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Add comments about non successfull attempt of implementing alternate INITDEC, DECODE and BYTEIN procedures (refs #921)

This commit is contained in:
Even Rouault 2017-05-15 14:09:51 +02:00
parent f7a126af61
commit 4431fa7265
2 changed files with 13 additions and 0 deletions
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5
src/lib/openjp2/mqc.c
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@ -448,6 +448,11 @@ void opj_mqc_segmark_enc(opj_mqc_t *mqc)
OPJ_BOOL opj_mqc_init_dec(opj_mqc_t *mqc, OPJ_BYTE *bp, OPJ_UINT32 len) OPJ_BOOL opj_mqc_init_dec(opj_mqc_t *mqc, OPJ_BYTE *bp, OPJ_UINT32 len)
{ {
/* Implements ISO 15444-1 C.3.5 Initialization of the decoder (INITDEC) */
/* Note: alternate "J.1 - Initialization of the software-conventions */
/* decoder" has been tried, but does */
/* not bring any improvement. */
/* See https://github.com/uclouvain/openjpeg/issues/921 */
opj_mqc_setcurctx(mqc, 0); opj_mqc_setcurctx(mqc, 0);
mqc->start = bp; mqc->start = bp;
mqc->end = bp + len; mqc->end = bp + len;

8
src/lib/openjp2/mqc_inl.h
View File

@ -93,6 +93,10 @@ static INLINE void opj_mqc_bytein(opj_mqc_t *const mqc)
#else #else
static INLINE void opj_mqc_bytein(opj_mqc_t *const mqc) static INLINE void opj_mqc_bytein(opj_mqc_t *const mqc)
{ {
/* Implements ISO 15444-1 C.3.4 Compressed image data input (BYTEIN) */
/* Note: alternate "J.3 - Inserting a new byte into the C register in the */
/* software-conventions decoder" has been tried, but does not bring any */
/* improvement. See https://github.com/uclouvain/openjpeg/issues/921 */
if (mqc->bp != mqc->end) { if (mqc->bp != mqc->end) {
OPJ_UINT32 c; OPJ_UINT32 c;
if (mqc->bp + 1 != mqc->end) { if (mqc->bp + 1 != mqc->end) {
@ -144,6 +148,10 @@ Decode a symbol
*/ */
static INLINE OPJ_INT32 opj_mqc_decode(opj_mqc_t *const mqc) static INLINE OPJ_INT32 opj_mqc_decode(opj_mqc_t *const mqc)
{ {
/* Implements ISO 15444-1 C.3.2 Decoding a decision (DECODE) */
/* Note: alternate "J.2 - Decoding an MPS or an LPS in the */
/* software-conventions decoder" has been tried, but does not bring any */
/* improvement. See https://github.com/uclouvain/openjpeg/issues/921 */
OPJ_INT32 d; OPJ_INT32 d;
mqc->a -= (*mqc->curctx)->qeval; mqc->a -= (*mqc->curctx)->qeval;
if ((mqc->c >> 16) < (*mqc->curctx)->qeval) { if ((mqc->c >> 16) < (*mqc->curctx)->qeval) {