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Diffstat (limited to 'webrtc/modules/video_coding/decoding_state.cc')
| -rw-r--r-- | webrtc/modules/video_coding/decoding_state.cc | 285 |
1 files changed, 285 insertions, 0 deletions
diff --git a/webrtc/modules/video_coding/decoding_state.cc b/webrtc/modules/video_coding/decoding_state.cc new file mode 100644 index 0000000000..89be9b66c1 --- /dev/null +++ b/webrtc/modules/video_coding/decoding_state.cc @@ -0,0 +1,285 @@ +/* + * Copyright (c) 2011 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/decoding_state.h" + +#include "webrtc/modules/include/module_common_types.h" +#include "webrtc/modules/video_coding/frame_buffer.h" +#include "webrtc/modules/video_coding/jitter_buffer_common.h" +#include "webrtc/modules/video_coding/packet.h" + +namespace webrtc { + +VCMDecodingState::VCMDecodingState() + : sequence_num_(0), + time_stamp_(0), + picture_id_(kNoPictureId), + temporal_id_(kNoTemporalIdx), + tl0_pic_id_(kNoTl0PicIdx), + full_sync_(true), + in_initial_state_(true) { + memset(frame_decoded_, 0, sizeof(frame_decoded_)); +} + +VCMDecodingState::~VCMDecodingState() {} + +void VCMDecodingState::Reset() { + // TODO(mikhal): Verify - not always would want to reset the sync + sequence_num_ = 0; + time_stamp_ = 0; + picture_id_ = kNoPictureId; + temporal_id_ = kNoTemporalIdx; + tl0_pic_id_ = kNoTl0PicIdx; + full_sync_ = true; + in_initial_state_ = true; + memset(frame_decoded_, 0, sizeof(frame_decoded_)); +} + +uint32_t VCMDecodingState::time_stamp() const { + return time_stamp_; +} + +uint16_t VCMDecodingState::sequence_num() const { + return sequence_num_; +} + +bool VCMDecodingState::IsOldFrame(const VCMFrameBuffer* frame) const { + assert(frame != NULL); + if (in_initial_state_) + return false; + return !IsNewerTimestamp(frame->TimeStamp(), time_stamp_); +} + +bool VCMDecodingState::IsOldPacket(const VCMPacket* packet) const { + assert(packet != NULL); + if (in_initial_state_) + return false; + return !IsNewerTimestamp(packet->timestamp, time_stamp_); +} + +void VCMDecodingState::SetState(const VCMFrameBuffer* frame) { + assert(frame != NULL && frame->GetHighSeqNum() >= 0); + if (!UsingFlexibleMode(frame)) + UpdateSyncState(frame); + sequence_num_ = static_cast<uint16_t>(frame->GetHighSeqNum()); + time_stamp_ = frame->TimeStamp(); + picture_id_ = frame->PictureId(); + temporal_id_ = frame->TemporalId(); + tl0_pic_id_ = frame->Tl0PicId(); + + if (UsingFlexibleMode(frame)) { + uint16_t frame_index = picture_id_ % kFrameDecodedLength; + if (in_initial_state_) { + frame_decoded_cleared_to_ = frame_index; + } else if (frame->FrameType() == kVideoFrameKey) { + memset(frame_decoded_, 0, sizeof(frame_decoded_)); + frame_decoded_cleared_to_ = frame_index; + } else { + if (AheadOfFramesDecodedClearedTo(frame_index)) { + while (frame_decoded_cleared_to_ != frame_index) { + frame_decoded_cleared_to_ = + (frame_decoded_cleared_to_ + 1) % kFrameDecodedLength; + frame_decoded_[frame_decoded_cleared_to_] = false; + } + } + } + frame_decoded_[frame_index] = true; + } + + in_initial_state_ = false; +} + +void VCMDecodingState::CopyFrom(const VCMDecodingState& state) { + sequence_num_ = state.sequence_num_; + time_stamp_ = state.time_stamp_; + picture_id_ = state.picture_id_; + temporal_id_ = state.temporal_id_; + tl0_pic_id_ = state.tl0_pic_id_; + full_sync_ = state.full_sync_; + in_initial_state_ = state.in_initial_state_; + frame_decoded_cleared_to_ = state.frame_decoded_cleared_to_; + memcpy(frame_decoded_, state.frame_decoded_, sizeof(frame_decoded_)); +} + +bool VCMDecodingState::UpdateEmptyFrame(const VCMFrameBuffer* frame) { + bool empty_packet = frame->GetHighSeqNum() == frame->GetLowSeqNum(); + if (in_initial_state_ && empty_packet) { + // Drop empty packets as long as we are in the initial state. + return true; + } + if ((empty_packet && ContinuousSeqNum(frame->GetHighSeqNum())) || + ContinuousFrame(frame)) { + // Continuous empty packets or continuous frames can be dropped if we + // advance the sequence number. + sequence_num_ = frame->GetHighSeqNum(); + time_stamp_ = frame->TimeStamp(); + return true; + } + return false; +} + +void VCMDecodingState::UpdateOldPacket(const VCMPacket* packet) { + assert(packet != NULL); + if (packet->timestamp == time_stamp_) { + // Late packet belonging to the last decoded frame - make sure we update the + // last decoded sequence number. + sequence_num_ = LatestSequenceNumber(packet->seqNum, sequence_num_); + } +} + +void VCMDecodingState::SetSeqNum(uint16_t new_seq_num) { + sequence_num_ = new_seq_num; +} + +bool VCMDecodingState::in_initial_state() const { + return in_initial_state_; +} + +bool VCMDecodingState::full_sync() const { + return full_sync_; +} + +void VCMDecodingState::UpdateSyncState(const VCMFrameBuffer* frame) { + if (in_initial_state_) + return; + if (frame->TemporalId() == kNoTemporalIdx || + frame->Tl0PicId() == kNoTl0PicIdx) { + full_sync_ = true; + } else if (frame->FrameType() == kVideoFrameKey || frame->LayerSync()) { + full_sync_ = true; + } else if (full_sync_) { + // Verify that we are still in sync. + // Sync will be broken if continuity is true for layers but not for the + // other methods (PictureId and SeqNum). + if (UsingPictureId(frame)) { + // First check for a valid tl0PicId. + if (frame->Tl0PicId() - tl0_pic_id_ > 1) { + full_sync_ = false; + } else { + full_sync_ = ContinuousPictureId(frame->PictureId()); + } + } else { + full_sync_ = + ContinuousSeqNum(static_cast<uint16_t>(frame->GetLowSeqNum())); + } + } +} + +bool VCMDecodingState::ContinuousFrame(const VCMFrameBuffer* frame) const { + // Check continuity based on the following hierarchy: + // - Temporal layers (stop here if out of sync). + // - Picture Id when available. + // - Sequence numbers. + // Return true when in initial state. + // Note that when a method is not applicable it will return false. + assert(frame != NULL); + // A key frame is always considered continuous as it doesn't refer to any + // frames and therefore won't introduce any errors even if prior frames are + // missing. + if (frame->FrameType() == kVideoFrameKey) + return true; + // When in the initial state we always require a key frame to start decoding. + if (in_initial_state_) + return false; + if (ContinuousLayer(frame->TemporalId(), frame->Tl0PicId())) + return true; + // tl0picId is either not used, or should remain unchanged. + if (frame->Tl0PicId() != tl0_pic_id_) + return false; + // Base layers are not continuous or temporal layers are inactive. + // In the presence of temporal layers, check for Picture ID/sequence number + // continuity if sync can be restored by this frame. + if (!full_sync_ && !frame->LayerSync()) + return false; + if (UsingPictureId(frame)) { + if (UsingFlexibleMode(frame)) { + return ContinuousFrameRefs(frame); + } else { + return ContinuousPictureId(frame->PictureId()); + } + } else { + return ContinuousSeqNum(static_cast<uint16_t>(frame->GetLowSeqNum())); + } +} + +bool VCMDecodingState::ContinuousPictureId(int picture_id) const { + int next_picture_id = picture_id_ + 1; + if (picture_id < picture_id_) { + // Wrap + if (picture_id_ >= 0x80) { + // 15 bits used for picture id + return ((next_picture_id & 0x7FFF) == picture_id); + } else { + // 7 bits used for picture id + return ((next_picture_id & 0x7F) == picture_id); + } + } + // No wrap + return (next_picture_id == picture_id); +} + +bool VCMDecodingState::ContinuousSeqNum(uint16_t seq_num) const { + return seq_num == static_cast<uint16_t>(sequence_num_ + 1); +} + +bool VCMDecodingState::ContinuousLayer(int temporal_id, int tl0_pic_id) const { + // First, check if applicable. + if (temporal_id == kNoTemporalIdx || tl0_pic_id == kNoTl0PicIdx) + return false; + // If this is the first frame to use temporal layers, make sure we start + // from base. + else if (tl0_pic_id_ == kNoTl0PicIdx && temporal_id_ == kNoTemporalIdx && + temporal_id == 0) + return true; + + // Current implementation: Look for base layer continuity. + if (temporal_id != 0) + return false; + return (static_cast<uint8_t>(tl0_pic_id_ + 1) == tl0_pic_id); +} + +bool VCMDecodingState::ContinuousFrameRefs(const VCMFrameBuffer* frame) const { + uint8_t num_refs = frame->CodecSpecific()->codecSpecific.VP9.num_ref_pics; + for (uint8_t r = 0; r < num_refs; ++r) { + uint16_t frame_ref = frame->PictureId() - + frame->CodecSpecific()->codecSpecific.VP9.p_diff[r]; + uint16_t frame_index = frame_ref % kFrameDecodedLength; + if (AheadOfFramesDecodedClearedTo(frame_index) || + !frame_decoded_[frame_index]) { + return false; + } + } + return true; +} + +bool VCMDecodingState::UsingPictureId(const VCMFrameBuffer* frame) const { + return (frame->PictureId() != kNoPictureId && picture_id_ != kNoPictureId); +} + +bool VCMDecodingState::UsingFlexibleMode(const VCMFrameBuffer* frame) const { + return frame->CodecSpecific()->codecType == kVideoCodecVP9 && + frame->CodecSpecific()->codecSpecific.VP9.flexible_mode; +} + +// TODO(philipel): change how check work, this check practially +// limits the max p_diff to 64. +bool VCMDecodingState::AheadOfFramesDecodedClearedTo(uint16_t index) const { + // No way of knowing for sure if we are actually ahead of + // frame_decoded_cleared_to_. We just make the assumption + // that we are not trying to reference back to a very old + // index, but instead are referencing a newer index. + uint16_t diff = + index > frame_decoded_cleared_to_ + ? kFrameDecodedLength - (index - frame_decoded_cleared_to_) + : frame_decoded_cleared_to_ - index; + return diff > kFrameDecodedLength / 2; +} + +} // namespace webrtc |