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- // Copyright 2014 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.
- #ifndef MEDIA_FILTERS_SOURCE_BUFFER_RANGE_H_
- #define MEDIA_FILTERS_SOURCE_BUFFER_RANGE_H_
- #include <stddef.h>
- #include <map>
- #include <memory>
- #include "base/callback.h"
- #include "base/memory/ref_counted.h"
- #include "base/time/time.h"
- #include "media/base/media_export.h"
- #include "media/base/stream_parser_buffer.h"
- namespace media {
- // Base class for representing a continuous range of buffered data in the
- // presentation timeline. All buffers in a SourceBufferRange are ordered
- // sequentially by GOP presentation interval, and within each GOP by decode
- // order. Unless constructed with |ALLOW_GAPS|, the range contains no internal
- // presentation gaps.
- class MEDIA_EXPORT SourceBufferRange {
- public:
- // Returns the maximum distance in time between any buffer seen in the stream
- // of which this range is a part. Used to estimate the duration of a buffer if
- // its duration is not known, and in GetFudgeRoom() for determining whether a
- // time or coded frame is close enough to be considered part of this range.
- using InterbufferDistanceCB = base::RepeatingCallback<base::TimeDelta()>;
- using BufferQueue = StreamParser::BufferQueue;
- // Policy for handling large gaps between buffers. Continuous media like
- // audio & video should use NO_GAPS_ALLOWED. Discontinuous media like
- // timed text should use ALLOW_GAPS because large differences in timestamps
- // are common and acceptable.
- enum GapPolicy {
- NO_GAPS_ALLOWED,
- ALLOW_GAPS
- };
- // Creates a range with |new_buffers|. |new_buffers| cannot be empty and the
- // front of |new_buffers| must be a keyframe.
- // |range_start_pts| refers to the starting timestamp for the coded
- // frame group to which these buffers belong.
- SourceBufferRange(GapPolicy gap_policy,
- const BufferQueue& new_buffers,
- base::TimeDelta range_start_pts,
- InterbufferDistanceCB interbuffer_distance_cb);
- SourceBufferRange(const SourceBufferRange&) = delete;
- SourceBufferRange& operator=(const SourceBufferRange&) = delete;
- ~SourceBufferRange();
- // Deletes all buffers in range.
- void DeleteAll(BufferQueue* deleted_buffers);
- // Seeks to the beginning of the range.
- void SeekToStart();
- // Updates |out_buffer| with the next buffer in presentation order by GOP and
- // by decode order within each GOP (in general, in sequence to feed a
- // decoder). Seek() must be called before calls to GetNextBuffer(), and
- // buffers are returned in order from the last call to Seek(). Returns true if
- // |out_buffer| is filled with a valid buffer, false if there is not enough
- // data to fulfill the request.
- bool GetNextBuffer(scoped_refptr<StreamParserBuffer>* out_buffer);
- bool HasNextBuffer() const;
- // Returns the config ID for the buffer that will be returned by
- // GetNextBuffer().
- int GetNextConfigId() const;
- // Returns true if the range knows the position of the next buffer it should
- // return, i.e. it has been Seek()ed. This does not necessarily mean that it
- // has the next buffer yet.
- bool HasNextBufferPosition() const;
- // Resets this range to an "unseeked" state.
- void ResetNextBufferPosition();
- // Appends the buffers from |range| into this range.
- // The first buffer in |range| must come directly after the last buffer
- // in this range.
- // If |transfer_current_position| is true, |range|'s |next_buffer_index_|
- // is transferred to this SourceBufferRange.
- // Note: Use these only to merge existing ranges. |range|'s first buffer
- // timestamp must be adjacent to this range. No group start timestamp
- // adjacency is involved in these methods.
- // During append, |highest_frame_| is updated, if necessary.
- void AppendRangeToEnd(const SourceBufferRange& range,
- bool transfer_current_position);
- bool CanAppendRangeToEnd(const SourceBufferRange& range) const;
- // Appends |buffers| to the end of the range and updates |keyframe_map_| as
- // it encounters new keyframes.
- // If |new_buffers_group_start_pts| is kNoTimestamp, then the
- // first buffer in |buffers| must come directly after the last buffer in this
- // range (within the fudge room) - specifically, if the first buffer in
- // |buffers| is not a keyframe, then it must be next in DTS order w.r.t. last
- // buffer in |buffers|. Otherwise, it's a keyframe that must be next in PTS
- // order w.r.t. |highest_frame_| or be immediately adjacent to the last buffer
- // in this range if that buffer has estimated duration (only allowed in WebM
- // streams).
- // If |new_buffers_group_start_pts| is set otherwise, then that time must come
- // directly after |highest_frame_| (within the fudge room), or directly after
- // the last buffered frame if it has estimated duration (only allowed in WebM
- // streams), and the first buffer in |buffers| must be a keyframe.
