text: // Copyright (c) 2012 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.
  
  // SourceBufferStream is a data structure that stores media Buffers in ranges.
  // Buffers can be appended out of presentation order. Buffers are retrieved by
  // seeking to the desired start point and calling GetNextBuffer(). Buffers are
  // returned in sequential presentation order.
  
  #ifndef MEDIA_FILTERS_SOURCE_BUFFER_STREAM_H_
  #define MEDIA_FILTERS_SOURCE_BUFFER_STREAM_H_
  
  #include <deque>
  #include <list>
  #include <string>
  #include <utility>
  #include <vector>
  
  #include "base/memory/ref_counted.h"
  #include "media/base/audio_decoder_config.h"
  #include "media/base/media_export.h"
  #include "media/base/media_log.h"
  #include "media/base/ranges.h"
  #include "media/base/stream_parser_buffer.h"
  #include "media/base/text_track_config.h"
  #include "media/base/video_decoder_config.h"
  
  namespace media {
  
  class SourceBufferRange;
  
  // See file-level comment for complete description.
  class MEDIA_EXPORT SourceBufferStream {
   public:
    typedef StreamParser::BufferQueue BufferQueue;
  
    // Status returned by GetNextBuffer().
    // kSuccess: Indicates that the next buffer was returned.
    // kNeedBuffer: Indicates that we need more data before a buffer can be
    //              returned.
    // kConfigChange: Indicates that the next buffer requires a config change.
    enum Status {
      kSuccess,
      kNeedBuffer,
      kConfigChange,
      kEndOfStream
    };
  
    enum Type {
      kAudio,
      kVideo,
      kText
    };
  
    SourceBufferStream(const AudioDecoderConfig& audio_config,
                       const LogCB& log_cb,
                       bool splice_frames_enabled);
    SourceBufferStream(const VideoDecoderConfig& video_config,
                       const LogCB& log_cb,
                       bool splice_frames_enabled);
    SourceBufferStream(const TextTrackConfig& text_config,
                       const LogCB& log_cb,
                       bool splice_frames_enabled);
  
    ~SourceBufferStream();
  
    // Signals that the next buffers appended are part of a new media segment
    // starting at |media_segment_start_time|.
    void OnNewMediaSegment(base::TimeDelta media_segment_start_time);
  
    // Add the |buffers| to the SourceBufferStream. Buffers within the queue are
    // expected to be in order, but multiple calls to Append() may add buffers out
    // of order or overlapping. Assumes all buffers within |buffers| are in
    // presentation order and are non-overlapping.
    // Returns true if Append() was successful, false if |buffers| are not added.
    // TODO(vrk): Implement garbage collection. (crbug.com/125070)
    bool Append(const BufferQueue& buffers);
  
    // Removes buffers between |start| and |end| according to the steps
    // in the "Coded Frame Removal Algorithm" in the Media Source
    // Extensions Spec.
    // https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/media-source.html#sourcebuffer-coded-frame-removal
    //
    // |duration| is the current duration of the presentation. It is
    // required by the computation outlined in the spec.
    void Remove(base::TimeDelta start, base::TimeDelta end,
                base::TimeDelta duration);
  
    // Changes the SourceBufferStream's state so that it will start returning
    // buffers starting from the closest keyframe before |timestamp|.
    void Seek(base::TimeDelta timestamp);
  
    // Returns true if the SourceBufferStream has seeked to a time without
    // buffered data and is waiting for more data to be appended.
    bool IsSeekPending() const;
  
    // Notifies the SourceBufferStream that the media duration has been changed to
    // |duration| so it should drop any data past that point.
    void OnSetDuration(base::TimeDelta duration);
  
    // Fills |out_buffer| with a new buffer. Buffers are presented in order from
    // the last call to Seek(), or starting with the first buffer appended if
    // Seek() has not been called yet.
    // |out_buffer|'s timestamp may be earlier than the |timestamp| passed to
    // the last Seek() call.
    // Returns kSuccess if |out_buffer| is filled with a valid buffer, kNeedBuffer
    // if there is not enough data buffered to fulfill the request, and
    // kConfigChange if the next buffer requires a config change.
    Status GetNextBuffer(scoped_refptr<StreamParserBuffer>* out_buffer);
  
    // Returns a list of the buffered time ranges.
    Ranges<base::TimeDelta> GetBufferedTime() const;
  
