0xFFFEU , k_ra8_jpeg_marker_rst0 = 0xFFD0U , k_ra8_jpeg_marker_rst7 = 0xFFD7U , k_ra8_jpeg_marker_pad = 0xFF00U , k_ra8_jpeg_marker_sof_lo = 0xFFC0U , k_ra8_jpeg_marker_sof_hi = k_jpeg_marker_sof_hi , k_ra8_jpeg_marker_dac = 0xFFC8U , k_ra8_jpeg_marker_high = 0xFF00U }
	JPEG segment marker bytes (T.81 sec B.1.1.3 "Marker assignments"). More...
enum	ra8_jpeg_const_t : uint16_t { k_ra8_jpeg_block_dim = 8U , k_ra8_jpeg_block_size = 64U , k_ra8_jpeg_max_comps = 3U , k_ra8_jpeg_mcu_max_dim = 16U , k_ra8_jpeg_huff_classes = 2U , k_ra8_jpeg_huff_ids = 2U , k_ra8_jpeg_huff_max = 256U , k_ra8_jpeg_marker_byte = 0xFFU , k_ra8_jpeg_quant_tabs = 2U , k_ra8_jpeg_enc_max_w = 1024U , k_ra8_jpeg_min_jpeg_len = 4U , k_ra8_jpeg_garbage_len = 5U , k_ra8_jpeg_mcu_align = 15U , k_ra8_jpeg_sof0_min_len = 8U , k_ra8_jpeg_dht_hdr = 1U , k_ra8_jpeg_sof0_hdr_len = 17U , k_ra8_jpeg_sos_len = 12U , k_ra8_jpeg_app0_len = 16U , k_ra8_jpeg_eob_band_max = 63U }
	Sizes and indices used throughout the codec. More...
enum	ra8_jpeg_shift_t : uint8_t { k_ra8_jpeg_byte_shift = 8U , k_ra8_jpeg_nibble_shift = 4U , k_ra8_jpeg_nibble_mask = 0x0FU , k_ra8_jpeg_signbit_pos = 7U , k_ra8_jpeg_signbit_pos16 = 15U , k_ra8_jpeg_level_offset = 128U , k_ra8_jpeg_pixel_max = 255U , k_ra8_jpeg_quality_pivot = 50U , k_ra8_jpeg_huff_lengths = 16U , k_ra8_jpeg_zrl_runlen = 16U , k_ra8_jpeg_zrl_symbol = 0xF0U , k_ra8_jpeg_eob_runlen = 0xFU , k_ra8_jpeg_dht_dc_class = 0U , k_ra8_jpeg_dht_ac_class = 0x10U , k_ra8_jpeg_y_sampling_420 = 0x22U , k_ra8_jpeg_c_sampling = 0x11U , k_ra8_jpeg_be_byte_mask = 0xFFU , k_ra8_jpeg_yuv_shift = 16U , k_ra8_jpeg_rgb_components = 3U }
	Shift amounts and signed-cast helpers. More...
enum	ra8_jpeg_color_coef_t : int32_t { k_ra8_jpeg_yr = 19595 , k_ra8_jpeg_yg = 38470 , k_ra8_jpeg_yb = 7471 , k_ra8_jpeg_cbr = -11059 , k_ra8_jpeg_cbg = -21709 , k_ra8_jpeg_cbb = 32768 , k_ra8_jpeg_crr = 32768 , k_ra8_jpeg_crg = -27439 , k_ra8_jpeg_crb = -5329 , k_ra8_jpeg_cr_r = 91881 , k_ra8_jpeg_cb_b = 116130 , k_ra8_jpeg_cr_g = -46802 , k_ra8_jpeg_cb_g = -22554 }
	BT.601 RGB<->YCbCr fixed-point coefficients (Q16). More...
enum	ra8_jpeg_dec_marker_action_t : uint8_t { k_ra8_jpeg_dec_continue = 0U , k_ra8_jpeg_dec_scan = 1U , k_ra8_jpeg_dec_eoi = 2U }
	Result of priv_jpeg_sw_dispatch(): what the driver does next. More...

Functions
static uint8_t	internal_clamp_u8 (int32_t v)
	Clamp v to the unsigned 8-bit pixel range.
static uint16_t	internal_read_be16 (const uint8_t *p)
	Read a 16-bit big-endian word from p.
static void	internal_write_be16 (uint8_t *p, uint16_t v)
	Write a 16-bit big-endian word into p.
int32_t	priv_jpeg_sw_br_get_bits (ra8_jpeg_bitreader_t *br, uint8_t n)
	Pop n bits MSB-first; returns -1 on underflow.
void	priv_jpeg_sw_htab_build (ra8_jpeg_htab_t *h)
	Build canonical code/size and mincode/maxcode tables.
int32_t	priv_jpeg_sw_htab_decode (ra8_jpeg_bitreader_t br, const ra8_jpeg_htab_t h)
	Decode one Huffman symbol from br using table h.
int32_t	priv_jpeg_sw_huff_extend (int32_t v, uint8_t n)
	Decode a signed n-bit DCT coefficient (T.81 F.1.2.1.3).
void	priv_jpeg_sw_idct8x8 (int32_t *block)
	Full 8x8 inverse DCT, in place.
void	priv_jpeg_sw_ycc_to_rgb (int32_t y, int32_t cb, int32_t cr, uint8_t out_r, uint8_t out_g, uint8_t *out_b)
	Convert a YCbCr triple to RGB (BT.601, fixed-point).
ra8_err_t	priv_jpeg_sw_skip_segment (ra8_jpeg_dec_ctx_t *d)
	Skip an unrecognized variable-length segment.
ra8_err_t	priv_jpeg_sw_parse_dqt (ra8_jpeg_dec_ctx_t *d)
	Parse a DQT segment (T.81 sec B.2.4.1) into d->qtab.
ra8_err_t	priv_jpeg_sw_parse_dht (ra8_jpeg_dec_ctx_t *d)
	Parse a DHT segment (T.81 sec B.2.4.2) and build its tables.
ra8_err_t	priv_jpeg_sw_parse_sof0 (ra8_jpeg_dec_ctx_t *d)
	Parse the SOF0 frame header (T.81 sec B.2.2).
ra8_err_t	priv_jpeg_sw_parse_sos (ra8_jpeg_dec_ctx_t *d)
	Parse the SOS scan header (T.81 sec B.2.3) selectors.
ra8_err_t	priv_jpeg_sw_block (ra8_jpeg_dec_ctx_t d, ra8_jpeg_bitreader_t br, uint8_t ci, int32_t *outblk)
	Entropy-decode one 8x8 block of dequantized coefficients.
void	priv_jpeg_sw_idct_into (int32_t coeffs, uint8_t tile)
	IDCT a coefficient block and emit level-shifted 8-bit samples.
ra8_err_t	priv_jpeg_sw_mcu_y (ra8_jpeg_dec_ctx_t d, ra8_jpeg_bitreader_t br, uint8_t *y_tile, uint16_t mcu_w_px)
	Decode the hmax*vmax luma blocks of one MCU into the Y tile.
ra8_err_t	priv_jpeg_sw_mcu_chroma (ra8_jpeg_dec_ctx_t d, ra8_jpeg_bitreader_t br, uint8_t cb_tile, uint8_t cr_tile)
	Decode the Cb and Cr 8x8 blocks of one MCU.
ra8_err_t	priv_jpeg_sw_dispatch (ra8_jpeg_dec_ctx_t d, bool got_sof, ra8_jpeg_dec_marker_action_t *action)
	Dispatch one JPEG marker segment in a decode driver loop.

