[pulseaudio-discuss] [PATCH v4 09/41] bluetooth: Implement org.bluez.MediaEndpoint1.SelectConfiguration()

[Tanu Kaskinen]

On Mon, 2013-09-23 at 08:39 -0500, João Paulo Rechi Vita wrote:
> On Sun, Sep 22, 2013 at 12:19 AM, Tanu Kaskinen
> <tanu.kaskinen at linux.intel.com> wrote:
> > On Sat, 2013-09-21 at 13:30 -0500, João Paulo Rechi Vita wrote:
> >> On Sat, Sep 21, 2013 at 5:16 AM, Tanu Kaskinen
> >> <tanu.kaskinen at linux.intel.com> wrote:
> >> > On Wed, 2013-09-18 at 16:17 -0500, jprvita at gmail.com wrote:
> >> >>  static DBusMessage *endpoint_select_configuration(DBusConnection *conn, DBusMessage *m, void *userdata) {
> >> >> +    pa_bluetooth_discovery *y = userdata;
> >> >> +    a2dp_sbc_t *cap, config;
> >> >> +    uint8_t *pconf = (uint8_t *) &config;
> >> >> +    int i, size;
> >> >>      DBusMessage *r;
> >> >> +    DBusError err;
> >> >>
> >> >> -    pa_assert_se(r = dbus_message_new_error(m, BLUEZ_MEDIA_ENDPOINT_INTERFACE ".Error.NotImplemented",
> >> >> -                                            "Method not implemented"));
> >> >> +    static const struct {
> >> >> +        uint32_t rate;
> >> >> +        uint8_t cap;
> >> >> +    } freq_table[] = {
> >> >> +        { 16000U, SBC_SAMPLING_FREQ_16000 },
> >> >> +        { 32000U, SBC_SAMPLING_FREQ_32000 },
> >> >> +        { 44100U, SBC_SAMPLING_FREQ_44100 },
> >> >> +        { 48000U, SBC_SAMPLING_FREQ_48000 }
> >> >> +    };
> >> >> +
> >> >> +    dbus_error_init(&err);
> >> >> +
> >> >> +    if (!dbus_message_get_args(m, &err, DBUS_TYPE_ARRAY, DBUS_TYPE_BYTE, &cap, &size, DBUS_TYPE_INVALID)) {
> >> >> +        pa_log_error("Endpoint SelectConfiguration(): %s", err.message);
> >> >> +        dbus_error_free(&err);
> >> >> +        goto fail;
> >> >> +    }
> >> >> +
> >> >> +    if (size != sizeof(config)) {
> >> >> +        pa_log_error("Capabilities array has invalid size");
> >> >> +        goto fail;
> >> >> +    }
> >> >> +
> >> >> +    pa_zero(config);
> >> >> +
> >> >> +    /* Find the lowest freq that is at least as high as the requested sampling rate */
> >> >> +    for (i = 0; (unsigned) i < PA_ELEMENTSOF(freq_table); i++)
> >> >> +        if (freq_table[i].rate >= y->core->default_sample_spec.rate && (cap->frequency & freq_table[i].cap)) {
> >> >> +            config.frequency = freq_table[i].cap;
> >> >> +            break;
> >> >> +        }
> >> >>
> >> >> +    if ((unsigned) i == PA_ELEMENTSOF(freq_table)) {
> >> >> +        for (--i; i >= 0; i--) {
> >> >> +            if (cap->frequency & freq_table[i].cap) {
> >> >> +                config.frequency = freq_table[i].cap;
> >> >> +                break;
> >> >> +            }
> >> >> +        }
> >> >> +
> >> >> +        if (i < 0) {
> >> >> +            pa_log_error("Not suitable sample rate");
> >> >> +            goto fail;
> >> >> +        }
> >> >> +    }
> >> >> +
> >> >> +    pa_assert((unsigned) i < PA_ELEMENTSOF(freq_table));
> >> >> +
> >> >> +    if (y->core->default_sample_spec.channels <= 1)
> >> >> +        if (cap->channel_mode & SBC_CHANNEL_MODE_MONO)
> >> >> +            config.channel_mode = SBC_CHANNEL_MODE_MONO;
> >> >
> >> > You forgot to fix this code. The problem still exists that if
> >> > default_sample_spec.channels is 1 and the cap->channel_mode doesn't
> >> > contain SBC_CHANNEL_MODE_MONO, then config.channel_mode is left
> >> > uninitialized.
> >> >
> >>
> >> No, I didn't, but I may have misunderstood you. Re-reading it new
> >> trying to give another interpretation, it seems you suggest that we
> >> don't differentiate between (y->core->default_sample_spec.channels <=
> >> 1) and (y->core->default_sample_spec.channels >= 2), but I don't think
> >> that's what you meant. Can you please explain how we should
> >> differentiate those two cases?
> >
> > There are four modes we support: mono, and three stereo modes. We should
> > always allow any any of those modes. Depending on
> > default_sample_spec.channels, we should either prefer the mono mode or
> > the stereo modes, but if the device doesn't support our preferred mode,
> > we should fall back to a mode that the device supports. In your code
> > that fallback is implemented when default_sample_spec.channels >= 2, but
> > not if default_sample_spec.channels == 1.
> >
> 
> Ok, and what preference order we should use between the stereo modes
> for default_sample_spec.channels == 1? (I'm assuming mono is the 1st
> preference in this case).

Yes, mono is the first preferred mode. I don't have any idea about the
ordering of the different stereo modes, except that the ordering should
be the same for both default_sample_spec.channels == 1 and
default_sample_spec.channels == 2, unless you know some reason to use
different ordering.

-- 
Tanu