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appsrc: Implement a leaky property similar to the queue element
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This allows dropping the newest or oldest buffer when the internal queue
is full instead of blocking or continuing to grow.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/1133>
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@sdroege
sdroege authored and GStreamer Marge Bot committed May 5, 2021
1 parent d987ec2 commit 02530e9
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Showing 3 changed files with 213 additions and 2 deletions.
12 changes: 12 additions & 0 deletions docs/plugins/gst_plugins_cache.json
View file
Expand Up @@ -556,6 +556,18 @@
"type": "gboolean",
"writable": true
},
"leaky-type": {
"blurb": "Whether to drop buffers once the internal queue is full",
"conditionally-available": false,
"construct": false,
"construct-only": false,
"controllable": false,
"default": "none (0)",
"mutable": "ready",
"readable": true,
"type": "GstAppLeakyType",
"writable": true
},
"max-buffers": {
"blurb": "The maximum number of buffers to queue internally (0 = unlimited)",
"conditionally-available": false,
Expand Down
180 changes: 178 additions & 2 deletions gst-libs/gst/app/gstappsrc.c
View file
Expand Up @@ -155,6 +155,13 @@ struct _GstAppSrcPrivate
* the next buffer of buffer list */
gboolean pending_custom_segment;

/* the next buffer that will be queued needs a discont flag
* because the previous one was dropped - GST_APP_LEAKY_TYPE_UPSTREAM */
gboolean need_discont_upstream;
/* the next buffer that will be dequeued needs a discont flag
* because the previous one was dropped - GST_APP_LEAKY_TYPE_DOWNSTREAM */
gboolean need_discont_downstream;

gint64 size;
GstClockTime duration;
GstAppStreamType stream_type;
Expand All @@ -180,6 +187,8 @@ struct _GstAppSrcPrivate
guint min_percent;
gboolean handle_segment_change;

GstAppLeakyType leaky_type;

Callbacks *callbacks;
};

Expand Down Expand Up @@ -219,6 +228,7 @@ enum
#define DEFAULT_PROP_CURRENT_LEVEL_TIME 0
#define DEFAULT_PROP_DURATION GST_CLOCK_TIME_NONE
#define DEFAULT_PROP_HANDLE_SEGMENT_CHANGE FALSE
#define DEFAULT_PROP_LEAKY_TYPE GST_APP_LEAKY_TYPE_NONE

enum
{
Expand All @@ -241,6 +251,7 @@ enum
PROP_CURRENT_LEVEL_TIME,
PROP_DURATION,
PROP_HANDLE_SEGMENT_CHANGE,
PROP_LEAKY_TYPE,
PROP_LAST
};

Expand Down Expand Up @@ -541,6 +552,24 @@ gst_app_src_class_init (GstAppSrcClass * klass)
G_PARAM_READWRITE | GST_PARAM_MUTABLE_READY |
G_PARAM_STATIC_STRINGS));

/**
* GstAppSrc:leaky-type:
*
* When set to any other value than GST_APP_LEAKY_TYPE_NONE then the appsrc
* will drop any buffers that are pushed into it once its internal queue is
* full. The selected type defines whether to drop the oldest or new
* buffers.
*
* Since: 1.20
*/
g_object_class_install_property (gobject_class, PROP_LEAKY_TYPE,
g_param_spec_enum ("leaky-type", "Leaky Type",
"Whether to drop buffers once the internal queue is full",
GST_TYPE_APP_LEAKY_TYPE,
DEFAULT_PROP_LEAKY_TYPE,
G_PARAM_READWRITE | GST_PARAM_MUTABLE_READY |
G_PARAM_STATIC_STRINGS));

/**
* GstAppSrc::need-data:
* @appsrc: the appsrc element that emitted the signal
Expand Down Expand Up @@ -719,6 +748,7 @@ gst_app_src_init (GstAppSrc * appsrc)
priv->emit_signals = DEFAULT_PROP_EMIT_SIGNALS;
priv->min_percent = DEFAULT_PROP_MIN_PERCENT;
priv->handle_segment_change = DEFAULT_PROP_HANDLE_SEGMENT_CHANGE;
priv->leaky_type = DEFAULT_PROP_LEAKY_TYPE;

gst_base_src_set_live (GST_BASE_SRC (appsrc), DEFAULT_PROP_IS_LIVE);
}
Expand Down Expand Up @@ -750,6 +780,8 @@ gst_app_src_flush_queued (GstAppSrc * src, gboolean retain_last_caps)
priv->queued_time = 0;
priv->last_in_running_time = GST_CLOCK_TIME_NONE;
priv->last_out_running_time = GST_CLOCK_TIME_NONE;
priv->need_discont_upstream = FALSE;
priv->need_discont_downstream = FALSE;
}