- // The latter scenario is required when a muxed coded frame group has such a
- // large jagged start across tracks that its first buffer is not within the
- // fudge room, yet its group start was.
- // The conditions around estimated duration are handled by
- // AllowableAppendAfterEstimatedDuration, and are intended to solve the edge
- // case in the SourceBufferStreamTest
- // MergeAllowedIfRangeEndTimeWithEstimatedDurationMatchesNextRangeStart.
- // During append, |highest_frame_| is updated, if necessary.
- void AppendBuffersToEnd(const BufferQueue& buffers,
- base::TimeDelta new_buffers_group_start_timestamp);
- bool AllowableAppendAfterEstimatedDuration(
- const BufferQueue& buffers,
- base::TimeDelta new_buffers_group_start_pts) const;
- bool CanAppendBuffersToEnd(const BufferQueue& buffers,
- base::TimeDelta new_buffers_group_start_pts) const;
- // Updates |next_buffer_index_| to point to the keyframe with presentation
- // timestamp at or before |timestamp|. Assumes |timestamp| is valid and in
- // this range.
- void Seek(base::TimeDelta timestamp);
- // Returns true if the range has enough data to seek to the specified
- // |timestamp|, false otherwise.
- bool CanSeekTo(base::TimeDelta timestamp) const;
- // Return the config ID for the buffer at |timestamp|. Precondition: callers
- // must first verify CanSeekTo(timestamp) == true.
- int GetConfigIdAtTime(base::TimeDelta timestamp) const;
- // Return true if all buffers in range of [start, end] have the same config
- // ID. Precondition: callers must first verify that
- // CanSeekTo(start) == CanSeekTo(end) == true.
- bool SameConfigThruRange(base::TimeDelta start, base::TimeDelta end) const;
- // Finds the next keyframe from |buffers_| starting at or after |timestamp|
- // and creates and returns a new SourceBufferRange with the buffers from
- // that keyframe onward. The buffers in the new SourceBufferRange are
- // moved out of this range. The start time of the new SourceBufferRange
- // is set to the later of |timestamp| and this range's GetStartTimestamp().
- // Note that this may result in temporary overlap of the new range and this
- // range until the caller truncates any nonkeyframes out of this range with
- // time > |timestamp|. If there is no keyframe at or after |timestamp|,
- // SplitRange() returns null and this range is unmodified. This range can
- // become empty if |timestamp| <= the PTS of the first buffer in this range.
- // |highest_frame_| is updated, if necessary.
- std::unique_ptr<SourceBufferRange> SplitRange(base::TimeDelta timestamp);
- // Deletes the buffers from this range starting at |timestamp|, exclusive if
- // |is_exclusive| is true, inclusive otherwise.
- // Resets |next_buffer_index_| if the buffer at |next_buffer_index_| was
- // deleted, and deletes the |keyframe_map_| entries for the buffers that
- // were removed.
- // |highest_frame_| is updated, if necessary.
- // |deleted_buffers| contains the buffers that were deleted from this range,
- // starting at the buffer that had been at |next_buffer_index_|.
- // Returns true if everything in the range was deleted. Otherwise
- // returns false.
- bool TruncateAt(base::TimeDelta timestamp,
- BufferQueue* deleted_buffers,
- bool is_exclusive);
- // Deletes a GOP from the front or back of the range and moves these
- // buffers into |deleted_buffers|. Returns the number of bytes deleted from
- // the range (i.e. the size in bytes of |deleted_buffers|).
- // |highest_frame_| is updated, if necessary.
- // This range must NOT be empty when these methods are called.
- // The GOP being deleted must NOT contain the next buffer position.
- size_t DeleteGOPFromFront(BufferQueue* deleted_buffers);
- size_t DeleteGOPFromBack(BufferQueue* deleted_buffers);
- // Gets the range of GOP to secure at least |bytes_to_free| from
- // [|start_timestamp|, |end_timestamp|).
- // Returns the size of the buffers to secure if the buffers of
- // [|start_timestamp|, |end_removal_timestamp|) is removed.
- // Will not update |end_removal_timestamp| if the returned size is 0.
- size_t GetRemovalGOP(base::TimeDelta start_timestamp,
- base::TimeDelta end_timestamp,
- size_t bytes_to_free,
- base::TimeDelta* end_removal_timestamp) const;
- // Returns true iff the buffered end time of the first GOP in this range is
- // at or before |media_time|.
- bool FirstGOPEarlierThanMediaTime(base::TimeDelta media_time) const;
- // Indicates whether the GOP at the beginning or end of the range contains the
- // next buffer position.
- bool FirstGOPContainsNextBufferPosition() const;
- bool LastGOPContainsNextBufferPosition() const;
- // Returns the timestamp of the next buffer that will be returned from
- // GetNextBuffer(), or kNoTimestamp if the timestamp is unknown.
