133 lines
3.1 KiB
C++
133 lines
3.1 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "media/formats/mp2t/ts_section_psi.h"
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#include "base/basictypes.h"
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#include "base/logging.h"
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#include "media/base/bit_reader.h"
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#include "media/formats/mp2t/mp2t_common.h"
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static bool IsCrcValid(const uint8* buf, int size) {
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uint32 crc = 0xffffffffu;
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const uint32 kCrcPoly = 0x4c11db7;
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for (int k = 0; k < size; k++) {
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int nbits = 8;
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uint32 data_msb_aligned = buf[k];
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data_msb_aligned <<= (32 - nbits);
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while (nbits > 0) {
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if ((data_msb_aligned ^ crc) & 0x80000000) {
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crc <<= 1;
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crc ^= kCrcPoly;
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} else {
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crc <<= 1;
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}
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data_msb_aligned <<= 1;
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nbits--;
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}
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}
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return (crc == 0);
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}
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namespace media {
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namespace mp2t {
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TsSectionPsi::TsSectionPsi()
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: wait_for_pusi_(true),
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leading_bytes_to_discard_(0) {
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}
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TsSectionPsi::~TsSectionPsi() {
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}
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bool TsSectionPsi::Parse(bool payload_unit_start_indicator,
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const uint8* buf, int size) {
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// Ignore partial PSI.
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if (wait_for_pusi_ && !payload_unit_start_indicator)
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return true;
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if (payload_unit_start_indicator) {
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// Reset the state of the PSI section.
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ResetPsiState();
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// Update the state.
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wait_for_pusi_ = false;
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DCHECK_GE(size, 1);
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int pointer_field = buf[0];
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leading_bytes_to_discard_ = pointer_field;
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buf++;
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size--;
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}
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// Discard some leading bytes if needed.
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if (leading_bytes_to_discard_ > 0) {
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int nbytes_to_discard = std::min(leading_bytes_to_discard_, size);
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buf += nbytes_to_discard;
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size -= nbytes_to_discard;
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leading_bytes_to_discard_ -= nbytes_to_discard;
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}
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if (size == 0)
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return true;
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// Add the data to the parser state.
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psi_byte_queue_.Push(buf, size);
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int raw_psi_size;
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const uint8* raw_psi;
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psi_byte_queue_.Peek(&raw_psi, &raw_psi_size);
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// Check whether we have enough data to start parsing.
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if (raw_psi_size < 3)
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return true;
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int section_length =
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((static_cast<int>(raw_psi[1]) << 8) |
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(static_cast<int>(raw_psi[2]))) & 0xfff;
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if (section_length >= 1021)
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return false;
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int psi_length = section_length + 3;
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if (raw_psi_size < psi_length) {
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// Don't throw an error when there is not enough data,
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// just wait for more data to come.
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return true;
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}
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// There should not be any trailing bytes after a PMT.
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// Instead, the pointer field should be used to stuff bytes.
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DVLOG_IF(1, raw_psi_size > psi_length)
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<< "Trailing bytes after a PSI section: "
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<< psi_length << " vs " << raw_psi_size;
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// Verify the CRC.
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RCHECK(IsCrcValid(raw_psi, psi_length));
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// Parse the PSI section.
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BitReader bit_reader(raw_psi, raw_psi_size);
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bool status = ParsePsiSection(&bit_reader);
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if (status)
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ResetPsiState();
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return status;
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}
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void TsSectionPsi::Flush() {
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}
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void TsSectionPsi::Reset() {
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ResetPsiSection();
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ResetPsiState();
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}
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void TsSectionPsi::ResetPsiState() {
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wait_for_pusi_ = true;
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psi_byte_queue_.Reset();
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leading_bytes_to_discard_ = 0;
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}
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} // namespace mp2t
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} // namespace media
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