Access unit queue for MediaCodecPlayer

media/base/android/access_unit_queue.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/base/android/access_unit_queue.h"
+
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "media/base/demuxer_stream.h"
+
+namespace media {
+
+namespace {
+// Amount of history chunks we keep by default. The zero size means we do not
+// keep chunks before the current one and the history is limited by the size
+// of one chunk.
+const int kDefaultHistoryChunksAmount = 0;
+}
+
+AccessUnitQueue::AccessUnitQueue()
+    : index_in_chunk_(0),
+      history_chunks_amount_(kDefaultHistoryChunksAmount),
+      has_eos_(false) {
+  current_chunk_ = chunks_.end();
+}
+
+AccessUnitQueue::~AccessUnitQueue() {
+  STLDeleteContainerPointers(chunks_.begin(), chunks_.end());
+}
+
+void AccessUnitQueue::PushBack(const DemuxerData& data) {
+  // Media thread
+  DCHECK(!data.access_units.empty());
+
+#if DCHECK_IS_ON()
+  // If there is an AU with |kConfigChanged| status, it must be the last
+  // AU in the chunk and the data should have exactly one corresponding
+  // DemuxerConfigs.
+  for (size_t i = 0; i < data.access_units.size(); ++i) {
+    const AccessUnit& unit = data.access_units[i];
+
+    // EOS must be the last unit in the chunk
+    if (unit.is_end_of_stream) {
+      DCHECK(i == data.access_units.size() - 1);
+    }
+
+    // kConfigChanged must be the last unit in the chunk.
+    if (unit.status == DemuxerStream::kConfigChanged) {
+      DCHECK(i == data.access_units.size() - 1);
+      DCHECK(data.demuxer_configs.size() == 1);
+    }
+  }
+#endif
+
+  // Ignore the input after we have received EOS.
+  if (has_eos_)
+    return;
+
+  // Create the next chunk and copy data to it.
+  DemuxerData* chunk = new DemuxerData(data);

[wolenetz, 2015/06/12 22:05:19]

aside: Is it always necessary to copy data? This could constitute some small
perf overhead. Maybe separate CL to follow-up if you see a way to
eliminate/reduce such copying.

[Tima Vaisburd, 2015/06/12 22:44:01]

Acknowledged.

+
+  // EOS flag can only be in the last access unit.
+  bool has_eos = chunk->access_units.back().is_end_of_stream;
+
+  // Append this chunk to the queue.
+  base::AutoLock lock(lock_);
+
+  bool was_empty = (current_chunk_ == chunks_.end());
+
+  // The container |chunks_| will own the chunk.
+  chunks_.push_back(chunk);
+
+  // Position the current chunk.
+  if (was_empty) {
+    current_chunk_ = --chunks_.end();
+    index_in_chunk_ = 0;
+  }
+
+  // We expect that the chunk containing EOS is the last chunk.
+  DCHECK(!has_eos_);
+  has_eos_ = has_eos;
+}
+
+void AccessUnitQueue::Advance() {
+  // Decoder thread
+  base::AutoLock lock(lock_);
+
+  if (current_chunk_ == chunks_.end())
+    return;
+
+  ++index_in_chunk_;
+  if (index_in_chunk_ < (*current_chunk_)->access_units.size())
+    return;
+
+  index_in_chunk_ = 0;
+  ++current_chunk_;
+
+  // Keep only |history_chunks_amount_| before the current one.
+

[wolenetz, 2015/06/12 22:05:19]

nit: remove empty line

[Tima Vaisburd, 2015/06/12 22:44:01]

Done.

+  // std::distance() and std::advance() do not work efficiently with std::list,
+  // but the history_size should be small (default is 0).
+  size_t num_consumed_chunks = std::distance(chunks_.begin(), current_chunk_);
+  if (num_consumed_chunks > history_chunks_amount_) {
+    DataChunkQueue::iterator first_to_keep = chunks_.begin();
+    std::advance(first_to_keep, num_consumed_chunks - history_chunks_amount_);
+    STLDeleteContainerPointers(chunks_.begin(), first_to_keep);

[wolenetz, 2015/06/12 22:05:19]

my stl-fu is failing me: does this and the following line cause double-free? (I
don't think so, but would be good to be sure...)

[wolenetz, 2015/06/12 22:17:15]

No double-free. Ignore my fu failure :)

+    chunks_.erase(chunks_.begin(), first_to_keep);
+  }
+}
+
+void AccessUnitQueue::Flush() {
+  // Media thread
+  base::AutoLock lock(lock_);
+
+  STLDeleteContainerPointers(chunks_.begin(), chunks_.end());
+  chunks_.clear();
+
+  current_chunk_ = chunks_.end();
+  index_in_chunk_ = 0;
+  has_eos_ = false;
+}
+
+bool AccessUnitQueue::RewindToLastKeyFrame() {
+  // Media thread
+  base::AutoLock lock(lock_);
+
+  // Search for the key frame backwards. Start with the current AU.
+
+  // Start with current chunk.
+  if (current_chunk_ != chunks_.end()) {
+    for (int i = (int)index_in_chunk_; i >= 0; --i) {
+      if ((*current_chunk_)->access_units[i].is_key_frame) {
+        index_in_chunk_ = i;
+        return true;
+      }
+    }
+  }
+
+  // Position reverse iterator before the current chunk.
+  DataChunkQueue::reverse_iterator rchunk(current_chunk_);
+
+  for (; rchunk != chunks_.rend(); ++rchunk) {
+    int i = (int)(*rchunk)->access_units.size() - 1;
+    for (; i >= 0; --i) {
+      if ((*rchunk)->access_units[i].is_key_frame) {
+        index_in_chunk_ = i;
+        current_chunk_ = --rchunk.base();
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+AccessUnitQueue::Info AccessUnitQueue::GetInfo() const {
+  // Media thread, Decoder thread
+
+  Info info;
+  base::AutoLock lock(lock_);
+
+  info.length = GetUnconsumedAccessUnitLength();
+  info.has_eos = has_eos_;
+  info.front_unit = nullptr;
+  info.configs = nullptr;
+
+  if (info.length > 0) {
+    DCHECK(current_chunk_ != chunks_.end());
+    DCHECK(index_in_chunk_ < (*current_chunk_)->access_units.size());
+    info.front_unit = &(*current_chunk_)->access_units[index_in_chunk_];
+
+    if (info.front_unit->status == DemuxerStream::kConfigChanged) {
+      DCHECK((*current_chunk_)->demuxer_configs.size() == 1);
+      info.configs = &(*current_chunk_)->demuxer_configs[0];
+    }
+  }
+  return info;
+}
+
+void AccessUnitQueue::SetHistorySizeForTesting(size_t history_chunks_amount) {
+  history_chunks_amount_ = history_chunks_amount;
+}
+
+int AccessUnitQueue::GetUnconsumedAccessUnitLength() const {
+  int result = 0;
+  DataChunkQueue::const_iterator chunk;
+  for (chunk = current_chunk_; chunk != chunks_.end(); ++chunk)
+    result += (*chunk)->access_units.size();
+
+  result -= index_in_chunk_;
+  return result;
+}
+
+}  // namespace media