AbstractFileStream Class Reference

A general class for on-disk stored streams. More...

#include <filestream.h>

Collaboration diagram for AbstractFileStream:

Public Member Functions
	AbstractFileStream ()
	Default constructor.
AbstractFileState	getState ()
void	setRefMstime (long int ms_streamtime_)
	Creates a correspondence with the current wallclock time and a desider stream time, by calculating FileStream::reftime. See Presention timing and playing.
void	play ()
	Start playing the stream.
void	stop ()
	Stop playing the strem.
long int	update (long int mstimestamp)
	Tries to achieve mstimestamp: calculates FileStream::target_mstimestamp_ and calls pullNextFrame. Returns the timeout for the next frame.
virtual void	seek (long int ms_streamtime_)
	Seek to a desider stream time.
virtual long int	pullNextFrame ()
	Tries to achieve FileStream::target_mstimestamp_ . Sends frames whose timestamps are less than that to the filterchain (e.g. to FileContext::framefilter). Returns timeout to the next frame.

Protected Attributes
long int	reftime
	Relation between the stream time and wallclock time. See Presention timing and playing.
long int	target_mstimestamp_
	Where the stream would like to be (underscore means stream time)
long int	frame_mstimestamp_
	Timestamp of previous frame sent, -1 means there was no previous frame (underscore means stream time)
AbstractFileState	state
	Decribes the FileStream state: errors, stopped, playing, etc.
Frame *	next_frame
	Pointer to the next frame about to be presented.
BasicFrame	out_frame
	BasicFrame payload that's passed on to the filterchain.

Detailed Description

A general class for on-disk stored streams.

This class keeps the books for each file stream, in particular:

• Desider target time (FileStream::target_mstimestamp_)
• Timestamp of the previous frame (FileStream::frame_mstimestamp_)
• State of the stream (FileStream::state)

Subclasses:

• For cached streams, should maintain cache
• For FFmpeg/libAV etc. streams, should maintain the file handles

In variable names, underscore means stream time. See Presention timing and playing

Threads use the (derived) class as follows:

• Thread should be generic / dummy
• Reads frames from a FrameFifo and feeds them to the AbstractFileStream
• At the same time "runs" the AbstractFileStream
• Passes commands to the AbstractFileStream (seek, play, stop, etc.)

while (loop):

 if ( (next_pts - mstime) <= 0)

     next_pts = AbstractFileStream->update(mstime)
         --> if called too early, returns
         => next_pts = AbstractFileStream->pullNextFrame()
             => writes frame into FrameFilter
             => take next time frame .. if frames with same timestamp, call recursively
             => return next_pts
             => set internal state : self.next_frame
     --> next_pts in wallclock time
     --> when seeking, next_pts is smaller than mstime for many consecutive frames  

 mstime = getCurrentMsTimestamp()
 --> handle signals if enough time has passed

 (refresh mstime)

 timeout = next_pts - mstime
 --> read incoming FrameFifo with timeout
 --> if frame, call AbstractFileStream->pushFrame(frame)
     => AbstractFileStream caches the frame

 (refresh mstime)

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The documentation for this class was generated from the following files:

• /home/sampsa/C/valkka/include/filestream.h
• /home/sampsa/C/valkka/src/filestream.cpp