static void
Expand Down Expand Up @@ -878,6 +910,9 @@ gst_app_src_set_property (GObject * object, guint prop_id,
case PROP_HANDLE_SEGMENT_CHANGE:
priv->handle_segment_change = g_value_get_boolean (value);
break;
case PROP_LEAKY_TYPE:
priv->leaky_type = g_value_get_enum (value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
Expand Down Expand Up @@ -957,6 +992,9 @@ gst_app_src_get_property (GObject * object, guint prop_id, GValue * value,
case PROP_HANDLE_SEGMENT_CHANGE:
g_value_set_boolean (value, priv->handle_segment_change);
break;
case PROP_LEAKY_TYPE:
g_value_set_enum (value, priv->leaky_type);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
Expand Down Expand Up @@ -1588,12 +1626,33 @@ gst_app_src_create (GstBaseSrc * bsrc, guint64 offset, guint size,
}

if (GST_IS_BUFFER (obj)) {
*buf = GST_BUFFER (obj);
GstBuffer *buffer = GST_BUFFER (obj);

/* Mark the buffer as DISCONT if we previously dropped a buffer
* instead of outputting it */
if (priv->need_discont_downstream) {
buffer = gst_buffer_make_writable (buffer);
GST_BUFFER_FLAG_SET (buffer, GST_BUFFER_FLAG_DISCONT);
priv->need_discont_downstream = FALSE;
}

*buf = buffer;
} else if (GST_IS_BUFFER_LIST (obj)) {
GstBufferList *buffer_list;

buffer_list = GST_BUFFER_LIST (obj);

/* Mark the first buffer of the buffer list as DISCONT if we
* previously dropped a buffer instead of outputting it */
if (priv->need_discont_downstream) {
GstBuffer *buffer;

buffer_list = gst_buffer_list_make_writable (buffer_list);
buffer = gst_buffer_list_get_writable (buffer_list, 0);
GST_BUFFER_FLAG_SET (buffer, GST_BUFFER_FLAG_DISCONT);
priv->need_discont_downstream = FALSE;
}

gst_base_src_submit_buffer_list (bsrc, buffer_list);
*buf = NULL;
} else if (GST_IS_EVENT (obj)) {
Expand Down Expand Up @@ -2223,6 +2282,45 @@ gst_app_src_set_latencies (GstAppSrc * appsrc, gboolean do_min, guint64 min,
}
}

/**
* gst_app_src_set_leaky_type:
* @appsrc: a #GstAppSrc
* @leaky: the #GstAppLeakyType
*
* When set to any other value than GST_APP_LEAKY_TYPE_NONE then the appsrc
* will drop any buffers that are pushed into it once its internal queue is
* full. The selected type defines whether to drop the oldest or new
* buffers.
*
* Since: 1.20
*/
void
gst_app_src_set_leaky_type (GstAppSrc * appsrc, GstAppLeakyType leaky)
{
g_return_if_fail (GST_IS_APP_SRC (appsrc));

appsrc->priv->leaky_type = leaky;
}

/**
* gst_app_src_get_leaky_type:
* @appsrc: a #GstAppSrc
*
* Returns the currently set #GstAppLeakyType. See gst_app_src_set_leaky_type()
* for more details.
*
* Returns: The currently set #GstAppLeakyType.
*
* Since: 1.20
*/
GstAppLeakyType
gst_app_src_get_leaky_type (GstAppSrc * appsrc)
{
g_return_val_if_fail (GST_IS_APP_SRC (appsrc), GST_APP_LEAKY_TYPE_NONE);

return appsrc->priv->leaky_type;
}

/**
* gst_app_src_set_latency:
* @appsrc: a #GstAppSrc
Expand Down Expand Up @@ -2402,6 +2500,43 @@ gst_app_src_push_internal (GstAppSrc * appsrc, GstBuffer * buffer,
priv->max_buffers, GST_TIME_ARGS (priv->queued_time),
GST_TIME_ARGS (priv->max_time));

if (priv->leaky_type == GST_APP_LEAKY_TYPE_UPSTREAM) {
priv->need_discont_upstream = TRUE;
goto dropped;
} else if (priv->leaky_type == GST_APP_LEAKY_TYPE_DOWNSTREAM) {
guint i, length = gst_queue_array_get_length (priv->queue);
GstMiniObject *item = NULL;

/* Find the oldest buffer or buffer list and drop it, then update the
* limits. Dropping one is sufficient to go below the limits again.
*/
for (i = 0; i < length; i++) {
item = gst_queue_array_peek_nth (priv->queue, i);
if (GST_IS_BUFFER (item) || GST_IS_BUFFER_LIST (item)) {
gst_queue_array_drop_element (priv->queue, i);
break;
}
/* To not accidentally have an event after the loop */
item = NULL;
}

if (!item) {
GST_FIXME_OBJECT (appsrc,
"No buffer or buffer list queued but queue is full");
/* This shouldn't really happen but in this case we can't really do
* anything apart from accepting the buffer / bufferlist */
break;
}

