Add support for VP9 packetization/depacketization.

webrtc/modules/rtp_rtcp/source/rtp_format_vp9.cc

+/*
+ *  Copyright (c) 2015 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/rtp_rtcp/source/rtp_format_vp9.h"
+
+#include <assert.h>
+#include <string.h>
+
+#include <cmath>
+
+#include "webrtc/base/bitbuffer.h"
+#include "webrtc/base/checks.h"
+#include "webrtc/system_wrappers/interface/logging.h"
+
+#define RETURN_FALSE_ON_ERROR(x) \
+  if (!(x)) {                    \
+    return false;                \
+  }
+
+namespace webrtc {
+namespace {
+// Length of VP9 payload descriptors' fixed part.
+const size_t kFixedPayloadDescriptorBytes = 1;
+
+// Packet fragmentation mode. If true, packets are split into (almost) equal
+// sizes. Otherwise, as many bytes as possible are fit into one packet.
+const bool kBalancedMode = true;
+
+const uint32_t kReservedBitValue0 = 0;
+
+uint8_t TemporalIdxField(const RTPVideoHeaderVP9& hdr, uint8_t def) {
+  return (hdr.temporalIdx == kNoTemporalIdx) ? def : hdr.temporalIdx;
+}
+
+uint8_t SpatialIdxField(const RTPVideoHeaderVP9& hdr, uint8_t def) {
+  return (hdr.spatialIdx == kNoSpatialIdx) ? def : hdr.spatialIdx;
+}
+
+int16_t Tl0PicIdxField(const RTPVideoHeaderVP9& hdr, uint8_t def) {
+  return (hdr.tl0PicIdx == kNoTl0PicIdx) ? def : hdr.tl0PicIdx;
+}
+
+uint8_t GofIdxField(const RTPVideoHeaderVP9& hdr, uint8_t def) {
+  return (hdr.gofIdx == kNoGofIdx) ? def : hdr.gofIdx;
+}
+
+// Picture ID:
+//
+//      +-+-+-+-+-+-+-+-+
+// I:   |M| PICTURE ID  |   M:0 => picture id is 7 bits.
+//      +-+-+-+-+-+-+-+-+   M:1 => picture id is 15 bits.
+// M:   | EXTENDED PID  |
+//      +-+-+-+-+-+-+-+-+
+//
+size_t PictureIdLength(const RTPVideoHeaderVP9& hdr) {
+  if (hdr.pictureId == kNoPictureId)
+    return 0;
+  return (hdr.maxPictureId == kMaxOneBytePictureId) ? 1 : 2;
+}
+
+bool PictureIdPresent(const RTPVideoHeaderVP9& hdr) {
+  return PictureIdLength(hdr) > 0;
+}
+
+// Layer indices:
+//
+// Flexible mode (F=1):     Non-flexible mode (F=0):
+//
+//      +-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+
+// L:   |  T  |U|  S  |D|   |GOF_IDX|  S  |D|
+//      +-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+
+//                          |   TL0PICIDX   |
+//                          +-+-+-+-+-+-+-+-+
+//
+size_t LayerInfoLength(const RTPVideoHeaderVP9& hdr) {
+  if (hdr.flexibleMode)

[stefan-webrtc, 2015/07/14 09:40:10]

if {} else {}

[åsapersson, 2015/07/14 10:53:55]

Done.

+    return (hdr.temporalIdx == kNoTemporalIdx &&
+            hdr.spatialIdx == kNoSpatialIdx) ? 0 : 1;
+  else
+    return (hdr.gofIdx == kNoGofIdx && hdr.spatialIdx == kNoSpatialIdx) ? 0 : 2;
+}
+
+bool LayerInfoPresent(const RTPVideoHeaderVP9& hdr) {
+  return LayerInfoLength(hdr) > 0;
+}
+
+// Reference indices:
+//
+//      +-+-+-+-+-+-+-+-+  -|           P=1,F=1: At least one reference index
+// P,F: | P_DIFF    |X|N|   .                    has to be specified.
+//      +-+-+-+-+-+-+-+-+   . up to 3 times
+// X:   |EXTENDED P_DIFF|   .               X=1: Extended P_DIFF is used (14
+//      +-+-+-+-+-+-+-+-+  -|                    bits). Else 6 bits is used.
+//                                          N=1: An additional P_DIFF follows
+//                                               current P_DIFF.
+size_t RefIndicesLength(const RTPVideoHeaderVP9& hdr) {
+  if (!hdr.interPicPredicted || !hdr.flexibleMode)
+    return 0;
+
+  DCHECK_GT(hdr.numRefPics, 0U);
+  DCHECK_LE(hdr.numRefPics, kMaxVp9RefPics);
+  size_t length = 0;
+  for (size_t i = 0; i < hdr.numRefPics; ++i) {
+    length += hdr.pidDiff[i] > 0x3F ? 2 : 1;

[stefan-webrtc, 2015/07/14 09:40:10]

It is not entirely clear to me where 0x3F comes from. Do you know?

