[pulseaudio-discuss] [PATCH v6 1/2] pipe-source: generate silence when no writers connected

[Georg Chini]

On 14.02.2018 23:16, Raman Shyshniou wrote:
> Currently the pipe-source does not produce any data if no
> writer is connected. This patch enable silence generator
> when last writer closed pipe. It will stop automatically
> when any data appears.
> ---
After my fixes to module-null-source, I think your logic is not yet
completely correct. I would propose to do it like that:

In source_process_msg():

           case PA_SOURCE_MESSAGE_GET_LATENCY:
                current_latency = now - time stamp
                if (u->corkfd < 0)
                    current_latency += data in pipe

           case PA_SOURCE_MESSAGE_SET_STATE:
                if (SUSPENDED or INIT -> IDLE || SUSPENDED or INIT -> 
RUNNING) {
                    get time stamp
                    u->starting = true
                }

In thread_func():

close u->corkfd
u->corkfd = -1
u->starting = true

timer_elapsed = false
revents = 0
get time stamp

for (;;) {
     if (source is open) {

         /* We have to wait at least one configured source latency 
before starting
          * to read data */
         if (revents & POLLIN && !u->starting) {
             read data from pipe
             if (u->corkfd >=0) {
                 close corkfd
                 u->corkfd = -1
            }

         } else if (timer_elapsed && u->corkfd > 0)
             generate silence

        if (data was read/generated) {
             post data
             time stamp += data written
        }

        set timer absolute time stamp + configured (or fixed) source latency
    } else
        set timer disabled

    run rtpoll
    get timer_elapsed

     if (u->starting && timer_elapsed)
         u->starting = false

    if (revents & POLLHUP) {
        open pipe for writing
        u->corkfd = write file descriptor
        revents = revents & ~POLLHUP
    }

    error check
}

You can also add a source_update_requested_latency_cb() like
in module-null-source and pass  PA_SOURCE_DYNAMIC_LATENCY
to pa_source_new() to make the latency configurable.

I hope I did not forget anything ...