Variables
static const uint8_t	s_zigzag [64]
	Zig-zag de-interleave order (T.81 Figure 5).
static const int32_t	s_dct_cos_q14 [8][8]
	Cosine table cos((2n+1)kpi/16) * 2^14, k = row, n = col.
static const int32_t	s_dct_w_q14 [8]
	sqrt(2/N)*C(k) DCT normalization weights, Q14.

Detailed Description

Module-private declarations shared across the software JPEG

codec translation units.

Tag: [Ring 4 / Domain] {World: NS}

The pure-software baseline JPEG codec is split across three translation units to keep each file under the maintainability line cap:

ra8_jpeg_sw.c – shared entropy/DSP primitives (bit reader, Huffman tables, inverse DCT, colour conversion) plus the lightweight ra8_jpeg_sw_get_dimensions() public API.
ra8_jpeg_sw_decode.c – the marker parser, MCU scan loop and the ra8_jpeg_sw_decode() public API.
ra8_jpeg_sw_encode.c – the forward DCT, quantization, Huffman code emission and ra8_jpeg_sw_encode().

Every symbol referenced by more than one of those units lives in this header: the shared C23 typed-enum constant blocks, the two read-only DSP look-up tables, the inline byte/pixel helpers, the bit-reader and Huffman-table struct types, and the prototypes for the decode primitives that the parser unit calls into.

Spec citations are tagged T.81 sec X.Y "..." and refer to ITU-T Recommendation T.81 (1992) | ISO/IEC 10918-1.

Copyright: Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since: 0.1.0

Definition in file ra8_jpeg_sw_internal.h.

Enumeration Type Documentation

◆ jpeg_dsp_shift_t

enum jpeg_dsp_shift_t : uint8_t

Fixed-point IDCT / YCbCr shift amounts.

Enumerator
k_jpeg_idct_p1_bias_sh	JPEG idct p1 bias sh.
k_jpeg_idct_p1_sh	JPEG idct p1 sh.
k_jpeg_idct_p2_bias_sh	JPEG idct p2 bias sh.
k_jpeg_q14_shift	JPEG q14 shift.
k_jpeg_ycc_q15_shift	JPEG ycc q15 shift.

Definition at line 63 of file ra8_jpeg_sw_internal.h.

◆ jpeg_enc_field_t

enum jpeg_enc_field_t : uint8_t

JPEG component sampling / table-selector bytes (positional).

Enumerator
k_jpeg_samp_2x2	JPEG samp 2x2.
k_jpeg_samp_1x1	JPEG samp 1x1.
k_jpeg_dht_ac_chroma	JPEG dht ac chroma.
k_jpeg_sos_sel_chroma	JPEG sos sel chroma.

Definition at line 100 of file ra8_jpeg_sw_internal.h.

◆ jpeg_enc_t

enum jpeg_enc_t : uint16_t

JPEG encoder quality scaling and segment field values.

Enumerator
k_jpeg_q_scale_low	JPEG q scale low.
k_jpeg_q_scale_high	JPEG q scale high.
k_jpeg_q_round_bias	JPEG q round bias.
k_jpeg_q_percent	JPEG q percent.
k_jpeg_sof_seg_len	JPEG sof seg length.
k_jpeg_sos_seg_len	JPEG sos seg length.
k_jpeg_spectral_end	JPEG spectral end.

Definition at line 89 of file ra8_jpeg_sw_internal.h.

◆ jpeg_marker_range_t

enum jpeg_marker_range_t : uint16_t

JPEG SOF marker range and stuffing markers.

Enumerator
k_jpeg_marker_sof_lo	JPEG marker sof lo.
k_jpeg_marker_sof1	JPEG marker sof1.
k_jpeg_marker_sof_hi	JPEG marker sof hi.
k_jpeg_marker_jpg	JPEG marker jpg.
k_jpeg_marker_ff00	JPEG marker ff00.

Definition at line 80 of file ra8_jpeg_sw_internal.h.

◆ jpeg_misc_t

enum jpeg_misc_t : uint16_t

Misc JPEG masks / offsets.

Enumerator
k_jpeg_byte_mask	JPEG byte mask.
k_jpeg_nibble_mask	JPEG nibble mask.
k_jpeg_reservoir_lo	JPEG reservoir lo.
k_jpeg_sof_dims_off	JPEG sof dims off.
k_jpeg_mcu_align	JPEG mcu align.
k_jpeg_zrl_symbol	JPEG zrl symbol.

Definition at line 53 of file ra8_jpeg_sw_internal.h.

◆ jpeg_ycc_coeff_t

enum jpeg_ycc_coeff_t : int16_t

Q15 BT.601 YCbCr->RGB coefficients (== Q16 / 2).

Enumerator
k_cr_r_q15	1.40200 / 2 * 2^15.
k_cb_b_q15	1.77200 / 2 * 2^15.
k_cb_g_q15	Cb g q15.
k_cr_g_q15	Cr g q15.

Definition at line 72 of file ra8_jpeg_sw_internal.h.

◆ ra8_jpeg_color_coef_t

enum ra8_jpeg_color_coef_t : int32_t

BT.601 RGB<->YCbCr fixed-point coefficients (Q16).

Same constants the IJG jccolor.c and jdcolor.c files use (see also T.871 / JFIF colour conversion). All values are fixed-point Q16 (multiply by 1 << 16 and round).