[åsapersson, 2015/07/14 10:53:54]

Added comment.

[stefan-webrtc, 2015/07/28 06:58:14]

Maybe we should DCHECK that P_DIFF doesn't become too big for the extended
version as well?

+  }
+  return length;
+}
+
+// Scalability structure (SS).
+//
+//      +-+-+-+-+-+-+-+-+
+// V:   | N_S |Y|  N_G  |
+//      +-+-+-+-+-+-+-+-+              -|
+// Y:   |     WIDTH     | (OPTIONAL)    .
+//      +               +               .
+//      |               | (OPTIONAL)    .
+//      +-+-+-+-+-+-+-+-+               . N_S + 1 times
+//      |     HEIGHT    | (OPTIONAL)    .
+//      +               +               .
+//      |               | (OPTIONAL)    .
+//      +-+-+-+-+-+-+-+-+              -|           -|
+// N_G: |  T  |U| R |-|-| (OPTIONAL)                 .
+//      +-+-+-+-+-+-+-+-+              -|            . N_G + 1 times
+//      |    P_DIFF     | (OPTIONAL)    . R times    .
+//      +-+-+-+-+-+-+-+-+              -|           -|
+//
+size_t SsDataLength(const RTPVideoHeaderVP9& hdr) {
+  if (!hdr.ssDataAvailable)
+    return 0;
+
+  DCHECK_GT(hdr.numSpatialLayers, 0U);
+  DCHECK_LE(hdr.numSpatialLayers, kMaxVp9NumberOfSpatialLayers);
+  DCHECK_GT(hdr.gof.numFramesInGof, 0U);
+  DCHECK_LE(hdr.gof.numFramesInGof, kMaxVp9FramesInGof);
+  size_t length = 1;                         // V
+  if (hdr.spatialLayerResolutionPresent) {
+    length += 4 * hdr.numSpatialLayers;      // Y
+  }
+  length += hdr.gof.numFramesInGof;          // N_G

[stefan-webrtc, 2015/07/14 09:40:10]

I'm not sure I follow this. Is this supposed to represent the length of:
      +-+-+-+-+-+-+-+-+
 N_G: |  T  |U| R |-|-|
      +-+-+-+-+-+-+-+-+

that is, 1 byte for each frame in the GOF? I guess that makes sense.

[åsapersson, 2015/07/14 10:53:54]

Updated comment.

