blob: 3a9fcc36f3af90d0aeede1b4713db4c0c396257e [file] [log] [blame]
// 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 "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "media/base/stream_parser_buffer.h"
namespace media {
// Helper class representing a range of buffered data. All buffers in a
// SourceBufferRange are ordered sequentially in decode timestamp order with no
// gaps.
class SourceBufferRange {
// Returns the maximum distance in time between any buffer seen in this
// stream. Used to estimate the duration of a buffer if its duration is not
// known.
typedef base::Callback<base::TimeDelta()> InterbufferDistanceCB;
typedef StreamParser::BufferQueue 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 {
// Return the config ID for the buffer at |timestamp|. Precondition: callers
// must first verify CanSeekTo(timestamp) == true.
int GetConfigIdAtTime(DecodeTimestamp timestamp);
// 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(DecodeTimestamp start, DecodeTimestamp end);
// Sequential buffers with the same decode timestamp make sense under certain
// conditions, typically when the first buffer is a keyframe. Due to some
// atypical media append behaviors where a new keyframe might have the same
// timestamp as a previous non-keyframe, the playback of the sequence might
// involve some throwaway decode work. This method supports detecting this
// situation so that callers can log warnings (it returns true in this case
// only).
// For all other cases, including more typical same-DTS sequences, this method
// returns false. Examples of typical situations where DTS of two consecutive
// frames can be equal:
// - Video: VP8 Alt-Ref frames.
// - Video: IPBPBP...: DTS for I frame and for P frame can be equal.
// - Text track cues that start at same time.
// Returns true if |prev_is_keyframe| and |current_is_keyframe| indicate a
// same timestamp situation that is atypical. False is returned otherwise.
static bool IsUncommonSameTimestampSequence(bool prev_is_keyframe,
bool current_is_keyframe);
// Creates a source buffer range with |new_buffers|. |new_buffers| cannot be
// empty and the front of |new_buffers| must be a keyframe.
// |range_start_time| refers to the starting timestamp for the coded frame
// group to which these buffers belong.
SourceBufferRange(GapPolicy gap_policy,
const BufferQueue& new_buffers,
DecodeTimestamp range_start_time,
const InterbufferDistanceCB& interbuffer_distance_cb);
// Appends |buffers| to the end of the range and updates |keyframe_map_| as
// it encounters new keyframes.
// If |new_buffers_group_start_timestamp| is kNoDecodeTimestamp(), then the
// first buffer in |buffers| must come directly after the last buffer in this
// range (within the fudge room).
// If |new_buffers_group_start_timestamp| is set otherwise, then that time
// must come directly after the last buffer in this range (within the fudge
// room). 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.
void AppendBuffersToEnd(const BufferQueue& buffers,
DecodeTimestamp new_buffers_group_start_timestamp);
bool CanAppendBuffersToEnd(
const BufferQueue& buffers,
DecodeTimestamp new_buffers_group_start_timestamp) const;
// 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 transfered 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.
void AppendRangeToEnd(const SourceBufferRange& range,
bool transfer_current_position);
bool CanAppendRangeToEnd(const SourceBufferRange& range) const;
// Updates |next_buffer_index_| to point to the Buffer containing |timestamp|.
// Assumes |timestamp| is valid and in this range.
void Seek(DecodeTimestamp timestamp);
// Updates |next_buffer_index_| to point to next keyframe after or equal to
// |timestamp|.
void SeekAheadTo(DecodeTimestamp timestamp);
// Updates |next_buffer_index_| to point to next keyframe strictly after
// |timestamp|.
void SeekAheadPast(DecodeTimestamp timestamp);
// Seeks to the beginning of the range.
void SeekToStart();
// 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. 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 DTS of the first buffer in this range.
SourceBufferRange* SplitRange(DecodeTimestamp 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.
// |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(DecodeTimestamp timestamp,
BufferQueue* deleted_buffers, bool is_exclusive);
// Deletes all buffers in range.
void DeleteAll(BufferQueue* deleted_buffers);
// 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|).
// 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(
DecodeTimestamp start_timestamp, DecodeTimestamp end_timestamp,
size_t bytes_to_free, DecodeTimestamp* end_removal_timestamp);
// Returns true iff the buffered end time of the first GOP in this range is
// at or before |media_time|.
bool FirstGOPEarlierThanMediaTime(DecodeTimestamp 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;
// Updates |out_buffer| with the next buffer in presentation order. 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();
// Returns the timestamp of the next buffer that will be returned from
// GetNextBuffer(), or kNoTimestamp if the timestamp is unknown.
