media/formats/mp2t/es_adapter_video.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/formats/mp2t/es_adapter_video.h"
   6
   7 #include "media/base/buffers.h"
   8 #include "media/base/video_decoder_config.h"
   9 #include "media/formats/mp2t/mp2t_common.h"
  10
  11 namespace media {
  12 namespace mp2t {
  13
  14 // Arbitrary decision about the frame duration when there is no previous
  15 // hint about what could be the frame duration.
  16 static const int kDefaultFrameDurationMs = 40;
  17
  18 // To calculate the frame duration, we make an assumption
  19 // that the timestamp of the next frame in presentation order
  20 // is no further than 5 frames away in decode order.
  21 // TODO(damienv): the previous assumption should cover most of the practical
  22 // cases. However, the right way to calculate the frame duration would be
  23 // to emulate the H264 dpb bumping process.
  24 static const size_t kHistorySize = 5;
  25
  26 EsAdapterVideo::EsAdapterVideo(
  27     const NewVideoConfigCB& new_video_config_cb,
  28     const EmitBufferCB& emit_buffer_cb)
  29     : new_video_config_cb_(new_video_config_cb),
  30       emit_buffer_cb_(emit_buffer_cb),
  31       has_valid_config_(false),
  32       has_valid_frame_(false),
  33       last_frame_duration_(
  34           base::TimeDelta::FromMilliseconds(kDefaultFrameDurationMs)),
  35       buffer_index_(0),
  36       has_valid_initial_timestamp_(false),
  37       discarded_frame_count_(0) {
  38 }
  39
  40 EsAdapterVideo::~EsAdapterVideo() {
  41 }
  42
  43 void EsAdapterVideo::Flush() {
  44   ProcessPendingBuffers(true);
  45 }
  46
  47 void EsAdapterVideo::Reset() {
  48   has_valid_config_ = false;
  49   has_valid_frame_ = false;
  50
  51   last_frame_duration_ =
  52       base::TimeDelta::FromMilliseconds(kDefaultFrameDurationMs);
  53
  54   config_list_.clear();
  55   buffer_index_ = 0;
  56   buffer_list_.clear();
  57   emitted_pts_.clear();
  58
  59   has_valid_initial_timestamp_ = false;
  60   min_pts_ = base::TimeDelta();
  61   min_dts_ = DecodeTimestamp();
  62
  63   discarded_frame_count_ = 0;
  64 }
  65
  66 void EsAdapterVideo::OnConfigChanged(
  67     const VideoDecoderConfig& video_decoder_config) {
  68   config_list_.push_back(
  69       ConfigEntry(buffer_index_ + buffer_list_.size(), video_decoder_config));
  70   has_valid_config_ = true;
  71   ProcessPendingBuffers(false);
  72 }
  73
  74 bool EsAdapterVideo::OnNewBuffer(
  75     const scoped_refptr<StreamParserBuffer>& stream_parser_buffer) {
  76   if (stream_parser_buffer->timestamp() == kNoTimestamp()) {
  77     if (has_valid_frame_) {
  78       // There is currently no error concealment for a missing timestamp
  79       // in the middle of the stream.
  80       DVLOG(1) << "Missing timestamp in the middle of the stream";
  81       return false;
  82     }
  83
  84     if (!has_valid_initial_timestamp_) {
  85       // MPEG-2 TS requires the first access unit to be given a timestamp.
  86       // However, some streams do not comply with this requirement.
  87       // So simply drop the frame if it is a leading frame with no timestamp.
  88       DVLOG(1)
  89           << "Stream not compliant: ignoring leading frame with no timestamp";
  90       return true;
  91     }
  92
  93     // In all the other cases, this frame will be replaced by the following
  94     // valid key frame, using timestamp interpolation.
  95     DCHECK(has_valid_initial_timestamp_);
  96     DCHECK_GE(discarded_frame_count_, 1);
  97     discarded_frame_count_++;
  98     return true;
  99   }
 100
 101   // At this point, timestamps of the incoming frame are valid.
 102   if (!has_valid_initial_timestamp_) {
 103     min_pts_ = stream_parser_buffer->timestamp();
 104     min_dts_ = stream_parser_buffer->GetDecodeTimestamp();
 105     has_valid_initial_timestamp_ = true;
 106   }
 107   if (stream_parser_buffer->timestamp() < min_pts_)
 108     min_pts_ = stream_parser_buffer->timestamp();
 109
 110   // Discard the incoming frame:
 111   // - if it is not associated with any config,
 112   // - or if no valid key frame has been found so far.
 113   if (!has_valid_config_ ||
 114       (!has_valid_frame_ && !stream_parser_buffer->is_key_frame())) {
 115     discarded_frame_count_++;
 116     return true;
 117   }
 118
 119   has_valid_frame_ = true;
 120
 121   if (discarded_frame_count_ > 0)
 122     ReplaceDiscardedFrames(stream_parser_buffer);
 123
 124   buffer_list_.push_back(stream_parser_buffer);
 125   ProcessPendingBuffers(false);
 126   return true;
 127 }
 128
 129 void EsAdapterVideo::ProcessPendingBuffers(bool flush) {
 130   DCHECK(has_valid_config_);
 131
 132   while (!buffer_list_.empty() &&
 133          (flush || buffer_list_.size() > kHistorySize)) {
 134     // Signal a config change, just before emitting the corresponding frame.