Enumerator
k_ra8_jpeg_yr	0.29900 * 65536.
k_ra8_jpeg_yg	0.58700 * 65536.
k_ra8_jpeg_yb	0.11400 * 65536.
k_ra8_jpeg_cbr	RA8 JPEG CBR.
k_ra8_jpeg_cbg	RA8 JPEG cbg.
k_ra8_jpeg_cbb	RA8 JPEG cbb.
k_ra8_jpeg_crr	RA8 JPEG crr.
k_ra8_jpeg_crg	RA8 JPEG crg.
k_ra8_jpeg_crb	RA8 JPEG crb.
k_ra8_jpeg_cr_r	1.40200.
k_ra8_jpeg_cb_b	1.77200.
k_ra8_jpeg_cr_g	RA8 JPEG cr g.
k_ra8_jpeg_cb_g	RA8 JPEG cb g.

Definition at line 195 of file ra8_jpeg_sw_internal.h.

◆ ra8_jpeg_const_t

enum ra8_jpeg_const_t : uint16_t

Sizes and indices used throughout the codec.

Enumerator
k_ra8_jpeg_block_dim	8x8 DCT block edge.
k_ra8_jpeg_block_size	Coefficients per block.
k_ra8_jpeg_max_comps	YCbCr or grayscale only.
k_ra8_jpeg_mcu_max_dim	4:2:0 MCU is 16x16 luma px.
k_ra8_jpeg_huff_classes	DC + AC.
k_ra8_jpeg_huff_ids	Luma + chroma table id.
k_ra8_jpeg_huff_max	Max symbols per Huffman table.
k_ra8_jpeg_marker_byte	RA8 JPEG marker byte.
k_ra8_jpeg_quant_tabs	One luma + one chroma table.
k_ra8_jpeg_enc_max_w	Encoder max image width (px).
k_ra8_jpeg_min_jpeg_len	Smallest plausible stream.
k_ra8_jpeg_garbage_len	Garbage-input cutoff.
k_ra8_jpeg_mcu_align	MCU alignment mask.
k_ra8_jpeg_sof0_min_len	Min SOF0 segment length.
k_ra8_jpeg_dht_hdr	DHT TcTh byte size.
k_ra8_jpeg_sof0_hdr_len	SOF0 segment length we emit.
k_ra8_jpeg_sos_len	SOS segment length we emit.
k_ra8_jpeg_app0_len	APP0 (JFIF) segment length.
k_ra8_jpeg_eob_band_max	Last AC zig-zag index.

Definition at line 138 of file ra8_jpeg_sw_internal.h.

◆ ra8_jpeg_dec_marker_action_t

enum ra8_jpeg_dec_marker_action_t : uint8_t

Result of priv_jpeg_sw_dispatch(): what the driver does next.

Enumerator
k_ra8_jpeg_dec_continue	Keep scanning markers.
k_ra8_jpeg_dec_scan	SOS reached; the driver should run its scan loop.
k_ra8_jpeg_dec_eoi	EOI reached; the driver should stop with an error.

Definition at line 600 of file ra8_jpeg_sw_internal.h.

◆ ra8_jpeg_marker_t

enum ra8_jpeg_marker_t : uint16_t

JPEG segment marker bytes (T.81 sec B.1.1.3 "Marker assignments").

The high byte is always 0xFF.

Enumerator
k_ra8_jpeg_marker_soi	Start of image.
k_ra8_jpeg_marker_eoi	End of image.
k_ra8_jpeg_marker_sos	Start of scan.
k_ra8_jpeg_marker_dqt	Define quantization table.
k_ra8_jpeg_marker_dht	Define Huffman table.
k_ra8_jpeg_marker_dri	Define restart interval.
k_ra8_jpeg_marker_sof0	Baseline DCT, Huffman.
k_ra8_jpeg_marker_sof1	Extended sequential DCT.
k_ra8_jpeg_marker_sof2	Progressive DCT.
k_ra8_jpeg_marker_sof3	Lossless.
k_ra8_jpeg_marker_app0	JFIF APP0.
k_ra8_jpeg_marker_com	Comment.
k_ra8_jpeg_marker_rst0	Restart 0.
k_ra8_jpeg_marker_rst7	Restart 7.
k_ra8_jpeg_marker_pad	Stuffed byte (data 0xFF).
k_ra8_jpeg_marker_sof_lo	First SOF marker code.
k_ra8_jpeg_marker_sof_hi	Last SOF marker code.
k_ra8_jpeg_marker_dac	DAC marker (skipped).
k_ra8_jpeg_marker_high	Marker high-byte mask.

Definition at line 112 of file ra8_jpeg_sw_internal.h.

◆ ra8_jpeg_shift_t

enum ra8_jpeg_shift_t : uint8_t

Shift amounts and signed-cast helpers.

Enumerator
k_ra8_jpeg_byte_shift	RA8 JPEG byte shift.
k_ra8_jpeg_nibble_shift	RA8 JPEG nibble shift.
k_ra8_jpeg_nibble_mask	RA8 JPEG nibble mask.
k_ra8_jpeg_signbit_pos	RA8 JPEG signbit pos.
k_ra8_jpeg_signbit_pos16	RA8 JPEG signbit pos16.
k_ra8_jpeg_level_offset	RA8 JPEG level offset.
k_ra8_jpeg_pixel_max	RA8 JPEG pixel maximum.
k_ra8_jpeg_quality_pivot	RA8 JPEG quality pivot.
k_ra8_jpeg_huff_lengths	16 BITS-list slots.
k_ra8_jpeg_zrl_runlen	Zero-Run-Length symbol skip.
k_ra8_jpeg_zrl_symbol	T.81 K.3.3 ZRL byte.
k_ra8_jpeg_eob_runlen	F0 high-nibble RRRR mask.
k_ra8_jpeg_dht_dc_class	RA8 JPEG dht dc class.
k_ra8_jpeg_dht_ac_class	RA8 JPEG dht ac class.
k_ra8_jpeg_y_sampling_420	SOF0 H/V byte for Y in 4:2:0.
k_ra8_jpeg_c_sampling	SOF0 H/V byte for chroma.
k_ra8_jpeg_be_byte_mask	Low-byte mask.
k_ra8_jpeg_yuv_shift	BT.601 fixed-point shift.
k_ra8_jpeg_rgb_components	RA8 JPEG RGB components.

Definition at line 164 of file ra8_jpeg_sw_internal.h.

Function Documentation

◆ internal_clamp_u8()

uint8_t internal_clamp_u8 ( int32_t v )

inlinestatic

Clamp v to the unsigned 8-bit pixel range.

