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/*
* Copyright (c) 2019 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 "modules/rtp_rtcp/source/video_rtp_depacketizer_vp8.h"
#include <stddef.h>
#include <stdint.h>
#include <optional>
#include <utility>
#include "api/array_view.h"
#include "api/video/video_codec_type.h"
#include "api/video/video_frame_type.h"
#include "modules/rtp_rtcp/source/rtp_video_header.h"
#include "modules/rtp_rtcp/source/video_rtp_depacketizer.h"
#include "modules/video_coding/codecs/vp8/include/vp8_globals.h"
#include "rtc_base/checks.h"
#include "rtc_base/copy_on_write_buffer.h"
#include "rtc_base/logging.h"
// VP8 payload descriptor
// https://datatracker.ietf.org/doc/html/rfc7741#section-4.2
//
// 0 1 2 3 4 5 6 7
// +-+-+-+-+-+-+-+-+
// |X|R|N|S|R| PID | (REQUIRED)
// +-+-+-+-+-+-+-+-+
// X: |I|L|T|K| RSV | (OPTIONAL)
// +-+-+-+-+-+-+-+-+
// I: |M| PictureID | (OPTIONAL)
// +-+-+-+-+-+-+-+-+
// | PictureID |
// +-+-+-+-+-+-+-+-+
// L: | TL0PICIDX | (OPTIONAL)
// +-+-+-+-+-+-+-+-+
// T/K: |TID|Y| KEYIDX | (OPTIONAL)
// +-+-+-+-+-+-+-+-+
//
// VP8 payload header. Considered part of the actual payload, sent to decoder.
// https://datatracker.ietf.org/doc/html/rfc7741#section-4.3
//
// 0 1 2 3 4 5 6 7
// +-+-+-+-+-+-+-+-+
// |Size0|H| VER |P|
// +-+-+-+-+-+-+-+-+
// : ... :
// +-+-+-+-+-+-+-+-+
namespace webrtc {
namespace {
constexpr int kFailedToParse = 0;
int ParseVP8Descriptor(RTPVideoHeaderVP8* vp8,
const uint8_t* data,
size_t data_length) {
RTC_DCHECK_GT(data_length, 0);
int parsed_bytes = 0;
// Parse mandatory first byte of payload descriptor.
bool extension = (*data & 0x80) ? true : false; // X bit
vp8->nonReference = (*data & 0x20) ? true : false; // N bit
vp8->beginningOfPartition = (*data & 0x10) ? true : false; // S bit
vp8->partitionId = (*data & 0x07); // PID field
data++;
parsed_bytes++;
data_length--;
if (!extension)
return parsed_bytes;
if (data_length == 0)
return kFailedToParse;
// Optional X field is present.
bool has_picture_id = (*data & 0x80) ? true : false; // I bit
bool has_tl0_pic_idx = (*data & 0x40) ? true : false; // L bit
bool has_tid = (*data & 0x20) ? true : false; // T bit
bool has_key_idx = (*data & 0x10) ? true : false; // K bit
// Advance data and decrease remaining payload size.
data++;
parsed_bytes++;
data_length--;
if (has_picture_id) {
if (data_length == 0)
return kFailedToParse;
vp8->pictureId = (*data & 0x7F);
if (*data & 0x80) {
data++;
parsed_bytes++;
if (--data_length == 0)
return kFailedToParse;
// PictureId is 15 bits
vp8->pictureId = (vp8->pictureId << 8) + *data;
}
data++;
parsed_bytes++;
data_length--;
}
if (has_tl0_pic_idx) {
if (data_length == 0)
return kFailedToParse;
vp8->tl0PicIdx = *data;
data++;
parsed_bytes++;
data_length--;
}
if (has_tid || has_key_idx) {
if (data_length == 0)
return kFailedToParse;
if (has_tid) {
vp8->temporalIdx = ((*data >> 6) & 0x03);
vp8->layerSync = (*data & 0x20) ? true : false; // Y bit
}
if (has_key_idx) {
vp8->keyIdx = *data & 0x1F;
}
data++;
parsed_bytes++;
data_length--;
}
return parsed_bytes;
}
} // namespace
std::optional<VideoRtpDepacketizer::ParsedRtpPayload>
VideoRtpDepacketizerVp8::Parse(CopyOnWriteBuffer rtp_payload) {
ArrayView<const uint8_t> payload(rtp_payload.cdata(), rtp_payload.size());
std::optional<ParsedRtpPayload> result(std::in_place);
int offset = ParseRtpPayload(payload, &result->video_header);
if (offset == kFailedToParse)
return std::nullopt;
RTC_DCHECK_LT(offset, rtp_payload.size());
result->video_payload =
rtp_payload.Slice(offset, rtp_payload.size() - offset);
return result;
}
int VideoRtpDepacketizerVp8::ParseRtpPayload(
ArrayView<const uint8_t> rtp_payload,
RTPVideoHeader* video_header) {
RTC_DCHECK(video_header);
if (rtp_payload.empty()) {
RTC_LOG(LS_ERROR) << "Empty rtp payload.";
return kFailedToParse;
}
video_header->simulcastIdx = 0;
video_header->codec = kVideoCodecVP8;
auto& vp8_header =
video_header->video_type_header.emplace<RTPVideoHeaderVP8>();
vp8_header.InitRTPVideoHeaderVP8();
const int descriptor_size =
ParseVP8Descriptor(&vp8_header, rtp_payload.data(), rtp_payload.size());
if (descriptor_size == kFailedToParse)
return kFailedToParse;
RTC_DCHECK_LT(vp8_header.partitionId, 8);
video_header->is_first_packet_in_frame =
vp8_header.beginningOfPartition && vp8_header.partitionId == 0;
int vp8_payload_size = rtp_payload.size() - descriptor_size;
if (vp8_payload_size == 0) {
RTC_LOG(LS_WARNING) << "Empty vp8 payload.";
return kFailedToParse;
}
const uint8_t* vp8_payload = rtp_payload.data() + descriptor_size;
// Read P bit from payload header (only at beginning of first partition).
if (video_header->is_first_packet_in_frame && (*vp8_payload & 0x01) == 0) {
video_header->frame_type = VideoFrameType::kVideoFrameKey;
if (vp8_payload_size < 10) {
// For an I-frame we should always have the uncompressed VP8 header
// in the beginning of the partition.
return kFailedToParse;
}
video_header->width = ((vp8_payload[7] << 8) + vp8_payload[6]) & 0x3FFF;
video_header->height = ((vp8_payload[9] << 8) + vp8_payload[8]) & 0x3FFF;
} else {
video_header->frame_type = VideoFrameType::kVideoFrameDelta;
video_header->width = 0;
video_header->height = 0;
}
return descriptor_size;
}
} // namespace webrtc
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