- base::TimeDelta GetNextTimestamp() const;
- // Returns the start timestamp of the range.
- base::TimeDelta GetStartTimestamp() const;
- // Returns the highest presentation timestamp of frames in the last GOP in the
- // range.
- base::TimeDelta GetEndTimestamp() const;
- // Returns the timestamp for the end of the buffered region in this range.
- // This is an approximation if the duration for the buffer with highest PTS in
- // the last GOP in the range is unset.
- base::TimeDelta GetBufferedEndTimestamp() const;
- // Returns whether a buffer with a starting timestamp of |timestamp| would
- // belong in this range. This includes a buffer that would be appended to
- // the end of the range.
- bool BelongsToRange(base::TimeDelta timestamp) const;
- // Returns the highest time from among GetStartTimestamp() and frame timestamp
- // (in order in |buffers_| beginning at the first keyframe at or before
- // |timestamp|) for buffers in this range up to and including |timestamp|.
- // Note that |timestamp| must belong to this range.
- base::TimeDelta FindHighestBufferedTimestampAtOrBefore(
- base::TimeDelta timestamp) const;
- // Gets the timestamp for the keyframe that is at or after |timestamp|. If
- // there isn't such a keyframe in the range then kNoTimestamp is returned.
- // If |timestamp| is in the "gap" between the value returned by
- // GetStartTimestamp() and the timestamp on the first buffer in |buffers_|,
- // then |timestamp| is returned.
- base::TimeDelta NextKeyframeTimestamp(base::TimeDelta timestamp) const;
- // Gets the timestamp for the closest keyframe that is <= |timestamp|. If
- // there isn't a keyframe before |timestamp| or |timestamp| is outside
- // this range, then kNoTimestamp is returned.
- base::TimeDelta KeyframeBeforeTimestamp(base::TimeDelta timestamp) const;
- // Adds all buffers which overlap [start, end) to the end of |buffers|. If no
- // buffers exist in the range returns false, true otherwise. This method is
- // only used for finding audio splice overlap buffers, so all buffers are
- // expected to be keyframes here, or if not keyframes, to at least be in PTS
- // order since the previous keyframe.
- bool GetBuffersInRange(base::TimeDelta start,
- base::TimeDelta end,
- BufferQueue* buffers) const;
- size_t size_in_bytes() const { return size_in_bytes_; }
- private:
- // Friend of private is only for IsNextInPresentationSequence testing.
- friend class SourceBufferStreamTest;
- using KeyframeMap = std::map<base::TimeDelta, int>;
- // Called during AppendBuffersToEnd to adjust estimated duration at the
- // end of the last append to match the delta in timestamps between
- // the last append and the upcoming append. This is a workaround for
- // WebM media where a duration is not always specified. Caller should take
- // care of updating |highest_frame_|.
- void AdjustEstimatedDurationForNewAppend(const BufferQueue& new_buffers);
- // Frees the buffers in |buffers_| from [|start_point|,|ending_point|) and
- // updates the |size_in_bytes_| accordingly. Note, this does not update
- // |keyframe_map_|.
- void FreeBufferRange(const BufferQueue::const_iterator& starting_point,
- const BufferQueue::const_iterator& ending_point);
- // Returns the distance in time estimating how far from the beginning or end
- // of this range a buffer can be to be considered in the range.
- base::TimeDelta GetFudgeRoom() const;
- // Returns the approximate duration of a buffer in this range.
- base::TimeDelta GetApproximateDuration() const;
- // Updates |highest_frame_| if |new_buffer| has a higher PTS than
- // |highest_frame_|, |new_buffer| has the same PTS as |highest_frame_| and
- // duration at least as long as |highest_frame_|, or if the range was
- // previously empty.
- void UpdateEndTime(scoped_refptr<StreamParserBuffer> new_buffer);
- // Returns true if |timestamp| is allowed in this range as the timestamp of
- // the next buffer in presentation sequence at or after |highest_frame_|.
- // |buffers_| must not be empty, and |highest_frame_| must not be nullptr.
- // Uses |gap_policy_| to potentially allow gaps.
- //
- // Due to potential for out-of-order decode vs presentation time, this method
- // should only be used to determine adjacency of keyframes with the end of
- // |buffers_|.
- bool IsNextInPresentationSequence(base::TimeDelta timestamp) const;
- // Returns true if |decode_timestamp| is allowed in this range as the decode
- // timestamp of the next buffer in decode sequence at or after the last buffer
- // in |buffers_|'s decode timestamp. |buffers_| must not be empty. Uses
- // |gap_policy_| to potentially allow gaps.
