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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.
#include <stddef.h>
#include <map>
#include <memory>
#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.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 {
// 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 {
// 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;
// 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_; }
// 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