diff options
Diffstat (limited to 'media/libaah_rtp/aah_rx_player_ring_buffer.cpp')
| -rw-r--r-- | media/libaah_rtp/aah_rx_player_ring_buffer.cpp | 366 |
1 files changed, 366 insertions, 0 deletions
diff --git a/media/libaah_rtp/aah_rx_player_ring_buffer.cpp b/media/libaah_rtp/aah_rx_player_ring_buffer.cpp new file mode 100644 index 0000000..779405e --- /dev/null +++ b/media/libaah_rtp/aah_rx_player_ring_buffer.cpp @@ -0,0 +1,366 @@ +/* + * Copyright (C) 2011 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#define LOG_TAG "LibAAH_RTP" +//#define LOG_NDEBUG 0 +#include <utils/Log.h> + +#include "aah_rx_player.h" + +namespace android { + +AAH_RXPlayer::RXRingBuffer::RXRingBuffer(uint32_t capacity) { + capacity_ = capacity; + rd_ = wr_ = 0; + ring_ = new PacketBuffer*[capacity]; + memset(ring_, 0, sizeof(PacketBuffer*) * capacity); + reset(); +} + +AAH_RXPlayer::RXRingBuffer::~RXRingBuffer() { + reset(); + delete[] ring_; +} + +void AAH_RXPlayer::RXRingBuffer::reset() { + AutoMutex lock(&lock_); + + if (NULL != ring_) { + while (rd_ != wr_) { + CHECK(rd_ < capacity_); + if (NULL != ring_[rd_]) { + PacketBuffer::destroy(ring_[rd_]); + ring_[rd_] = NULL; + } + rd_ = (rd_ + 1) % capacity_; + } + } + + rd_ = wr_ = 0; + rd_seq_known_ = false; + waiting_for_fast_start_ = true; + fetched_first_packet_ = false; + rtp_activity_timeout_valid_ = false; +} + +bool AAH_RXPlayer::RXRingBuffer::pushBuffer(PacketBuffer* buf, + uint16_t seq) { + AutoMutex lock(&lock_); + CHECK(NULL != ring_); + CHECK(NULL != buf); + + rtp_activity_timeout_valid_ = true; + rtp_activity_timeout_ = monotonicUSecNow() + kRTPActivityTimeoutUSec; + + // If the ring buffer is totally reset (we have never received a single + // payload) then we don't know the rd sequence number and this should be + // simple. We just store the payload, advance the wr pointer and record the + // initial sequence number. + if (!rd_seq_known_) { + CHECK(rd_ == wr_); + CHECK(NULL == ring_[wr_]); + CHECK(wr_ < capacity_); + + ring_[wr_] = buf; + wr_ = (wr_ + 1) % capacity_; + rd_seq_ = seq; + rd_seq_known_ = true; + return true; + } + + // Compute the seqence number of this payload and of the write pointer, + // normalized around the read pointer. IOW - transform the payload seq no + // and the wr pointer seq no into a space where the rd pointer seq no is + // zero. This will define 4 cases we can consider... + // + // 1) norm_seq == norm_wr_seq + // This payload is contiguous with the last. All is good. + // + // 2) ((norm_seq < norm_wr_seq) && (norm_seq >= norm_rd_seq) + // aka ((norm_seq < norm_wr_seq) && (norm_seq >= 0) + // This payload is in the past, in the unprocessed region of the ring + // buffer. It is probably a retransmit intended to fill in a dropped + // payload; it may be a duplicate. + // + // 3) ((norm_seq - norm_wr_seq) & 0x8000) != 0 + // This payload is in the past compared to the write pointer (or so very + // far in the future that it has wrapped the seq no space), but not in + // the unprocessed region of the ring buffer. This could be a duplicate + // retransmit; we just drop these payloads unless we are waiting for our + // first fast start packet. If we are waiting for fast start, than this + // packet is probably the first packet of the fast start retransmission. + // If it will fit in the buffer, back up the read pointer to its position + // and clear the fast start flag, otherwise just drop it. + // + // 4) ((norm_seq - norm_wr_seq) & 0x8000) == 0 + // This payload which is ahead of the next write pointer. This indicates + // that we have missed some payloads and need to request a retransmit. + // If norm_seq >= (capacity - 1), then the gap is so large that it would + // overflow the ring buffer and we should probably start to panic. + + uint16_t norm_wr_seq = ((wr_ + capacity_ - rd_) % capacity_); + uint16_t norm_seq = seq - rd_seq_; + + // Check for overflow first. + if ((!