Just putting the finishing touches to my dissertation in preperation for a final revision.
over 35 pages
over 10,000 words
looking forward to a five minute break.
Monday 18 May 2009
Tuesday 31 March 2009
Reset
If you think you need to reset something, then it's highly likely that the library has a reset call in it.
DiracReset(true, m_pDiracSystem);
Doh!
DiracReset(true, m_pDiracSystem);
Doh!
Sunday 29 March 2009
Cue The Music
I ran into a slight hiccup earlier in the week when I realised one of two possible problems; either my timing calculation algorithm produced unavoidable rounding errors or Reason 3 was not writing files out with exactly the right amount of PCM samples in them. This resulted in any track that was the full length of the sequence going out of time with the click track, which is not good.
No matter which of these reasons were causing this the solution seemed the same - Add some silent PCM samples at the end of the audio sample to make up the 0.01 percent (guesstimate) missing, or time stretch the sample by the small amount to account for the missing samples. The second solution was my first choice as the first could introduce some pops/clicks in the sound if the discrepancy was large, although if the discrepancy is too large then that will cause other issues of timing. As the DIRAC time stretching library had already been integrated it was just a case of finding the percent of missing samples and process the sound to the new length. This worked a charm and now my sequences can loop indefinitely.
With the timing and the layering systems all functioning correctly it was now time to move on to the audio cues. In general there are two different roles that a cue can perform: alter the playback of a given sequence; provide a transition between sequences. To help keep track of the various different cues I use these two basic roles as separators. A cue manager is used to create each instance of a cue so that a record of it can be stored, to allow access to the cue at a later date. Here is a diagram of how the cue creation process is structured.
In this structure the cue manager uses a template Factory Method to instantiate cues of varying types, ensuring that the data type at least inherits the AudioCue class by only returning pointers to objects of that data type. For recording purposes two STL maps are used to store pointers to objects that are of type "SequenceCue" or "TransitionCue". As stated before, these types define the two distinguishing roles of any cue.
The foundation of these cues is based on the virtual method "Perform". Every concrete class must override this method in order to allow the cue to manipulate a sequence or set of sequences in some way. Structure wise this design is similar to the Command pattern, in the way that the core of the design is based around an "execute" method. Now when calling a cue the application need not know what concrete type of cue it is calling, only that it is either a SequenceCue or a TransitionCue - the overridden "Perform" method handles all the intricate logic related to the cue.
There can be three methods of triggering a cue: on a beat; on a bar; instantly. On a beat or bar could signify a specific number in the sequence or just the next beat or bar that will be played. This is where the click track proves useful here, as the callback from it instantly (instantly when we call system::update ... those darn synchronous callbacks) tells us when we've hit a beat or bar, and from that we can start an activated cue.
The design structure of the cue system keeps it highly modular, allowing for easy addition of new cues that could incorporate features such as standard DSP effects or additional sounds to be layered in the sequence.
No matter which of these reasons were causing this the solution seemed the same - Add some silent PCM samples at the end of the audio sample to make up the 0.01 percent (guesstimate) missing, or time stretch the sample by the small amount to account for the missing samples. The second solution was my first choice as the first could introduce some pops/clicks in the sound if the discrepancy was large, although if the discrepancy is too large then that will cause other issues of timing. As the DIRAC time stretching library had already been integrated it was just a case of finding the percent of missing samples and process the sound to the new length. This worked a charm and now my sequences can loop indefinitely.
With the timing and the layering systems all functioning correctly it was now time to move on to the audio cues. In general there are two different roles that a cue can perform: alter the playback of a given sequence; provide a transition between sequences. To help keep track of the various different cues I use these two basic roles as separators. A cue manager is used to create each instance of a cue so that a record of it can be stored, to allow access to the cue at a later date. Here is a diagram of how the cue creation process is structured.
In this structure the cue manager uses a template Factory Method to instantiate cues of varying types, ensuring that the data type at least inherits the AudioCue class by only returning pointers to objects of that data type. For recording purposes two STL maps are used to store pointers to objects that are of type "SequenceCue" or "TransitionCue". As stated before, these types define the two distinguishing roles of any cue.
The foundation of these cues is based on the virtual method "Perform". Every concrete class must override this method in order to allow the cue to manipulate a sequence or set of sequences in some way. Structure wise this design is similar to the Command pattern, in the way that the core of the design is based around an "execute" method. Now when calling a cue the application need not know what concrete type of cue it is calling, only that it is either a SequenceCue or a TransitionCue - the overridden "Perform" method handles all the intricate logic related to the cue.
There can be three methods of triggering a cue: on a beat; on a bar; instantly. On a beat or bar could signify a specific number in the sequence or just the next beat or bar that will be played. This is where the click track proves useful here, as the callback from it instantly (instantly when we call system::update ... those darn synchronous callbacks) tells us when we've hit a beat or bar, and from that we can start an activated cue.
The design structure of the cue system keeps it highly modular, allowing for easy addition of new cues that could incorporate features such as standard DSP effects or additional sounds to be layered in the sequence.
Subscribe to:
Posts (Atom)