Saturating cast used by the IDCT output stage so out-of-range coefficients map to the legal 8-bit pixel domain. Pure helper.

Parameters

[in] v Signed integer value to saturate.

Returns: Saturated 8-bit value.

Return values

0	v was negative.
255	v was > 255.
(u8)v	v was in 0..255.

Precondition: v is a valid signed integer (no preconditions on range).; Caller is using the result for an 8-bit pixel slot.

Postcondition: Return value is in 0..255 (k_ra8_jpeg_pixel_max).; No global state is touched.

Note: Pure helper; safe from any context.

Since: 0.1.0

Definition at line 294 of file ra8_jpeg_sw_internal.h.

References k_ra8_jpeg_pixel_max, and RA8_INTERNAL.

Referenced by priv_jpeg_sw_idct_into(), and priv_jpeg_sw_ycc_to_rgb().

◆ internal_read_be16()

uint16_t internal_read_be16 ( const uint8_t * p )

inlinestatic

Read a 16-bit big-endian word from p.

JPEG marker payloads use big-endian length prefixes. Inline helper keeps the parser sites free of byte-shifting noise.

Parameters

[in] p Non-NULL pointer to two readable bytes.

Returns: Decoded big-endian word.

Return values

0..65535 (p[0] << 8) | p[1].

Precondition: p is non-NULL.; At least two bytes are readable starting at p.

Postcondition: No memory has been written.; Return value reflects the bytes at the call site.

Note: Pure helper; safe from any context.

Since: 0.1.0

Definition at line 325 of file ra8_jpeg_sw_internal.h.

References k_ra8_jpeg_byte_shift, and RA8_INTERNAL.

Referenced by internal_dims_parse_sof0(), internal_dims_step(), internal_js_begin(), priv_jpeg_sw_parse_dht(), priv_jpeg_sw_parse_dqt(), priv_jpeg_sw_parse_sof0(), priv_jpeg_sw_parse_sos(), priv_jpeg_sw_skip_segment(), ra8_jpeg_sw_decode(), and ra8_jpeg_sw_get_dimensions().

◆ internal_write_be16()

void internal_write_be16	(	uint8_t *	p,
		uint16_t	v )

inlinestatic

Write a 16-bit big-endian word into p.

Encoder helper for emitting JPEG marker payloads (length prefixes, SOFn / DHT / DQT field counts).

Parameters

[out]	p	Non-NULL pointer to two writable bytes.
[in]	v	Value to encode.

Precondition: p is non-NULL.; At least two bytes are writable starting at p.

Postcondition: p[0] holds the high byte of v, p[1] the low byte.; No global state is touched.

Note: Pure helper; safe from any context.

Since: 0.1.0

Definition at line 348 of file ra8_jpeg_sw_internal.h.

References k_jpeg_byte_mask, k_ra8_jpeg_byte_shift, and RA8_INTERNAL.

◆ priv_jpeg_sw_block()

ra8_err_t priv_jpeg_sw_block	(	ra8_jpeg_dec_ctx_t *	d,
		ra8_jpeg_bitreader_t *	br,
		uint8_t	ci,
		int32_t *	outblk )

Entropy-decode one 8x8 block of dequantized coefficients.

T.81 sec F.2.2: DC difference + AC run-length decode against the component's Huffman tables, dequantized through its quant table, de-zigzagged into row-major order.

Parameters

[in,out]	d	Decoder context (DC predictor mutates).
[in,out]	br	Bit reader over the entropy-coded segment.
[in]	ci	Component index (0 = luma).
[out]	outblk	64-entry coefficient block.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Block decoded.
k_ra8_err_protocol_error	Stream underflow / illegal symbol.

Precondition: d tables for component ci were parsed.; outblk holds 64 writable int32 slots.

Postcondition: On success outblk holds dequantized row-major coefficients.; On error the scan aborts.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Entropy-decode one 8x8 block of dequantized coefficients.

Definition at line 392 of file ra8_jpeg_sw_decode.c.

References ra8_jpeg_dec_ctx_t::comp_dc_id, ra8_jpeg_dec_ctx_t::comp_dc_pred, ra8_jpeg_dec_ctx_t::comp_qid, ra8_jpeg_dec_ctx_t::hdc, internal_dec_block_ac(), k_ra8_err_protocol_error, k_ra8_jpeg_block_size, priv_jpeg_sw_br_get_bits(), priv_jpeg_sw_htab_decode(), priv_jpeg_sw_huff_extend(), ra8_jpeg_dec_ctx_t::qtab, and RA8_PRIV.

Referenced by priv_jpeg_sw_mcu_chroma(), and priv_jpeg_sw_mcu_y().

◆ priv_jpeg_sw_br_get_bits()

int32_t priv_jpeg_sw_br_get_bits	(	ra8_jpeg_bitreader_t *	br,
		uint8_t	n )

Pop n bits MSB-first; returns -1 on underflow.

Tops off the accumulator from the entropy stream, then drains n MSBs as a non-negative integer. Defined in ra8_jpeg_sw.c; the parser unit calls it while decoding DC/AC magnitude bits.

Parameters

[in,out]	br	Bit reader (state mutated in place).
[in]	n	Number of bits to consume (0..16).

Returns: Decoded bit pattern, or -1 on stream underflow.

Return values

>=0	n-bit unsigned value drained from the accumulator.
-1	Underflow / EOI before n bits were available.

Precondition: br is non-NULL.; n <= 16 (caller-enforced).

Postcondition: br->nbits decreases by n on success.; Accumulator is masked to its remaining bits.

Note: Internal helper; not thread-safe.

Since: 0.1.0

Calls internal_br_fill to top off the accumulator, then drains n MSBs as a non-negative integer.

Parameters

[in,out]	br	Bit reader (state mutated in place).
[in]	n	Number of bits to consume (0..16).

Returns: Decoded bit pattern, or -1 on stream underflow.

Return values

>=0	n-bit unsigned value drained from the accumulator.
-1	Underflow / EOI before n bits were available.

Precondition: br is non-NULL.; n <= 16 (caller-enforced).

Postcondition: br->nbits decreases by n on success.; Accumulator is masked to its remaining bits.

Note: Internal helper; not thread-safe.

Since: 0.1.0

Definition at line 134 of file ra8_jpeg_sw.c.

References ra8_jpeg_bitreader_t::acc, internal_br_fill(), ra8_jpeg_bitreader_t::nbits, and RA8_PRIV.

Referenced by internal_dec_block_ac(), priv_jpeg_sw_block(), and priv_jpeg_sw_htab_decode().

