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fec: simplify fec generation

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since the fec packets are initialized to 0 there is no need
to special-case the first packet since
  A XOR 0
is the identity operator.

BUG=None

Change-Id: I0cb55283ecdca06f8e3a7b5856ec1f9fbbad1ffb
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/251522
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37378}
This commit is contained in:
Philipp Hancke
2022-02-10 20:02:10 +01:00
committed by WebRTC LUCI CQ
parent 42b163f236
commit fb60796b64
1 changed files with 3 additions and 22 deletions
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25
modules/rtp_rtcp/source/forward_error_correction.cc
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@ -218,13 +218,11 @@ void ForwardErrorCorrection::GenerateFecPayloads(
ParseSequenceNumber((*media_packets_it)->data.data());
while (media_packets_it != media_packets.end()) {
Packet* const media_packet = media_packets_it->get();
const uint8_t* media_packet_data = media_packet->data.cdata();
// Should `media_packet` be protected by `fec_packet`?
if (packet_masks_[pkt_mask_idx] & (1 << (7 - media_pkt_idx))) {
size_t media_payload_length =
media_packet->data.size() - kRtpHeaderSize;
bool first_protected_packet = (fec_packet->data.size() == 0);
size_t fec_packet_length = fec_header_size + media_payload_length;
if (fec_packet_length > fec_packet->data.size()) {
// Recall that XORing with zero (which the FEC packets are prefilled
@ -232,26 +230,9 @@ void ForwardErrorCorrection::GenerateFecPayloads(
// still correct even though we expand the packet length here.
fec_packet->data.SetSize(fec_packet_length);
}
if (first_protected_packet) {
uint8_t* data = fec_packet->data.MutableData();
// Write P, X, CC, M, and PT recovery fields.
// Note that bits 0, 1, and 16 are overwritten in FinalizeFecHeaders.
memcpy(&data[0], &media_packet_data[0], 2);
// Write length recovery field. (This is a temporary location for
// ULPFEC.)
ByteWriter<uint16_t>::WriteBigEndian(&data[2], media_payload_length);
// Write timestamp recovery field.
memcpy(&data[4], &media_packet_data[4], 4);
// Write payload.
if (media_payload_length > 0) {
memcpy(&data[fec_header_size], &media_packet_data[kRtpHeaderSize],
media_payload_length);
}
} else {
XorHeaders(*media_packet, fec_packet);
XorPayloads(*media_packet, media_payload_length, fec_header_size,
fec_packet);
}
XorHeaders(*media_packet, fec_packet);
XorPayloads(*media_packet, media_payload_length, fec_header_size,
fec_packet);
}
media_packets_it++;
if (media_packets_it != media_packets.end()) {