Support HLS MPEG2 TS with SAMPLE-AES encryption.

media/formats/mp2t/ts_section_cets_ecm.cc

Index: media/formats/mp2t/ts_section_cets_ecm.cc
diff --git a/media/formats/mp2t/ts_section_cets_ecm.cc b/media/formats/mp2t/ts_section_cets_ecm.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1679c0307181cbc319e56ac9a407458b0327abae
--- /dev/null
+++ b/media/formats/mp2t/ts_section_cets_ecm.cc
@@ -0,0 +1,84 @@
+// 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/ts_section_cets_ecm.h"
+
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+#include "media/base/decrypt_config.h"
+#include "media/formats/mp2t/mp2t_common.h"
+
+namespace media {
+namespace mp2t {
+
+TsSectionCetsEcm::TsSectionCetsEcm(
+    const RegisterDecryptConfigCb& register_decrypt_config_cb)
+    : register_decrypt_config_cb_(register_decrypt_config_cb) {}
+
+TsSectionCetsEcm::~TsSectionCetsEcm() {}
+
+bool TsSectionCetsEcm::Parse(bool payload_unit_start_indicator,
+                             const uint8_t* buf,
+                             int size) {
+  DCHECK(buf);
+  BitReader bit_reader(buf, size);
+  int num_states;
+  bool next_key_id_flag;
+  bool no_byte_align;
+  int iv_size;
+  std::string key_id;
+  int transport_scrambling_control;
+  int num_au;
+  bool key_id_flag;
+  int au_byte_offset_size;
+  std::string iv;
+  std::vector<SubsampleEntry> subsamples_empty;
+  // TODO(dougsteed). Currently we allow only a subset of the possible values.
+  // When we flesh out this implementation to cover all of ISO/IEC 23001-9 we
+  // will need to generalize this.
+  RCHECK(bit_reader.ReadBits(2, &num_states));
+  RCHECK(num_states == 1);
+  RCHECK(bit_reader.ReadFlag(&next_key_id_flag) && !next_key_id_flag);
+  // TODO(dougsteed). The standard (ISO/IEC 23001-9:2014) reserves 3 bits,
+  // whereas it likely was intended to be 5 bits to follow the usual practice of
+  // syncing to a byte boundary for the byte oriented fields that follow.
+  // For now, we plan to use it with byte alignment for convenience. Rather than
+  // just having an unadvertized deviation from the standard, I have repurposed
+  // the first reserved bit as a flag. This approach gives flexibility for the
+  // future if the standard is fixed or comes into wide use in its present form.
+  RCHECK(bit_reader.ReadFlag(&no_byte_align));
+  if (no_byte_align)
+    RCHECK(bit_reader.SkipBits(2));
+  else
+    RCHECK(bit_reader.SkipBits(4));
+  RCHECK(bit_reader.ReadBits(8, &iv_size));
+  RCHECK(iv_size == 16);
+  RCHECK(bit_reader.ReadString(128, &key_id));
+  RCHECK(bit_reader.ReadBits(2, &transport_scrambling_control));
+  RCHECK(transport_scrambling_control == 0);
+  RCHECK(bit_reader.ReadBits(6, &num_au));
+  RCHECK(num_au == 1);
+  RCHECK(bit_reader.ReadFlag(&key_id_flag) && !key_id_flag);
+  RCHECK(bit_reader.SkipBits(3));
+  RCHECK(bit_reader.ReadBits(4, &au_byte_offset_size));
+  RCHECK(au_byte_offset_size == 0);
+  RCHECK(bit_reader.ReadString(128, &iv));
+  // The CETS-ECM is supposed to  use adaptation field stuffing to fill the TS
+  // packet, so there should be no data left to read.
+  RCHECK(bit_reader.bits_available() == 0);
+  DecryptConfig decrypt_config(key_id, iv, subsamples_empty);
+  register_decrypt_config_cb_.Run(decrypt_config);
+  return true;
+}
+
+void TsSectionCetsEcm::Flush() {
+  // No pending state.
+}
+
+void TsSectionCetsEcm::Reset() {
+  // No state to clean up.
+}
+
+}  // namespace mp2t
+}  // namespace media