(norm_seq & 0x8000)) && (norm_seq >= (capacity_ - 1))) { + ALOGW("Ring buffer overflow; cap = %u, [rd, wr] = [%hu, %hu]," + " seq = %hu", capacity_, rd_seq_, norm_wr_seq + rd_seq_, seq); + PacketBuffer::destroy(buf); + return false; + } + + // Check for case #1 + if (norm_seq == norm_wr_seq) { + CHECK(wr_ < capacity_); + CHECK(NULL == ring_[wr_]); + + ring_[wr_] = buf; + wr_ = (wr_ + 1) % capacity_; + + CHECK(wr_ != rd_); + return true; + } + + // Check case #2 + uint32_t ring_pos = (rd_ + norm_seq) % capacity_; + if ((norm_seq < norm_wr_seq) && (!(norm_seq & 0x8000))) { + // Do we already have a payload for this slot? If so, then this looks + // like a duplicate retransmit. Just ignore it. + if (NULL != ring_[ring_pos]) { + ALOGD("RXed duplicate retransmit, seq = %hu", seq); + PacketBuffer::destroy(buf); + } else { + // Looks like we were missing this payload. Go ahead and store it. + ring_[ring_pos] = buf; + } + + return true; + } + + // Check case #3 + if ((norm_seq - norm_wr_seq) & 0x8000) { + if (!waiting_for_fast_start_) { + ALOGD("RXed duplicate retransmit from before rd pointer, seq = %hu", + seq); + PacketBuffer::destroy(buf); + } else { + // Looks like a fast start fill-in. Go ahead and store it, assuming + // that we can fit it in the buffer. + uint32_t implied_ring_size = static_cast<uint32_t>(norm_wr_seq) + + (rd_seq_ - seq); + + if (implied_ring_size >= (capacity_ - 1)) { + ALOGD("RXed what looks like a fast start packet (seq = %hu)," + " but packet is too far in the past to fit into the ring" + " buffer. Dropping.", seq); + PacketBuffer::destroy(buf); + } else { + ring_pos = (rd_ + capacity_ + seq - rd_seq_) % capacity_; + rd_seq_ = seq; + rd_ = ring_pos; + waiting_for_fast_start_ = false; + + CHECK(ring_pos < capacity_); + CHECK(NULL == ring_[ring_pos]); + ring_[ring_pos] = buf; + } + + } + return true; + } + + // Must be in case #4 with no overflow. This packet fits in the current + // ring buffer, but is discontiuguous. Advance the write pointer leaving a + // gap behind. + uint32_t gap_len = (ring_pos + capacity_ - wr_) % capacity_; + ALOGD("Drop detected; %u packets, seq_range [%hu, %hu]", + gap_len, + rd_seq_ + norm_wr_seq, + rd_seq_ + norm_wr_seq + gap_len - 1); + + CHECK(NULL == ring_[ring_pos]); + ring_[ring_pos] = buf; + wr_ = (ring_pos + 1) % capacity_; + CHECK(wr_ != rd_); + + return true; +} + +AAH_RXPlayer::PacketBuffer* +AAH_RXPlayer::RXRingBuffer::fetchBuffer(bool* is_discon) { + AutoMutex lock(&lock_); + CHECK(NULL != ring_); + CHECK(NULL != is_discon); + + // If the read seqence number is not known, then this ring buffer has not + // received a packet since being reset and there cannot be any packets to + // return. If we are still waiting for the first fast start packet to show + // up, we don't want to let any buffer be consumed yet because we expect to + // see a packet before the initial read sequence number show up shortly. + if (!rd_seq_known_ || waiting_for_fast_start_) { + *is_discon = false; + return NULL; + } + + PacketBuffer* ret = NULL; + *is_discon = !fetched_first_packet_; + + while ((rd_ != wr_) && (NULL == ret)) { + CHECK(rd_ < capacity_); + + // If we hit a gap, stall and do not advance the read pointer. Let the + // higher level code deal with requesting retries and/or deciding to + // skip the current