◆ priv_jpeg_sw_dispatch()

ra8_err_t priv_jpeg_sw_dispatch	(	ra8_jpeg_dec_ctx_t *	d,
		bool *	got_sof,
		ra8_jpeg_dec_marker_action_t *	action )

Dispatch one JPEG marker segment in a decode driver loop.

Parses one marker following the 0xFF prefix at d->cursor and updates the decoder context. Unknown APPn/COM payloads are skipped; RST markers are consumed as standalone bytes.

Parameters

[in,out]	d	Decoder context (cursor advances).
[in,out]	got_sof	Tracks whether SOF0 has been parsed yet.
[out]	action	What the driver should do next.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Marker handled (see *action).
k_ra8_err_protocol_error	Malformed marker / truncated stream / SOS before SOF.
k_ra8_err_not_supported	Unsupported SOFn (progressive, ...).

Precondition: d->cursor < d->src_len (caller checks).; The whole next segment is inside d->src (window drivers ensure).

Postcondition: d->cursor advanced past the marker and any sized payload.; *action is a ra8_jpeg_dec_marker_action_t value.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Dispatch one JPEG marker segment in a decode driver loop.

Definition at line 810 of file ra8_jpeg_sw_decode.c.

References ra8_jpeg_dec_ctx_t::cursor, internal_dec_dispatch_tail(), k_jpeg_marker_ff00, k_jpeg_marker_jpg, k_jpeg_marker_sof1, k_jpeg_marker_sof_hi, k_ra8_err_not_supported, k_ra8_err_protocol_error, k_ra8_jpeg_dec_continue, k_ra8_jpeg_marker_byte, k_ra8_jpeg_marker_dht, k_ra8_jpeg_marker_sof0, k_ra8_ok, priv_jpeg_sw_parse_sof0(), RA8_PRIV, ra8_jpeg_dec_ctx_t::src, and ra8_jpeg_dec_ctx_t::src_len.

Referenced by internal_dec_run(), and internal_js_parse_markers().

◆ priv_jpeg_sw_htab_build()

void priv_jpeg_sw_htab_build ( ra8_jpeg_htab_t * h )

Build canonical code/size and mincode/maxcode tables.

Implements T.81 Annex C "Generation of size table" + "Generation of code table" plus the Annex F.2.2.3 mincode/maxcode/valptr tables used by the symbol decoder. Defined in ra8_jpeg_sw.c; the parser unit calls it from dec_parse_dht().

Parameters

[in,out] h Huffman table (BITS / VALS in, derived tables out).

Precondition: h is non-NULL.; h->bits and h->vals populated from the JPEG DHT marker.

Postcondition: h->huffcode, h->huffsize, h->mincode, h->maxcode and h->valptr are populated.; h->total reflects the symbol count.

Note: Internal helper; not thread-safe.

Since: 0.1.0

Definition at line 192 of file ra8_jpeg_sw.c.

References ra8_jpeg_htab_t::bits, ra8_jpeg_htab_t::huffcode, ra8_jpeg_htab_t::huffsize, internal_htab_build_lookup(), k_ra8_jpeg_huff_lengths, RA8_PRIV, and ra8_jpeg_htab_t::total.

Referenced by internal_dec_parse_dht_one().

◆ priv_jpeg_sw_htab_decode()

int32_t priv_jpeg_sw_htab_decode	(	ra8_jpeg_bitreader_t *	br,
		const ra8_jpeg_htab_t *	h )

Decode one Huffman symbol from br using table h.

Single-bit greedy lookup per T.81 F.2.2.3 "Decoder code-length algorithm". Returns -1 on stream underflow or table miss. Defined in ra8_jpeg_sw.c; the parser unit calls it from dec_block().

Parameters

[in,out]	br	Bit reader (state mutated in place).
[in]	h	Pre-built canonical Huffman table.

Returns: Decoded symbol or -1 on error.

Return values

>=0	Symbol value from h->vals.
-1	Stream underflow or table miss.

Precondition: br and h non-NULL.; h was previously populated by priv_jpeg_sw_htab_build.

Postcondition: br advances by the consumed code length on success.; No table state is mutated.

Note: Internal helper; not thread-safe.

Since: 0.1.0

Single-bit greedy lookup per T.81 F.2.2.3 "Decoder code-length algorithm". Returns -1 on stream underflow or table miss.

Parameters

[in,out]	br	Bit reader (state mutated in place).
[in]	h	Pre-built canonical Huffman table.

Returns: Decoded symbol or -1 on error.

Return values

>=0	Symbol value from h->vals.
-1	Stream underflow or table miss.

Precondition: br and h non-NULL.; h was previously populated by priv_jpeg_sw_htab_build.

Postcondition: br advances by the consumed code length on success.; No table state is mutated.

Note: Internal helper; not thread-safe.

Since: 0.1.0

Definition at line 250 of file ra8_jpeg_sw.c.

References internal_br_fill(), k_ra8_jpeg_huff_lengths, ra8_jpeg_htab_t::mincode, ra8_jpeg_bitreader_t::nbits, priv_jpeg_sw_br_get_bits(), RA8_PRIV, ra8_jpeg_htab_t::total, ra8_jpeg_htab_t::valptr, and ra8_jpeg_htab_t::vals.

Referenced by internal_dec_block_ac(), and priv_jpeg_sw_block().

◆ priv_jpeg_sw_huff_extend()

int32_t priv_jpeg_sw_huff_extend	(	int32_t	v,
		uint8_t	n )

Decode a signed n-bit DCT coefficient (T.81 F.1.2.1.3).

Extends a non-negative n-bit pattern into the signed range documented at T.81 Figure F.12 "EXTEND". A leading-zero pattern is treated as the negative of the symmetric positive value. Defined in ra8_jpeg_sw.c; the parser unit calls it from dec_block().

Parameters

[in]	v	Non-negative bit pattern from the bit reader.
[in]	n	Number of significant bits.

Returns: Signed coefficient.

Return values

0..(1<<n)-1	v had its high bit set (positive value).
-(1<<n)+1..0	v had its high bit clear (negative value).

Precondition: v is in 0..(1 << n) - 1.; n <= 16 (caller-enforced from JPEG stream).

Postcondition: Return value is in (-(1<<n))+1 .. (1<<n)-1.; No global state is mutated.

Note: Pure helper; safe from any context.

Since: 0.1.0

Extends a non-negative n-bit pattern into the signed range documented at T.81 Figure F.12 "EXTEND". A leading-zero pattern is treated as the negative of the symmetric positive value.