 135     if (!config_list_.empty() && config_list_.front().first == buffer_index_) {
 136       new_video_config_cb_.Run(config_list_.front().second);
 137       config_list_.pop_front();
 138     }
 139
 140     scoped_refptr<StreamParserBuffer> buffer = buffer_list_.front();
 141     buffer_list_.pop_front();
 142     buffer_index_++;
 143
 144     if (buffer->duration() == kNoTimestamp()) {
 145       base::TimeDelta next_frame_pts = GetNextFramePts(buffer->timestamp());
 146       if (next_frame_pts == kNoTimestamp()) {
 147         // This can happen when emitting the very last buffer
 148         // or if the stream do not meet the assumption behind |kHistorySize|.
 149         DVLOG(LOG_LEVEL_ES) << "Using last frame duration: "
 150                             << last_frame_duration_.InMilliseconds();
 151         buffer->set_duration(last_frame_duration_);
 152       } else {
 153         base::TimeDelta duration = next_frame_pts - buffer->timestamp();
 154         DVLOG(LOG_LEVEL_ES) << "Frame duration: " << duration.InMilliseconds();
 155         buffer->set_duration(duration);
 156       }
 157     }
 158
 159     emitted_pts_.push_back(buffer->timestamp());
 160     if (emitted_pts_.size() > kHistorySize)
 161       emitted_pts_.pop_front();
 162
 163     last_frame_duration_ = buffer->duration();
 164     emit_buffer_cb_.Run(buffer);
 165   }
 166 }
 167
 168 base::TimeDelta EsAdapterVideo::GetNextFramePts(base::TimeDelta current_pts) {
 169   base::TimeDelta next_pts = kNoTimestamp();
 170
 171   // Consider the timestamps of future frames (in decode order).
 172   // Note: the next frame is not enough when the GOP includes some B frames.
 173   for (BufferQueue::const_iterator it = buffer_list_.begin();
 174        it != buffer_list_.end(); ++it) {
 175     if ((*it)->timestamp() < current_pts)
 176       continue;
 177     if (next_pts == kNoTimestamp() || next_pts > (*it)->timestamp())
 178       next_pts = (*it)->timestamp();
 179   }
 180
 181   // Consider the timestamps of previous frames (in decode order).
 182   // In a simple GOP structure with B frames, the frame next to the last B
 183   // frame (in presentation order) is located before in decode order.
 184   for (std::list<base::TimeDelta>::const_iterator it = emitted_pts_.begin();
 185        it != emitted_pts_.end(); ++it) {
 186     if (*it < current_pts)
 187       continue;
 188     if (next_pts == kNoTimestamp() || next_pts > *it)
 189       next_pts = *it;
 190   }
 191
 192   return next_pts;
 193 }
 194
 195 void EsAdapterVideo::ReplaceDiscardedFrames(
 196     const scoped_refptr<StreamParserBuffer>& stream_parser_buffer) {
 197   DCHECK_GT(discarded_frame_count_, 0);
 198   DCHECK(stream_parser_buffer->is_key_frame());
 199
 200   // PTS/DTS are interpolated between the min PTS/DTS of discarded frames
 201   // and the PTS/DTS of the first valid buffer.
 202   // Note: |pts_delta| and |dts_delta| are calculated using integer division.
 203   // Interpolation thus accumulutes small errors. However, since timestamps
 204   // are given in microseconds, only a high number of discarded frames
 205   // (in the order of 10000s) could have an impact and create a gap (from MSE
 206   // point of view) between the last interpolated frame and
 207   // |stream_parser_buffer|.
 208   base::TimeDelta pts = min_pts_;
 209   base::TimeDelta pts_delta =
 210       (stream_parser_buffer->timestamp() - pts) / discarded_frame_count_;
 211   DecodeTimestamp dts = min_dts_;
 212   base::TimeDelta dts_delta =
 213       (stream_parser_buffer->GetDecodeTimestamp() - dts) /
 214       discarded_frame_count_;
 215
 216   for (int i = 0; i < discarded_frame_count_; i++) {
 217     scoped_refptr<StreamParserBuffer> frame =
 218         StreamParserBuffer::CopyFrom(
 219             stream_parser_buffer->data(),
 220             stream_parser_buffer->data_size(),
 221             stream_parser_buffer->is_key_frame(),
 222             stream_parser_buffer->type(),
 223             stream_parser_buffer->track_id());
 224     frame->SetDecodeTimestamp(dts);
 225     frame->set_timestamp(pts);
 226     frame->set_duration(pts_delta);
 227     buffer_list_.push_back(frame);
 228     pts += pts_delta;
 229     dts += dts_delta;
 230   }
 231   discarded_frame_count_ = 0;
 232 }
 233
 234 }  // namespace mp2t
 235 }  // namespace media