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[core] Use SND buffer delay for TL Packet Drop instead of the timespan #2230

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Jan 24, 2022
Merged

[core] Use SND buffer delay for TL Packet Drop instead of the timespan #2230

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dc31bd0
[core] Use SND buffer delay for TL Packet Drop
maxsharabayko Jan 21, 2022
8d99e1c
[core] Added missing lock to CSndBuffer::readData
maxsharabayko Jan 21, 2022
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9 changes: 7 additions & 2 deletions srtcore/buffer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -402,6 +402,7 @@ int CSndBuffer::readData(CPacket& w_packet, steady_clock::time_point& w_srctime,
int readlen = 0;
w_seqnoinc = 0;

ScopedLock bufferguard(m_BufLock);
while (m_pCurrBlock != m_pLastBlock)
{
// Make the packet REFLECT the data stored in the buffer.
Expand Down Expand Up @@ -686,10 +687,14 @@ int CSndBuffer::getCurrBufSize(int& w_bytes, int& w_timespan)
return m_iCount;
}

CSndBuffer::time_point CSndBuffer::getOldestTime() const
CSndBuffer::duration CSndBuffer::getBufferingDelay(const time_point& tnow) const
{
ScopedLock lck(m_BufLock);
SRT_ASSERT(m_pFirstBlock);
return m_pFirstBlock->m_tsOriginTime;
if (m_iCount == 0)
return duration(0);

return tnow - m_pFirstBlock->m_tsOriginTime;
}

int CSndBuffer::dropLateData(int& w_bytes, int32_t& w_first_msgno, const steady_clock::time_point& too_late_time)
Expand Down
15 changes: 12 additions & 3 deletions srtcore/buffer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -133,12 +133,14 @@ class CSndBuffer
/// @param [in] data pointer to the user data block.
/// @param [in] len size of the block.
/// @param [inout] w_mctrl Message control data
SRT_ATTR_EXCLUDES(m_BufLock)
void addBuffer(const char* data, int len, SRT_MSGCTRL& w_mctrl);

/// Read a block of data from file and insert it into the sending list.
/// @param [in] ifs input file stream.
/// @param [in] len size of the block.
/// @return actual size of data added from the file.
SRT_ATTR_EXCLUDES(m_BufLock)
int addBufferFromFile(std::fstream& ifs, int len);

/// Find data position to pack a DATA packet from the furthest reading point.
Expand All @@ -147,6 +149,7 @@ class CSndBuffer
/// @param [in] kflags Odd|Even crypto key flag
/// @param [out] seqnoinc the number of packets skipped due to TTL, so that seqno should be incremented.
/// @return Actual length of data read.
SRT_ATTR_EXCLUDES(m_BufLock)
int readData(CPacket& w_packet, time_point& w_origintime, int kflgs, int& w_seqnoinc);

/// Find data position to pack a DATA packet for a retransmission.
Expand All @@ -155,12 +158,14 @@ class CSndBuffer
/// @param [out] origintime origin time stamp of the message
/// @param [out] msglen length of the message
/// @return Actual length of data read (return 0 if offset too large, -1 if TTL exceeded).
SRT_ATTR_EXCLUDES(m_BufLock)
int readData(const int offset, CPacket& w_packet, time_point& w_origintime, int& w_msglen);

/// Get the time of the last retransmission (if any) of the DATA packet.
/// @param [in] offset offset from the last ACK point (backward sequence number difference)
///
/// @return Last time of the last retransmission event for the corresponding DATA packet.
SRT_ATTR_EXCLUDES(m_BufLock)
time_point getPacketRexmitTime(const int offset);

/// Update the ACK point and may release/unmap/return the user data according to the flag.
Expand All @@ -173,13 +178,17 @@ class CSndBuffer
/// @return Current size of the data in the sending list.
int getCurrBufSize() const;

