23.06.2018, 14:52, "Subhashini Rao Beerisetty" <[email protected]>: > Hello All,
Hello, > I’m trying to understand how audio samples transferred between user mode to > kernel mode during playback and capture. I’m using aplay & arecord alsa > utilities for playback and capture. > > Let us take a PCM wav file of sample rate 48000 and it has a total number of > samples 480000 (Approx.Duration in seconds=10). Size of each sample is 8 > bytes(two channels). After invocation of aplay from user mode, how does these > audio samples gets copied to kernel mode? Can someone explain me on this? > > Is it possible to capture the timestamps for the first and last audio samples > that arrive at the driver level? > > Can I consider the .trigger(for playback & capture) callback in > SNDRV_PCM_TRIGGER_START case is timestamp for the first audio sample? > > Similarly does .trigger callbacks SNDRV_PCM_TRIGGER_STOP gives the last audio > sample timestamp? I think no, because the SNDRV_PCM_TRIGGER_START and SNDRV_PCM_TRIGGER_STOP functions only system call to the PCM transmitted. So, will want two different functions as playback / capture and the method depends on you use alsa or pulse. I think you want to: snd_mychip_playback_open snd_mychip_playback_close snd_mychip_capture_open snd_mychip_capture_close Trigger funcs times are not real playback or capture time-stamps. Regards Ozgur > Thanks, _______________________________________________ Kernelnewbies mailing list [email protected] https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
