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