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.
+    int raw_psi_size = 0;

[acolwell GONE FROM CHROMIUM, 2013/09/05 18:29:10]

nit: remove initialization since it is immediately overridden.

[damienv1, 2013/09/09 23:29:45]

Not relevant anymore (code removed).

+    const uint8* raw_psi = NULL;
+    psi_byte_queue_.Peek(&raw_psi, &raw_psi_size);
+    LOG_IF(WARNING, raw_psi_size > 0)

[acolwell GONE FROM CHROMIUM, 2013/09/05 18:29:10]

DVLOG here and below

[damienv1, 2013/09/09 23:29:45]

Ditto.

+      << "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) {

[acolwell GONE FROM CHROMIUM, 2013/09/05 18:29:10]

nit: remove{} here and all 1 line ifs below

[damienv1, 2013/09/09 23:29:45]

Done.

+    return true;
+  }
+
+  // Add the data to the parser state.
+  psi_byte_queue_.Push(buf, size);
+  int raw_psi_size = 0;

[acolwell GONE FROM CHROMIUM, 2013/09/05 18:29:10]

ditto

[damienv1, 2013/09/09 23:29:45]

Done.

+  const uint8* raw_psi = NULL;
+  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.
+  LOG_IF(WARNING, 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);

[acolwell GONE FROM CHROMIUM, 2013/09/05 18:29:10]

This appears to be the only call site for this method. Since the CRC is only
ever updated a byte at a time, change the signature of Update() to just take a
uint8 to reflect that this is the only way this method is being used right now.
If the required usage changes in the future, then we can always revert the
signature.

[damienv1, 2013/09/09 23:29:45]

Done.

+  }
+  if (!crc.IsValid()) {
+    return false;
+  }
+
+  // Parse the PSI section.
+  BitReader bit_reader(raw_psi, raw_psi_size);
+  bool status = ParsePsiSection(&bit_reader);
+  if (status) {
+    ResetState();
+  }
+
+  return status;
+}
+
+void Mpeg2TsPsiParser::Flush() {
+  ResetState();
+}
+
+void Mpeg2TsPsiParser::ResetState() {
+  wait_for_pusi_ = true;
+  psi_byte_queue_.Reset();
+  leading_bytes_to_discard_ = 0;
+}
+
+}  // namespace mpeg2ts
+}  // namespace media