| Message ID | 1531986609-10437-1-git-send-email-twischer@de.adit-jv.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 19 Jul 2018 09:50:09 +0200, <twischer@de.adit-jv.com> wrote: > > From: Laxmi Devi <ldevi@de.adit-jv.com> > > There is a higher Xrun probability whenever the ALSA period is not a > multiple of the JACKd period and the ALSA buffer is only twice the period. > Allowing ALSA buffers of min. 3x period is not a good solution because this > would increase the latency. > > As an example in case of ALSA is using a period of 11 frames and JACK a > period of 12 frames and a buffer of 22 frames (2x ALSA period) is used: > - The buffer is filled and contains 22 frames > - JACK is reading 12 frames. Buffer is only containing 10 frames > - Now, ALSA has to be scheduled exactly after the last JACK read and > before the next read. Otherwise we will get an Xrun > In case of ALSA is using a multiple period of JACK, JACK can always read > 2 periods before an Xrun if the buffer was full. > > In case of ALSA is using a period of 12 frames and JACK a period of 11 > frames and a buffer of 24 frames (2x ALSA period) is used: > - The buffer is filled and contains 24 frames > - JACK is reading 11 frames. Buffer is now containing 13 frames. But ALSA > can still not write to the buffer > - JACK reads 11 additional frames. Buffer contains 2 frames > - Now, ALSA has to be scheduled exactly after the last JACK read and > before the next read. Otherwise we will get an Xrun > In case of ALSA is using a multiple period of JACK, ALSA can always write > to the buffer as long as the buffer is filled with less or equal of half > of buffer. > > Therefore this patch enforces an ALSA period which is always a multiple > of the JACKd period. > > Signed-off-by: Laxmi Devi <ldevi@de.adit-jv.com> > Signed-off-by: Timo Wischer <twischer@de.adit-jv.com> Applied now. Thanks. Takashi
diff --git a/jack/pcm_jack.c b/jack/pcm_jack.c index fbc9daf..b39835e 100644 --- a/jack/pcm_jack.c +++ b/jack/pcm_jack.c @@ -29,6 +29,8 @@ #include <alsa/asoundlib.h> #include <alsa/pcm_external.h> +#define MAX_PERIODS_MULTIPLE 64 + typedef enum _jack_format { SND_PCM_JACK_FORMAT_RAW } snd_pcm_jack_format_t; @@ -364,8 +366,20 @@ static int jack_set_hw_constraint(snd_pcm_jack_t *jack) }; unsigned int format = SND_PCM_FORMAT_FLOAT; unsigned int rate = jack_get_sample_rate(jack->client); + unsigned int psize_list[MAX_PERIODS_MULTIPLE]; + unsigned int nframes = jack_get_buffer_size(jack->client); + unsigned int jack_buffer_bytes = (snd_pcm_format_size(format, nframes) * + jack->channels); + unsigned int i; int err; + if (!jack_buffer_bytes) { + SNDERR("Buffer size is zero"); + return -EINVAL; + } + for (i = 1; i <= ARRAY_SIZE(psize_list); i++) + psize_list[i-1] = jack_buffer_bytes * i; + jack->sample_bits = snd_pcm_format_physical_width(format); if ((err = snd_pcm_ioplug_set_param_list(&jack->io, SND_PCM_IOPLUG_HW_ACCESS, ARRAY_SIZE(access_list), access_list)) < 0 || @@ -375,8 +389,8 @@ static int jack_set_hw_constraint(snd_pcm_jack_t *jack) jack->channels, jack->channels)) < 0 || (err = snd_pcm_ioplug_set_param_minmax(&jack->io, SND_PCM_IOPLUG_HW_RATE, rate, rate)) < 0 || - (err = snd_pcm_ioplug_set_param_minmax(&jack->io, SND_PCM_IOPLUG_HW_PERIOD_BYTES, - 128, 64*1024)) < 0 || + (err = snd_pcm_ioplug_set_param_list(&jack->io, SND_PCM_IOPLUG_HW_PERIOD_BYTES, + ARRAY_SIZE(psize_list), psize_list)) < 0 || (err = snd_pcm_ioplug_set_param_minmax(&jack->io, SND_PCM_IOPLUG_HW_PERIODS, 2, 64)) < 0) return err;