- //
- // Due to potential for out-of-order decode vs presentation time, this method
- // should only be used to determine adjacency of non-keyframes with the end of
- // |buffers_|, when determining if a non-keyframe with |decode_timestamp|
- // continues the decode sequence of the coded frame group at the end of
- // |buffers_|.
- bool IsNextInDecodeSequence(DecodeTimestamp decode_timestamp) const;
- // Helper method for Appending |range| to the end of this range. If |range|'s
- // first buffer time is before the time of the last buffer in this range,
- // returns kNoTimestamp. Otherwise, returns the closest time within
- // [|range|'s start time, |range|'s first buffer time] that is at or after the
- // this range's GetEndTimestamp(). This allows |range| to potentially be
- // determined to be adjacent within fudge room for appending to the end of
- // this range, especially if |range| has a start time that is before its first
- // buffer's time.
- base::TimeDelta NextRangeStartTimeForAppendRangeToEnd(
- const SourceBufferRange& range) const;
- // Returns an index (or iterator) into |buffers_| pointing to the first buffer
- // at or after |timestamp|. If |skip_given_timestamp| is true, this returns
- // the first buffer with timestamp strictly greater than |timestamp|. If
- // |buffers_| has no such buffer, returns |buffers_.size()| (or
- // |buffers_.end()|).
- size_t GetBufferIndexAt(base::TimeDelta timestamp,
- bool skip_given_timestamp) const;
- BufferQueue::const_iterator GetBufferItrAt(base::TimeDelta timestamp,
- bool skip_given_timestamp) const;
- // Returns an iterator in |keyframe_map_| pointing to the next keyframe after
- // |timestamp|. If |skip_given_timestamp| is true, this returns the first
- // keyframe with a timestamp strictly greater than |timestamp|.
- KeyframeMap::const_iterator GetFirstKeyframeAt(
- base::TimeDelta timestamp,
- bool skip_given_timestamp) const;
- // Returns an iterator in |keyframe_map_| pointing to the first keyframe
- // before or at |timestamp|.
- KeyframeMap::const_iterator GetFirstKeyframeAtOrBefore(
- base::TimeDelta timestamp) const;
- // Helper method to delete buffers in |buffers_| starting at
- // |starting_point|, an index in |buffers_|.
- // Returns true if everything in the range was removed. Returns
- // false if the range still contains buffers.
- bool TruncateAt(const size_t starting_point, BufferQueue* deleted_buffers);
- // Updates |highest_frame_| to be the frame with highest PTS in the last GOP
- // in this range. If there are no buffers in this range, resets
- // |highest_frame_|.
- // Normally, incremental additions to this range should just use
- // UpdateEndTime(). When removing buffers from this range (which could be out
- // of order presentation vs decode order), inspecting the last buffer in
- // decode order of this range can be insufficient to determine the correct
- // presentation end time of this range. Hence this helper method.
- void UpdateEndTimeUsingLastGOP();
- // Helper for debugging state.
- std::string ToStringForDebugging() const;
- // Keeps track of whether gaps are allowed.
- const GapPolicy gap_policy_;
- // The ordered list of buffers in this range.
- BufferQueue buffers_;
- // Index into |buffers_| for the next buffer to be returned by
- // GetNextBuffer(), set to -1 by ResetNextBufferPosition().
- int next_buffer_index_;
- // Caches the buffer, if any, with the highest PTS currently in |buffers_|.
- // This is nullptr if this range is empty. This is useful in determining
- // range membership and adjacency.
- scoped_refptr<StreamParserBuffer> highest_frame_;
- // Called to get the largest interbuffer distance seen so far in the stream.
- InterbufferDistanceCB interbuffer_distance_cb_;
- // Stores the amount of memory taken up by the data in |buffers_|.
- size_t size_in_bytes_;
- // If the first buffer in this range is the beginning of a coded frame group,
- // |range_start_pts_| is the presentation time when the coded frame group
- // begins. This is especially important in muxed media where the first coded
- // frames for each track do not necessarily begin at the same time.
- // |range_start_pts_| may be <= the timestamp of the first buffer in
- // |buffers_|. |range_start_pts_| is kNoTimestamp if this range does not start
- // at the beginning of a coded frame group, which can happen by range removal
- // or split when we don't have a way of knowing, across potentially multiple
- // muxed streams, the coded frame group start timestamp for the new range.
- base::TimeDelta range_start_pts_;
- // Index base of all positions in |keyframe_map_|. In other words, the
- // real position of entry |k| of |keyframe_map_| in the range is:
- // keyframe_map_[k] - keyframe_map_index_base_
- int keyframe_map_index_base_;
- // Maps keyframe presentation timestamps to GOP start index of |buffers_|
- // (with index adjusted by |keyframe_map_index_base_|);
- KeyframeMap keyframe_map_;
- };
- } // namespace media
- #endif // MEDIA_FILTERS_SOURCE_BUFFER_RANGE_H_
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