Processing/Getting Info on a MIDI File Before Saving

[dblondin]

I’m currently working on debugging a MIDI file before saving it. I was unsuccessful getting notes to quantize so I started experimenting and I can’t even get a note count. All the values in the output debug are zeros. Here's the output I'm getting:

Extracted notes count: 0
No note details to print.
Total notes: 0
Quantized notes: 0
MIDI file saved to: /Users/xxx/Desktop/MidiFiles/Test.mid

I’m able to import the MIDI file into my DAW and it works fine. The notes are on channel 11. In the debug I expected to at least see the count of notes. Can you suggest why I'm only getting zeros in the debug output and what I might be doing wrong with quantizing? I’ve set the quantizing class up the same as your ’Soft Quantizer’ example:

public void SaveRecording(string fileName)
    {
        if (!fileName.EndsWith(".mid") && !fileName.EndsWith(".midi"))
        {
            fileName += ".mid";
        }

        string desktopPath = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
        string folderPath = Path.Combine(desktopPath, "MidiFiles");
        Directory.CreateDirectory(folderPath);

        string originalFilePath = Path.Combine(folderPath, fileName);

        Task.Run(() =>
        {
            string filePath = originalFilePath;
            int fileNumber = 1;

            while (File.Exists(filePath))
            {
                string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(originalFilePath);
                string fileExtension = Path.GetExtension(originalFilePath);
                string fileNumberSuffix = "_" + fileNumber.ToString();
                filePath = Path.Combine(folderPath, fileNameWithoutExtension + fileNumberSuffix + fileExtension);
                fileNumber++;
            }

            IReadOnlyList<TimedEvent> recordedEvents = recording.GetEvents();

            var midiFile = new MidiFile();
            var trackChunks = new Dictionary<int, TrackChunk>();
            var lastEventTimes = new Dictionary<int, long>();

            TempoMap tempoMap = midiFile.GetTempoMap();

            foreach (var timedEvent in recordedEvents)
            {
                if (timedEvent.Event == null)
                    continue;

                var midiEvent = timedEvent.Event;
                int channelNumber = GetChannelNumber(midiEvent) + 1;

                if (!trackChunks.ContainsKey(channelNumber))
                {
                    var trackChunk = new TrackChunk();
                    trackChunk.Events.Add(new SequenceTrackNameEvent($"Channel {channelNumber}"));
                    trackChunks[channelNumber] = trackChunk;
                    lastEventTimes[channelNumber] = 0;
                }

                lastEventTimes[channelNumber] = AddEventToTrackChunk(trackChunks[channelNumber], timedEvent, tempoMap, lastEventTimes[channelNumber]);
            }

            foreach (var channel in trackChunks.Keys.OrderBy(k => k))
            {
                midiFile.Chunks.Add(trackChunks[channel]);
            }

            //DEBUG
            // Count and print notes before quantization
            int noteCountBefore = CountNotes(midiFile);
            var notesBeforeQuantization = GetNoteDetails(midiFile);
            PrintNotes(notesBeforeQuantization);

            // Quantize and count notes again
            midiFile = Quantize(midiFile);
            int noteCountAfter = CountNotes(midiFile);
            var notesAfterQuantization = GetNoteDetails(midiFile);
            PrintNotes(notesAfterQuantization);

            // Count how many notes were quantized
            int quantizedNotesCount = CountQuantizedNotes(notesBeforeQuantization, notesAfterQuantization);

            Debug.Log($"Total notes: {noteCountBefore}");
            Debug.Log($"Quantized notes: {quantizedNotesCount}");

            midiFile.Write(filePath, overwriteFile: true, format: MidiFileFormat.MultiTrack, settings: new WritingSettings { UseRunningStatus = true, NoteOffAsSilentNoteOn = false });
            Debug.Log("MIDI file saved to: " + filePath);
        });
    }