    // Returns the duration of the buffered ranges, which is equivalent
    // to the end timestamp of the last buffered range. If no data is buffered
    // then base::TimeDelta() is returned.
    base::TimeDelta GetBufferedDuration() const;
  
    // Notifies this object that end of stream has been signalled.
    void MarkEndOfStream();
  
    // Clear the end of stream state set by MarkEndOfStream().
    void UnmarkEndOfStream();
  
    const AudioDecoderConfig& GetCurrentAudioDecoderConfig();
    const VideoDecoderConfig& GetCurrentVideoDecoderConfig();
    const TextTrackConfig& GetCurrentTextTrackConfig();
  
    // Notifies this object that the audio config has changed and buffers in
    // future Append() calls should be associated with this new config.
    bool UpdateAudioConfig(const AudioDecoderConfig& config);
  
    // Notifies this object that the video config has changed and buffers in
    // future Append() calls should be associated with this new config.
    bool UpdateVideoConfig(const VideoDecoderConfig& config);
  
    // Returns the largest distance between two adjacent buffers in this stream,
    // or an estimate if no two adjacent buffers have been appended to the stream
    // yet.
    base::TimeDelta GetMaxInterbufferDistance() const;
  
    void set_memory_limit_for_testing(int memory_limit) {
      memory_limit_ = memory_limit;
    }
  
   private:
    friend class SourceBufferStreamTest;
  
    typedef std::list<SourceBufferRange*> RangeList;
  
    // Frees up space if the SourceBufferStream is taking up too much memory.
    void GarbageCollectIfNeeded();
  
    // Attempts to delete approximately |total_bytes_to_free| amount of data
    // |ranges_|, starting at the front of |ranges_| and moving linearly forward
    // through the buffers. Deletes starting from the back if |reverse_direction|
    // is true. Returns the number of bytes freed.
    int FreeBuffers(int total_bytes_to_free, bool reverse_direction);
  
    // Attempts to delete approximately |total_bytes_to_free| amount of data from
    // |ranges_|, starting after the last appended buffer before the current
    // playback position.
    int FreeBuffersAfterLastAppended(int total_bytes_to_free);
  
    // Gets the removal range to secure |byte_to_free| from
    // [|start_timestamp|, |end_timestamp|).
    // Returns the size of buffers to secure if future
    // Remove(|start_timestamp|, |removal_end_timestamp|, duration) is called.
    // Will not update |removal_end_timestamp| if the returned size is 0.
    int GetRemovalRange(base::TimeDelta start_timestamp,
        base::TimeDelta end_timestamp, int byte_to_free,
        base::TimeDelta* removal_end_timestamp);
  
    // Prepares |range_for_next_append_| so |new_buffers| can be appended.
    // This involves removing buffers between the end of the previous append
    // and any buffers covered by the time range in |new_buffers|.
    // |deleted_buffers| is an output parameter containing candidates for
    // |track_buffer_| if this method ends up removing the current playback
    // position from the range.
    void PrepareRangesForNextAppend(const BufferQueue& new_buffers,
                                    BufferQueue* deleted_buffers);
  
    // Removes buffers, from the |track_buffer_|, that come after |timestamp|.
    void PruneTrackBuffer(const base::TimeDelta timestamp);
  
    // Checks to see if |range_with_new_buffers_itr| can be merged with the range
    // next to it, and merges them if so.
    void MergeWithAdjacentRangeIfNecessary(
        const RangeList::iterator& range_with_new_buffers_itr);
  
    // Returns true if |second_timestamp| is the timestamp of the next buffer in
    // sequence after |first_timestamp|, false otherwise.
    bool AreAdjacentInSequence(
        base::TimeDelta first_timestamp, base::TimeDelta second_timestamp) const;
  
    // Helper method that returns the timestamp for the next buffer that
    // |selected_range_| will return from GetNextBuffer() call, or kNoTimestamp()
    // if in between seeking (i.e. |selected_range_| is null).
    base::TimeDelta GetNextBufferTimestamp();
  
    // Returns the timestamp of the last buffer in the |selected_range_| or
    // kNoTimestamp() if |selected_range_| is null.
    base::TimeDelta GetEndBufferTimestamp();
  
    // Finds the range that should contain a media segment that begins with
    // |start_timestamp| and returns the iterator pointing to it. Returns
    // |ranges_.end()| if there's no such existing range.
    RangeList::iterator FindExistingRangeFor(base::TimeDelta start_timestamp);
  
