H264SpsPpsTracker class which keep tracks of SPS/PPS.

webrtc/modules/video_coding/h264_sps_pps_tracker.cc

+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/modules/video_coding/h264_sps_pps_tracker.h"
+
+#include <string>
+
+#include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
+#include "webrtc/common_video/h264/h264_common.h"
+#include "webrtc/modules/video_coding/frame_object.h"
+#include "webrtc/modules/video_coding/packet_buffer.h"
+
+namespace webrtc {
+namespace video_coding {
+
+namespace {
+const uint8_t start_code_h264[] = {0, 0, 0, 1};
+}  // namespace
+
+bool H264SpsPpsTracker::CopyAndFixBitstream(VCMPacket* packet) {
+  RTC_DCHECK(packet->codec == kVideoCodecH264);
+
+  const uint8_t* data = packet->dataPtr;
+  const size_t data_size = packet->sizeBytes;
+  const RTPVideoHeader& video_header = packet->video_header;
+  const RTPVideoHeaderH264& codec_header = video_header.codecHeader.H264;
+
+  // Packets that only contains SPS/PPS are not decodable by themselves, and
+  // to avoid frames being created containing only these two nalus we don't
+  // insert them into the PacketBuffer. Instead we save the SPS/PPS and
+  // prepend the bitstream of first packet of an IDR referring to the
+  // corresponding SPS/PPS id.
+  bool insert_packet = codec_header.nalus_length == 0 ? true : false;
+
+  int pps_id = -1;
+  size_t required_size = 0;
+  for (size_t i = 0; i < codec_header.nalus_length; ++i) {
+    const NaluInfo& nalu = codec_header.nalus[i];
+    switch (nalu.type) {
+      case H264::NaluType::kSps: {
+        // Save SPS.
+        sps_data_[nalu.sps_id].size = nalu.size;
+        sps_data_[nalu.sps_id].data.reset(new uint8_t[nalu.size]);
+        memcpy(sps_data_[nalu.sps_id].data.get(), data + nalu.offset,
+               nalu.size);
+        break;
+      }
+      case H264::NaluType::kPps: {
+        // Save PPS.
+        pps_data_[nalu.pps_id].sps_id = nalu.sps_id;
+        pps_data_[nalu.pps_id].size = nalu.size;
+        pps_data_[nalu.pps_id].data.reset(new uint8_t[nalu.size]);
+        memcpy(pps_data_[nalu.pps_id].data.get(), data + nalu.offset,
+               nalu.size);
+        break;
+      }
+      case H264::NaluType::kIdr: {
+        // If this is the first packet of an IDR, make sure we have the required
+        // SPS/PPS and also calculate how much extra space we need in the buffer
+        // to prepend the SPS/PPS to the bitstream with start codes.
+        if (video_header.isFirstPacket) {
+          if (nalu.pps_id == -1) {
+            LOG(LS_WARNING) << "No PPS id in IDR nalu.";
+            return false;
+          }
+
+          auto pps = pps_data_.find(nalu.pps_id);
+          if (pps == pps_data_.end()) {
+            LOG(LS_WARNING) << "No PPS with id << " << nalu.pps_id
+                            << " received";
+            return false;
+          }
+
+          auto sps = sps_data_.find(pps->second.sps_id);
+          if (sps == sps_data_.end()) {
+            LOG(LS_WARNING) << "No SPS with id << "
+                            << pps_data_[nalu.pps_id].sps_id << " received";
+            return false;
+          }
+
+          pps_id = nalu.pps_id;
+          required_size += pps->second.size + sizeof(start_code_h264);
+          required_size += sps->second.size + sizeof(start_code_h264);
+        }
+        FALLTHROUGH();
+      }
+      default: {
+        // Something other than an SPS/PPS nalu in this packet, then it should
+        // be inserted into the PacketBuffer.
+        insert_packet = true;
+      }
+    }
+  }
+
+  if (!insert_packet)
+    return false;
+
+  // Calculate how much space we need for the rest of the bitstream.
+  if (codec_header.packetization_type == kH264StapA) {
+    const uint8_t* nalu_ptr = data + 1;
+    while (nalu_ptr < data + data_size) {
+      RTC_DCHECK(video_header.isFirstPacket);
+      required_size += sizeof(start_code_h264);
+
+      // The first two bytes describe the length of a segment.
+      uint16_t segment_length = nalu_ptr[0] << 8 | nalu_ptr[1];
+      nalu_ptr += 2;
+
+      required_size += segment_length;
+      nalu_ptr += segment_length;
+    }
+  } else {
+    if (video_header.isFirstPacket)
+      required_size += sizeof(start_code_h264);
+    required_size += data_size;
+  }
+
+  // Then we copy to the new buffer.
+  uint8_t* buffer = new uint8_t[required_size];
+  uint8_t* insert_at = buffer;
+
+  // If pps_id != -1 then we have the SPS/PPS and they should be prepended
+  // to the bitstream with start codes inserted.
+  if (pps_id != -1) {
+    // Insert SPS.
+    memcpy(insert_at, start_code_h264, sizeof(start_code_h264));
+    insert_at += sizeof(start_code_h264);
+    memcpy(insert_at, sps_data_[pps_data_[pps_id].sps_id].data.get(),
+           sps_data_[pps_data_[pps_id].sps_id].size);
+    insert_at += sps_data_[pps_data_[pps_id].sps_id].size;
+
+    // Insert PPS.
+    memcpy(insert_at, start_code_h264, sizeof(start_code_h264));
+    insert_at += sizeof(start_code_h264);
+    memcpy(insert_at, pps_data_[pps_id].data.get(), pps_data_[pps_id].size);
+    insert_at += pps_data_[pps_id].size;
+  }
+
+  // Copy the rest of the bitstream and insert start codes.
+  if (codec_header.packetization_type == kH264StapA) {
+    const uint8_t* nalu_ptr = data + 1;
+    while (nalu_ptr < data + data_size) {
+      memcpy(insert_at, start_code_h264, sizeof(start_code_h264));
+      insert_at += sizeof(start_code_h264);
+
+      // The first two bytes describe the length of a segment.
+      uint16_t segment_length = nalu_ptr[0] << 8 | nalu_ptr[1];
+      nalu_ptr += 2;
+
+      size_t copy_end = nalu_ptr - data + segment_length;
+      if (copy_end > data_size) {
+        delete[] buffer;
+        return false;
+      }
+
+      memcpy(insert_at, nalu_ptr, segment_length);
+      insert_at += segment_length;
+      nalu_ptr += segment_length;
+    }
+  } else {
+    if (video_header.isFirstPacket) {
+      memcpy(insert_at, start_code_h264, sizeof(start_code_h264));
+      insert_at += sizeof(start_code_h264);
+    }
+    memcpy(insert_at, data, data_size);
+  }
+
+  packet->dataPtr = buffer;
+  packet->sizeBytes = required_size;
+  return true;
+}
+
+}  // namespace video_coding
+}  // namespace webrtc