    MidiFile Quantize(MidiFile midiFile)
    {
        midiFile.QuantizeObjects(
            new NoteQuantizer(),
            ObjectType.Note,
            new SteppedGrid(MusicalTimeSpan.Whole),
            new QuantizingSettings
            {
                DistanceCalculationType = TimeSpanType.Musical
            });

        return midiFile;
    }

    static int CountNotes(MidiFile midiFile)
    {
        var notes = midiFile.GetNotes();
        // DEBUG: Check notes count
        Debug.Log($"Extracted notes count: {notes.Count}");
        return notes.Count;
    }

    static int CountQuantizedNotes(List<(string Note, string Time, string Length)> before, List<(string Note, string Time, string Length)> after)
    {
        int quantizedCount = 0;
        for (int i = 0; i < before.Count; i++)
        {
            if (before[i].Time != after[i].Time || before[i].Length != after[i].Length)
            {
                quantizedCount++;
            }
        }
        return quantizedCount;
    }

    static void PrintNotes(List<(string Note, string Time, string Length)> noteDetails)
    {
        // DEBUG: Check if noteDetails is empty
        if (!noteDetails.Any())
        {
            Debug.Log("No note details to print.");
        }

        foreach (var noteDetail in noteDetails)
        {
            Console.WriteLine($"Note [{noteDetail.Note}]: time = [{noteDetail.Time}], length = [{noteDetail.Length}]");
        }
    }

[melanchall]

Hi,

Well, as a first step please write this code:

var recordedFile = recording.ToFile();
var notes = recordedFile.GetNotes();
Debug.Log($"Recorded notes count: {notes.Count}");

below that line:

IReadOnlyList<TimedEvent> recordedEvents = recording.GetEvents();

What number does the "Recorded notes count" line show?

What about this?

var recordedFile2 = recording.GetEvents().ToFile();
var notes2 = recordedFile2.GetNotes();
Debug.Log($"Recorded notes count 2: {notes2.Count}");

Do you see the correct number again?

[dblondin]

Thanks for your response! I followed your suggestions to debug it. Here's the relevant part of the code:

IReadOnlyList<TimedEvent> recordedEvents = recording.GetEvents();

// Debugging as per your suggestion
var recordedFile = recording.ToFile();
var notes = recordedFile.GetNotes();
Debug.Log($"Recorded notes count: {notes.Count}");

var recordedFile2 = recording.GetEvents().ToFile();
var notes2 = recordedFile2.GetNotes();
Debug.Log($"Recorded notes count 2: {notes2.Count}");

After adding these lines to my SaveRecording method, I found that both recordedFile.GetNotes() and recordedFile2.GetNotes() returned a count of zero. Considering that the MIDI files contain notes when loaded into Ableton Live, I'm puzzled by GetNotes() returning zero.

[melanchall]

Well, what output do you get with this code?

foreach (var e in recording.GetEvents())
{
    Debug.Log($"Recorded event: {e}");
}

Considering that the MIDI files contain notes when loaded into Ableton Live

Sounds pretty strange. If recording is empty, the resulting file will also be empty. You obviously have a bug in your code somewhere so let's find it.

Also can you use the debugger in your IDE to go step by step through your code to see what's going on?

[dblondin]

Ok on stepping through with the debugger! In the meantime here's some example output from the GetEvents debug log. That seems to be working and accurate.