+  for (size_t i = 0; i < hdr.gof.numFramesInGof; ++i) {
+    DCHECK_LE(hdr.gof.numRefPics[i], kMaxVp9RefPics);
+    length += hdr.gof.numRefPics[i];
+  }
+  return length;
+}
+
+size_t PayloadDescriptorLengthMinusSsData(const RTPVideoHeaderVP9& hdr) {
+  return kFixedPayloadDescriptorBytes + PictureIdLength(hdr) +
+         LayerInfoLength(hdr) + RefIndicesLength(hdr);
+}
+
+size_t PayloadDescriptorLength(const RTPVideoHeaderVP9& hdr) {
+  return PayloadDescriptorLengthMinusSsData(hdr) + SsDataLength(hdr);
+}
+
+void QueuePacket(size_t start_pos,
+                 size_t size,
+                 bool layer_begin,
+                 bool layer_end,
+                 RtpPacketizerVp9::PacketInfoQueue* packets) {
+  RtpPacketizerVp9::PacketInfo packet_info;
+  packet_info.payload_start_pos = start_pos;
+  packet_info.size = size;
+  packet_info.layer_begin = layer_begin;
+  packet_info.layer_end = layer_end;
+  packets->push(packet_info);
+}
+
+// Picture ID:
+//
+//      +-+-+-+-+-+-+-+-+
+// I:   |M| PICTURE ID  |   M:0 => picture id is 7 bits.
+//      +-+-+-+-+-+-+-+-+   M:1 => picture id is 15 bits.
+// M:   | EXTENDED PID  |
+//      +-+-+-+-+-+-+-+-+
+//
+bool WritePictureId(const RTPVideoHeaderVP9& vp9,
+                    rtc::BitBufferWriter* writer) {
+  uint32_t m_bit = (PictureIdLength(vp9) == 2) ? 1 : 0;
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(m_bit, 1));
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.pictureId, m_bit ? 15 : 7));
+  return true;
+}
+
+// Layer indices:
+//
+// Flexible mode (F=1):
+//
+//      +-+-+-+-+-+-+-+-+
+// L:   |  T  |U|  S  |D|
+//      +-+-+-+-+-+-+-+-+
+//
+bool WriteLayerInfoFlexibleMode(const RTPVideoHeaderVP9& vp9,
+                                rtc::BitBufferWriter* writer) {
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(TemporalIdxField(vp9, 0), 3));
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.temporalUpSwitch ? 1 : 0, 1));
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(SpatialIdxField(vp9, 0), 3));
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.interLayerPredicted ? 1 : 0, 1));
+  return true;
+}
+
+// Non-flexible mode (F=0):
+//
+//      +-+-+-+-+-+-+-+-+
+// L:   |GOF_IDX|  S  |D|
+//      +-+-+-+-+-+-+-+-+
+//      |   TL0PICIDX   |
+//      +-+-+-+-+-+-+-+-+
+//
+bool WriteLayerInfoNonFlexibleMode(const RTPVideoHeaderVP9& vp9,
+                                   rtc::BitBufferWriter* writer) {
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(GofIdxField(vp9, 0), 4));
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(SpatialIdxField(vp9, 0), 3));
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.interLayerPredicted ? 1 : 0, 1));
+  RETURN_FALSE_ON_ERROR(writer->WriteUInt8(Tl0PicIdxField(vp9, 0)));
+  return true;
+}
+
+bool WriteLayerInfo(const RTPVideoHeaderVP9& vp9,
+                    rtc::BitBufferWriter* writer) {
+  if (vp9.flexibleMode) {
+    return WriteLayerInfoFlexibleMode(vp9, writer);
+  } else {
+    return WriteLayerInfoNonFlexibleMode(vp9, writer);
+  }
+}
+
+// Reference indices:
+//
+//      +-+-+-+-+-+-+-+-+  -|           P=1,F=1: At least one reference index
+// P,F: | P_DIFF    |X|N|   .                    has to be specified.
+//      +-+-+-+-+-+-+-+-+   . up to 3 times
+// X:   |EXTENDED P_DIFF|   .               X=1: Extended P_DIFF is used (14
+//      +-+-+-+-+-+-+-+-+  -|                    bits). Else 6 bits is used.
+//                                          N=1: An additional P_DIFF follows
+//                                               current P_DIFF.
+bool WriteRefIndices(const RTPVideoHeaderVP9& vp9,
+                     rtc::BitBufferWriter* writer) {
+  if (!PictureIdPresent(vp9) ||
+      vp9.numRefPics == 0 || vp9.numRefPics > kMaxVp9RefPics) {
+    return false;
+  }
+  for (size_t i = 0; i < vp9.numRefPics; ++i) {
+    uint32_t x_bit = (vp9.pidDiff[i] > 0x3F) ? 1 : 0;
+    uint32_t n_bit = (i == vp9.numRefPics - 1) ? 0 : 1;
+    if (x_bit) {
+      RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.pidDiff[i] >> 8, 6));
+      RETURN_FALSE_ON_ERROR(writer->WriteBits(x_bit, 1));
+      RETURN_FALSE_ON_ERROR(writer->WriteBits(n_bit, 1));
+      RETURN_FALSE_ON_ERROR(writer->WriteUInt8(vp9.pidDiff[i]));
+    } else {
+      RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.pidDiff[i], 6));
+      RETURN_FALSE_ON_ERROR(writer->WriteBits(x_bit, 1));
+      RETURN_FALSE_ON_ERROR(writer->WriteBits(n_bit, 1));
+    }
+  }
+  return true;
+}
+
+// Scalability structure (SS).
+//
+//      +-+-+-+-+-+-+-+-+
+// V:   | N_S |Y|  N_G  |
+//      +-+-+-+-+-+-+-+-+              -|
+// Y:   |     WIDTH     | (OPTIONAL)    .
+//      +               +               .
+//      |               | (OPTIONAL)    .
+//      +-+-+-+-+-+-+-+-+               . N_S + 1 times
+//      |     HEIGHT    | (OPTIONAL)    .
+//      +               +               .
+//      |               | (OPTIONAL)    .
+//      +-+-+-+-+-+-+-+-+              -|           -|
+// N_G: |  T  |U| R |-|-| (OPTIONAL)                 .
+//      +-+-+-+-+-+-+-+-+              -|            . N_G + 1 times
+//      |    P_DIFF     | (OPTIONAL)    . R times    .
+//      +-+-+-+-+-+-+-+-+              -|           -|
+//
+bool WriteSsData(const RTPVideoHeaderVP9& vp9, rtc::BitBufferWriter* writer) {
+  if (vp9.numSpatialLayers == 0 ||
+      vp9.numSpatialLayers > kMaxVp9NumberOfSpatialLayers ||
+      vp9.gof.numFramesInGof == 0 ||
+      vp9.gof.numFramesInGof > kMaxVp9FramesInGof) {
+    return false;
+  }

