diff options
| author | Joshua Schueler <joshua.schueler@rohde-schwarz.com> | 2017-06-29 14:58:10 +0200 |
|---|---|---|
| committer | Martin Braun <martin.braun@ettus.com> | 2018-12-13 20:19:03 -0800 |
| commit | 97dff6c55c42d10ec9bc540edf959e11bb82cad8 (patch) | |
| tree | d52de344ce6568bae26cef61b7939324fe866978 /gr-dtv | |
| parent | f00e76c8b87d8b45db4e8f053658d54fb9cde0ad (diff) | |
gr-dtv: Change the layout of the ldpc table
Previous behaviour with two tables:
ldpc_encode.d has all data bits
[0, 0, 0, 0, 1, 1, 1, 1 ...]
ldpc_encode.p has the corresponding parity bits
[40, 333, 4342, 11, 231, 32, 555, 2332, ...]
the general work function iterates over both and xors each
data bit in the corresponding parity bit position.
The new algorithm uses a two-dimensional array
[ number of entries, entry1, entry2, ...
[5, 4343, 42, 2342, 42342, 244], // parity bit 0
[5, 22, 4455, 6456, 6345, 2424], // parity bit 1
...
]
This makes the general work function a bit simpler and
apparently improves the CPU caching behaviour
originally written by Team "3-QAM" @ Rohde & Schwarz Engineering
Competition 2017
Diffstat (limited to 'gr-dtv')
| -rw-r--r-- | gr-dtv/lib/dvb/dvb_ldpc_bb_impl.cc | 66 | ||||
| -rw-r--r-- | gr-dtv/lib/dvb/dvb_ldpc_bb_impl.h | 9 |
2 files changed, 49 insertions, 26 deletions
diff --git a/gr-dtv/lib/dvb/dvb_ldpc_bb_impl.cc b/gr-dtv/lib/dvb/dvb_ldpc_bb_impl.cc index 84328e1200..e907bbb499 100644 --- a/gr-dtv/lib/dvb/dvb_ldpc_bb_impl.cc +++ b/gr-dtv/lib/dvb/dvb_ldpc_bb_impl.cc @@ -364,6 +364,8 @@ namespace gr { */ dvb_ldpc_bb_impl::~dvb_ldpc_bb_impl() { + delete[] ldpc_lut[0]; + delete[] ldpc_lut; } void @@ -373,29 +375,48 @@ namespace gr { } #define LDPC_BF(TABLE_NAME, ROWS) \ +for (int row = 0; row < ROWS; row++) { /* count the entries in the table */ \ + max_lut_arraysize += TABLE_NAME[row][0]; \ +} \ +max_lut_arraysize *= 360; /* 360 bits per table entry */ \ +max_lut_arraysize /= pbits; /* spread over all parity bits */ \ +max_lut_arraysize += 2; /* 1 for the size at the start of the array, one as buffer */ \ +\ +/* Allocate a 2D Array with pbits * max_lut_arraysize + * while preserving two-subscript access + * see https://stackoverflow.com/questions/29375797/copy-2d-array-using-memcpy/29375830#29375830 + */ \ +ldpc_lut = new int*[pbits]; \ +ldpc_lut[0] = new int[pbits * max_lut_arraysize]; \ +ldpc_lut[0][0] = 1; \ +for (int i = 1; i < pbits; i++) { \ + ldpc_lut[i] = ldpc_lut[i-1] + max_lut_arraysize; \ + ldpc_lut[i][0] = 1; \ +} \ for (int row = 0; row < ROWS; row++) { \ for (int n = 0; n < 360; n++) { \ for (int col = 1; col <= TABLE_NAME[row][0]; col++) { \ - ldpc_encode.p[index] = (TABLE_NAME[row][col] + (n * q)) % pbits; \ - ldpc_encode.d[index] = im; \ - index++; \ + int current_pbit = (TABLE_NAME[row][col] + (n * q)) % pbits; \ + ldpc_lut[current_pbit][ldpc_lut[current_pbit][0]] = im; \ + ldpc_lut[current_pbit][0]++; \ } \ im++; \ } \ -} +} + /* + * fill the lookup table, for each paritybit it contains + * {number of infobits, infobit1, infobit2, ... ] + * maximum number of infobits is calculated using the entries + * in the ldpc tables + */ void dvb_ldpc_bb_impl::ldpc_lookup_generate(void) { - int im; - int index; - int pbits; - int q; - index = 0; - im = 0; - - pbits = (frame_size_real + Xp) - nbch; //number of parity bits - q = q_val; + int im = 0; + int pbits = (frame_size_real + Xp) - nbch; //number of parity bits + int q = q_val; + int max_lut_arraysize = 0; if (frame_size_type == FECFRAME_NORMAL) { if (code_rate == C1_4) { @@ -593,7 +614,6 @@ for (int row = 0; row < ROWS; row++) { \ LDPC_BF(ldpc_tab_1_3M, 30); } } - ldpc_encode.table_length = index; } int @@ -628,14 +648,20 @@ for (int row = 0; row < ROWS; row++) { \ } // First zero all the parity bits memset(p, 0, sizeof(unsigned char) * plen); - for (int j = 0; j < (int)nbch; j++) { - out[i + j] = in[consumed]; - consumed++; - } + + // copy the information bits + memcpy(&out[i], &in[consumed], sizeof(unsigned char)*nbch); + consumed += nbch; + // now do the parity checking - for (int j = 0; j < ldpc_encode.table_length; j++) { - p[ldpc_encode.p[j]] ^= d[ldpc_encode.d[j]]; + for (int i_p = 0; i_p < plen; i_p++) { + unsigned char pbit = 0; + for (int i_d = 1; i_d < ldpc_lut[i_p][0]; i_d++) { + pbit ^= d[ldpc_lut[i_p][i_d]]; + } + p[i_p] = pbit; } + if (P != 0) { puncture = 0; for (int j = 0; j < plen; j += P) { diff --git a/gr-dtv/lib/dvb/dvb_ldpc_bb_impl.h b/gr-dtv/lib/dvb/dvb_ldpc_bb_impl.h index c8f0fab698..5506411956 100644 --- a/gr-dtv/lib/dvb/dvb_ldpc_bb_impl.h +++ b/gr-dtv/lib/dvb/dvb_ldpc_bb_impl.h @@ -23,12 +23,8 @@ #include <gnuradio/dtv/dvb_ldpc_bb.h> #include "dvb_defines.h" +#include <boost/smart_ptr.hpp> -typedef struct{ - int table_length; - int d[LDPC_ENCODE_TABLE_LENGTH]; - int p[LDPC_ENCODE_TABLE_LENGTH]; -}ldpc_encode_table; namespace gr { namespace dtv { @@ -50,7 +46,8 @@ namespace gr { unsigned char puncturing_buffer[FRAME_SIZE_NORMAL]; unsigned char shortening_buffer[FRAME_SIZE_NORMAL]; void ldpc_lookup_generate(void); - ldpc_encode_table ldpc_encode; + + int** ldpc_lut; const static int ldpc_tab_1_4N[45][13]; const static int ldpc_tab_1_3N[60][13]; |