Parameters

[in]	v	Non-negative bit pattern from the bit reader.
[in]	n	Number of significant bits.

Returns: Signed coefficient.

Return values

0..(1<<n)-1	v had its high bit set (positive value).
-(1<<n)+1..0	v had its high bit clear (negative value).

Precondition: v is in 0..(1 << n) - 1.; n <= 16 (caller-enforced from JPEG stream).

Postcondition: Return value is in (-(1<<n))+1 .. (1<<n)-1.; No global state is mutated.

Note: Pure helper; safe from any context.

Since: 0.1.0

Definition at line 305 of file ra8_jpeg_sw.c.

References RA8_PRIV.

Referenced by internal_dec_block_ac(), and priv_jpeg_sw_block().

◆ priv_jpeg_sw_idct8x8()

void priv_jpeg_sw_idct8x8 ( int32_t * block )

Full 8x8 inverse DCT, in place.

Two-pass separable IDCT (rows then columns) using the shared Q14 cosine basis. Defined in ra8_jpeg_sw.c; the parser unit calls it from dec_idct_into().

Parameters

[in,out] block 64-entry row-major coefficient block, IDCTed in place.

Precondition: block is non-NULL with at least 64 writable int32 slots.; block holds dequantized DCT coefficients.

Postcondition: block holds the reconstructed spatial samples.; No global state is touched.

Note: Internal helper; not thread-safe.

Since: 0.1.0

Definition at line 352 of file ra8_jpeg_sw.c.

References internal_inv_dct_1d_norm(), k_ra8_jpeg_block_dim, k_ra8_jpeg_block_size, and RA8_PRIV.

Referenced by priv_jpeg_sw_idct_into().

◆ priv_jpeg_sw_idct_into()

void priv_jpeg_sw_idct_into	(	int32_t *	coeffs,
		uint8_t *	tile )

IDCT a coefficient block and emit level-shifted 8-bit samples.

Runs the shared 8x8 IDCT, then level-shifts and clamps each sample.

Parameters

[in,out]	coeffs	64-entry coefficient block (IDCTed in place).
[out]	tile	64-byte destination sample tile.

Precondition: coeffs holds dequantized coefficients.; tile holds 64 writable bytes.

Postcondition: tile holds clamped 8-bit spatial samples.; coeffs content is clobbered by the in-place IDCT.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

IDCT a coefficient block and emit level-shifted 8-bit samples.

Definition at line 425 of file ra8_jpeg_sw_decode.c.

References internal_clamp_u8(), k_ra8_jpeg_block_size, k_ra8_jpeg_level_offset, priv_jpeg_sw_idct8x8(), and RA8_PRIV.

Referenced by priv_jpeg_sw_mcu_chroma(), and priv_jpeg_sw_mcu_y().

◆ priv_jpeg_sw_mcu_chroma()

ra8_err_t priv_jpeg_sw_mcu_chroma	(	ra8_jpeg_dec_ctx_t *	d,
		ra8_jpeg_bitreader_t *	br,
		uint8_t *	cb_tile,
		uint8_t *	cr_tile )

Decode the Cb and Cr 8x8 blocks of one MCU.

Consumes one Cb block then one Cr block, IDCTing each into its tile.

Parameters

[in,out]	d	Decoder context (DC predictors mutate).
[in,out]	br	Bit-reader positioned at the next chroma block.
[out]	cb_tile	64-byte buffer for reconstructed Cb pixels.
[out]	cr_tile	64-byte buffer for reconstructed Cr pixels.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Both chroma blocks decoded.
k_ra8_err_protocol_error	Underlying block decode failed.

Precondition: d->ncomp == 3 (caller verifies).; Both tiles hold 64 writable bytes.

Postcondition: On success both tiles are fully populated.; On error the scan aborts.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Decode the Cb and Cr 8x8 blocks of one MCU.

Definition at line 493 of file ra8_jpeg_sw_decode.c.

References k_ra8_jpeg_block_size, k_ra8_ok, priv_jpeg_sw_block(), priv_jpeg_sw_idct_into(), and RA8_PRIV.

Referenced by internal_dec_decode_mcu(), and internal_js_decode_mcu().

◆ priv_jpeg_sw_mcu_y()

ra8_err_t priv_jpeg_sw_mcu_y	(	ra8_jpeg_dec_ctx_t *	d,
		ra8_jpeg_bitreader_t *	br,
		uint8_t *	y_tile,
		uint16_t	mcu_w_px )

Decode the hmax*vmax luma blocks of one MCU into the Y tile.

Decodes hmax*vmax successive luma blocks into their tile sub-rectangles.

Parameters

[in,out]	d	Decoder context (DC predictors mutate).
[in,out]	br	Bit-reader positioned at the next luma block.
[out]	y_tile	Output tile of (mcu_w_px x mcu_h_px) luma px.
[in]	mcu_w_px	MCU width in pixels.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	All luma blocks consumed.
k_ra8_err_protocol_error	Underlying block decode failed.

Precondition: d->hmax and d->vmax are non-zero (SOF0-enforced).; y_tile covers mcu_w_px * (8 * vmax) bytes.

Postcondition: On success y_tile is fully populated.; On error the scan aborts.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Decode the hmax*vmax luma blocks of one MCU into the Y tile.

Definition at line 472 of file ra8_jpeg_sw_decode.c.

References ra8_jpeg_dec_ctx_t::hmax, internal_dec_copy_block_to_tile(), k_ra8_jpeg_block_size, k_ra8_ok, priv_jpeg_sw_block(), priv_jpeg_sw_idct_into(), RA8_PRIV, and ra8_jpeg_dec_ctx_t::vmax.

Referenced by internal_dec_decode_mcu(), and internal_js_decode_mcu().

◆ priv_jpeg_sw_parse_dht()

ra8_err_t priv_jpeg_sw_parse_dht ( ra8_jpeg_dec_ctx_t * d )

Parse a DHT segment (T.81 sec B.2.4.2) and build its tables.

T.81 sec B.2.4.2: reads the BITS/VALS lists and canonical-builds the table.

Parameters

[in,out] d Decoder context (cursor advances; tables written).

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Table(s) parsed and built.
k_ra8_err_protocol_error	Truncated / malformed segment.
k_ra8_err_not_supported	Table class / id out of range.

Precondition: d->cursor points at the DHT length field.; d->src covers d->src_len readable bytes.

Postcondition: On success the referenced Huffman tables are canonical-built.; On error the decode aborts; table state is partial.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Parse a DHT segment (T.81 sec B.2.4.2) and build its tables.

