[Spice-devel] [PATCH spice-gtk] gst-audio: Do not update mmtime without real audio channel

[Pavel Grunt]

This also fixes the huge memore leak reported by Christophe.
Steps to reproduce:
1. ./configure --disable-pulse --enable-gstaudio
2. connect to a vm streaming video with no audio playing
3. see the memory grow really fast

It seems to be due to the fact that the "fake audio" channel updates the mmtime
in a way that schedules the frames to the future ((unsigned) 0 - delay) and then
gstreamer starts to queue the frames (they should be played later)

Pavel

On Fri, 2017-07-14 at 13:19 +0200, Pavel Grunt wrote:
> The fake channel has been introduced to get the audio volume by starting
> the gstreamer's audio pipeline and querring its volume info (see commit
> aa8d044417bbf60685f59163b874ecb4f157c3c9).
> 
> Hovewer starting the pipeline updates the mmtime as a side effect. This
> may cause a (big) delay in displaying a video stream.
> 
> Because the fake channel is only needed to get the volume info, make
> sure to not update the mm-time with it.
> 
> Reported-by: Christophe de Dinechin <dinechin at redhat.com>
> ---
>  src/spice-gstaudio.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/src/spice-gstaudio.c b/src/spice-gstaudio.c
> index 014c3a5..715f824 100644
> --- a/src/spice-gstaudio.c
> +++ b/src/spice-gstaudio.c
> @@ -38,6 +38,7 @@ struct stream {
>      GstElement              *sink;
>      guint                   rate;
>      guint                   channels;
> +    gboolean                fake; /* fake channel just for getting info about
> audio (volume) */
>  };
>  
>  struct _SpiceGstaudioPrivate {
> @@ -264,6 +265,8 @@ static gboolean update_mmtime_timeout_cb(gpointer data)
>      SpiceGstaudioPrivate *p = gstaudio->priv;
>      GstQuery *q;
>  
> +    g_return_val_if_fail(!p->playback.fake, TRUE);
> +
>      q = gst_query_new_latency();
>      if (gst_element_query(p->playback.pipe, q)) {
>          gboolean live;
> @@ -326,7 +329,7 @@ cleanup:
>      if (p->playback.pipe)
>          gst_element_set_state(p->playback.pipe, GST_STATE_PLAYING);
>  
> -    if (p->mmtime_id == 0) {
> +    if (!p->playback.fake && p->mmtime_id == 0) {
>          update_mmtime_timeout_cb(gstaudio);
>          p->mmtime_id = g_timeout_add_seconds(1, update_mmtime_timeout_cb,
> gstaudio);
>      }
> @@ -569,7 +572,6 @@ static gboolean
> spice_gstaudio_get_playback_volume_info_finish(SpiceAudio *audio
>      GstElement *e;
>      gboolean lmute;
>      gdouble vol;
> -    gboolean fake_channel = FALSE;
>      GTask *task = G_TASK(res);
>  
>      g_return_val_if_fail(g_task_is_valid(task, audio), FALSE);
> @@ -584,9 +586,9 @@ static gboolean
> spice_gstaudio_get_playback_volume_info_finish(SpiceAudio *audio
>  
>      if (p->playback.sink == NULL || p->playback.channels == 0) {
>          SPICE_DEBUG("PlaybackChannel not created yet, force start");
> +        p->playback.fake = TRUE;
>          /* In order to get system volume, we start the pipeline */
>          playback_start(NULL, SPICE_AUDIO_FMT_S16, 2, 48000, audio);
> -        fake_channel = TRUE;
>      }
>  
>      if (GST_IS_BIN(p->playback.sink))
> @@ -604,9 +606,10 @@ static gboolean
> spice_gstaudio_get_playback_volume_info_finish(SpiceAudio *audio
>      }
>      g_object_unref(e);
>  
> -    if (fake_channel) {
> +    if (p->playback.fake) {
>          SPICE_DEBUG("Stop faked PlaybackChannel");
>          playback_stop(SPICE_GSTAUDIO(audio));
> +        p->playback.fake = FALSE;
>      }
>  
>      if (mute != NULL) {