Hi paul blakeley! On 2007.11.20 at 12:26:29 +0000, paul blakeley wrote next: > Can someone please explain the differences between these? What impact > they have on the application? plughw supports much more sample formats / channel configurations than underlying hardware supports natively, and performs conversion if needed. hw performs no conversion, but supports less configuration, sometimes only very obscure ones, but when used you can rest assured that no conversion takes place. Mostly you'd want these conversions to take place, like mono->stereo conversion or S16LE->S32LE conversion etc (all depending on your hardware) > If I need to drive the sound card directly should I use 'hw'? You can use hw, but it isn't really recommended unless you REALLY know how to use it and have support of every weird format in all possible combinations. That's about underlying hardware details, and most applications don't want to deal with them. For example my soundcard supports only S24_3BE format; you can't open hw device in any other mode, if you want to output S16LE (most applications never heard of S24_3 formats, let alone BE variations), you must use plughw, there is no other choice. Or p16v device on audigy2 supports only 8-channel modes; you can't output stereo signal to it, no matter how you try. So you either can output 8 channels to hw device or let plughw to do stereo->8ch conversion for you automatically. Unless you want to take care of all these little details, using hw is probably not a good idea. Though it's required for some applications because you don't actually know if/what kind of conversion takes place when you use plughw, most application would trouble users much less if they were to use plughw instead of hw. Actually, almost all application shouldn't even use plughw, sticking to "default" device, to allow software mixing, jack/pulse routing plugins, user choosen conversions to take place. If you do anything else, you create problems for users, so you must have really good reasons to do so.. -- Vladimir ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
