Versione delle 19:26, 17 gen 2024

Utilizzando i plugin di GStreamer con le Classi MediaControl e MediaPipeline del Componente gb.media, è possibile ottenere un file audio da un file MIDI.

I plugin specifici da utilizzare per il MIDI sono:

• midiparse: interpreta i file MIDI e li converte in eventi MIDI;
• fluiddec: effettua il render degli eventi MIDI in campioni audio grezzi.

Mostriamo di seguito un esempio pratico, nel quale si otterrà un file WAV da un file MIDI:

Private bo As Boolean


Public Sub Main()
 
 Dim filemidi As String
 Dim pl As MediaPipeline
 Dim src, par, fdc, con, res, vol, enc, snk As MediaControl
 Dim flt As MediaFilter

 filemidi = "/percorso/del/file.mid"

 pl = New MediaPipeline As "PLine"

 src = New MediaControl(pl, "filesrc")
 src["location"] = filemidi
  
 par = New MediaControl(pl, "midiparse")
 fdc = New MediaControl(pl, "fluiddec")
 con = New MediaControl(pl, "audioconvert")
 res = New MediaControl(pl, "audioresample")
 flt = New MediaFilter(pl, "audio/x-raw,format=S16LE,rate=44100,channels=2,depth=16")
 vol = New MediaControl(pl, "volume")
 vol["volume"] = 0.5                         ' <1.0 = volume <100% | 1.0 = volume 100% | >1.0 = volume >100%
 enc = New MediaControl(pl, "wavenc")
 snk = New MediaControl(pl, "filesink")
 snk["location"] = "/tmp" &/ File.BaseName(filemidi) & ".wav"

 src.LinkTo(par)
 par.LinkTo(fdc)
 fdc.LinkTo(con)
 con.LinkTo(res)
 res.LinkTo(flt)
 flt.LinkTo(vol)
 vol.LinkTo(enc)
 enc.LinkTo(snk)

 pl.Play()

 Print "Durata del file Midi: "; Str(Time(0, 0, 0, pl.Duration * 1000))
 While Not bo
   Write "\r\e[0mTempo di conversione:     \e[31m" & Str(Time(0, 0, 0, pl.Position * 1000))
   Wait 0.01
 Wend

 pl.Stop
 pl.Close

 Print "\n\e[0mConversione terminata !"

End


Public Sub PLine_End()   ' Questo Evento viene sollevato, quando la conversione è terminata
 
 bo = True
 
End

In quest'altro esempio si otterrà un file OGG-Vorbis da un file MIDI:

Private bo As Boolean


Public Sub Main()

 Dim filemidi As String
 Dim pl As MediaPipeline
 Dim src, par, fdc, con, res, vol, vor, mux, snk As MediaControl

 filemidi = "/percorso/del/file.mid"

 pl = New MediaPipeline As "PLine"

 src = New MediaControl(pl, "filesrc")
 src["location"] = filemidi

 par = New MediaControl(pl, "midiparse")
 fdc = New MediaControl(pl, "fluiddec")
 con = New MediaControl(pl, "audioconvert")
 res = New MediaControl(pl, "audioresample")
 vol = New MediaControl(pl, "volume")
 vol["volume"] = 0.4                          ' <1.0 = volume <100% | 1.0 = volume 100% | >1.0 = volume >100%
 vor = New MediaControl(pl, "vorbisenc")
 mux = New MediaControl(pl, "oggmux")
 snk = New MediaControl(pl, "filesink")
 snk["location"] = "/tmp" &/ File.BaseName(filemidi) & ".ogg"

 src.LinkTo(par)
 par.LinkTo(fdc)
 fdc.LinkTo(res)
 res.LinkTo(cnv)
 cnv.LinkTo(vol)
 vol.LinkTo(vor)
 vor.LinkTo(mux)
 mux.LinkTo(snk)

 pl.Play()

 Print "Durata del file Midi: "; Str(Time(0, 0, 0, pl.Duration * 1000))
 While Not bo
   Write "\r\e[0mTempo conversione:     \e[31m" & Str(Time(0, 0, 0, pl.Position * 1000))
   Wait 0.01
 Wend

 pl.Stop
 pl.Close

 Print "\n\e[0mConversione terminata !"