Recorded event: Event at 1: Start
Recorded event: Event at 1: Pitch Bend [2] (64)
Recorded event: Event at 1: Note On [10] (46, 64)
Recorded event: Event at 1: Note On [10] (74, 0)
Recorded event: Event at 4: Pitch Bend [5] (159)
Recorded event: Event at 5: Timing Clock
Recorded event: Event at 8: Timing Clock
Recorded event: Event at 12: Timing Clock
Recorded event: Event at 16: Timing Clock
Recorded event: Event at 20: Timing Clock
Recorded event: Event at 24: Pitch Bend [5] (158)
Recorded event: Event at 24: Timing Clock
Recorded event: Event at 25: Control Change [0] (24, 3)
Recorded event: Event at 28: Timing Clock
Recorded event: Event at 32: Timing Clock
Recorded event: Event at 35: Pitch Bend [5] (157)
Recorded event: Event at 36: Timing Clock
Recorded event: Event at 40: Timing Clock
Recorded event: Event at 44: Pitch Bend [5] (156)
Recorded event: Event at 44: Timing Clock
Recorded event: Event at 48: Timing Clock
Recorded event: Event at 49: Control Change [0] (24, 4)
Recorded event: Event at 49: Pitch Bend [2] (80)
Recorded event: Event at 49: Note On [10] (53, 64)
Recorded event: Event at 49: Note On [10] (46, 0)
Recorded event: Event at 52: Timing Clock
Recorded event: Event at 53: Pitch Bend [5] (155)
Recorded event: Event at 57: Timing Clock
Recorded event: Event at 60: Timing Clock
Recorded event: Event at 63: Pitch Bend [5] (154)
Recorded event: Event at 64: Timing Clock
Recorded event: Event at 68: Timing Clock
Recorded event: Event at 72: Pitch Bend [5] (153)
Recorded event: Event at 72: Timing Clock
Recorded event: Event at 73: Control Change [0] (24, 1)
Recorded event: Event at 76: Timing Clock
Recorded event: Event at 80: Timing Clock
Recorded event: Event at 83: Pitch Bend [5] (152)
Recorded event: Event at 84: Timing Clock
Recorded event: Event at 88: Timing Clock
Recorded event: Event at 92: Timing Clock
Recorded event: Event at 96: Pitch Bend [5] (151)
Recorded event: Event at 96: Timing Clock
Recorded event: Event at 97: Control Change [0] (24, 2)
Recorded event: Event at 97: Pitch Bend [2] (96)
Recorded event: Event at 97: Note On [10] (60, 64)
Recorded event: Event at 97: Note On [10] (53, 0)
Recorded event: Event at 101: Timing Clock
Recorded event: Event at 105: Timing Clock
Recorded event: Event at 108: Timing Clock
Recorded event: Event at 110: Pitch Bend [5] (150)
Recorded event: Event at 112: Timing Clock
Recorded event: Event at 116: Timing Clock
Recorded event: Event at 120: Timing Clock
Recorded event: Event at 121: Control Change [0] (24, 3)
Recorded event: Event at 125: Timing Clock
Recorded event: Event at 126: Pitch Bend [5] (149)
Recorded event: Event at 128: Timing Clock
Recorded event: Event at 132: Timing Clock
Recorded event: Event at 136: Timing Clock
Recorded event: Event at 140: Pitch Bend [5] (148)
Recorded event: Event at 140: Timing Clock
Recorded event: Event at 144: Timing Clock
Recorded event: Event at 145: Control Change [0] (24, 4)
Recorded event: Event at 145: Pitch Bend [2] (112)
Recorded event: Event at 145: Note On [10] (67, 64)
Recorded event: Event at 145: Note On [10] (60, 0)

[melanchall]

Well, now I see the problem. Your device sends Note Off messages as Note On ones with zero velocity. It's a common practice. But DryWetMIDI receives events as is by default. But you can change this behavior.

Somewhere in your code you get InputDevice that is passed to the constructor of the Recording class. Just set SilentNoteOnPolicy property of the device to SilentNoteOnPolicy.NoteOff before recording started:

inputDevice.SilentNoteOnPolicy = SilentNoteOnPolicy.NoteOff;

That should fix your problem.

[dblondin]

Ah yes! Indeed that fixed it! Thanks so much for your assistance in this. I’ll probably implement a method to ensure uniform handling of note-off events, whether they are explicitly sent as note-offs or as note-ons with zero velocity, assuming the performance hit is negligible. I’m curious how common it is for devices to send zero velocity note-offs vs explicit. I have a lot of vintage gear and have noticed the zero velocity version. So glad this is solved, it had me stumped. Thank you!