On Fri, Jun 3, 2011 at 17:45, Alexandre Ratchov <[email protected]> wrote: > On Fri, Jun 03, 2011 at 02:10:37PM +0300, Alexey Suslikov wrote: >> Hello tech@. >> >> aucat(1) manual says: >> >> Streams created with the -t option export the server clock using MTC, >> allowing non-audio software or hardware to be synchronized to the audio >> stream. The following sample rates (-r) and block sizes (-z) are >> recommended for maximum accuracy: >> >> o 44100Hz, 441 frames >> o 48000Hz, 400 frames >> o 48000Hz, 480 frames >> o 48000Hz, 500 frames >> >> For me, it was unclear why manual suggests different block sizes >> for one frequency until I understood MTC resolution being 96, 100 >> or 120 which is described much earlier in the manual. >> >> This is because I expected a bit self-explanatory text here so I can >> think "aha, I saw these numbers earlier" or "ok, let's search why >> these are 96, 100 and 120". Something like >> >> o 44100Hz, 441 frames (MTC resolution is 100) >> o 48000Hz, 400 frames (MTC resolution is 120) >> o 48000Hz, 480 frames (MTC resolution is 100) >> o 48000Hz, 500 frames (MTC resolution is 96) >> > > ok, what about the diff below?
For me, it's clearer. You use Hz across diff, but -z description tells about "ticks per second". Is that on purpose? > >> Moreover, above explanation of MTC and examples are somewhat >> duplicate/overlap earlier -z description: >> >> -z nframes >> The audio device block size in frames. This is the number of >> frames between audio clock ticks, i.e. the clock resolution. If >> a stream is created with the -t option, and MTC is used for >> synchronization, the clock resolution must be 96, 100 or 120 >> ticks per second for maximum accuracy. For instance, 120 ticks >> per second at 48000Hz corresponds to a 400 frame block size. >> >> Is there any better way to explain this? With current text I forced to >> jump up and down to understand what is what. > > I don't know, I take any ideas & diffs. > > Currently, we try to keep the DESCRIPTION section complete and > self-consistent. > > Other sections are to give advices, and/or explain a little bit more > how aucat works. If you don't use mtc (or you already know how mtc > works), you don't need to read other sections and so no need to jump > up and down. > > IMHO we need a section (or separate man page) about audio and midi > concepts and about how aucat works. > > -- Alexandre > > Index: aucat.1 > =================================================================== > RCS file: /home/alex/sndio/cvs/sndio/aucat/aucat.1,v > retrieving revision 1.16 > diff -u -p -r1.16 aucat.1 > --- aucat.1 3 Jun 2011 09:07:16 -0000 1.16 > +++ aucat.1 3 Jun 2011 14:14:36 -0000 > @@ -517,21 +517,23 @@ Streams created with the > .Fl t > option export the server clock using MTC, allowing non-audio > software or hardware to be synchronized to the audio stream. > +Maximum accuracy is achieved when the number of blocks per > +second is equal to one of the standard MTC clock rates (96, 100 and 120Hz). > The following sample rates > .Pq Fl r > and block sizes > .Pq Fl z > -are recommended for maximum accuracy: > +are recommended: > .Pp > .Bl -bullet -offset indent -compact > .It > -44100Hz, 441 frames > +44100Hz, 441 frames (MTC rate is 100Hz) > .It > -48000Hz, 400 frames > +48000Hz, 400 frames (MTC rate is 120Hz) > .It > -48000Hz, 480 frames > +48000Hz, 480 frames (MTC rate is 100Hz) > .It > -48000Hz, 500 frames > +48000Hz, 500 frames (MTC rate is 96Hz) > .El > .Pp > For instance, the following command will create two devices:
