diff options
Diffstat (limited to 'chromium/media/formats/mp2t/ts_section_psi.cc')
-rw-r--r-- | chromium/media/formats/mp2t/ts_section_psi.cc | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/chromium/media/formats/mp2t/ts_section_psi.cc b/chromium/media/formats/mp2t/ts_section_psi.cc new file mode 100644 index 00000000000..f9db8805376 --- /dev/null +++ b/chromium/media/formats/mp2t/ts_section_psi.cc @@ -0,0 +1,132 @@ +// Copyright 2014 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_psi.h" + +#include "base/basictypes.h" +#include "base/logging.h" +#include "media/base/bit_reader.h" +#include "media/formats/mp2t/mp2t_common.h" + +static bool IsCrcValid(const uint8* buf, int size) { + uint32 crc = 0xffffffffu; + const uint32 kCrcPoly = 0x4c11db7; + + for (int k = 0; k < size; k++) { + int nbits = 8; + uint32 data_msb_aligned = buf[k]; + data_msb_aligned <<= (32 - nbits); + + while (nbits > 0) { + if ((data_msb_aligned ^ crc) & 0x80000000) { + crc <<= 1; + crc ^= kCrcPoly; + } else { + crc <<= 1; + } + + data_msb_aligned <<= 1; + nbits--; + } + } + + return (crc == 0); +} + +namespace media { +namespace mp2t { + +TsSectionPsi::TsSectionPsi() + : wait_for_pusi_(true), + leading_bytes_to_discard_(0) { +} + +TsSectionPsi::~TsSectionPsi() { +} + +bool TsSectionPsi::Parse(bool payload_unit_start_indicator, + const uint8* buf, int size) { + // Ignore partial PSI. + if (wait_for_pusi_ && !payload_unit_start_indicator) + return true; + + if (payload_unit_start_indicator) { + // Reset the state of the PSI section. + ResetPsiState(); + + // Update the state. + wait_for_pusi_ = false; + DCHECK_GE(size, 1); + int pointer_field = buf[0]; + leading_bytes_to_discard_ = pointer_field; + buf++; + size--; + } + + // Discard some leading bytes if needed. + if (leading_bytes_to_discard_ > 0) { + int nbytes_to_discard = std::min(leading_bytes_to_discard_, size); + buf += nbytes_to_discard; + size -= nbytes_to_discard; + leading_bytes_to_discard_ -= nbytes_to_discard; + } + if (size == 0) + return true; + + // Add the data to the parser state. + psi_byte_queue_.Push(buf, size); + int raw_psi_size; + const uint8* raw_psi; + psi_byte_queue_.Peek(&raw_psi, &raw_psi_size); + + // Check whether we have enough data to start parsing. + if (raw_psi_size < 3) + return true; + int section_length = + ((static_cast<int>(raw_psi[1]) << 8) | + (static_cast<int>(raw_psi[2]))) & 0xfff; + if (section_length >= 1021) + return false; + int psi_length = section_length + 3; + if (raw_psi_size < psi_length) { + // Don't throw an error when there is not enough data, + // just wait for more data to come. + return true; + } + + // There should not be any trailing bytes after a PMT. + // Instead, the pointer field should be used to stuff bytes. + DVLOG_IF(1, raw_psi_size > psi_length) + << "Trailing bytes after a PSI section: " + << psi_length << " vs " << raw_psi_size; + + // Verify the CRC. + RCHECK(IsCrcValid(raw_psi, psi_length)); + + // Parse the PSI section. + BitReader bit_reader(raw_psi, raw_psi_size); + bool status = ParsePsiSection(&bit_reader); + if (status) + ResetPsiState(); + + return status; +} + +void TsSectionPsi::Flush() { +} + +void TsSectionPsi::Reset() { + ResetPsiSection(); + ResetPsiState(); +} + +void TsSectionPsi::ResetPsiState() { + wait_for_pusi_ = true; + psi_byte_queue_.Reset(); + leading_bytes_to_discard_ = 0; +} + +} // namespace mp2t +} // namespace media + |