Support HLS MPEG2 TS with SAMPLE-AES encryption.

media/formats/mp2t/descriptors.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/formats/mp2t/descriptors.h"
+
+#include <vector>
+
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+#include "media/formats/mp2t/mp2t_common.h"
+
+namespace media {
+namespace mp2t {
+
+namespace {
+
+// Tag values for various kinds of descriptors for which there is specific
+// parsing support herein.
+enum DescriptorTag {
+  DESCRIPTOR_TAG_REGISTRATION = 5,
+  DESCRIPTOR_TAG_CA = 9,
+  DESCRIPTOR_TAG_PRIVATE_DATA_INDICATOR = 15,
+};
+
+const int kCASystemIdCenc = 0x6365;  // 'ce'
+
+class StringBitReader : public BitReader {
+ public:
+  StringBitReader(const std::string& input);
+  ~StringBitReader() override;
+};
+
+StringBitReader::StringBitReader(const std::string& input)
+    : BitReader(reinterpret_cast<const uint8_t*>(input.data()), input.size()) {}
+
+StringBitReader::~StringBitReader() {}
+
+}  // namespace
+
+Descriptors::Descriptors() {}
+
+Descriptors::~Descriptors() {}
+
+bool Descriptors::Read(BitReader* reader, int size) {
+  DCHECK(reader);
+  DCHECK(size >= 0);
+  descriptors_.clear();
+  if (size == 0)
+    return true;
+  int initial_bits_read = reader->bits_read();
+  int bits_read = 0;
+  int bits_available = reader->bits_available();
+  int size_in_bits = 8 * size;
+  if (size_in_bits > bits_available)
+    return false;
+  bits_available = size_in_bits;
+  do {
+    int tag;
+    size_t length;
+    RCHECK(reader->ReadBits(8, &tag));
+    RCHECK(reader->ReadBits(8, &length));
+    char data[256];
+    for (size_t i = 0; i < length; i++) {
+      RCHECK(reader->ReadBits(8, &data[i]));
+    }
+    descriptors_.insert(Descriptor(tag, std::string(data, length)));
+    bits_read = reader->bits_read() - initial_bits_read;
+  } while (bits_read < bits_available);
+  return bits_read == bits_available;
+}
+
+bool Descriptors::HasRegistrationDescriptor(
+    int64_t* format_identifier,
+    std::string* additional_info) const {
+  DCHECK(format_identifier);
+  DCHECK(additional_info);
+  auto search = descriptors_.find(DESCRIPTOR_TAG_REGISTRATION);
+  if (search == descriptors_.end())
+    return false;
+  const std::string& data = search->second;
+  StringBitReader reader(data);
+  RCHECK(reader.ReadBits(32, format_identifier));
+  size_t extra_bits = reader.bits_available();
+  RCHECK(extra_bits % 8 == 0);

[ddorwin, 2016/04/12 00:40:47]

You might also need to check that it's > 0 if you assume that in ReadString()

[dougsteed, 2016/05/08 23:18:44]

Done.

+  RCHECK(reader.ReadString(extra_bits, additional_info));
+  return true;
+}
+
+bool Descriptors::HasCADescriptor(int* system_id,
+                                  int* pid,
+                                  std::string* private_data) const {
+  DCHECK(system_id);
+  DCHECK(pid);
+  DCHECK(private_data);
+  auto search = descriptors_.find(DESCRIPTOR_TAG_CA);
+  if (search == descriptors_.end())
+    return false;
+  const std::string& data = search->second;
+  StringBitReader reader(data);
+  RCHECK(reader.ReadBits(16, system_id));
+  RCHECK(reader.SkipBits(3));
+  RCHECK(reader.ReadBits(13, pid));
+  size_t extra_bits = reader.bits_available();
+  RCHECK(extra_bits % 8 == 0);
+  RCHECK(reader.ReadString(extra_bits, private_data));
+  return true;
+}
+
+bool Descriptors::HasCADescriptorCenc(int* ca_pid, int* pssh_pid) const {
+  DCHECK(ca_pid);
+  DCHECK(pssh_pid);
+  int system_id;
+  std::string private_data;
+  if (!HasCADescriptor(&system_id, ca_pid, &private_data))
+    return false;
+  if (system_id != kCASystemIdCenc)
+    return false;
+  StringBitReader reader(private_data);
+  uint32_t scheme_type;
+  uint32_t scheme_version;
+  int num_systems;
+  int encryption_algorithm;
+  char pssh_system_id[16];
+  // TODO(dougsteed). Currently we don't check many of the following values.
+  // When we flesh out this implementation to cover all of ISO/IEC 23001-9 we
+  // will need to use and check these values.
+  RCHECK(reader.ReadBits(32, &scheme_type));
+  RCHECK(reader.ReadBits(32, &scheme_version));
+  RCHECK(reader.ReadBits(8, &num_systems));
+  RCHECK(num_systems == 1);
+  RCHECK(reader.ReadBits(24, &encryption_algorithm));
+  for (size_t i = 0; i < 16; i++) {
+    RCHECK(reader.ReadBits(8, &pssh_system_id[i]));
+  }
+  RCHECK(reader.ReadBits(13, pssh_pid));
+  return true;
+}
+
+bool Descriptors::HasPrivateDataIndicator(int64_t value) const {
+  int64_t private_data_indicator;
+  auto search = descriptors_.find(DESCRIPTOR_TAG_PRIVATE_DATA_INDICATOR);
+  if (search == descriptors_.end())
+    return false;
+  const std::string& data = search->second;
+  StringBitReader reader(data);
+  RCHECK(reader.ReadBits(32, &private_data_indicator));
+  RCHECK(reader.bits_available() == 0);
+  return private_data_indicator == value;
+}
+
+}  // namespace mp2t
+}  // namespace media