[pulseaudio-tickets] [Bug 54243] New: [cleanup] When creating a new sink input, the core could request a rewind

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=54243

             Bug #: 54243
           Summary: [cleanup] When creating a new sink input, the core
                    could request a rewind
    Classification: Unclassified
           Product: PulseAudio
           Version: unspecified
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: medium
         Component: core
        AssignedTo: pulseaudio-bugs at lists.freedesktop.org
        ReportedBy: tanuk at iki.fi
         QAContact: pulseaudio-bugs at lists.freedesktop.org
                CC: lennart at poettering.net


Comment in the PA_SINK_MESSAGE_ADD_INPUT handler in sink.c:

/* We don't rewind here automatically. This is left to the
 * sink input implementor because some sink inputs need a
 * slow start, i.e. need some time to buffer client
 * samples before beginning streaming. */


Not doing the rewind automatically has led to a situation where every filter
sink (and some other sink input implementations, like module-sine) has this
sink input state change callback:

static void sink_input_state_change_cb(pa_sink_input *i, pa_sink_input_state_t
state) {
    struct userdata *u;

    pa_sink_input_assert_ref(i);
    pa_assert_se(u = i->userdata);

    pa_log_debug("Sink input %d state %d", i->index, state);

    /* If we are added for the first time, ask for a rewinding so that
     * we are heard right-away. */
    if (PA_SINK_INPUT_IS_LINKED(state) &&
        i->thread_info.state == PA_SINK_INPUT_INIT) {
        pa_log_debug("Requesting rewind due to state change.");
        pa_sink_input_request_rewind(i, 0, FALSE, TRUE, TRUE);
    }
}


Repeating that in every filter sink shouldn't be needed. The core could request
the rewind itself, without pushing the responsibility to the sink input
implementors. Avoiding the rewind when it's not needed is only an optimization.
In my opinion the optimization is good to have, but it could be implemented by
having a sink input flag that says that this input "needs a slow start".

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