End

Public Sub PLine_End()
 
 bo = True
 
End

In questo terzo esempio si otterrà un file MP3 da un file MIDI:

Private bo As Boolean


Public Sub Main()

 Dim filemidi As String
 Dim pl As MediaPipeline
 Dim src, par, fdc, con, res, vol, lam, snk As MediaControl

 filemidi = "/percorso/del/file.mid"

 pl = New MediaPipeline As "PLine"

 src = New MediaControl(pl, "filesrc")
 src["location"] = filemidi

 par = New MediaControl(pl, "midiparse")
 fdc = New MediaControl(pl, "fluiddec")
 con = New MediaControl(pl, "audioconvert")
 res = New MediaControl(pl, "audioresample")
 vol = New MediaControl(pl, "volume")
 vol["volume"] = 0.4                          ' <1.0 = volume <100% | 1.0 = volume 100% | >1.0 = volume >100%
 lam = New MediaControl(pl, "lamemp3enc")
 snk = New MediaControl(pl, "filesink")
 snk["location"] = "/tmp" &/ File.BaseName(filemidi) & ".mp3"

 src.LinkTo(par)
 par.LinkTo(fdc)
 fdc.LinkTo(res)
 res.LinkTo(cnv)
 cnv.LinkTo(vol)
 vol.LinkTo(lam)
 lam.LinkTo(snk)

 pl.Play()
 
 Print "Durata del file Midi: "; Str(Time(0, 0, 0, pl.Duration * 1000))
 While Not bo
   Write "\r\e[0mTempo conversione:     \e[31m" & Str(Time(0, 0, 0, pl.Position * 1000))
   Wait 0.01
 Wend

 pl.Stop
 pl.Close

 Print "\n\e[0mConversione terminata !"

End


Public Sub PLine_End()

 bo = True

End

In questo quarto esempio si otterrà un file AAC da un file MIDI:

Private bo As Boolean


Public Sub Main()
 
 Dim filemidi As String
 Dim pl As MediaPipeline
 Dim src, par, fdc, con, res, vol, faa, snk As MediaControl
 Dim flt1, flt2 As MediaFilter

 filemidi = "/percorso/del/file.mid"

 pl = New MediaPipeline As "PLine"

 src = New MediaControl(pl, "filesrc")
 src["location"] = filemidi
  
 par = New MediaControl(pl, "midiparse")
 fdc = New MediaControl(pl, "fluiddec")
 con = New MediaControl(pl, "audioconvert")
 res = New MediaControl(pl, "audioresample")
 flt1 = New MediaFilter(pl, "audio/x-raw,format=S16LE,rate=44100,channels=2,depth=16")
 vol = New MediaControl(pl, "volume")
 vol["volume"] = 1.0                         ' <1.0 = volume <100% | 1.0 = volume 100% | >1.0 = volume >100%
 faa = New MediaControl(pl, "faac")
 flt2 = New MediaFilter(pl, "audio/mpeg,stream-format=adts,channels=2,rate=44100")
 snk = New MediaControl(pl, "filesink")
 snk["location"] = "/tmp" &/ File.BaseName(filemidi) & ".aac"

 src.LinkTo(par)
 par.LinkTo(fdc)
 fdc.LinkTo(con)
 con.LinkTo(res)
 res.LinkTo(flt1)
 flt1.LinkTo(vol)
 vol.LinkTo(faa)
 faa.LinkTo(flt2)
 flt2.LinkTo(snk)

 pl.Play()

 Print "Durata del file Midi: "; Str(Time(0, 0, 0, pl.Duration * 1000))
 While Not bo
   Write "\r\e[0mTempo di conversione:     \e[31m" & Str(Time(0, 0, 0, pl.Position * 1000))
   Wait 0.01
 Wend

 pl.Stop
 pl.Close

 Print "\n\e[0mConversione terminata !"

End


Public Sub PLine_End()   ' Questo Evento viene sollevato, quando la conversione è terminata
 
 bo = True
 
End

Riferimenti

• https://github.com/Xilinx/gstreamer/blob/master/docs/random/uraeus/gstreamer_and_midi.txt