media/cast/logging/log_serializer.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 // The serialization format is as follows:
   6 //   16-bit integer describing the following LogMetadata proto size in bytes.
   7 //   The LogMetadata proto.
   8 //   32-bit integer describing number of frame events.
   9 //   (The following repeated for number of frame events):
  10 //     16-bit integer describing the following AggregatedFrameEvent proto size
  11 //         in bytes.
  12 //     The AggregatedFrameEvent proto.
  13 //   32-bit integer describing number of packet events.
  14 //   (The following repeated for number of packet events):
  15 //     16-bit integer describing the following AggregatedPacketEvent proto
  16 //         size in bytes.
  17 //     The AggregatedPacketEvent proto.
  18
  19 #include "media/cast/logging/log_serializer.h"
  20
  21 #include "base/big_endian.h"
  22 #include "base/logging.h"
  23 #include "base/memory/scoped_ptr.h"
  24 #include "third_party/zlib/zlib.h"
  25
  26 namespace media {
  27 namespace cast {
  28
  29 namespace {
  30
  31 using media::cast::proto::AggregatedFrameEvent;
  32 using media::cast::proto::AggregatedPacketEvent;
  33 using media::cast::proto::LogMetadata;
  34
  35 // Use 30MB of temp buffer to hold uncompressed data if |compress| is true.
  36 const int kMaxUncompressedBytes = 30 * 1000 * 1000;
  37
  38 // The maximum allowed size per serialized proto.
  39 const int kMaxSerializedProtoBytes = (1 << 16) - 1;
  40 bool DoSerializeEvents(const LogMetadata& metadata,
  41                        const FrameEventList& frame_events,
  42                        const PacketEventList& packet_events,
  43                        const int max_output_bytes,
  44                        char* output,
  45                        int* output_bytes) {
  46   base::BigEndianWriter writer(output, max_output_bytes);
  47
  48   int proto_size = metadata.ByteSize();
  49   DCHECK(proto_size <= kMaxSerializedProtoBytes);
  50   if (!writer.WriteU16(proto_size))
  51     return false;
  52   if (!metadata.SerializeToArray(writer.ptr(), writer.remaining()))
  53     return false;
  54   if (!writer.Skip(proto_size))
  55     return false;
  56
  57   RtpTimestamp prev_rtp_timestamp = 0;
  58   for (media::cast::FrameEventList::const_iterator it = frame_events.begin();
  59        it != frame_events.end();
  60        ++it) {
  61     media::cast::proto::AggregatedFrameEvent frame_event(**it);
  62
  63     // Adjust relative RTP timestamp so that it is relative to previous frame,
  64     // rather than relative to first RTP timestamp.
  65     // This is done to improve encoding size.
  66     RtpTimestamp old_relative_rtp_timestamp =
  67         frame_event.relative_rtp_timestamp();
  68     frame_event.set_relative_rtp_timestamp(
  69         old_relative_rtp_timestamp - prev_rtp_timestamp);
  70     prev_rtp_timestamp = old_relative_rtp_timestamp;
  71
  72     proto_size = frame_event.ByteSize();
  73     DCHECK(proto_size <= kMaxSerializedProtoBytes);
  74
  75     // Write size of the proto, then write the proto.
  76     if (!writer.WriteU16(proto_size))
  77       return false;
  78     if (!frame_event.SerializeToArray(writer.ptr(), writer.remaining()))
  79       return false;
  80     if (!writer.Skip(proto_size))
  81       return false;
  82   }
  83
  84   // Write packet events.
  85   prev_rtp_timestamp = 0;
  86   for (media::cast::PacketEventList::const_iterator it = packet_events.begin();
  87        it != packet_events.end();
  88        ++it) {
  89     media::cast::proto::AggregatedPacketEvent packet_event(**it);
  90     RtpTimestamp old_relative_rtp_timestamp =
  91         packet_event.relative_rtp_timestamp();
  92     packet_event.set_relative_rtp_timestamp(
  93         old_relative_rtp_timestamp - prev_rtp_timestamp);
  94     prev_rtp_timestamp = old_relative_rtp_timestamp;
  95
  96     proto_size = packet_event.ByteSize();
  97     DCHECK(proto_size <= kMaxSerializedProtoBytes);
  98
  99     // Write size of the proto, then write the proto.
 100     if (!writer.WriteU16(proto_size))
 101       return false;
 102     if (!packet_event.SerializeToArray(writer.ptr(), writer.remaining()))
 103       return false;
 104     if (!writer.Skip(proto_size))
 105       return false;
 106   }
 107
 108   *output_bytes = max_output_bytes - writer.remaining();
 109   return true;
 110 }
 111
 112 bool Compress(char* uncompressed_buffer,
 113               int uncompressed_bytes,
 114               int max_output_bytes,
 115               char* output,
 116               int* output_bytes) {
 117   z_stream stream = {0};
 118   int result = deflateInit2(&stream,
 119                             Z_DEFAULT_COMPRESSION,
 120                             Z_DEFLATED,
 121                             // 16 is added to produce a gzip header + trailer.
 122                             MAX_WBITS + 16,
 123                             8,  // memLevel = 8 is default.
 124                             Z_DEFAULT_STRATEGY);
 125   DCHECK_EQ(Z_OK, result);
 126
 127   stream.next_in = reinterpret_cast<uint8*>(uncompressed_buffer);
 128   stream.avail_in = uncompressed_bytes;
 129   stream.next_out = reinterpret_cast<uint8*>(output);
 130   stream.avail_out = max_output_bytes;
 131
 132   // Do a one-shot compression. This will return Z_STREAM_END only if |output|
 133   // is large enough to hold all compressed data.
 134   result = deflate(&stream, Z_FINISH);
 135   bool success = (result == Z_STREAM_END);
 136
 137   if (!success)
 138     DVLOG(2) << "deflate() failed. Result: " << result;
 139
 140   result = deflateEnd(&stream);
 141   DCHECK(result == Z_OK || result == Z_DATA_ERROR);
 142
 143   if (success)
 144     *output_bytes = max_output_bytes - stream.avail_out;
 145
 146   return success;
 147 }
 148
 149 }  // namespace
 150
 151 bool SerializeEvents(const LogMetadata& log_metadata,
 152                      const FrameEventList& frame_events,
 153                      const PacketEventList& packet_events,
 154                      bool compress,
 155                      int max_output_bytes,
 156                      char* output,
 157                      int* output_bytes) {
 158   DCHECK_GT(max_output_bytes, 0);
 159   DCHECK(output);
 160   DCHECK(output_bytes);
 161
 162   if (compress) {
 163     // Allocate a reasonably large temp buffer to hold uncompressed data.
 164     scoped_ptr<char[]> uncompressed_buffer(new char[kMaxUncompressedBytes]);
 165     int uncompressed_bytes;
 166     bool success = DoSerializeEvents(log_metadata,
 167                                      frame_events,
 168                                      packet_events,
 169                                      kMaxUncompressedBytes,
 170                                      uncompressed_buffer.get(),
 171                                      &uncompressed_bytes);
 172     if (!success)
 173       return false;
 174     return Compress(uncompressed_buffer.get(),
 175                     uncompressed_bytes,
 176                     max_output_bytes,
 177                     output,
 178                     output_bytes);
 179   } else {
 180     return DoSerializeEvents(log_metadata,
 181                              frame_events,
 182                              packet_events,
 183                              max_output_bytes,
 184                              output,
 185                              output_bytes);
 186   }
 187 }
 188
 189 }  // namespace cast
 190 }  // namespace media