[alsa-devel] [PATCH RFC 0/9] audio timestamping evolutions

[Raymond Yau]

>>
>> It seem that audio_time.c is hardcoded to use 48000Hz which is the hda
>> link rate, do the measurement still valid when application use 44100Hz ?
>
>
> If you use a wallclock then you really abstract away the actual sampling
frequency and the transmission pattern discontinuity
(12-11-11-12-11-11-12-11-11-11 pattern, with an invalid sample every 12 or
11 samples for HDAudio). It wouldn't matter if you transmitted 44.1 or
48kHz since they use the same wall clock ticks.
>
>

#define PERIOD 6000

#define PLAYBACK_BUFFERS 4

unsigned char buffer_p[PERIOD*4*4];
unsigned char buffer_c[PERIOD*4*4];

I don't understand why you hard coded PERIOD and PLAYBACK_BUFFERS
when you use snd_pcm_set_params

since period size and buffer size can be obtained by snd_pcm_get_params()
after calling snd_pcm_set_params()

if ((err = snd_pcm_set_params(handle_p,
                              SND_PCM_FORMAT_S16,
                              SND_PCM_ACCESS_RW_INTERLEAVED,
                              2,
                              48000,
                              0,
                              500000)) < 0) { /* 0.5sec */