Subject: Glitch-free presentations with Windows 7 and Matlab From: Trevor Agus <Trevor.Agus@xxxxxxxx> Date: Tue, 18 Oct 2011 17:52:47 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>I've found it surprisingly difficult to present glitch-free sounds with Windows 7. The short answer is that Padraig Kitterick's "asioWavPlay" seems to be the simplest reliable method (remembering to buffer the waveforms with 256 samples of silence to avoid truncation issues). For those with more complex needs, perhaps soundmexpro or PsychToolbox would be better. I'd value any second opinions and double-checking, so a review of the options follows, with all the gory details. I've been using a relatively old version of Matlab (R2007b) with a Fireface UC soundcard. If the problems are fixed in another version or soundcard, I'd love to know about it. ===Matlab's native functions (sound, wavplay, audioplayer) Large, unpredictable truncations were the least of our problems. We also often got mid-sound glitches, ranging from sporadic (just a few subtle glitches per minute) to frequent (making the sound barely recognisable). The magic formula for eliminating the glitches seemed to be to keep the soundcard turned off until the desktop was ready, with all background programs loaded. (Restarting either the soundcard or the computer alone guaranteed some glitches.) So this formula seems to work, but it's a bit too Harry Potter for my liking, and the spell might change with the next Windows update. I think I read that Fireface were no longer supporting Microsoft's vagaries, and they recommended using ASIO. I'm not sure if other high-end soundcard manufacturers are any different. Since Matlab's native functions don't support ASIO (unless the new versions do?), I think we're forced to look at the ASIO options. ===playrec This seems to be potentially the most flexible method of presenting sounds but I've hit a brick wall compiling it for Windows 7. I think its author stopped providing support for it a few years ago. Has anyone had more success than me? ===asioWavPlay This simply presents a .wav file using ASIO. It's a little annoying that you have to save your sound to disk before presenting it, but as Joachim pointed out, it's not too difficult to automate this process. While doing that, I add 256 samples of silence to the end to work around the truncation problem. ===pa_wavplay This is nearly the perfect solution except (1) the number of samples truncated from the end is slightly unpredictable and (2) it prints a message on the screen after every sound ("Playing on device 0"). For these two reasons, I prefer asioWavPlay. ===soundmexpro This might be best choice for the high-end user (I've just had a quick look at the demo version today). It's easy to install and there are good tutorials, but it involves initialising sound objects, etc. -- it's not just a replacement for Matlab's "sound" command. Also it looks like it's €500+. ===PsychToolbox Originally designed for visual experiments, PsychToolbox has now got quite extensive low-latency sound functions, including realtime continuous playing/recording. It's also free. However, it's slightly challenging to install Like soundmexpro, it's object-oriented -- so don't expect to play a sound with a simple one-liner. ===PortAudio Most of above programs are based on this C library. If you're an experienced programmer, perhaps you'd prefer to go direct the source? And while you're there, perhaps you could write the perfect Matlab-ASIO interfaces for the rest of us? (Please!) Has anyone found a simpler solution? I'd be glad to hear it. Trevor