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Use pointer to generated FEC packet.

Browse Source 
Removes multiple index lookups to generated_fec_packets_ speeding up
FecTest.FecTest with >2x in both Debug and Release, improving
performance but also readability.

On Debug this means that the slowest test in modules_tests now takes
~15-20 seconds instead of 50+ seconds, reducing the overall bottleneck.

BUG=webrtc:4712
R=stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1552563003 .

Cr-Commit-Position: refs/heads/master@{#11166}
This commit is contained in:
Peter Boström
2016-01-07 15:33:49 +01:00
parent 46ea3ce580
commit 3886fc8f57
1 changed files with 26 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

52
webrtc/modules/rtp_rtcp/source/forward_error_correction.cc
View File

@ -217,6 +217,7 @@ void ForwardErrorCorrection::GenerateFecBitStrings(
kFecHeaderSize + ulp_header_size - kRtpHeaderSize;
for (int i = 0; i < num_fec_packets; ++i) {
Packet* const fec_packet = &generated_fec_packets_[i];
PacketList::const_iterator media_list_it = media_packet_list.begin();
uint32_t pkt_mask_idx = i * num_mask_bytes;
uint32_t media_pkt_idx = 0;
@ -234,42 +235,40 @@ void ForwardErrorCorrection::GenerateFecBitStrings(
fec_packet_length = media_packet->length + fec_rtp_offset;
// On the first protected packet, we don't need to XOR.
if (generated_fec_packets_[i].length == 0) {
if (fec_packet->length == 0) {
// Copy the first 2 bytes of the RTP header.
memcpy(generated_fec_packets_[i].data, media_packet->data, 2);
memcpy(fec_packet->data, media_packet->data, 2);
// Copy the 5th to 8th bytes of the RTP header.
memcpy(&generated_fec_packets_[i].data[4], &media_packet->data[4], 4);
memcpy(&fec_packet->data[4], &media_packet->data[4], 4);
// Copy network-ordered payload size.
memcpy(&generated_fec_packets_[i].data[8], media_payload_length, 2);
memcpy(&fec_packet->data[8], media_payload_length, 2);
// Copy RTP payload, leaving room for the ULP header.
memcpy(
&generated_fec_packets_[i].data[kFecHeaderSize + ulp_header_size],
&media_packet->data[kRtpHeaderSize],
media_packet->length - kRtpHeaderSize);
memcpy(&fec_packet->data[kFecHeaderSize + ulp_header_size],
&media_packet->data[kRtpHeaderSize],
media_packet->length - kRtpHeaderSize);
} else {
// XOR with the first 2 bytes of the RTP header.
generated_fec_packets_[i].data[0] ^= media_packet->data[0];
generated_fec_packets_[i].data[1] ^= media_packet->data[1];
fec_packet->data[0] ^= media_packet->data[0];
fec_packet->data[1] ^= media_packet->data[1];
// XOR with the 5th to 8th bytes of the RTP header.
for (uint32_t j = 4; j < 8; ++j) {
generated_fec_packets_[i].data[j] ^= media_packet->data[j];
fec_packet->data[j] ^= media_packet->data[j];
}
// XOR with the network-ordered payload size.
generated_fec_packets_[i].data[8] ^= media_payload_length[0];
generated_fec_packets_[i].data[9] ^= media_payload_length[1];
fec_packet->data[8] ^= media_payload_length[0];
fec_packet->data[9] ^= media_payload_length[1];
// XOR with RTP payload, leaving room for the ULP header.
for (int32_t j = kFecHeaderSize + ulp_header_size;
j < fec_packet_length; j++) {
generated_fec_packets_[i].data[j] ^=
media_packet->data[j - fec_rtp_offset];
fec_packet->data[j] ^= media_packet->data[j - fec_rtp_offset];
}
}
if (fec_packet_length > generated_fec_packets_[i].length) {
generated_fec_packets_[i].length = fec_packet_length;
if (fec_packet_length > fec_packet->length) {
fec_packet->length = fec_packet_length;
}
}
media_list_it++;
@ -281,7 +280,7 @@ void ForwardErrorCorrection::GenerateFecBitStrings(
pkt_mask_idx += media_pkt_idx / 8;
media_pkt_idx %= 8;
}
RTC_DCHECK_GT(generated_fec_packets_[i].length, 0u)
RTC_DCHECK_GT(fec_packet->length, 0u)
<< "Packet mask is wrong or poorly designed.";
}
}
@ -424,28 +423,29 @@ void ForwardErrorCorrection::GenerateFecUlpHeaders(
l_bit ? kUlpHeaderSizeLBitSet : kUlpHeaderSizeLBitClear;
for (int i = 0; i < num_fec_packets; ++i) {
Packet* const fec_packet = &generated_fec_packets_[i];
// -- FEC header --
generated_fec_packets_[i].data[0] &= 0x7f; // Set E to zero.
fec_packet->data[0] &= 0x7f; // Set E to zero.
if (l_bit == 0) {
generated_fec_packets_[i].data[0] &= 0xbf; // Clear the L bit.
fec_packet->data[0] &= 0xbf; // Clear the L bit.
} else {
generated_fec_packets_[i].data[0] |= 0x40; // Set the L bit.
fec_packet->data[0] |= 0x40; // Set the L bit.
}
// Two byte sequence number from first RTP packet to SN base.
// We use the same sequence number base for every FEC packet,
// but that's not required in general.
memcpy(&generated_fec_packets_[i].data[2], &media_packet->data[2], 2);
memcpy(&fec_packet->data[2], &media_packet->data[2], 2);
// -- ULP header --
// Copy the payload size to the protection length field.
// (We protect the entire packet.)
ByteWriter<uint16_t>::WriteBigEndian(
&generated_fec_packets_[i].data[10],
generated_fec_packets_[i].length - kFecHeaderSize - ulp_header_size);
&fec_packet->data[10],
fec_packet->length - kFecHeaderSize - ulp_header_size);
// Copy the packet mask.
memcpy(&generated_fec_packets_[i].data[12],
&packet_mask[i * num_mask_bytes], num_mask_bytes);
memcpy(&fec_packet->data[12], &packet_mask[i * num_mask_bytes],
num_mask_bytes);
}
}