    // Inserts |new_range| into |ranges_| preserving sorted order. Returns an
    // iterator in |ranges_| that points to |new_range|.
    RangeList::iterator AddToRanges(SourceBufferRange* new_range);
  
    // Returns an iterator that points to the place in |ranges_| where
    // |selected_range_| lives.
    RangeList::iterator GetSelectedRangeItr();
  
    // Sets the |selected_range_| to |range| and resets the next buffer position
    // for the previous |selected_range_|.
    void SetSelectedRange(SourceBufferRange* range);
  
    // Seeks |range| to |seek_timestamp| and then calls SetSelectedRange() with
    // |range|.
    void SeekAndSetSelectedRange(SourceBufferRange* range,
                                 base::TimeDelta seek_timestamp);
  
    // Resets this stream back to an unseeked state.
    void ResetSeekState();
  
    // Returns true if |seek_timestamp| refers to the beginning of the first range
    // in |ranges_|, false otherwise or if |ranges_| is empty.
    bool ShouldSeekToStartOfBuffered(base::TimeDelta seek_timestamp) const;
  
    // Returns true if the timestamps of |buffers| are monotonically increasing
    // since the previous append to the media segment, false otherwise.
    bool IsMonotonicallyIncreasing(const BufferQueue& buffers) const;
  
    // Returns true if |next_timestamp| and |next_is_keyframe| are valid for
    // the first buffer after the previous append.
    bool IsNextTimestampValid(base::TimeDelta next_timestamp,
                              bool next_is_keyframe) const;
  
    // Returns true if |selected_range_| is the only range in |ranges_| that
    // HasNextBufferPosition().
    bool OnlySelectedRangeIsSeeked() const;
  
    // Measures the distances between buffer timestamps and tracks the max.
    void UpdateMaxInterbufferDistance(const BufferQueue& buffers);
  
    // Sets the config ID for each buffer to |append_config_index_|.
    void SetConfigIds(const BufferQueue& buffers);
  
    // Called to complete a config change. Updates |current_config_index_| to
    // match the index of the next buffer. Calling this method causes
    // GetNextBuffer() to stop returning kConfigChange and start returning
    // kSuccess.
    void CompleteConfigChange();
  
    // Sets |selected_range_| and seeks to the nearest keyframe after
    // |timestamp| if necessary and possible. This method only attempts to
    // set |selected_range_| if |seleted_range_| is null and |track_buffer_|
    // is empty.
    void SetSelectedRangeIfNeeded(const base::TimeDelta timestamp);
  
    // Find a keyframe timestamp that is >= |start_timestamp| and can be used to
    // find a new selected range.
    // Returns kNoTimestamp() if an appropriate keyframe timestamp could not be
    // found.
    base::TimeDelta FindNewSelectedRangeSeekTimestamp(
        const base::TimeDelta start_timestamp);
  
    // Searches |ranges_| for the first keyframe timestamp that is >= |timestamp|.
    // If |ranges_| doesn't contain a GOP that covers |timestamp| or doesn't
    // have a keyframe after |timestamp| then kNoTimestamp() is returned.
    base::TimeDelta FindKeyframeAfterTimestamp(const base::TimeDelta timestamp);
  
    // Returns "VIDEO" for a video SourceBufferStream, "AUDIO" for an audio
    // stream, and "TEXT" for a text stream.
    std::string GetStreamTypeName() const;
  
    // Returns true if we don't have any ranges or the last range is selected
    // or there is a pending seek beyond any existing ranges.
    bool IsEndSelected() const;
  
    // Deletes the range pointed to by |*itr| and removes it from |ranges_|.
    // If |*itr| points to |selected_range_|, then |selected_range_| is set to
    // NULL. After the range is removed, |*itr| is to the range after the one that
    // was removed or to |ranges_.end()| if the last range was removed.
    void DeleteAndRemoveRange(RangeList::iterator* itr);
  
    // Helper function used by Remove() and PrepareRangesForNextAppend() to
    // remove buffers and ranges between |start| and |end|.
    // |is_exclusive| - If set to true, buffers with timestamps that
    // match |start| are not removed. If set to false, buffers with
    // timestamps that match |start| will be removed.
    // |*deleted_buffers| - Filled with buffers for the current playback position
    // if the removal range included the current playback position. These buffers
    // can be used as candidates for placing in the |track_buffer_|.
    void RemoveInternal(
        base::TimeDelta start, base::TimeDelta end, bool is_exclusive,
        BufferQueue* deleted_buffers);
  