[stefan-webrtc, 2015/07/14 09:40:10]

I think we should DCHECK on these instead.

[åsapersson, 2015/07/14 10:53:55]

Done.

+  RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.numSpatialLayers - 1, 3));
+  RETURN_FALSE_ON_ERROR(
+      writer->WriteBits(vp9.spatialLayerResolutionPresent ? 1 : 0, 1));
+  RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.gof.numFramesInGof - 1, 4));
+
+  if (vp9.spatialLayerResolutionPresent) {
+    for (size_t i = 0; i < vp9.numSpatialLayers; ++i) {
+      RETURN_FALSE_ON_ERROR(writer->WriteUInt16(vp9.width[i]));
+      RETURN_FALSE_ON_ERROR(writer->WriteUInt16(vp9.height[i]));
+    }
+  }
+  for (size_t i = 0; i < vp9.gof.numFramesInGof; ++i) {
+    RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.gof.temporalIdx[i], 3));
+    RETURN_FALSE_ON_ERROR(
+        writer->WriteBits(vp9.gof.temporalUpSwitch[i] ? 1 : 0, 1));
+    RETURN_FALSE_ON_ERROR(writer->WriteBits(vp9.gof.numRefPics[i], 2));
+    RETURN_FALSE_ON_ERROR(writer->WriteBits(kReservedBitValue0, 2));
+    for (size_t r = 0; r < vp9.gof.numRefPics[i]; ++r) {
+      RETURN_FALSE_ON_ERROR(writer->WriteUInt8(vp9.gof.pidDiff[i][r]));
+    }
+  }
+  return true;
+}
+
+// Picture ID:
+//
+//      +-+-+-+-+-+-+-+-+
+// I:   |M| PICTURE ID  |   M:0 => picture id is 7 bits.
+//      +-+-+-+-+-+-+-+-+   M:1 => picture id is 15 bits.
+// M:   | EXTENDED PID  |
+//      +-+-+-+-+-+-+-+-+
+//
+bool ParsePictureId(rtc::BitBuffer* parser, RTPVideoHeaderVP9* vp9) {
+  uint32_t picture_id;
+  uint32_t m_bit;
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&m_bit, 1));
+  if (m_bit) {
+    RETURN_FALSE_ON_ERROR(parser->ReadBits(&picture_id, 15));
+    vp9->maxPictureId = kMaxTwoBytePictureId;
+  } else {
+    RETURN_FALSE_ON_ERROR(parser->ReadBits(&picture_id, 7));
+    vp9->maxPictureId = kMaxOneBytePictureId;
+  }
+  vp9->pictureId = picture_id;
+  return true;
+}
+
+// Layer indices (flexible mode):
+//
+//      +-+-+-+-+-+-+-+-+
+// L:   |  T  |U|  S  |D|
+//      +-+-+-+-+-+-+-+-+
+//
+bool ParseLayerInfoFlexibleMode(rtc::BitBuffer* parser,
+                                RTPVideoHeaderVP9* vp9) {
+  uint32_t t, u_bit, s, d_bit;
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&t, 3));
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&u_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&s, 3));
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&d_bit, 1));
+  vp9->temporalIdx = t;
+  vp9->temporalUpSwitch = u_bit ? true : false;
+  vp9->spatialIdx = s;
+  vp9->interLayerPredicted = d_bit ? true : false;
+  return true;
+}
+
+// Layer indices (non-flexible mode):
+//
+//      +-+-+-+-+-+-+-+-+
+// L:   |GOF_IDX|  S  |D|
+//      +-+-+-+-+-+-+-+-+
+//      |   TL0PICIDX   |
+//      +-+-+-+-+-+-+-+-+
+//
+bool ParseLayerInfoNonFlexibleMode(rtc::BitBuffer* parser,
+                                   RTPVideoHeaderVP9* vp9) {
+  uint32_t gof_idx, s, d_bit;
+  uint8_t tl0picidx;
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&gof_idx, 4));
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&s, 3));
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&d_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser->ReadUInt8(&tl0picidx));
+  vp9->gofIdx = gof_idx;
+  vp9->spatialIdx = s;
+  vp9->interLayerPredicted = d_bit ? true : false;
+  vp9->tl0PicIdx = tl0picidx;
+  return true;
+}
+
+bool ParseLayerInfo(rtc::BitBuffer* parser, RTPVideoHeaderVP9* vp9) {
