Perhaps someone else knows how to do this easily. On storage: Store NSData with a valid message; parse the data to get client-friendly properties. This optimizes the message for reading and writing, but still provides client friendly construction, modification and access. We need to get messages in and out of Objective-C as efficiently as possible. Use only one class with categories rather than several classes in a hierarchy. For these reasons:. We construct under three circumstances: A Reading from file or packetlist where data may be invalid.
B Client creates a message to send somewhere set with user-friendly property values. C Internal constructor calls with valid data i. For example, the constructors takes the type, channel and the length of the variable data, to hide the status byte and allocate memory. Thus, this interface hides all details except the most essential and implements only the simplest cases.
I divided the endpoints into three classes for clarity see explanation in the header file. There is shared code, but none of the code is shared between all three types of end points. Two types might have some very similar code -- the s share some code, s share some code, external endpoints have similar "search" routines, all of them have some kind of port. This code is subtly different for each type of endpoint. I could have combined the shared code into the superclass, of course, but that would have these pluses and minuses:.
These classes obey what I call the "non-modal" principal: if the object exists, then it is valid and ready to operate. Any time between init and dealloc, the endpoint is fully capable of handling any method call whatsoever.
With ARC, this means that if you have a valid pointer to the object then you are pointing to a fully functional object. We only add to these lists and never remove objects from it. While it's theoretically possible that this list could grow large if we never remove anything, I doubt this will ever be an issue in practice. Because of ARC, I know that no endpoint will be deallocated as long as the pointer in these lists exists.
I also know that any endpoint is valid as long as it exists. The properties used here endpointRef, port can not be changed after initialization, and no one can have a pointer to this object until it is initialized.
A method that uses "outputUnit" is NOT thread safe, because the output unit may be changed while the routine is in progress. Always grab a synchronized pointer to the outputUnit in these routines and synchronize as well when a caller changes the output unit.
I can't place the pointer in the refcon, because ARC won't guarantee that this object is still valid. This index is always valid and correct because we only add to these lists and never remove from them. Invariant: "clockTicked" always sends every tick, in order, regardless of tempo changes or if the clock is started or stopped. Only setting the currentTick can break this principle. Invariant: clock. Thus the "currentTick" property always returns the most recent tick sent.
Between two clock ticks even after the ClockTicked messages have all been sent, the clock. The next tick sent should be t. Suppose I'm using the transport, and I want it to start on a particular beat.
The most natural thing in the world is to set the time to the exact tick that starts the bar, and then hit start. It should send the first tick of the bar. Feature: after you stop, if you don't reset the "currentTick" it starts on precisely the next tick. CClock handles all the conversions, client calls, and other details for complete functionality.
This could be rebuilt with some other form of timer, if we can find one with an accuracy of about 1 millisecond. NSTimer is off by microseconds. Store tempo as an integer because this prevents floating point errors. Ticks are also signed, which prevents another set of potential problems. Each of the five entry points has a sync lock, and the code inside the sync lock does not leave the object.
This guarantees that the clock's properties will never be out of sync with itself. There are three ways the thread safety can fail that I can see and all of them are extremely unlikely.
Note that, outside this hole, nothing can happen: User initiates operation. CoreMIDI initiates tick on high priroity thread before operation hits synchronized.
No lock, thread executes tick. This the operation happens "after" the tick, which is fine. I think this shows that, except for this hole, it is impossible that there is a tick waiting to execute when we exit an operation. Each operation sends the "nextTick" as the last step, and the next tick is typically more than milliseconds away -- there is very little chance that the tick will come in and start doing anything before the operation has finished sending all it's messages unless of course processing the messages takes more than milliseconds, which is highly unlikely, and bad for lots of reasons.
So the messages at the end of an operation will always be sent in order. This would require two very unlikely impossible? In this case, the message will be a little weird, but note that they are only out of order by one, and I don't really think that this will have an effect.
These are the problems I have with CAClock:. After stopping, it continues to send timing messages to the endpoints it is attached to.
This is confusing, but I am told this is by design so that downstream units can keep syncing themselves even when the clock is stopped. In other words, it's a feature. However I need a clock that can be stopped and reset to a new position without losing ticks. It continues to move "media time" forward after a stop, even though the media time should be halted. This adds another layer of confusion. Also, it's impossible to query the system to know where, exactly, it is stopped on the media timeline.
After stopping, "start" does not begin at the next tick -- it may jump forward or backward several ticks. This is bad for an application that assumes it will receive every tick; in a sequence it may skip downbeats and note-off points. It seems to always send a "move" just before it starts. Here is an example of how that can be done with the midifile library.
To delete a MIDI message, clear its vector base class. This will leave an empty MidiEvent in the track, but the MidiFile::write function will ignore any empty MidiMessage s. The MidiFile::removeEmpties function can be called to explicitly remove any empty MidiEvents from the track.
This example shows how to transpose notes in a MIDI file. The following example lists all of the instrument numbers used in a MIDI file. It does not analyze the drum track. If you want to simulate temperaments in a Standard MIDI file without a synthesizer that specifically knows about temperaments, then this example is useful.
Each pitch-class is placed into a separate track and MIDI channel. A pitch-bend message is then added to the start of each track in each channel to control the temperament. The MidiFile::splitTracks function will generate 13 or 14 tracks. Percussion notes will be placed in track 13, but remain on channel The use of MidiEvent::seq being set to 1 and 2 in the program is used to force the first notes at tick time 0 to be placed after the pitch bend messages inserted at the same timestamp when MidiFile::sortTracks is called events with a lower sequence number will be placed before those with a higher number if they occur at the same time in a track when sorting the events in the track.
The pitch-bend messages would probably be sorted before the notes anyway, but using seq should guarantee they are placed before the first notes. Here is the first file extracted from the MIDI file input for the temperament example:. This example demonstrates the generation of a constant vibrato for notes in a MIDI file on a particular channel. The program adds an extra track at the end of the file to store the pitch bends.
The vibrato rate is constant regardless of the tempo setting for the MIDI file, since the vibrato is calculated in physical time rather than tick time. This program demonstrates how to set the ticks-per-quarter-note value in the MIDI header. A tempo meta-message is also calculated based on the desired duration of a cycle.
For example, try the options -a 3 -b 4 -c -d 1 -o 3x4. Or here is against for cycles: -a 11 -b 13 -c -d 5 -o 11x Skip to content. Star BSDClause License. Branches Tags. Could not load branches. Could not load tags. Latest commit. Git stats commits. Failed to load latest commit information. Add getBase64 helper function. Jun 25, Fix for issue Move src-programs to tools and src-library to src.
Apr 13, Add more file types to. Learn more. Asked 11 years ago. Active 7 years, 3 months ago. Viewed 3k times. How can we do midi file parsing using objective-C? Would be of great help if anybody of you send a reply.. Thanks in advance. Improve this question. Add a comment. Active Oldest Votes. Improve this answer. Daniel Schlaug 1, 1 1 gold badge 13 13 silver badges 16 16 bronze badges. James Andrews James Andrews 3, 3 3 gold badges 29 29 silver badges 43 43 bronze badges.
Ben Smiley saved me about 10 hours today.
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