From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Rigg Date: Tue, 10 Jan 2006 00:53:59 +0000 Subject: Re: [Alsa-devel] Re: [OT] ALSA userspace API complexity Message-Id: <20060110010235.GA5224@localhost.localdomain> List-Id: References: <20050726150837.GT3160@stusta.de> <200601091405.23939.rene@exactcode.de> <200601091812.55943.rene@exactcode.de> <20060109232043.GA5013@localhost.localdomain> <20060110001617.GA5154@localhost.localdomain> In-Reply-To: <20060110001617.GA5154@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Cc: John Rigg , David Lang , =?iso-8859-1?Q?Ren=E9?= Rebe , Hannu Savolainen , Jaroslav Kysela , Takashi Iwai , linux-sound@vger.kernel.org, ALSA development , LKML On Tue, Jan 10, 2006 at 12:16:17AM +0000, John Rigg wrote: > On Mon, Jan 09, 2006 at 03:21:21PM -0800, David Lang wrote: > > does the CPU touch the data for these, or do you DMA directly from > > userspace (i.e. "zero-copy")? > > The cards I mentioned use DMA. RME actually advertises that some of their > cards can handle 52 channels with zero CPU load. Their onboard DSPs can > also do routing and mixing, again without touching the CPU. Of course I should also mention that the sound cards deal with PCM audio samples in integer format, but audio apps like jackd and its clients use floating point, so in practice the CPU is still processing audio data much of the time. John