+  if (vp9->flexibleMode) {
+    return ParseLayerInfoFlexibleMode(parser, vp9);
+  } else {
+    return ParseLayerInfoNonFlexibleMode(parser, vp9);
+  }
+}
+
+// Reference indices:
+//
+//      +-+-+-+-+-+-+-+-+  -|           P=1,F=1: At least one reference index
+// P,F: | P_DIFF    |X|N|   .                    has to be specified.
+//      +-+-+-+-+-+-+-+-+   . up to 3 times
+// X:   |EXTENDED P_DIFF|   .               X=1: Extended P_DIFF is used (14
+//      +-+-+-+-+-+-+-+-+  -|                    bits). Else 6 bits is used.
+//                                          N=1: An additional P_DIFF follows
+//                                               current P_DIFF.
+bool ParseRefIndices(rtc::BitBuffer* parser, RTPVideoHeaderVP9* vp9) {
+  if (vp9->pictureId == kNoPictureId)
+    return false;
+
+  vp9->numRefPics = 0;
+  uint32_t n_bit;
+  do {
+    if (vp9->numRefPics == kMaxVp9RefPics)
+      return false;
+
+    uint32_t p_diff, x_bit;
+    RETURN_FALSE_ON_ERROR(parser->ReadBits(&p_diff, 6));
+    RETURN_FALSE_ON_ERROR(parser->ReadBits(&x_bit, 1));
+    RETURN_FALSE_ON_ERROR(parser->ReadBits(&n_bit, 1));
+
+    if (x_bit) {
+      // P_DIFF is 14 bits.
+      uint8_t ext_p_diff;
+      RETURN_FALSE_ON_ERROR(parser->ReadUInt8(&ext_p_diff));
+      p_diff = (p_diff << 8) + ext_p_diff;
+    }
+
+    vp9->pidDiff[vp9->numRefPics] = p_diff;
+    uint32_t scaled_pid = vp9->pictureId;
+    while (p_diff > scaled_pid) {
+      scaled_pid += vp9->maxPictureId + 1;
+    }
+    vp9->refPictureId[vp9->numRefPics++] = scaled_pid - p_diff;
+  } while (n_bit);
+
+  return true;
+}
+
+// Scalability structure (SS).
+//
+//      +-+-+-+-+-+-+-+-+
+// V:   | N_S |Y|  N_G  |
+//      +-+-+-+-+-+-+-+-+              -|
+// Y:   |     WIDTH     | (OPTIONAL)    .
+//      +               +               .
+//      |               | (OPTIONAL)    .
+//      +-+-+-+-+-+-+-+-+               . N_S + 1 times
+//      |     HEIGHT    | (OPTIONAL)    .
+//      +               +               .
+//      |               | (OPTIONAL)    .
+//      +-+-+-+-+-+-+-+-+              -|           -|
+// N_G: |  T  |U| R |-|-| (OPTIONAL)                 .
+//      +-+-+-+-+-+-+-+-+              -|            . N_G + 1 times
+//      |    P_DIFF     | (OPTIONAL)    . R times    .
+//      +-+-+-+-+-+-+-+-+              -|           -|
+//
+bool ParseSsData(rtc::BitBuffer* parser, RTPVideoHeaderVP9* vp9) {
+  uint32_t n_s, y_bit, n_g;
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&n_s, 3));
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&y_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser->ReadBits(&n_g, 4));
+  vp9->numSpatialLayers = n_s + 1;
+  vp9->spatialLayerResolutionPresent = y_bit ? true : false;
+  vp9->gof.numFramesInGof = n_g + 1;
+
+  if (y_bit) {
+    for (size_t i = 0; i < vp9->numSpatialLayers; ++i) {
+      RETURN_FALSE_ON_ERROR(parser->ReadUInt16(&vp9->width[i]));
+      RETURN_FALSE_ON_ERROR(parser->ReadUInt16(&vp9->height[i]));
+    }
+  }
+  for (size_t i = 0; i < vp9->gof.numFramesInGof; ++i) {
+    uint32_t t, u_bit, r;
+    RETURN_FALSE_ON_ERROR(parser->ReadBits(&t, 3));
+    RETURN_FALSE_ON_ERROR(parser->ReadBits(&u_bit, 1));
+    RETURN_FALSE_ON_ERROR(parser->ReadBits(&r, 2));
+    RETURN_FALSE_ON_ERROR(parser->ConsumeBits(2));
+    vp9->gof.temporalIdx[i] = t;
+    vp9->gof.temporalUpSwitch[i] = u_bit ? true : false;
