kilx

/* Set the hardware parameters of the given ALSA device. Returns the
 * selected fragment settings in *period and *period_size */
int pa_alsa_set_hw_params(
        snd_pcm_t *pcm_handle,
        pa_sample_spec *ss,
        uint32_t *periods,
        snd_pcm_uframes_t *period_size,
        snd_pcm_uframes_t tsched_size,
        pa_bool_t *use_mmap,
        pa_bool_t *use_tsched,
        pa_bool_t require_exact_channel_number) {

    int ret = -1;
    snd_pcm_uframes_t _period_size = *period_size;
    unsigned int _periods = *periods;
    snd_pcm_uframes_t buffer_size;
    unsigned int r = ss->rate;
    unsigned int c = ss->channels;
    pa_sample_format_t f = ss->format;
    snd_pcm_hw_params_t *hwparams;
    pa_bool_t _use_mmap = use_mmap && *use_mmap;
    pa_bool_t _use_tsched = use_tsched && *use_tsched;
    int dir;

    pa_assert(pcm_handle);
    pa_assert(ss);
    pa_assert(periods);
    pa_assert(period_size);

    snd_pcm_hw_params_alloca(&hwparams);

    if ((ret = snd_pcm_hw_params_any(pcm_handle, hwparams)) < 0)
        goto finish;

    if ((ret = snd_pcm_hw_params_set_rate_resample(pcm_handle, hwparams, 0)) < 0)
        goto finish;

    if (_use_mmap) {
        if ((ret = snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_MMAP_INTERLEAVED)) < 0) {

            /* mmap() didn't work, fall back to interleaved */

            if ((ret = snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0)
                goto finish;

            _use_mmap = FALSE;
        }

    } else if ((ret = snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0)
        goto finish;

    if (!_use_mmap)
        _use_tsched = FALSE;

    if ((ret = set_format(pcm_handle, hwparams, &f)) < 0)
        goto finish;

    if ((ret = snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, &r, NULL)) < 0)
        goto finish;

    /* Adjust the buffer sizes, if we didn't get the rate we were asking for */
    _period_size = (snd_pcm_uframes_t) (((uint64_t) _period_size * r) / ss->rate);
    tsched_size = (snd_pcm_uframes_t) (((uint64_t) tsched_size * r) / ss->rate);

    if (require_exact_channel_number) {
        if ((ret = snd_pcm_hw_params_set_channels(pcm_handle, hwparams, c)) < 0)
            goto finish;
    } else {
        if ((ret = snd_pcm_hw_params_set_channels_near(pcm_handle, hwparams, &c)) < 0)
            goto finish;
    }

    if (_use_tsched) {
        _period_size = tsched_size;
        _periods = 1;

        pa_assert_se(snd_pcm_hw_params_get_buffer_size_max(hwparams, &buffer_size) == 0);
        pa_log_debug("Maximum hw buffer size is %u ms", (unsigned) buffer_size * 1000 / r);
    }

    buffer_size = _periods * _period_size;

    if ((ret = snd_pcm_hw_params_set_periods_integer(pcm_handle, hwparams)) < 0)
        goto finish;

    if (_periods > 0) {

        /* First we pass 0 as direction to get exactly what we asked
         * for. That this is necessary is presumably a bug in ALSA */

        dir = 0;
        if ((ret = snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &_periods, &dir)) < 0) {
            dir = 1;
            if ((ret = snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &_periods, &dir)) < 0) {
                dir = -1;
                if ((ret = snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &_periods, &dir)) < 0)
                    goto finish;
            }
        }
    }

    if (_period_size > 0)
        if ((ret = snd_pcm_hw_params_set_buffer_size_near(pcm_handle, hwparams, &buffer_size)) < 0)
            goto finish;

    if  ((ret = snd_pcm_hw_params(pcm_handle, hwparams)) < 0)
        goto finish;

    if (ss->rate != r)
        pa_log_warn("Device %s doesn't support %u Hz, changed to %u Hz.", snd_pcm_name(pcm_handle), ss->rate, r);

    if (ss->channels != c)
        pa_log_warn("Device %s doesn't support %u channels, changed to %u.", snd_pcm_name(pcm_handle), ss->channels, c);

    if (ss->format != f)
        pa_log_warn("Device %s doesn't support sample format %s, changed to %s.", snd_pcm_name(pcm_handle), pa_sample_format_to_string(ss->format), pa_sample_format_to_string(f));

    if ((ret = snd_pcm_prepare(pcm_handle)) < 0)
        goto finish;

    if ((ret = snd_pcm_hw_params_get_period_size(hwparams, &_period_size, &dir)) < 0 ||
        (ret = snd_pcm_hw_params_get_periods(hwparams, &_periods, &dir)) < 0)
        goto finish;

    /* If the sample rate deviates too much, we need to resample */
    if (r < ss->rate*.95 || r > ss->rate*1.05)
        ss->rate = r;
    ss->channels = (uint8_t) c;
    ss->format = f;

    pa_assert(_periods > 0);
    pa_assert(_period_size > 0);

    *periods = _periods;
    *period_size = _period_size;

    if (use_mmap)
        *use_mmap = _use_mmap;

    if (use_tsched)
        *use_tsched = _use_tsched;

    ret = 0;

    snd_pcm_nonblock(pcm_handle, 1);

finish:

    return ret;
}