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Frames
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======
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Frames are needed for passing data between decoders around.
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A decoder gets an mpeg audio encoded frame as input and
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writes data to an audioFrame (pcm/float)
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frame
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audioFrame
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/ \
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pcmFrame floatFrame
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FrameQueues
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===========
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FrameQueues are needed for storing some frames. (For example
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you store 100 pre-decoded pcmFrames.)
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A FrameQueue is a queue, simply not more.
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IOFrameQueues
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=============
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IOFrameQueues deal with the problem, that you first start
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with an empty FrameQueue (this is a FrameQueue which tqcontains
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prealloceated data, but the data is empty (eg:all pcm samples zero)
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Only after converting an "empty" Frame by a decoder (mp3decoder)
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the frame if "full" (== Frame with data)
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So: IOFrameQueues mark frames with
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i) empty
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ii) data
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You can get an empty Frame from the empty-frame-queue and
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then enqueue it in the data-frame-queue.
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After the frame was used (played) we dequeue it from the
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data queue and put them back in the empty queue.
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You can see IOFrameQueues as a ringbuffer.
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(get free space. write to it. read data. mark space as free,....)
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FrameQueue
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IOFrameQueue
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/
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audioFrameQueue
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AudioFrameQueue
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===============
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A IOFrameQueue, which allows converting "dataFrames back to continous
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stream".
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What is this?
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Lets say an application wants only 20 byte from a dataFrame which
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tqcontains 3KB of data?
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There must be some mechanism to read less or more data from the
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queue. And the data should be written to a continus memory
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segment.
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AudioFrameQueue deals with this problem.You can read data from
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the queue to a given pointer location.
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