DecodeTimestamp GetNextTimestamp() const;
// Returns the start timestamp of the range.
DecodeTimestamp GetStartTimestamp() const;
// Returns the timestamp of the last buffer in the range.
DecodeTimestamp GetEndTimestamp() const;
// Returns the timestamp for the end of the buffered region in this range.
// This is an approximation if the duration for the last buffer in the range
// is unset.
DecodeTimestamp GetBufferedEndTimestamp() const;
// Gets the timestamp for the keyframe that is after |timestamp|. If
// there isn't a keyframe in the range after |timestamp| 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.
DecodeTimestamp NextKeyframeTimestamp(DecodeTimestamp timestamp);
// 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.
DecodeTimestamp KeyframeBeforeTimestamp(DecodeTimestamp timestamp);
// 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(DecodeTimestamp timestamp) const;
// Returns true if the range has enough data to seek to the specified
// |timestamp|, false otherwise.
bool CanSeekTo(DecodeTimestamp timestamp) const;
// Returns true if this range's buffered timespan completely overlaps the
// buffered timespan of |range|.
bool CompletelyOverlaps(const SourceBufferRange& range) const;
// Returns true if the end of this range contains buffers that overlaps with
// the beginning of |range|.
bool EndOverlaps(const SourceBufferRange& range) const;
// Returns true if |timestamp| is the timestamp of the next buffer in
// sequence after |buffers_.back()|, false otherwise.
bool IsNextInSequence(DecodeTimestamp 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.
bool GetBuffersInRange(DecodeTimestamp start, DecodeTimestamp end,
BufferQueue* buffers);
size_t size_in_bytes() const { return size_in_bytes_; }
typedef std::map<DecodeTimestamp, int> KeyframeMap;
// 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.
void AdjustEstimatedDurationForNewAppend(const BufferQueue& new_buffers);
// Seeks the range to the next keyframe after |timestamp|. If
// |skip_given_timestamp| is true, the seek will go to a keyframe with a
// timestamp strictly greater than |timestamp|.
void SeekAhead(DecodeTimestamp timestamp, bool skip_given_timestamp);
// Returns an iterator in |buffers_| pointing to the buffer at |timestamp|.
// If |skip_given_timestamp| is true, this returns the first buffer with
// timestamp greater than |timestamp|.
BufferQueue::iterator GetBufferItrAt(
DecodeTimestamp timestamp, bool skip_given_timestamp);
// 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::iterator GetFirstKeyframeAt(
DecodeTimestamp timestamp, bool skip_given_timestamp);
// Returns an iterator in |keyframe_map_| pointing to the first keyframe
// before or at |timestamp|.
KeyframeMap::iterator GetFirstKeyframeAtOrBefore(DecodeTimestamp timestamp);
// Helper method to delete buffers in |buffers_| starting at
// |starting_point|, an iterator in |buffers_|.
// Returns true if everything in the range was removed. Returns
// false if the range still contains buffers.
bool TruncateAt(const BufferQueue::iterator& starting_point,
BufferQueue* deleted_buffers);
// Frees the buffers in |buffers_| from [|start_point|,|ending_point|) and
// updates the |size_in_bytes_| accordingly. Does not update |keyframe_map_|.
void FreeBufferRange(const BufferQueue::iterator& starting_point,
const BufferQueue::iterator& ending_point);
// Returns the distance in time estimating how far from the beginning or end
// of this range a buffer can be to considered in the range.
base::TimeDelta GetFudgeRoom() const;
// Returns the approximate duration of a buffer in this range.
base::TimeDelta GetApproximateDuration() const;
// Keeps track of whether gaps are allowed.
const GapPolicy gap_policy_;
// An ordered list of buffers in this range.
BufferQueue buffers_;
// Maps keyframe timestamps to its index position in |buffers_|.
KeyframeMap keyframe_map_;
// 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_;
// Index into |buffers_| for the next buffer to be returned by
// GetNextBuffer(), set to -1 before Seek().
int next_buffer_index_;
// If the first buffer in this range is the beginning of a coded frame group,
// |range_start_time_| is the 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_time_| may be <= the timestamp of the first buffer in
// |buffers_|. |range_start_time_| is kNoDecodeTimestamp() 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.
DecodeTimestamp range_start_time_;
// 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_;
} // namespace media