+    vp9->gof.numRefPics[i] = r;
+
+    for (size_t p = 0; p < vp9->gof.numRefPics[i]; ++p) {
+      uint8_t p_diff;
+      RETURN_FALSE_ON_ERROR(parser->ReadUInt8(&p_diff));
+      vp9->gof.pidDiff[i][p] = p_diff;
+    }
+  }
+  return true;
+}
+
+// Gets the size of next payload chunk to send. Returns 0 on error.
+size_t CalcNextSize(size_t max_length, size_t rem_bytes) {
+  if (max_length == 0 || rem_bytes == 0) {
+    return 0;
+  }
+  if (kBalancedMode) {
+    size_t num_frags = std::ceil(static_cast<double>(rem_bytes) / max_length);
+    return static_cast<size_t>(
+        static_cast<double>(rem_bytes) / num_frags + 0.5);
+  }
+  return max_length >= rem_bytes ? rem_bytes : max_length;
+}
+}  // namespace
+
+
+RtpPacketizerVp9::RtpPacketizerVp9(const RTPVideoHeaderVP9& hdr,
+                                   size_t max_payload_length)
+    : hdr_(hdr),
+      max_payload_length_(max_payload_length),
+      payload_(nullptr),
+      payload_size_(0) {
+}
+
+RtpPacketizerVp9::~RtpPacketizerVp9() {
+}
+
+ProtectionType RtpPacketizerVp9::GetProtectionType() {
+  bool protect =
+      hdr_.temporalIdx == 0 || hdr_.temporalIdx == kNoTemporalIdx;
+  return protect ? kProtectedPacket : kUnprotectedPacket;
+}
+
+StorageType RtpPacketizerVp9::GetStorageType(uint32_t retransmission_settings) {
+  StorageType storage = kAllowRetransmission;
+  if (hdr_.temporalIdx == 0 &&
+      !(retransmission_settings & kRetransmitBaseLayer)) {
+    storage = kDontRetransmit;
+  } else if (hdr_.temporalIdx != kNoTemporalIdx && hdr_.temporalIdx > 0 &&
+             !(retransmission_settings & kRetransmitHigherLayers)) {
+    storage = kDontRetransmit;
+  }
+  return storage;
+}
+
+std::string RtpPacketizerVp9::ToString() {
+  return "RtpPacketizerVp9";
+}
+
+void RtpPacketizerVp9::SetPayloadData(
+    const uint8_t* payload,
+    size_t payload_size,
+    const RTPFragmentationHeader* fragmentation) {
+  payload_ = payload;
+  payload_size_ = payload_size;
+  GeneratePackets();
+}
+
+void RtpPacketizerVp9::GeneratePackets() {
+  if (max_payload_length_ < PayloadDescriptorLength(hdr_) + 1) {
+    LOG(LS_ERROR) << "Payload header and one payload byte won't fit.";
+    return;
+  }
+  size_t bytes_processed = 0;
+  while (bytes_processed < payload_size_) {
+    size_t rem_bytes = payload_size_ - bytes_processed;
+    size_t rem_payload_len = max_payload_length_ -
+         (bytes_processed ? PayloadDescriptorLengthMinusSsData(hdr_)
+                          : PayloadDescriptorLength(hdr_));
+
+    size_t packet_bytes = CalcNextSize(rem_payload_len, rem_bytes);
+    if (packet_bytes == 0) {
+      LOG(LS_ERROR) << "Failed to generate VP9 packets.";
+      while (!packets_.empty())
+        packets_.pop();
+      return;
+    }
+    QueuePacket(bytes_processed, packet_bytes, bytes_processed == 0,
+                rem_bytes == packet_bytes, &packets_);
+    bytes_processed += packet_bytes;
+  }
+  assert(bytes_processed == payload_size_);
+}
+
+bool RtpPacketizerVp9::NextPacket(uint8_t* buffer,
+                                  size_t* bytes_to_send,
+                                  bool* last_packet) {
+  if (packets_.empty()) {
+    return false;
+  }
+  PacketInfo packet_info = packets_.front();
+  packets_.pop();
+
+  if (!WriteHeaderAndPayload(packet_info, buffer, bytes_to_send)) {
+    return false;
+  }
+  *last_packet = packets_.empty();
