[alsa-devel] [alsa-lib][PATCH] test/seq-decoder: enable timestamping for external subscribers

[Takashi Iwai]

On Tue, 26 Sep 2017 16:44:49 +0200,
Antonio Ospite wrote:
> 
> Events sent by external clients subscribed to the input port are not
> timestamped.
> 
> This inconsistent behavior may surprise newbies who look at seq-decoder as
> a reference example.
> 
> See the example below using "vkeybd --addr 128:0" to connect to seq-decoder,
> the events sent by vkeybd are on a different queue with no timestamps:
> 
>   ...
>   EVENT>>> Type = 66, flags = 0x0, time = 0 ticks
>            Source = 0.1, dest = 128.0, queue = 253
>            Event = Port Subscribed; 129:0 -> 128:0
>   EVENT>>> Type = 66, flags = 0x1, time = 4.829712627
>            Source = 0.1, dest = 128.0, queue = 0
>            Event = Port Subscribed; 129:0 -> 128:0
>   EVENT>>> Type = 10, flags = 0x0, time = 0 ticks
>            Source = 129.0, dest = 128.0, queue = 253
>            Event = Controller; ch=0, param=0, value=0
>   EVENT>>> Type = 11, flags = 0x0, time = 0 ticks
>            Source = 129.0, dest = 128.0, queue = 253
>            Event = Program Change; ch=0, program=0
>   ...
> 
> After the change events are on the main queue and are timestamped:
> 
>   ...
>   EVENT>>> Type = 66, flags = 0x1, time = 4.280907223
>            Source = 0.1, dest = 128.0, queue = 0
>            Event = Port Subscribed; 129:0 -> 128:0
>   EVENT>>> Type = 66, flags = 0x1, time = 4.280912063
>            Source = 0.1, dest = 128.0, queue = 0
>            Event = Port Subscribed; 129:0 -> 128:0
>   EVENT>>> Type = 10, flags = 0x1, time = 4.280990702
>            Source = 129.0, dest = 128.0, queue = 0
>            Event = Controller; ch=0, param=0, value=0
>   EVENT>>> Type = 11, flags = 0x1, time = 4.280994862
>            Source = 129.0, dest = 128.0, queue = 0
>            Event = Program Change; ch=0, program=0
>   ...
> 
> Signed-off-by: Antonio Ospite <ao2 at ao2.it>
> ---
> 
> Hi,
> 
> while looking into improving the alsamidisrc[1,2] GStreamer element, I took
> a better look at what the sequencer API could do and started using
> test/seq-decoder.c as a reference example.
> 
> I noticed the issue discussed above and I tried to fix it in order to have
> a more consistent behavior of event timestamping.
> 
> I think the new behavior is less surprising for newbies but I may still be
> missing something, please let me know if I am.

This looks like a sensible change, so I applied it now.
Thanks!


Takashi