GST_WARNING_OBJECT (appsrc, "Dropping old item %" GST_PTR_FORMAT, item);

gst_app_src_update_queued_pop (appsrc, item, FALSE);
gst_mini_object_unref (item);

priv->need_discont_downstream = TRUE;
continue;
}

if (first) {
Callbacks *callbacks = NULL;
gboolean emit;
Expand Down Expand Up @@ -2438,8 +2573,9 @@ gst_app_src_push_internal (GstAppSrc * appsrc, GstBuffer * buffer,
* stops pushing buffers. */
break;
}
} else
} else {
break;
}
}

if (priv->pending_custom_segment) {
Expand All @@ -2451,11 +2587,39 @@ gst_app_src_push_internal (GstAppSrc * appsrc, GstBuffer * buffer,
}

if (buflist != NULL) {
/* Mark the first buffer of the buffer list as DISCONT if we previously
* dropped a buffer instead of queueing it */
if (priv->need_discont_upstream) {
if (!steal_ref) {
buflist = gst_buffer_list_copy (buflist);
steal_ref = TRUE;
} else {
buflist = gst_buffer_list_make_writable (buflist);
}
buffer = gst_buffer_list_get_writable (buflist, 0);
GST_BUFFER_FLAG_SET (buffer, GST_BUFFER_FLAG_DISCONT);
priv->need_discont_upstream = FALSE;
}

GST_DEBUG_OBJECT (appsrc, "queueing buffer list %p", buflist);

if (!steal_ref)
gst_buffer_list_ref (buflist);
gst_queue_array_push_tail (priv->queue, buflist);
} else {
/* Mark the buffer as DISCONT if we previously dropped a buffer instead of
* queueing it */
if (priv->need_discont_upstream) {
if (!steal_ref) {
buffer = gst_buffer_copy (buffer);
steal_ref = TRUE;
} else {
buffer = gst_buffer_make_writable (buffer);
}
GST_BUFFER_FLAG_SET (buffer, GST_BUFFER_FLAG_DISCONT);
priv->need_discont_upstream = FALSE;
}

GST_DEBUG_OBJECT (appsrc, "queueing buffer %p", buffer);
if (!steal_ref)
gst_buffer_ref (buffer);
Expand Down Expand Up @@ -2497,6 +2661,18 @@ gst_app_src_push_internal (GstAppSrc * appsrc, GstBuffer * buffer,
g_mutex_unlock (&priv->mutex);
return GST_FLOW_EOS;
}
dropped:
{
GST_DEBUG_OBJECT (appsrc, "dropped new buffer %p, we are full", buffer);
if (steal_ref) {
if (buflist)
gst_buffer_list_unref (buflist);
else
gst_buffer_unref (buffer);
}
g_mutex_unlock (&priv->mutex);
return GST_FLOW_EOS;
}
}

static GstFlowReturn
Expand Down
23 changes: 23 additions & 0 deletions gst-libs/gst/app/gstappsrc.h
View file
Expand Up @@ -88,6 +88,23 @@ typedef enum
GST_APP_STREAM_TYPE_RANDOM_ACCESS
} GstAppStreamType;

/**
* GstAppLeakyType:
* @GST_APP_LEAKY_TYPE_NONE: Not Leaky
* @GST_APP_LEAKY_TYPE_UPSTREAM: Leaky on upstream (new buffers)
* @GST_APP_LEAKY_TYPE_DOWNSTREAM: Leaky on downstream (old buffers)
*
* Buffer dropping scheme to avoid the element's internal queue to block when
* full.
*
* Since: 1.20
*/
typedef enum {
GST_APP_LEAKY_TYPE_NONE,
GST_APP_LEAKY_TYPE_UPSTREAM,
GST_APP_LEAKY_TYPE_DOWNSTREAM
} GstAppLeakyType;

struct _GstAppSrc
{
GstBaseSrc basesrc;
Expand Down Expand Up @@ -172,6 +189,12 @@ GstClockTime gst_app_src_get_max_time (GstAppSrc *appsrc);
GST_APP_API
GstClockTime gst_app_src_get_current_level_time (GstAppSrc *appsrc);

GST_APP_API
void gst_app_src_set_leaky_type (GstAppSrc *appsrc, GstAppLeakyType leaky);

GST_APP_API
GstAppLeakyType gst_app_src_get_leaky_type (GstAppSrc *appsrc);

GST_APP_API
void gst_app_src_set_latency (GstAppSrc *appsrc, guint64 min, guint64 max);

Expand Down

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