Hi,
I'm adding latency control to an application and didn't find much documentation about the pcm status functions aside from a very brief description and the latency.c example. What exactly are the "trigger timestamp" and "now timestamp" returned by snd_pcm_status_get_trigger_tstamp() and snd_pcm_status_get_tstamp()? I collected both from my output pcm handle to find values (in tv_sec.tv_usec format) such as
1195518180.938427 938427.557702 1195518180.938441 938441.557702 1195518181.300395 300395.557702 1195518181.300441 300441.557702
where the "trigger" tv_sec matches the "now" tv_usec, and the "trigger" tv_usec varies in large steps. Also the example latency.c says:
00703 showinmax(in_max); 00704 if (p_tstamp.tv_sec == p_tstamp.tv_sec && 00705 p_tstamp.tv_usec == c_tstamp.tv_usec) 00706 printf("Hardware sync\n"); 00707 snd_pcm_drop(chandle);
In line 704, shouldn't it be p_tstamp.tv_sec == c_tstamp.tv_sec?
My final goal is to sync on-screen events with the sound output. I'd like to do something like storing output metadata associated with a certain timestamp and collecting it back based on the timestamp of the currently playing pcm data (like the OSS sequencer echoback events), is that possible, or is there a better way to do this?