+  return true;
+}
+
+// VP9 format:
+//
+// Payload descriptor for F = 1 (flexible mode)
+//       0 1 2 3 4 5 6 7
+//      +-+-+-+-+-+-+-+-+
+//      |I|P|L|F|B|E|V|-| (REQUIRED)
+//      +-+-+-+-+-+-+-+-+
+// I:   |M| PICTURE ID  | (RECOMMENDED)
+//      +-+-+-+-+-+-+-+-+
+// M:   | EXTENDED PID  | (RECOMMENDED)
+//      +-+-+-+-+-+-+-+-+
+// L:   |  T  |U|  S  |D| (CONDITIONALLY RECOMMENDED)
+//      +-+-+-+-+-+-+-+-+                             -|
+// P,F: | P_DIFF    |X|N| (CONDITIONALLY RECOMMENDED)  .
+//      +-+-+-+-+-+-+-+-+                              . up to 3 times
+// X:   |EXTENDED P_DIFF|                              .
+//      +-+-+-+-+-+-+-+-+                             -|
+// V:   | SS            |
+//      | ..            |
+//      +-+-+-+-+-+-+-+-+
+//
+// Payload descriptor for F = 0 (non-flexible mode)
+//       0 1 2 3 4 5 6 7
+//      +-+-+-+-+-+-+-+-+
+//      |I|P|L|F|B|E|V|-| (REQUIRED)
+//      +-+-+-+-+-+-+-+-+
+// I:   |M| PICTURE ID  | (RECOMMENDED)
+//      +-+-+-+-+-+-+-+-+
+// M:   | EXTENDED PID  | (RECOMMENDED)
+//      +-+-+-+-+-+-+-+-+
+// L:   |GOF_IDX|  S  |D| (CONDITIONALLY RECOMMENDED)
+//      +-+-+-+-+-+-+-+-+
+//      |   TL0PICIDX   | (CONDITIONALLY REQUIRED)
+//      +-+-+-+-+-+-+-+-+
+// V:   | SS            |
+//      | ..            |
+//      +-+-+-+-+-+-+-+-+
+
+bool RtpPacketizerVp9::WriteHeaderAndPayload(const PacketInfo& packet_info,
+                                             uint8_t* buffer,
+                                             size_t* bytes_to_send) const {
+  size_t header_length;
+  if (!WriteHeader(packet_info, buffer, &header_length))
+    return false;
+
+  // Copy payload data.
+  memcpy(&buffer[header_length],
+         &payload_[packet_info.payload_start_pos], packet_info.size);
+
+  *bytes_to_send = header_length + packet_info.size;
+  return true;
+}
+
+bool RtpPacketizerVp9::WriteHeader(const PacketInfo& packet_info,
+                                   uint8_t* buffer,
+                                   size_t* header_length) const {
+  // Required payload descriptor byte.
+  uint32_t i_bit = PictureIdPresent(hdr_) ? 1 : 0;
+  uint32_t p_bit = hdr_.interPicPredicted ? 1 : 0;
+  uint32_t l_bit = LayerInfoPresent(hdr_) ? 1 : 0;
+  uint32_t f_bit = hdr_.flexibleMode ? 1 : 0;
+  uint32_t b_bit = (hdr_.beginningOfFrame &&
+                    packet_info.layer_begin) ? 1 : 0;
+  uint32_t e_bit = (hdr_.endOfFrame && packet_info.layer_end) ? 1 : 0;
+  uint32_t v_bit = (hdr_.ssDataAvailable && b_bit) ? 1 : 0;
+
+  rtc::BitBufferWriter writer(buffer, max_payload_length_);
+  RETURN_FALSE_ON_ERROR(writer.WriteBits(i_bit, 1));
+  RETURN_FALSE_ON_ERROR(writer.WriteBits(p_bit, 1));
+  RETURN_FALSE_ON_ERROR(writer.WriteBits(l_bit, 1));
+  RETURN_FALSE_ON_ERROR(writer.WriteBits(f_bit, 1));
+  RETURN_FALSE_ON_ERROR(writer.WriteBits(b_bit, 1));
+  RETURN_FALSE_ON_ERROR(writer.WriteBits(e_bit, 1));
+  RETURN_FALSE_ON_ERROR(writer.WriteBits(v_bit, 1));
+  RETURN_FALSE_ON_ERROR(writer.WriteBits(kReservedBitValue0, 1));
+
+  // Add fields that are present.
+  if (i_bit && !WritePictureId(hdr_, &writer)) {
+    LOG(LS_ERROR) << "Failed writing VP9 picture id.";
+    return false;
+  }
+  if (l_bit && !WriteLayerInfo(hdr_, &writer)) {
+    LOG(LS_ERROR) << "Failed writing VP9 layer info.";
+    return false;
+  }
+  if (p_bit && f_bit && !WriteRefIndices(hdr_, &writer)) {
