linuxaudio.org

On 05/08/2012 05:07 AM, Egor Sanin wrote:

quoted text
> Hi folks.

Hi Egor,
> I've got a question about SMPTE frames and jack period size.

quoted text
> In the "worst case" of 30 frames/second, each frame spans 1/30 seconds.

> Does that mean that if jackd is called such that (period size)/(rate)

> ≥ (1/30) seconds, we will drop SMPTE frames?

s/drop/skip/
JACK does not know anything about SMPTE, does it? It counts audio-frames.
JACK-transport timecode (as returned by jack_transport_query())

increases in steps of the period size. It depends on the application

what to make with this.
jack_frame_time() OTOH estimates the time and includes the offset

jack_frames_since_cycle_start(); but I don't know how accurate this is.
@Paul, Fons,..: does it use a PLL or simply return the difference from

clock_gettime() since the beginning of the cycle?

IIRC Fons reworked some of jack timing functions not too long ago when

writing zita-a2j, zita-j2a, but don't know if they also affect the

transport API.
> Large period sizes are rare these days, but this is still a possible

quoted text
> scenario and I want to understand it properly.

Where does the SMPTE come into play? MTC?
robin

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