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Optimize FindNaluIndices

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We can add i by 3 even if it's not 001, because in any xx1 combination, 1 could not be part of start code.

Bug: None
Change-Id: Ica653d9e49b9f7c665027b9cf4453753c5fdd3ed
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159721
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30064}
This commit is contained in:
Piasy
2019-11-29 21:35:19 +08:00
committed by Commit Bot
parent 1154915024
commit 75bc75ccef
1 changed files with 14 additions and 10 deletions
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24
common_video/h264/h264_common.cc
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@ -27,22 +27,26 @@ std::vector<NaluIndex> FindNaluIndices(const uint8_t* buffer,
if (buffer_size < kNaluShortStartSequenceSize)
return sequences;
static_assert(kNaluShortStartSequenceSize >= 2,
"kNaluShortStartSequenceSize must be larger or equals to 2");
const size_t end = buffer_size - kNaluShortStartSequenceSize;
for (size_t i = 0; i < end;) {
if (buffer[i + 2] > 1) {
i += 3;
} else if (buffer[i + 2] == 1 && buffer[i + 1] == 0 && buffer[i] == 0) {
// We found a start sequence, now check if it was a 3 of 4 byte one.
NaluIndex index = {i, i + 3, 0};
if (index.start_offset > 0 && buffer[index.start_offset - 1] == 0)
--index.start_offset;
} else if (buffer[i + 2] == 1) {
if (buffer[i + 1] == 0 && buffer[i] == 0) {
// We found a start sequence, now check if it was a 3 of 4 byte one.
NaluIndex index = {i, i + 3, 0};
if (index.start_offset > 0 && buffer[index.start_offset - 1] == 0)
--index.start_offset;
// Update length of previous entry.
auto it = sequences.rbegin();
if (it != sequences.rend())
it->payload_size = index.start_offset - it->payload_start_offset;
// Update length of previous entry.
auto it = sequences.rbegin();
if (it != sequences.rend())
it->payload_size = index.start_offset - it->payload_start_offset;
sequences.push_back(index);
sequences.push_back(index);
}
i += 3;
} else {