+    LOG(LS_ERROR) << "Failed writing VP9 ref indices.";
+    return false;
+  }
+  if (v_bit && !WriteSsData(hdr_, &writer)) {
+    LOG(LS_ERROR) << "Failed writing VP9 SS data.";
+    return false;
+  }
+
+  size_t offset_bytes = 0;
+  size_t offset_bits = 0;
+  writer.GetCurrentOffset(&offset_bytes, &offset_bits);
+  assert(offset_bits == 0);
+
+  *header_length = offset_bytes;
+  return true;
+}
+
+bool RtpDepacketizerVp9::Parse(ParsedPayload* parsed_payload,
+                               const uint8_t* payload,
+                               size_t payload_length) {
+  assert(parsed_payload != nullptr);
+  if (payload_length == 0) {
+    LOG(LS_ERROR) << "Payload length is zero.";
+    return false;
+  }
+
+  // Parse mandatory first byte of payload descriptor.
+  rtc::BitBuffer parser(payload, payload_length);
+  uint32_t i_bit, p_bit, l_bit, f_bit, b_bit, e_bit, v_bit;
+  RETURN_FALSE_ON_ERROR(parser.ReadBits(&i_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser.ReadBits(&p_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser.ReadBits(&l_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser.ReadBits(&f_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser.ReadBits(&b_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser.ReadBits(&e_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser.ReadBits(&v_bit, 1));
+  RETURN_FALSE_ON_ERROR(parser.ConsumeBits(1));
+
+  // Parsed payload.
+  parsed_payload->type.Video.width = 0;
+  parsed_payload->type.Video.height = 0;
+  parsed_payload->type.Video.simulcastIdx = 0;
+  // TODO(asapersson): Add when type is added.
+  // parsed_payload->type.Video.codec = kRtpVideoVp9;
+
+  parsed_payload->frame_type = p_bit ? kVideoFrameDelta : kVideoFrameKey;
+
+  RTPVideoHeaderVP9* vp9 = &parsed_payload->type.Video.codecHeader.VP9;
+  vp9->InitRTPVideoHeaderVP9();
+  vp9->interPicPredicted = p_bit ? true : false;
+  vp9->flexibleMode = f_bit ? true : false;
+  vp9->beginningOfFrame = b_bit ? true : false;
+  vp9->endOfFrame = e_bit ? true : false;
+  vp9->ssDataAvailable = v_bit ? true : false;
+  vp9->temporalIdx = 0;
+  vp9->spatialIdx = 0;
+
+  // Parse fields that are present.
+  if (i_bit && !ParsePictureId(&parser, vp9)) {
+    LOG(LS_ERROR) << "Failed parsing VP9 picture id.";
+    return false;
+  }
+  if (l_bit && !ParseLayerInfo(&parser, vp9)) {
+    LOG(LS_ERROR) << "Failed parsing VP9 layer info.";
+    return false;
+  }
+  if (p_bit && f_bit && !ParseRefIndices(&parser, vp9)) {
+    LOG(LS_ERROR) << "Failed parsing VP9 ref indices.";
+    return false;
+  }
+  if (v_bit) {
+    if (!ParseSsData(&parser, vp9)) {
+      LOG(LS_ERROR) << "Failed parsing VP9 SS data.";
+      return false;
+    }
+    if (vp9->spatialLayerResolutionPresent) {
+      // TODO(asapersson): Add support for spatial layers.
+      parsed_payload->type.Video.width = vp9->width[0];
+      parsed_payload->type.Video.height = vp9->height[0];
+    }
+  }
+  parsed_payload->type.Video.isFirstPacket = b_bit && (vp9->spatialIdx == 0);
+
+  uint64_t rem_bits = parser.RemainingBitCount();
+  assert(rem_bits % 8 == 0);
+  parsed_payload->payload_length = rem_bits / 8;
+  if (parsed_payload->payload_length == 0) {
+    LOG(LS_ERROR) << "Failed parsing VP9 payload data.";
+    return false;
+  }
+  parsed_payload->payload =
+      payload + payload_length - parsed_payload->payload_length;
+
+  return true;
+}
+}  // namespace webrtc