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ORAN: Decompress block floating point numbers (used in ext11).

This commit is contained in:
Martin Mathieson 2021-08-19 15:25:44 +01:00
parent 8bcd077eb0
commit 82b1092fe9
1 changed files with 53 additions and 15 deletions
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68
epan/dissectors/packet-oran.c
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@ -487,7 +487,8 @@ addSeqid(tvbuff_t *tvb, proto_tree *oran_tree, gint *offset)
proto_item_append_text(seqIdItem, ", SeqId: %d, SubSeqId: %d, E: %d", seqId, subSeqId, e); proto_item_append_text(seqIdItem, ", SeqId: %d, SubSeqId: %d, E: %d", seqId, subSeqId, e);
} }
static float scale_to_float(guint32 h) /* Special case for uncompressed/16-bit value */
static float uncompressed_to_float(guint32 h)
{ {
gint16 i16 = h & 0x0000ffff; gint16 i16 = h & 0x0000ffff;
return ((float)i16) / 0x7fff; return ((float)i16) / 0x7fff;
@ -506,26 +507,28 @@ static int dissect_bfwCompHdr(tvbuff_t *tvb, proto_tree *tree, gint offset,
/* Fields present (if any) depend upon passed-in bfwCompMeth */ /* Fields present (if any) depend upon passed-in bfwCompMeth */
static int dissect_bfwCompParam(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, gint offset, static int dissect_bfwCompParam(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, gint offset,
proto_item *ti, guint32 bfwcomphdr_comp_method, gboolean *supported) proto_item *ti, guint32 bfwcomphdr_comp_method,
guint32 *exponent, gboolean *supported)
{ {
*supported = FALSE; *supported = FALSE;
switch (bfwcomphdr_comp_method) { switch (bfwcomphdr_comp_method) {
case 0: /* no compression */ case COMP_NONE:
/* In this case, bfwCompParam is absent */ /* In this case, bfwCompParam is absent */
*supported = TRUE; *supported = TRUE;
break; break;
case 1: /* block fl. point */ case COMP_BLOCK_FP:
/* 4 reserved bits + exponent */ /* 4 reserved bits + exponent */
proto_tree_add_item(tree, hf_oran_exponent, proto_tree_add_item_ret_uint(tree, hf_oran_exponent,
tvb, offset, 1, ENC_BIG_ENDIAN); tvb, offset, 1, ENC_BIG_ENDIAN, exponent);
*supported = TRUE;
offset++; offset++;
break; break;
case 2: /* block scaling */ case COMP_BLOCK_SCALE:
proto_tree_add_item(tree, hf_oran_blockScaler, proto_tree_add_item(tree, hf_oran_blockScaler,
tvb, offset, 1, ENC_BIG_ENDIAN); tvb, offset, 1, ENC_BIG_ENDIAN);
offset++; offset++;
break; break;
case 3: /* u-law */ case COMP_U_LAW:
/* compBitWidth, compShift */ /* compBitWidth, compShift */
proto_tree_add_item(tree, hf_oran_compBitWidth, proto_tree_add_item(tree, hf_oran_compBitWidth,
tvb, offset, 1, ENC_BIG_ENDIAN); tvb, offset, 1, ENC_BIG_ENDIAN);
@ -533,7 +536,7 @@ static int dissect_bfwCompParam(tvbuff_t *tvb, proto_tree *tree, packet_info *pi
tvb, offset, 1, ENC_BIG_ENDIAN); tvb, offset, 1, ENC_BIG_ENDIAN);
offset++; offset++;
break; break;
case 4: /* beamspace */ case COMP_MODULATION: /* beamspace */
/* TODO: activeBeamspaceCoefficientMask - ceil(K/8) octets */ /* TODO: activeBeamspaceCoefficientMask - ceil(K/8) octets */
/* proto_tree_add_item(extension_tree, hf_oran_blockScaler, /* proto_tree_add_item(extension_tree, hf_oran_blockScaler,
tvb, offset, 1, ENC_BIG_ENDIAN); tvb, offset, 1, ENC_BIG_ENDIAN);
@ -554,6 +557,38 @@ static int dissect_bfwCompParam(tvbuff_t *tvb, proto_tree *tree, packet_info *pi
return offset; return offset;
} }
static gfloat decompress_value(guint32 bits, guint32 comp_method, guint8 iq_width _U_, guint32 exponent)
{
switch (comp_method) {
case COMP_NONE: /* no compression */
return uncompressed_to_float(bits);
case COMP_BLOCK_FP: /* block floating point */
{
/* A.1.2 Block Floating Point Decompression Algorithm */
gint32 cPRB = bits;
guint32 scaler = 2 << (exponent-1); /* i.e. 2^exponent */
/* Check last bit, in case we need to flip to -ve */
if (cPRB >= (1<<(iq_width-1))) {
cPRB -= (1<<iq_width);
}
const guint8 mantissa_bits = iq_width-1;
return (cPRB / (gfloat)(1 << (15+mantissa_bits))) * scaler;
}
case COMP_BLOCK_SCALE:
case COMP_U_LAW:
case COMP_MODULATION:
default:
/* Not supported! */
return 0.0;
}
}
#define ORPHAN_BUNDLE_NUMBER 999 #define ORPHAN_BUNDLE_NUMBER 999
static guint32 dissect_bfw_bundle(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint offset, static guint32 dissect_bfw_bundle(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint offset,
@ -563,8 +598,9 @@ static guint32 dissect_bfw_bundle(tvbuff_t *tvb, proto_tree *tree, packet_info *
{ {
/* bfwCompParam */ /* bfwCompParam */
