Subject: Re: [linux-audio-dev] Timestamping?
From: Paul Davis (pbd_AT_Op.Net)
Date: Sat Jun 09 2001 - 06:05:47 EEST
>> the engine always makes the frame time available. thats the only sort
>> of time we can establish, but even that relies on having a client that
>> can tell the engine. in order:
>
>How? I don't see it explicit in the API. And what exactly is frame
>time? How is it different from sample time?
its not part of the regular client API. very few clients are capable
of acting as clock masters. they need to be doing sequencing or HDR to
accomplish this, since otherwise, they have no "zero" reference point.
it was covered in an earlier version of my proposed API, and i'll add
it back to the "extended client" API at some point once the basic one
is done.
"frame time" simply means the current audio frame with respect to the
current zero reference, in units of frames. if you have an HDR system,
and you're running at 48kHz and are 10 seconds past the start of the
recording, then the frame time is 480,000 frames.
this is different than SMPTE time, which in units of
[hrs:mins:secs:smpte-frames] (and note that smpte-frames are not
related in any way to audio frames).
>Oh, another thing: I see audioengine_port_lock in the API, but no
>unlock. Can you explain..?
its just missing. i would prefer a different name for this, since the
name evokes mutexes, and its really quite different. or perhaps not.
--p
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