Fix ALSA available buffersize detection:

buffer-size = periods * period-size

Previously, buffersize was used for period-size.

This fixes an issue with a dedicated .asoundrc configuring a specific
period-size or buffer-size that has to be exact.
Ardour's device configuration failed in this case.

This has not been an issues since most hardware devices offer a wide
range: 8 < period-size < 262144 ; 16 < buffer-size < 524288.
Only a subset of which (32 .8192) is allowed by Ardour.

diff --git a/libs/ardouralsautil/deviceparams.cc b/libs/ardouralsautil/deviceparams.cc
index 2e9f121a1586c1b4365fb8071b68b84880f00852..381f5b8f759c10940ac8145af315e4f1053cf960 100644 (file)
--- a/libs/ardouralsautil/deviceparams.cc
+++ b/libs/ardouralsautil/deviceparams.cc
@@ -33,6 +33,10 @@ ARDOUR::get_alsa_device_parameters (const char* device_name, const bool play, AL
 
        nfo->valid = false;
 
+       unsigned long min_psiz, max_psiz;
+       unsigned long min_bufz, max_bufz;
+       unsigned int min_nper, max_nper;
+
        err = snd_pcm_open (&pcm, device_name,
                        play ? SND_PCM_STREAM_PLAYBACK : SND_PCM_STREAM_CAPTURE,
                        SND_PCM_NONBLOCK);
@@ -66,17 +70,67 @@ ARDOUR::get_alsa_device_parameters (const char* device_name, const bool play, AL
                goto error_out;
        }
 
-       err = snd_pcm_hw_params_get_buffer_size_min (hw_params, &nfo->min_size);
+       err = snd_pcm_hw_params_get_period_size_min (hw_params, &min_psiz, 0);
+       if (err < 0) {
+               errmsg = "Cannot get minimum period size";
+               goto error_out;
+       }
+       err = snd_pcm_hw_params_get_period_size_max (hw_params, &max_psiz, 0);
+       if (err < 0) {
+               errmsg = "Cannot get maximum period size";
+               goto error_out;
+       }
+
+       err = snd_pcm_hw_params_get_buffer_size_min (hw_params, &min_bufz);
        if (err < 0) {
                errmsg = "Cannot get minimum buffer size";
                goto error_out;
        }
-       err = snd_pcm_hw_params_get_buffer_size_max (hw_params, &nfo->max_size);
+       err = snd_pcm_hw_params_get_buffer_size_max (hw_params, &max_bufz);
        if (err < 0) {
                errmsg = "Cannot get maximum buffer size";
                goto error_out;
        }
+
+       err = snd_pcm_hw_params_get_periods_min (hw_params, &min_nper, 0);
+       if (err < 0) {
+               errmsg = "Cannot get minimum period count";
+               goto error_out;
+       }
+       err = snd_pcm_hw_params_get_periods_max (hw_params, &max_nper, 0);
+       if (err < 0) {
+               errmsg = "Cannot get maximum period count";
+               goto error_out;
+       }
+
        snd_pcm_close (pcm);
+
+       /* see also libs/backends/alsa/zita-alsa-pcmi.cc
+        * If any debug parameter is set, print device info.
+        */
+       if (getenv ("ZITA_ALSA_PCMI_DEBUG")) {
+               fprintf (stdout, "ALSA: *%s* device-info\n", play ? "playback" : "capture");
+               fprintf (stdout, "  dev_name : %s\n", device_name);
+               fprintf (stdout, "  channels : %u\n", nfo->max_channels);
+               fprintf (stdout, "  min_rate : %u\n", nfo->min_rate);
+               fprintf (stdout, "  max_rate : %u\n", nfo->max_rate);
+               fprintf (stdout, "  min_psiz : %lu\n", nfo->min_size);
+               fprintf (stdout, "  max_psiz : %lu\n", nfo->max_size);
+               fprintf (stdout, "  min_bufz : %lu\n", min_bufz);
+               fprintf (stdout, "  max_bufz : %lu\n", max_bufz);
+               fprintf (stdout, "  min_nper : %d\n", min_nper);
+               fprintf (stdout, "  max_nper : %d\n", max_nper);
+               fprintf (stdout, "  possible : %lu .. %lu\n", nfo->min_size, nfo->max_size);
+       }
+
+       /* AlsaAudioBackend supports n-periods 2, 3 */
+       if (min_nper > 2 || max_nper < 3) {
+               errmsg = "Unsupported period count";
+               return 1;
+       }
+
+       nfo->min_size = std::max (min_psiz, min_bufz / 3);
+       nfo->max_size = std::min (max_psiz, max_bufz / 2);
        nfo->valid = true;
        return 0;