[pulseaudio-discuss] [PATCH] stream-interaction: Don't reset interaction state when ducking

[Tanu Kaskinen]

On Mon, 2018-07-02 at 15:22 +0300, Juho Hämäläinen wrote:
> If the interaction state would be reset when ducking, it could happen
> that we apply volume factor to a sink-input that already has volume
> factor applied by us. For example when volume factor is applied while
> a sink-input is running and the sink-input is moved to another sink,
> there will be assertion failure from pa_sink_input_add_volume_factor()
> when calling pa_hashmap_put().
> 
> Signed-off-by: Juho Hämäläinen <jusa at hilvi.org>
> ---
>  src/modules/stream-interaction.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/src/modules/stream-interaction.c b/src/modules/stream-interaction.c
> index 4184786..88cbd5d 100644
> --- a/src/modules/stream-interaction.c
> +++ b/src/modules/stream-interaction.c
> @@ -243,7 +243,10 @@ static pa_hook_result_t process(struct userdata *u, pa_sink_input *i, bool creat
>      pa_assert(u);
>      pa_sink_input_assert_ref(i);
>  
> -    if (!create)
> +    /* Reset interaction states only for cork/mute. If we would reset interaction state
> +     * for ducking, we could apply volume factor to sink-input that already has volume
> +     * factor applied by us. */
> +    if (!u->duck && !create)
>          for (j = 0; j < u->n_groups; j++)
>              pa_hashmap_remove(u->groups[j]->interaction_state, i);

I would be in favour of removing this code altogether. It has only
effect on moving streams that we have muted/corked, and the effect is
(if I understand the code correctly) to re-mute/cork the stream when
starting the move, which doesn't really make sense to me. Maybe there
is some valid reason for doing it, but I don't think it's a good policy
to keep undocumented code around just in case, if the code seems to be
doing nonsensical things.

If removing the code seems too risky, I can also apply this patch and
then add a comment that explains that nobody really knows what the
purpose of the code is.

-- 
Tanu

https://liberapay.com/tanuk
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