SRT_ATTR_EXCLUDES(m_BufLock)
int dropLateData(int& bytes, int32_t& w_first_msgno, const time_point& too_late_time);

void updAvgBufSize(const time_point& time);
int getAvgBufSize(int& bytes, int& timespan);
int getCurrBufSize(int& bytes, int& timespan);

time_point getOldestTime() const;
/// @brief Get the buffering delay of the oldest message in the buffer.
/// @return the delay value.
SRT_ATTR_EXCLUDES(m_BufLock)
duration getBufferingDelay(const time_point& tnow) const;

uint64_t getInRatePeriod() const { return m_InRatePeriod; }

Expand Down Expand Up @@ -207,7 +216,7 @@ class CSndBuffer
static const int INPUTRATE_INITIAL_BYTESPS = BW_INFINITE;

private:
sync::Mutex m_BufLock; // used to synchronize buffer operation
mutable sync::Mutex m_BufLock; // used to synchronize buffer operation

struct Block
{
Expand All @@ -216,7 +225,7 @@ class CSndBuffer

int32_t m_iMsgNoBitset; // message number
int32_t m_iSeqNo; // sequence number for scheduling
time_point m_tsOriginTime; // block origin time (either provided from above or equials the time a message was submitted for sending.
time_point m_tsOriginTime; // block origin time (either provided from above or equals the time a message was submitted for sending.
time_point m_tsRexmitTime; // packet retransmission time
int m_iTTL; // time to live (milliseconds)

Expand Down
25 changes: 11 additions & 14 deletions srtcore/core.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6338,31 +6338,28 @@ bool srt::CUDT::checkNeedDrop()
throw CUDTException(MJ_NOTSUP, MN_INVALBUFFERAPI, 0);
}

int bytes, timespan_ms;
// (returns buffer size in buffer units, ignored)
m_pSndBuffer->getCurrBufSize((bytes), (timespan_ms));
const time_point tnow = steady_clock::now();
const int buffdelay_ms = count_milliseconds(m_pSndBuffer->getBufferingDelay(tnow));

// high threshold (msec) at tsbpd_delay plus sender/receiver reaction time (2 * 10ms)
// Minimum value must accomodate an I-Frame (~8 x average frame size)
// >>need picture rate or app to set min treshold
// >>using 1 sec for worse case 1 frame using all bit budget.
// picture rate would be useful in auto SRT setting for min latency
// XXX Make SRT_TLPKTDROP_MINTHRESHOLD_MS option-configurable
int threshold_ms = 0;
if (m_config.iSndDropDelay >= 0)
{
threshold_ms = std::max(m_iPeerTsbPdDelay_ms + m_config.iSndDropDelay, +SRT_TLPKTDROP_MINTHRESHOLD_MS) +
(2 * COMM_SYN_INTERVAL_US / 1000);
}
const int threshold_ms = (m_config.iSndDropDelay >= 0)
? std::max(m_iPeerTsbPdDelay_ms + m_config.iSndDropDelay, +SRT_TLPKTDROP_MINTHRESHOLD_MS)
+ (2 * COMM_SYN_INTERVAL_US / 1000)
: 0;

bool bCongestion = false;
if (threshold_ms && timespan_ms > threshold_ms)
if (threshold_ms && buffdelay_ms > threshold_ms)
{
// protect packet retransmission
enterCS(m_RecvAckLock);
int dbytes;
int32_t first_msgno;
int dpkts = m_pSndBuffer->dropLateData((dbytes), (first_msgno), steady_clock::now() - milliseconds_from(threshold_ms));
int dpkts = m_pSndBuffer->dropLateData((dbytes), (first_msgno), tnow - milliseconds_from(threshold_ms));
if (dpkts > 0)
{
enterCS(m_StatsLock);
Expand All @@ -6385,7 +6382,7 @@ bool srt::CUDT::checkNeedDrop()
}

HLOGC(aslog.Debug, log << "SND-DROP: %(" << realack << "-" << m_iSndCurrSeqNo << ") n="
<< dpkts << "pkt " << dbytes << "B, span=" << timespan_ms << " ms, FIRST #" << first_msgno);
<< dpkts << "pkt " << dbytes << "B, span=" << buffdelay_ms << " ms, FIRST #" << first_msgno);

#if ENABLE_EXPERIMENTAL_BONDING
// This is done with a presumption that the group
Expand Down Expand Up @@ -6413,10 +6410,10 @@ bool srt::CUDT::checkNeedDrop()
bCongestion = true;
leaveCS(m_RecvAckLock);
}
else if (timespan_ms > (m_iPeerTsbPdDelay_ms / 2))
else if (buffdelay_ms > (m_iPeerTsbPdDelay_ms / 2))
{
HLOGC(aslog.Debug,
log << "cong, BYTES " << bytes << ", TMSPAN " << timespan_ms << "ms");
log << "cong TIMESPAN " << buffdelay_ms << "ms");

bCongestion = true;
}
Expand Down