Definition at line 158 of file ra8_jpeg_sw_decode.c.

References ra8_jpeg_dec_ctx_t::cursor, internal_dec_parse_dht_one(), internal_read_be16(), k_ra8_err_protocol_error, k_ra8_ok, RA8_PRIV, ra8_jpeg_dec_ctx_t::src, and ra8_jpeg_dec_ctx_t::src_len.

Referenced by internal_dec_dispatch_tail().

◆ priv_jpeg_sw_parse_dqt()

ra8_err_t priv_jpeg_sw_parse_dqt ( ra8_jpeg_dec_ctx_t * d )

Parse a DQT segment (T.81 sec B.2.4.1) into d->qtab.

T.81 sec B.2.4.1: de-zigzags each 8-bit table into d->qtab.

Parameters

[in,out] d Decoder context (cursor advances; tables written).

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Table(s) parsed.
k_ra8_err_protocol_error	Truncated / malformed segment.
k_ra8_err_not_supported	16-bit precision table.

Precondition: d->cursor points at the DQT length field.; d->src covers d->src_len readable bytes.

Postcondition: On success the referenced quant tables are de-zigzagged in place.; On error the decode aborts; table state is partial.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Parse a DQT segment (T.81 sec B.2.4.1) into d->qtab.

Definition at line 68 of file ra8_jpeg_sw_decode.c.

References ra8_jpeg_dec_ctx_t::cursor, internal_read_be16(), k_ra8_err_not_supported, k_ra8_err_protocol_error, k_ra8_jpeg_block_size, k_ra8_jpeg_nibble_mask, k_ra8_jpeg_nibble_shift, k_ra8_jpeg_quant_tabs, k_ra8_ok, ra8_jpeg_dec_ctx_t::qtab, RA8_PRIV, s_zigzag, ra8_jpeg_dec_ctx_t::src, and ra8_jpeg_dec_ctx_t::src_len.

Referenced by internal_dec_dispatch_tail().

◆ priv_jpeg_sw_parse_sof0()

ra8_err_t priv_jpeg_sw_parse_sof0 ( ra8_jpeg_dec_ctx_t * d )

Parse the SOF0 frame header (T.81 sec B.2.2).

T.81 sec B.2.2: reads precision, dimensions and per-component sampling.

Parameters

[in,out] d Decoder context (dims/sampling written).

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Baseline frame accepted.
k_ra8_err_protocol_error	Truncated / malformed segment.
k_ra8_err_not_supported	Non-8-bit precision, component count not 1/3, or a chroma layout other than 4:4:4 / 4:2:0.

Precondition: d->cursor points at the SOF0 length field.; d->src covers d->src_len readable bytes.

Postcondition: On success width/height/ncomp/hmax/vmax are set non-zero.; On error the decode aborts.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Parse the SOF0 frame header (T.81 sec B.2.2).

Definition at line 258 of file ra8_jpeg_sw_decode.c.

References ra8_jpeg_dec_ctx_t::cursor, ra8_jpeg_dec_ctx_t::height, internal_dec_check_chroma_layout(), internal_dec_parse_sof0_components(), internal_read_be16(), k_ra8_err_not_supported, k_ra8_err_protocol_error, ra8_jpeg_dec_ctx_t::ncomp, RA8_PRIV, ra8_jpeg_dec_ctx_t::src, ra8_jpeg_dec_ctx_t::src_len, and ra8_jpeg_dec_ctx_t::width.

Referenced by priv_jpeg_sw_dispatch().

◆ priv_jpeg_sw_parse_sos()

ra8_err_t priv_jpeg_sw_parse_sos ( ra8_jpeg_dec_ctx_t * d )

Parse the SOS scan header (T.81 sec B.2.3) selectors.

T.81 sec B.2.3: binds each scan component to its DC/AC table selectors.

Parameters

[in,out] d Decoder context (per-component table ids written).

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Scan header accepted.
k_ra8_err_protocol_error	Truncated / malformed segment.
k_ra8_err_not_supported	Component count mismatch or selector out of range.

Precondition: d->cursor points at the SOS length field.; A successful SOF0 parse preceded this call.

Postcondition: On success d->cursor sits at the entropy-coded data.; On error the decode aborts.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Parse the SOS scan header (T.81 sec B.2.3) selectors.

Definition at line 291 of file ra8_jpeg_sw_decode.c.

References ra8_jpeg_dec_ctx_t::comp_ac_id, ra8_jpeg_dec_ctx_t::comp_dc_id, ra8_jpeg_dec_ctx_t::comp_id, ra8_jpeg_dec_ctx_t::cursor, internal_read_be16(), k_ra8_err_not_supported, k_ra8_err_protocol_error, k_ra8_jpeg_huff_ids, k_ra8_jpeg_nibble_mask, k_ra8_jpeg_nibble_shift, k_ra8_ok, ra8_jpeg_dec_ctx_t::ncomp, RA8_PRIV, ra8_jpeg_dec_ctx_t::src, and ra8_jpeg_dec_ctx_t::src_len.

Referenced by internal_dec_dispatch_tail().

◆ priv_jpeg_sw_skip_segment()

ra8_err_t priv_jpeg_sw_skip_segment ( ra8_jpeg_dec_ctx_t * d )

Skip an unrecognized variable-length segment.

Reads the 16-bit big-endian segment length at d->cursor and advances past the payload, bounds-checked against d->src_len.

Parameters

[in,out] d Decoder context (cursor advances).

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Segment skipped.
k_ra8_err_protocol_error	Truncated / malformed length field.

Precondition: d is non-NULL with src/src_len set.; d->cursor points at a segment length field.

Postcondition: On success d->cursor advanced past the whole segment.; On error d->cursor is unspecified; the decode aborts.

Note: Not thread-safe; caller serializes via decoder context.

Since: 0.1.0

Skip an unrecognized variable-length segment.

Definition at line 54 of file ra8_jpeg_sw_decode.c.

References ra8_jpeg_dec_ctx_t::cursor, internal_read_be16(), k_ra8_err_protocol_error, k_ra8_ok, RA8_PRIV, ra8_jpeg_dec_ctx_t::src, and ra8_jpeg_dec_ctx_t::src_len.

Referenced by internal_dec_dispatch_tail().

◆ priv_jpeg_sw_ycc_to_rgb()

void priv_jpeg_sw_ycc_to_rgb	(	int32_t	y,
		int32_t	cb,
		int32_t	cr,
		uint8_t *	out_r,
		uint8_t *	out_g,
		uint8_t *	out_b )

Convert a YCbCr triple to RGB (BT.601, fixed-point).

