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This is useful to explain the various terms in the code. It took me sometime to understand the quantities and what they mean, and therefore I want to leave a version of it for future work. I will simplify the code after this.

This commit is contained in:
Aous Naman 2021-09-15 20:31:00 +10:00
parent 7bf2684cdb
commit fad594ede2
1 changed files with 59 additions and 32 deletions
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91
src/lib/openjp2/fbc_dec.c
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@ -56,14 +56,21 @@
#endif
//************************************************************************/
/** @brief Displays the error message for disabling the decoding of CUP
* pass due to insufficient precision once
/** @brief Displays the error message when 32 bits are not sufficient to
* decode any passes
*/
static OPJ_BOOL cannot_decode_due_to_insufficient_precision = OPJ_FALSE;
//************************************************************************/
/** @brief Displays the error message when we do not have enough precision
* to decode the cleanup pass and set the bin center to 1. The code can
* be modified to support this case.
*/
static OPJ_BOOL modify_code_to_support_this_precision = OPJ_FALSE;
//************************************************************************/
/** @brief Displays the error message for disabling the decoding of SPP and
* MRP passes once
* MRP passes
*/
static OPJ_BOOL cannot_decode_spp_mrp_msg = OPJ_FALSE;
@ -1070,6 +1077,7 @@ OPJ_BOOL opj_t1_ht_decode_cblk(opj_t1_t *t1,
OPJ_BYTE* cblkdata = NULL;
OPJ_UINT8* coded_data;
OPJ_UINT32* decoded_data;
OPJ_UINT32 missing_msbs;
OPJ_UINT32 num_passes;
OPJ_UINT32 lengths1;
OPJ_UINT32 lengths2;
@ -1122,6 +1130,9 @@ OPJ_BOOL opj_t1_ht_decode_cblk(opj_t1_t *t1,
return OPJ_TRUE;
}
/* Mb = Kmax, numbps = Kmax + 1 - missing_msbs */
missing_msbs = (cblk->Mb + 1) - cblk->numbps;
/* Even if we have a single chunk, in multi-threaded decoding */
/* the insertion of our synthetic marker might potentially override */
/* valid codestream of other codeblocks decoded in parallel. */
@ -1231,47 +1242,62 @@ OPJ_BOOL opj_t1_ht_decode_cblk(opj_t1_t *t1,
return OPJ_FALSE;
}
if (cblk->numbps == 1 && num_passes > 1) {
// We do not have enough precision to decode SgnProp nor MagRef passes.
// We decode the cleanup passes only
if (cannot_decode_spp_mrp_msg == OPJ_FALSE) {
if (p_manager_mutex) {
opj_mutex_lock(p_manager_mutex);
}
cannot_decode_spp_mrp_msg = OPJ_TRUE;
opj_event_msg(p_manager, EVT_WARNING, "Not enough precision to decode "
"the SgnProp nor MagRef passes. This message "
"will not be displayed again.\n");
if (p_manager_mutex) {
opj_mutex_unlock(p_manager_mutex);
}
}
num_passes = 1;
}
if (cblk->numbps == 0) {
// We do not have enough precision to decode the CUP pass with the
// center of bin bit set. The code can be modified to support this
// case, without using the center of the bin.
if (missing_msbs > 30) {
/* We do not have enough precision to decode any passes */
if (cannot_decode_due_to_insufficient_precision == OPJ_FALSE) {
if (p_manager_mutex) {
opj_mutex_lock(p_manager_mutex);
}
cannot_decode_due_to_insufficient_precision = OPJ_TRUE;
opj_event_msg(p_manager, EVT_WARNING, "Not enough precision to decode "
"the cleanup pass. The code should be "
"modified to support this case. This message "
opj_event_msg(p_manager, EVT_ERROR, "32 bits are not enough to "
"decode this codeblock. This message "
"will not be displayed again.\n");
if (p_manager_mutex) {
opj_mutex_unlock(p_manager_mutex);
}
}
return OPJ_TRUE;
return OPJ_FALSE;
} else if (missing_msbs == 30) {
/* We do not have enough precision to decode the CUP pass with the
center of bin bit set. The code can be modified to support this
case, where we do not set the center of the bin. */
if (modify_code_to_support_this_precision == OPJ_FALSE) {
if (p_manager_mutex) {
opj_mutex_lock(p_manager_mutex);
}
modify_code_to_support_this_precision = OPJ_TRUE;
opj_event_msg(p_manager, EVT_ERROR, "Not enough precision to decode "
"the cleanup pass. The code can be modified to "
"support this case. This message will not be "
"displayed again.\n");
if (p_manager_mutex) {
opj_mutex_unlock(p_manager_mutex);
}
}
return OPJ_FALSE;
} else if (missing_msbs == 29) { /* if p is 1, then num_passes must be 1 */
if (num_passes > 1) {
num_passes = 1;
if (cannot_decode_spp_mrp_msg == OPJ_FALSE) {
if (p_manager_mutex) {
opj_mutex_lock(p_manager_mutex);
}
cannot_decode_spp_mrp_msg = OPJ_TRUE;
opj_event_msg(p_manager, EVT_WARNING, "Not enough precision to decode "
"the SgnProp nor MagRef passes, which will be skipped. "
"This message will not be displayed again.\n");
if (p_manager_mutex) {
opj_mutex_unlock(p_manager_mutex);
}
}
}
}
// OPJ_UINT32
p = cblk->numbps;
/* OPJ_UINT32 */
p = 30 - missing_msbs;
// OPJ_UINT32 zero planes plus 1
zero_planes_p1 = cblk->Mb - cblk->numbps + 1;
zero_planes_p1 = missing_msbs + 1;
// read scup and fix the bytes there
lcup = (int)lengths1; // length of CUP
@ -2502,10 +2528,11 @@ OPJ_BOOL opj_t1_ht_decode_cblk(opj_t1_t *t1,
{
OPJ_INT32 x, y;
OPJ_UINT32 shift = 29u - cblk->Mb;
for (y = 0; y < height; ++y) {
OPJ_INT32* sp = (OPJ_INT32*)decoded_data + y * stride;
for (x = 0; x < width; ++x, ++sp) {
OPJ_INT32 val = (*sp & 0x7FFFFFFF);
OPJ_INT32 val = (*sp & 0x7FFFFFFF) >> shift;
*sp = ((OPJ_UINT32) * sp & 0x80000000) ? -val : val;
}
}