gap. + ret = ring_[rd_]; + if (NULL == ret) { + break; + } + + ring_[rd_] = NULL; + rd_ = (rd_ + 1) % capacity_; + ++rd_seq_; + } + + if (NULL != ret) { + fetched_first_packet_ = true; + } + + return ret; +} + +AAH_RXPlayer::GapStatus +AAH_RXPlayer::RXRingBuffer::fetchCurrentGap(SeqNoGap* gap) { + AutoMutex lock(&lock_); + CHECK(NULL != ring_); + CHECK(NULL != gap); + + // If the read seqence number is not known, then this ring buffer has not + // received a packet since being reset and there cannot be any gaps. + if (!rd_seq_known_) { + return kGS_NoGap; + } + + // If we are waiting for fast start, then the current gap is a fast start + // gap and it includes all packets before the read sequence number. + if (waiting_for_fast_start_) { + gap->start_seq_ = + gap->end_seq_ = rd_seq_ - 1; + return kGS_FastStartGap; + } + + // If rd == wr, then the buffer is empty and there cannot be any gaps. + if (rd_ == wr_) { + return kGS_NoGap; + } + + // If rd_ is currently pointing at an unprocessed packet, then there is no + // current gap. + CHECK(rd_ < capacity_); + if (NULL != ring_[rd_]) { + return kGS_NoGap; + } + + // Looks like there must be a gap here. The start of the gap is the current + // rd sequence number, all we need to do now is determine its length in + // order to compute the end sequence number. + gap->start_seq_ = rd_seq_; + uint16_t end = rd_seq_; + uint32_t tmp = (rd_ + 1) % capacity_; + while ((tmp != wr_) && (NULL == ring_[tmp])) { + ++end; + tmp = (tmp + 1) % capacity_; + } + gap->end_seq_ = end; + + return kGS_NormalGap; +} + +void AAH_RXPlayer::RXRingBuffer::processNAK(const SeqNoGap* nak) { + AutoMutex lock(&lock_); + CHECK(NULL != ring_); + + // If we were waiting for our first fast start fill-in packet, and we + // received a NAK, then apparantly we are not getting our fast start. Just + // clear the waiting flag and go back to normal behavior. + if (waiting_for_fast_start_) { + waiting_for_fast_start_ = false; + } + + // If we have not received a packet since last reset, or there is no data in + // the ring, then there is nothing to skip. + if ((!rd_seq_known_) || (rd_ == wr_)) { + return; + } + + // If rd_ is currently pointing at an unprocessed packet, then there is no + // gap to skip. + CHECK(rd_ < capacity_); + if (NULL != ring_[rd_]) { + return; + } + + // Looks like there must be a gap here. Advance rd until we have passed + // over the portion of it indicated by nak (or all of the gap if nak is + // NULL). Then reset fetched_first_packet_ so that the next read will show + // up as being discontiguous. + uint16_t seq_after_gap = (NULL == nak) ? 0 : nak->end_seq_ + 1; + while ((rd_ != wr_) && + (NULL == ring_[rd_]) && + ((NULL == nak) || (seq_after_gap != rd_seq_))) { + rd_ = (rd_ + 1) % capacity_; + ++rd_seq_; + } + fetched_first_packet_ = false; +} + +int AAH_RXPlayer::RXRingBuffer::computeInactivityTimeout() { + AutoMutex lock(&lock_); + + if (!rtp_activity_timeout_valid_) { + return -1; + } + + uint64_t now = monotonicUSecNow(); + if (rtp_activity_timeout_ <= now) { + return 0; + } + + return (rtp_activity_timeout_ - now) / 1000; +} + +AAH_RXPlayer::PacketBuffer* +AAH_RXPlayer::PacketBuffer::allocate(ssize_t length) { + if (length <= 0) { + return NULL; + } + + uint32_t alloc_len = sizeof(PacketBuffer) + length; + PacketBuffer* ret = reinterpret_cast<PacketBuffer*>( + new uint8_t[alloc_len]); + + if (NULL != ret) { + ret->length_ = length; + } + + return ret; +} + +void AAH_RXPlayer::PacketBuffer::destroy(PacketBuffer* pb) { + uint8_t* kill_me = reinterpret_cast<uint8_t*>(pb); + delete[] kill_me; +} + +} // namespace android |