    Type GetType() const;
  
    // See GetNextBuffer() for additional details.  The internal method hands out
    // buffers from the |track_buffer_| and |selected_range_| without additional
    // processing for splice frame buffers; which is handled by GetNextBuffer().
    Status GetNextBufferInternal(scoped_refptr<StreamParserBuffer>* out_buffer);
  
    // Called by PrepareRangesForNextAppend() before pruning overlapped buffers to
    // generate a splice frame with a small portion of the overlapped buffers.  If
    // a splice frame is generated, the first buffer in |new_buffers| will have
    // its timestamps, duration, and fade out preroll updated.
    void GenerateSpliceFrame(const BufferQueue& new_buffers);
  
    // Callback used to report error strings that can help the web developer
    // figure out what is wrong with the content.
    LogCB log_cb_;
  
    // List of disjoint buffered ranges, ordered by start time.
    RangeList ranges_;
  
    // Indicates which decoder config is being used by the decoder.
    // GetNextBuffer() is only allows to return buffers that have a
    // config ID that matches this index. If there is a mismatch then
    // it must signal that a config change is needed.
    int current_config_index_;
  
    // Indicates which decoder config to associate with new buffers
    // being appended. Each new buffer appended has its config ID set
    // to the value of this field.
    int append_config_index_;
  
    // Holds the audio/video configs for this stream. |current_config_index_|
    // and |append_config_index_| represent indexes into one of these vectors.
    std::vector<AudioDecoderConfig> audio_configs_;
    std::vector<VideoDecoderConfig> video_configs_;
  
    // Holds the text config for this stream.
    TextTrackConfig text_track_config_;
  
    // True if more data needs to be appended before the Seek() can complete,
    // false if no Seek() has been requested or the Seek() is completed.
    bool seek_pending_;
  
    // True if the end of the stream has been signalled.
    bool end_of_stream_;
  
    // Timestamp of the last request to Seek().
    base::TimeDelta seek_buffer_timestamp_;
  
    // Pointer to the seeked-to Range. This is the range from which
    // GetNextBuffer() calls are fulfilled after the |track_buffer_| has been
    // emptied.
    SourceBufferRange* selected_range_;
  
    // Queue of the next buffers to be returned from calls to GetNextBuffer(). If
    // |track_buffer_| is empty, return buffers from |selected_range_|.
    BufferQueue track_buffer_;
  
    // The start time of the current media segment being appended.
    base::TimeDelta media_segment_start_time_;
  
    // Points to the range containing the current media segment being appended.
    RangeList::iterator range_for_next_append_;
  
    // True when the next call to Append() begins a new media segment.
    bool new_media_segment_;
  
    // The timestamp of the last buffer appended to the media segment, set to
    // kNoTimestamp() if the beginning of the segment.
    base::TimeDelta last_appended_buffer_timestamp_;
    bool last_appended_buffer_is_keyframe_;
  
    // The decode timestamp on the last buffer returned by the most recent
    // GetNextBuffer() call. Set to kNoTimestamp() if GetNextBuffer() hasn't been
    // called yet or a seek has happened since the last GetNextBuffer() call.
    base::TimeDelta last_output_buffer_timestamp_;
  
    // Stores the largest distance between two adjacent buffers in this stream.
    base::TimeDelta max_interbuffer_distance_;
  
    // The maximum amount of data in bytes the stream will keep in memory.
    int memory_limit_;
  
    // Indicates that a kConfigChanged status has been reported by GetNextBuffer()
    // and GetCurrentXXXDecoderConfig() must be called to update the current
    // config. GetNextBuffer() must not be called again until
    // GetCurrentXXXDecoderConfig() has been called.
    bool config_change_pending_;
  
    // Used by GetNextBuffer() when a buffer with fade out is returned from
    // GetNextBufferInternal().  Will be set to the returned buffer and will be
    // destroyed after the splice_buffers() section has been exhausted.
    scoped_refptr<StreamParserBuffer> splice_buffer_;
  
    // Indicates which of the splice buffers in |splice_buffer_| should be
    // handled out next.
    size_t splice_buffers_index_;
  
    // Indicates that splice frame generation is enabled.
    const bool splice_frames_enabled_;
  
    DISALLOW_COPY_AND_ASSIGN(SourceBufferStream);
  };
  
  }  // namespace media
  
  #endif  // MEDIA_FILTERS_SOURCE_BUFFER_STREAM_H_
  