blob: d458c06fb5c86b8f034bf1e1c4e445cf9496e736 [file] [log] [blame]
// 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/check.h"
#include "media/base/bit_reader.h"
#include "media/formats/mp2t/mp2t_common.h"
namespace media {
namespace mp2t {
const RegisterNewKeyIdAndIvCB& register_new_key_id_and_iv_cb)
: register_new_key_id_and_iv_cb_(register_new_key_id_and_iv_cb) {}
TsSectionCetsEcm::~TsSectionCetsEcm() {}
bool TsSectionCetsEcm::Parse(bool payload_unit_start_indicator,
const uint8_t* buf,
int size) {
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;
// 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.
if (no_byte_align)
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.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);
register_new_key_id_and_iv_cb_.Run(key_id, iv);
return true;
void TsSectionCetsEcm::Flush() {
// No pending state.
void TsSectionCetsEcm::Reset() {
// No state to clean up.
} // namespace mp2t
} // namespace media