gboolean compression_method_supported = FALSE; gboolean compression_method_supported = FALSE;
guint32 exponent = 0;
offset = dissect_bfwCompParam(tvb, tree, pinfo, offset, comp_meth_ti, offset = dissect_bfwCompParam(tvb, tree, pinfo, offset, comp_meth_ti,
bfwcomphdr_comp_meth, &compression_method_supported); bfwcomphdr_comp_meth, &exponent, &compression_method_supported);
/* Can't show details of unsupported compression method */ /* Can't show details of unsupported compression method */
if (!compression_method_supported) { if (!compression_method_supported) {
@ -618,7 +654,8 @@ static guint32 dissect_bfw_bundle(tvbuff_t *tvb, proto_tree *tree, packet_info *
/* I */ /* I */
/* Get bits, and convert to float. */ /* Get bits, and convert to float. */
guint32 bits = tvb_get_bits(tvb, bit_offset, iq_width, ENC_BIG_ENDIAN); guint32 bits = tvb_get_bits(tvb, bit_offset, iq_width, ENC_BIG_ENDIAN);
gfloat value = scale_to_float(bits); gfloat value = decompress_value(bits, bfwcomphdr_comp_meth, iq_width, exponent);
/* Add to tree. */ /* Add to tree. */
proto_tree_add_float_format_value(bfw_tree, hf_oran_bfw_i, tvb, bit_offset/8, (iq_width+7)/8, value, "#%u=%f", m, value); proto_tree_add_float_format_value(bfw_tree, hf_oran_bfw_i, tvb, bit_offset/8, (iq_width+7)/8, value, "#%u=%f", m, value);
bit_offset += iq_width; bit_offset += iq_width;
@ -627,7 +664,7 @@ static guint32 dissect_bfw_bundle(tvbuff_t *tvb, proto_tree *tree, packet_info *
/* Q */ /* Q */
/* Get bits, and convert to float. */ /* Get bits, and convert to float. */
bits = tvb_get_bits(tvb, bit_offset, iq_width, ENC_BIG_ENDIAN); bits = tvb_get_bits(tvb, bit_offset, iq_width, ENC_BIG_ENDIAN);
value = scale_to_float(bits); value = decompress_value(bits, bfwcomphdr_comp_meth, iq_width, exponent);
/* Add to tree. */ /* Add to tree. */
proto_tree_add_float_format_value(bfw_tree, hf_oran_bfw_q, tvb, bit_offset/8, (iq_width+7)/8, value, "#%u=%f", m, value); proto_tree_add_float_format_value(bfw_tree, hf_oran_bfw_q, tvb, bit_offset/8, (iq_width+7)/8, value, "#%u=%f", m, value);
bit_offset += iq_width; bit_offset += iq_width;
@ -801,9 +838,10 @@ static int dissect_oran_c_section(tvbuff_t *tvb, proto_tree *tree, packet_info *
} }
/* bfwCompParam */ /* bfwCompParam */
guint32 exponent = 0;
gboolean compression_method_supported = FALSE; gboolean compression_method_supported = FALSE;
offset = dissect_bfwCompParam(tvb, extension_tree, pinfo, offset, comp_meth_ti, offset = dissect_bfwCompParam(tvb, extension_tree, pinfo, offset, comp_meth_ti,
bfwcomphdr_comp_meth, &compression_method_supported); bfwcomphdr_comp_meth, &exponent, &compression_method_supported);
/* Can't show details of unsupported compression method */ /* Can't show details of unsupported compression method */
if (!compression_method_supported) { if (!compression_method_supported) {
@ -841,7 +879,7 @@ static int dissect_oran_c_section(tvbuff_t *tvb, proto_tree *tree, packet_info *
for (guint m=0; m < pref_num_bf_weights; m++) { for (guint m=0; m < pref_num_bf_weights; m++) {
/* Get bits, and convert to float. */ /* Get bits, and convert to float. */
guint32 bits = tvb_get_bits(tvb, bit_offset, iq_width, ENC_BIG_ENDIAN); guint32 bits = tvb_get_bits(tvb, bit_offset, iq_width, ENC_BIG_ENDIAN);
gfloat value = scale_to_float(bits); gfloat value = uncompressed_to_float(bits);
/* Add to tree. */ /* Add to tree. */
proto_tree_add_float_format_value(bfw_tree, hf_oran_bfw_i, tvb, bit_offset/8, (iq_width+7)/8, value, "#%u=%f", m, value); proto_tree_add_float_format_value(bfw_tree, hf_oran_bfw_i, tvb, bit_offset/8, (iq_width+7)/8, value, "#%u=%f", m, value);
bit_offset += iq_width; bit_offset += iq_width;
@ -855,7 +893,7 @@ static int dissect_oran_c_section(tvbuff_t *tvb, proto_tree *tree, packet_info *
for (guint m=0; m < pref_num_bf_weights; m++) { for (guint m=0; m < pref_num_bf_weights; m++) {
/* Get bits, and convert to float. */ /* Get bits, and convert to float. */
guint32 bits = tvb_get_bits(tvb, bit_offset, iq_width, ENC_BIG_ENDIAN); guint32 bits = tvb_get_bits(tvb, bit_offset, iq_width, ENC_BIG_ENDIAN);
gfloat value = scale_to_float(bits); gfloat value = uncompressed_to_float(bits);
/* Add to tree. */ /* Add to tree. */
proto_tree_add_float_format_value(bfw_tree, hf_oran_bfw_q, tvb, bit_offset/8, (iq_width+7)/8, value, "#%u=%f", m, value); proto_tree_add_float_format_value(bfw_tree, hf_oran_bfw_q, tvb, bit_offset/8, (iq_width+7)/8, value, "#%u=%f", m, value);
bit_offset += iq_width; bit_offset += iq_width;