Defined in ra8_jpeg_sw.c; the parser unit calls it from the MCU pixel-emit loop. The MVE-accelerated row helper is enabled when __ARM_FEATURE_MVE is defined; the scalar path is what host tests exercise.

Parameters

[in]	y	Luma sample.
[in]	cb	Cb chroma sample (level-offset removed inside).
[in]	cr	Cr chroma sample (level-offset removed inside).
[out]	out_r	Receives the red channel byte.
[out]	out_g	Receives the green channel byte.
[out]	out_b	Receives the blue channel byte.

Precondition: out_r, out_g, out_b are non-NULL.; y/cb/cr are valid reconstructed samples.

Postcondition: Each output byte is in 0..255.; No global state is touched.

Note: Not thread-safe unless documented otherwise.

Since: 0.1.0

MVE-accelerated path is enabled when __ARM_FEATURE_MVE is defined (Cortex-M85 target). Host tests run the scalar path.

Parameters

[in,out]	cb	See function signature.
[in,out]	cr	See function signature.
[in,out]	out_b	See function signature.
[in,out]	out_g	See function signature.
[in,out]	out_r	See function signature.
[in,out]	y	See function signature.

Precondition: Module has been initialized.; Caller has validated arguments.

Postcondition: Side effects bounded to documented state.; State reflects operation result.

Note: Not thread-safe unless documented otherwise.

Since: 0.1.0

Definition at line 402 of file ra8_jpeg_sw.c.

References internal_clamp_u8(), k_ra8_jpeg_cb_b, k_ra8_jpeg_cb_g, k_ra8_jpeg_cr_g, k_ra8_jpeg_cr_r, k_ra8_jpeg_level_offset, k_ra8_jpeg_yuv_shift, and RA8_PRIV.

Referenced by internal_dec_emit_mcu_rgb(), and internal_js_emit_mcu().

Variable Documentation

◆ s_dct_cos_q14

const int32_t s_dct_cos_q14[8][8]

static

Initial value:

                                   = {
  {16384, 16384, 16384, 16384, 16384, 16384, 16384, 16384},
  {16069, 13623, 9102, 3196, -3196, -9102, -13623, -16069},
  {15137, 6270, -6270, -15137, -15137, -6270, 6270, 15137},
  {13623, -3196, -16069, -9102, 9102, 16069, 3196, -13623},
  {11585, -11585, -11585, 11585, 11585, -11585, -11585, 11585},
  {9102, -16069, 3196, 13623, -13623, -3196, 16069, -9102},
  {6270, -15137, 15137, -6270, -6270, 15137, -15137, 6270},
  {3196, -9102, 13623, -16069, 16069, -13623, 9102, -3196},
}

Cosine table cos((2n+1)*k*pi/16) * 2^14, k = row, n = col.

Shared by both forward and inverse 1-D DCT so the encoder and decoder are guaranteed to use a numerically identical basis. Q14 picks the largest scale that lets a row sum fit in int32_t for 16-bit pre-normalized inputs. Read-only; each translation unit holds its own copy.

Definition at line 235 of file ra8_jpeg_sw_internal.h.

Referenced by internal_fwd_dct_1d_norm(), and internal_inv_dct_1d_norm().

◆ s_dct_w_q14

const int32_t s_dct_w_q14[8]

static

Initial value:

sqrt(2/N)*C(k) DCT normalization weights, Q14.

The cosine table is Q14; this sqrt(2/N)*C(k) weight is also Q14 so the inner accumulator is Q28, which the DCT row loops shift back to Q0 with a >>14 round on emit. Read-only; each translation unit holds its own copy.

Definition at line 255 of file ra8_jpeg_sw_internal.h.

Referenced by internal_fwd_dct_1d_norm(), and internal_inv_dct_1d_norm().

◆ s_zigzag

const uint8_t s_zigzag[64]

static

Initial value:

                              = {
  0,  1,  8,  16, 9,  2,  3,  10, 17, 24, 32, 25, 18, 11, 4,  5,  12, 19, 26, 33, 40, 48,
  41, 34, 27, 20, 13, 6,  7,  14, 21, 28, 35, 42, 49, 56, 57, 50, 43, 36, 29, 22, 15, 23,
  30, 37, 44, 51, 58, 59, 52, 45, 38, 31, 39, 46, 53, 60, 61, 54, 47, 55, 62, 63,
}

Zig-zag de-interleave order (T.81 Figure 5).

s_zigzag[i] returns the row-major 0..63 position that the i-th transmitted coefficient lives at inside an 8x8 block. Read-only; each translation unit holds its own copy.

Definition at line 219 of file ra8_jpeg_sw_internal.h.

Referenced by internal_dec_block_ac(), internal_enc_block(), internal_enc_emit_dqt(), and priv_jpeg_sw_parse_dqt().

Data Structures

Enumerations

Functions

Variables

Detailed Description

Enumeration Type Documentation

◆ jpeg_dsp_shift_t

◆ jpeg_enc_field_t

◆ jpeg_enc_t

◆ jpeg_marker_range_t

◆ jpeg_misc_t

◆ jpeg_ycc_coeff_t

◆ ra8_jpeg_color_coef_t

◆ ra8_jpeg_const_t

◆ ra8_jpeg_dec_marker_action_t

◆ ra8_jpeg_marker_t

◆ ra8_jpeg_shift_t

Function Documentation

◆ internal_clamp_u8()

◆ internal_read_be16()

◆ internal_write_be16()

◆ priv_jpeg_sw_block()

◆ priv_jpeg_sw_br_get_bits()

◆ priv_jpeg_sw_dispatch()

◆ priv_jpeg_sw_htab_build()

◆ priv_jpeg_sw_htab_decode()

◆ priv_jpeg_sw_huff_extend()

◆ priv_jpeg_sw_idct8x8()

◆ priv_jpeg_sw_idct_into()

◆ priv_jpeg_sw_mcu_chroma()

◆ priv_jpeg_sw_mcu_y()

◆ priv_jpeg_sw_parse_dht()

◆ priv_jpeg_sw_parse_dqt()

◆ priv_jpeg_sw_parse_sof0()

◆ priv_jpeg_sw_parse_sos()

◆ priv_jpeg_sw_skip_segment()

◆ priv_jpeg_sw_ycc_to_rgb()

Variable Documentation

◆ s_dct_cos_q14

◆ s_dct_w_q14

◆ s_zigzag