Mpeg2 TS stream parser for media source.

media/mpeg2/mpeg2ts_psi.cc

+// Copyright (c) 2013 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/mpeg2/mpeg2ts_psi.h"
+
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+#include "media/mpeg2/mpeg2ts_crc.h"
+
+namespace media {
+namespace mpeg2ts {
+
+Mpeg2TsPsiParser::Mpeg2TsPsiParser()
+    : wait_for_pusi_(true),
+      leading_bytes_to_discard_(0) {
+}
+
+Mpeg2TsPsiParser::~Mpeg2TsPsiParser() {
+}
+
+bool Mpeg2TsPsiParser::Parse(bool payload_unit_start_indicator,
+                             const uint8* buf, int size) {
+  bool parse_result =
+      ParseInternal(payload_unit_start_indicator,
+                    buf, size);
+  if (parse_result == false) {
+    ResetState();
+  }
+  return parse_result;
+}
+
+bool Mpeg2TsPsiParser::ParseInternal(bool payload_unit_start_indicator,
+                                     const uint8* buf, int size) {
+  if (wait_for_pusi_ && !payload_unit_start_indicator) {
+    // Ignore partial PSI.
+    return true;
+  }
+
+  if (payload_unit_start_indicator) {
+    // Reset the state of the PSI section.
+    LOG_IF(WARNING, raw_psi_.size() > 0)
+      << "Dropping state: len=" << raw_psi_.size();
+    ResetState();
+
+    // 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.
+  int old_size = raw_psi_.size();
+  raw_psi_.resize(old_size + size);
+  memcpy(&raw_psi_[old_size], buf, 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 (static_cast<int>(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.
+  LOG_IF(WARNING, static_cast<int>(raw_psi_.size()) > psi_length)
+      << "Trailing bytes after a PSI section: "
+      << psi_length << " vs " << raw_psi_.size();
+
+  // Verify the CRC.
+  Mpeg2TsCrc crc;
+  for (int k = 0; k < psi_length; k++) {
+    crc.Update(raw_psi_[k], 8);
+  }
+  if (!crc.IsValid()) {
+    return false;
+  }
+
+  // Parse the PSI section.
+  BitReader bit_reader(&raw_psi_[0], raw_psi_.size());
+  bool status = ParsePsiSection(&bit_reader);
+  if (status) {
+    ResetState();
+  }
+
+  return status;
+}
+
+void Mpeg2TsPsiParser::Flush() {
+  ResetState();
+}
+
+void Mpeg2TsPsiParser::ResetState() {
+  wait_for_pusi_ = true;
+  raw_psi_.resize(0);
+  leading_bytes_to_discard_ = 0;
+}
+
+}  // namespace mpeg2ts
+}  // namespace media