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diff --git a/portaudio/src/hostapi/wdmks/readme.txt b/portaudio/src/hostapi/wdmks/readme.txt new file mode 100644 index 0000000..611acc7 --- /dev/null +++ b/portaudio/src/hostapi/wdmks/readme.txt @@ -0,0 +1,85 @@ +Notes about WDM-KS host API +--------------------------- + +Status history +-------------- +16th January 2011: +Added support for WaveRT device API (Vista and later) for even lesser +latency support. + +10th November 2005: +Made following changes: + * OpenStream: Try all PaSampleFormats internally if the the chosen + format is not supported natively. This fixed several problems + with soundcards that did not take kindly to using 24-bit 3-byte formats. + * OpenStream: Make the minimum framesPerHostIBuffer (and framesPerHostOBuffer) + the default frameSize for the playback/recording pin. + * ProcessingThread: Added a switch to only call PaUtil_EndBufferProcessing + if the total input frames equals the total output frames + +5th September 2004: +This is the first public version of the code. It should be considered +an alpha release with zero guarantee not to crash on any particular +system. So far it has only been tested in the author's development +environment, which means a Win2k/SP2 PIII laptop with integrated +SoundMAX driver and USB Tascam US-428 compiled with both MinGW +(GCC 3.3) and MSVC++6 using the MS DirectX 9 SDK. +It has been most widely tested with the MinGW build, with most of the +test programs (particularly paqa_devs and paqa_errs) passing. +There are some notable failures: patest_out_underflow and both of the +blocking I/O tests (as blocking I/O is not implemented). +At this point the code needs to be tested with a much wider variety +of configurations and feedback provided from testers regarding +both working and failing cases. + +What is the WDM-KS host API? +---------------------------- +PortAudio for Windows currently has 3 functional host implementations. +MME uses the oldest Windows audio API which does not offer good +play/record latency. +DirectX improves this, but still imposes a penalty +of 10s of milliseconds due to the system mixing of streams from +multiple applications. +ASIO offers very good latency, but requires special drivers which are +not always available for cheaper audio hardware. Also, when ASIO +drivers are available, they are not always so robust because they +bypass all of the standardised Windows device driver architecture +and hit the hardware their own way. +Alternatively there are a couple of free (but closed source) ASIO +implementations which connect to the lower level Windows +"Kernel Streaming" API, but again these require special installation +by the user, and can be limited in functionality or difficult to use. + +This is where the PortAudio "WDM-KS" host implementation comes in. +It directly connects PortAudio to the same Kernel Streaming API which +those ASIO bridges use. This avoids the mixing penalty of DirectX, +giving at least as good latency as any ASIO driver, but it has the +advantage of working with ANY Windows audio hardware which is available +through the normal MME/DirectX routes without the user requiring +any additional device drivers to be installed, and allowing all +device selection to be done through the normal PortAudio API. + +Note that in general you should only be using this host API if your +application has a real requirement for very low latency audio (<20ms), +either because you are generating sounds in real-time based upon +user input, or you a processing recorded audio in real time. + +The only thing to be aware of is that using the KS interface will +block that device from being used by the rest of system through +the higher level APIs, or conversely, if the system is using +a device, the KS API will not be able to use it. MS recommend that +you should keep the device open only when your application has focus. +In PortAudio terms, this means having a stream Open on a WDMKS device. + +Usage +----- +To add the WDMKS backend to your program which is already using +PortAudio, you must define PA_USE_WDMKS=1 in your build file, +and include the pa_win_wdmks\pa_win_wdmks.c into your build. +The file should compile in both C and C++. +You will need a DirectX SDK installed on your system for the +ks.h and ksmedia.h header files. +You will need to link to the system "setupapi" library. +Note that if you use MinGW, you will get more warnings from +the DX header files when using GCC(C), and still a few warnings +with G++(CPP). |