Caching Frames

FileCacherThread::run

walltime == wallclock time 

target_mstimestamp_ = 0 
    current target frametime, transformed from current walltime : stopStreams, seekStreams, run

next = NULL 
    points to next frame : run
    
reftime = 0 
    value for transforming frametime <-> walltime : playStreams, seekStreams, run

next_mstimestamp = 0 : run
    timestamp of the next frame in wallclock time

    
while True:
    
    if next != NULL and reftime > 0:
        # next frame exists and we can get it's wallclock time
        next_mstimestamp = next.mstimestamp + reftime # from frametime to walltime
        # => calculate timeout to the next frame
        timeout = ..
    else:
        timeout = default_timeout
    
    f = infifo.read(timeout)
    
    # there's either a frame or this was a timeout
    
    if TIMEOUT:
        pass
        
    elif GOT_FRAME:
        
        if f is signal:
            # handle the signal => seekStreams, playStreams, stopStreams
            
        elif f is marker:
            if marker == TM_START # transmission start
                # do nothing .. frames are flowing to tmp cache
                
            elif marker == TM_END # transmission end
                switchCache() # tmp cache becomes the play_cache
                next = NULL
                if target_mstimestamp_ <= 0: # no seek time set yet
                    # this can happen: seek has not yet called, but block transmission has been requested
                    # that's fixed with the next seek call
                    print WARNING
                else:
                    if state == SEEK or state == STOP:
                        i = play_cache->keySeek
                    elif state == PLAY:
                        i = play_cache->seek
                    else:
                        print WARNING
                        
                    if seek succeeded:
                        next = play_cache.pullNextFrame()
                        
                    if next != None:
                        walltime = getCurrentMsTimestamp();
                        reftime = walltime - target_mstimestamp_; # match walltime to target frametime
                        
        
    # frame handled
    
    mstime = getCurrentMsTimestamp() # update current time
    
    if reftime > 0 and & state == PLAY: # walltime get's updated constantly
        walltime = mstime
        target_mstimestamp_ = walltime - reftime; # update current frametime
            
    # FRAME PULL LOOP: pull all necessary frames from the cache
    while next != NULL and (next_mstimestamp - walltime) <= 0:
        
        if reftime == 0: # no reftime set .. take it from the first frame
            reftime = mstime - target_mstimestamp_
            stopStreams() # state => STOP, send SetupFrames
        
        # create & send a SetupFrame for decoder init if necessary
        ...
        
        # send frame to correct framefilter with this timestamp:
        frame.mstimestamp = next.mstimestamp + reftime # from frametime to walltime
        
        next = play_cache.pullNextFrame()
        if next != NULL:
            next_mstimestamp = next.mstimestamp + reftime # from frametime to walltime
            
        if next == NULL or next_mstimestamp - walltime > 0: # while loop is about to break
            if state == SEEK
                stopStreams() # state => STOP, send SetupFrames
    
    # handle signals etc


- seek sets the reftime
- play : stream's been stopped, so there's a fixed target_mstimestamp_ => get reftime == walltime <-> frametime mapping from there
- stop : stream's been playing / seeking, so there's reftime (wall-time <-> frametime mapping) => get target_mstimestamp_ from walltime

stopStreams:
    if reftime > 0:
        walltime = getCurrentMsTimestamp()
        target_mstimestamp_ = walltime - reftime # get current frametime from walltime
        
playStreams:
    if target_mstimestamp_ > 0:
        walltime = getCurrentMsTimestamp()
        reftime = walltime - target_mstimestamp_ # get reftime from current frametime
        
seekStreams(mstimestamp_): # if target frame time mstimestamp_ is found in play_cache, do immediate seek, otherwise, set reftime = 0
    target_mstimestamp_ = mstimestamp_
    if play_cache has the target frame, then:
        walltime = getCurrentMsTimestamp()
        reftime = walltime - target_mstimestamp_
    else:
        reftime = 0