[subsynth-devel] [Task #46956] test PortAudio ostream / fix segfault

[<no...@so...>]

Task #46956 has been updated. 

Project: subsynth
Subproject: audio iostreams
Summary: test PortAudio ostream / fix segfault
Complete: 100%
Status: Closed
Authority  : subatomic
Assigned to: subatomic

Description: with loki ging out of business, and with openal streams sucking so badly under unix.... we really need an OSS or sdl output stream implementation

Follow-Ups:

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Date: 2002-07-01 22:22
By: subatomic

Comment:
portaudio bug has been fixed.  it was a sync  problem, fixed with a mutex, and better buffer queuing.

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Date: 2002-06-03 21:40
By: subatomic

Comment:
I'm using portaudio regularly now.  it is good...  there is possibly one small glitch when pa is starving, it can segfault.  need to fix this, then strongly test the PortAudioOstream...

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Date: 2002-04-19 14:51
By: subatomic

Comment:
port audio works, but is in only one test.  I'll close this once I am using it regularly in all tests.  The initial results are good, Port Audio is SO much better than OpenAL for streaming of audio data...

port audio operates with an asyncronous callback.  since our audio ostream uses the polling method, I needed to cache the data sent in with write(), then dequeue the data inside the callback as needed.  

This was... interesting.  Ostream allows arbitrary buffer sizes to be sent to write(), but portaudio only reads N frames at a time.  This meant write() needed to enqueue a variable length buffer, and then the portaudio callback reads N frames from the available queued buffers.  If no buffers are left to read, then of course there is an underun (starvation), and portaudio emits a little click (not good).

TODO: if starvation detected, fade the value to zero, or fill in the rest of the buf with the last written value to prevent high frequency aliasing...

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Date: 2002-04-08 17:20
By: subatomic

Comment:
we should implement a portaudio stream first.  portaudio was designed by the music-dsp people, and is in use by many software synths.  also has ASIO, DirectX, Win, Linux, SGI, etc... support.

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