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docs/design/part-block.txt: Further explain the use of flushing on blocked pads.
Original commit message from CVS: * docs/design/part-block.txt: Further explain the use of flushing on blocked pads. * docs/gst/gstreamer-sections.txt: * gst/gstpad.c: (gst_pad_is_blocking), (handle_pad_block), (gst_pad_push_event): * gst/gstpad.h: Added new GstPadFlag : GST_PAD_BLOCKING. Adds the notion of pads really blocking, which enables to properly handle FLUSH_START/FLUSH_STOP events on blocked pads. Fixes #358999 API: gst_pad_is_blocking() API: GST_PAD_IS_BLOCKING() macro API: GST_PAD_BLOCKING GstPadFlag
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Edward Hervey
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commit
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5 changed files with 110 additions and 4 deletions
17
ChangeLog
17
ChangeLog
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@ -1,3 +1,20 @@
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2006-10-02 Edward Hervey <edward@fluendo.com>
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* docs/design/part-block.txt:
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Further explain the use of flushing on blocked pads.
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* docs/gst/gstreamer-sections.txt:
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* gst/gstpad.c: (gst_pad_is_blocking), (handle_pad_block),
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(gst_pad_push_event):
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* gst/gstpad.h:
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Added new GstPadFlag : GST_PAD_BLOCKING.
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Adds the notion of pads really blocking, which enables to properly
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handle FLUSH_START/FLUSH_STOP events on blocked pads.
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Fixes #358999
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API: gst_pad_is_blocking()
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API: GST_PAD_IS_BLOCKING() macro
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API: GST_PAD_BLOCKING GstPadFlag
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2006-10-02 Wim Taymans <wim@fluendo.com>
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Patch by: mrcgran <mrc.gran at gmail dot com>
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@ -23,6 +23,8 @@ Flushing
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The flushing event is used to clear any data out of the
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downstream elements.
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* Generic case
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Consider the following pipeline:
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.-----. .-------. .-------.
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@ -48,6 +50,39 @@ Flushing
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fr the same reason. From then on, the new data after the flushing seek
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will be queued when the pad block is taken again.
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* Case where the stream is blocking downstream
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The example above is only valid if the elem1.src pad is really blocking
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(callback called or sync block returned).
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In the case where the stream is blocking further downstream (on elem2.src
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for example, or on a blocking queue), extra care has to be taken.
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Consider the following pipeline:
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.-----. .-------. .-------.
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| src | | elem1 |\/ | elem2 |
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| src -> sink src -> sink src .... Blocking somewhere downstream
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'-----' '-------'/\ '-------'
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A pad block has been requested by the user on elem1.src , but since the stream
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is blocking somewhere downstream, the callback is not called or the sync block
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does not return.
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In order for the block to happen, a FLUSH_START needs to be:
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_ either sent directly on the downstream blocking element/pad so that it
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release the stream lock, and it gives a chance for the elem1.src pad to
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block.
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_ A FLUSH_START is sent downstream from an upstream element, causing all the
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pads down to the blocking element/pad (including elem1.src) to go to the
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FLUSHING state. A FLUSH_STOP can now be sent downstream, causing all the
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pads down to the previously blocking element to unset their FLUSHING state.
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The next push will then properly block on elem1.src.
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In this case, the pads have to be careful when handling the FLUSH events
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forwarding. Those events should only be forwarded downstream is the BLOCKED
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pad was previously BLOCKING.
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Use cases:
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----------
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@ -1183,6 +1183,7 @@ gst_pad_set_blocked
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gst_pad_set_blocked_async
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GstPadBlockCallback
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gst_pad_is_blocked
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gst_pad_is_blocking
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gst_pad_add_data_probe
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gst_pad_add_buffer_probe
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@ -1345,6 +1346,7 @@ GST_PAD_ACTIVATE_MODE
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GST_PAD_DO_BUFFER_SIGNALS
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GST_PAD_DO_EVENT_SIGNALS
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GST_PAD_IS_BLOCKED
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GST_PAD_IS_BLOCKING
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GST_PAD_IS_IN_SETCAPS
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GST_PAD_SET_FLUSHING
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GST_PAD_TASK
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56
gst/gstpad.c
56
gst/gstpad.c
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@ -1048,6 +1048,35 @@ gst_pad_is_blocked (GstPad * pad)
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return result;
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}
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/**
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* gst_pad_is_blocking:
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* @pad: the #GstPad to query
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*
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* Checks if the pad is blocking or not. This is a guaranteed state
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* of whether the pad is actually blocking on a #GstBuffer or a #GstEvent.
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*
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* Returns: TRUE if the pad is blocking.
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*
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* MT safe.
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*/
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gboolean
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gst_pad_is_blocking (GstPad * pad)
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{
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gboolean result = FALSE;
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g_return_val_if_fail (GST_IS_PAD (pad), result);
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GST_OBJECT_LOCK (pad);
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/* the blocking flag is only valid if the pad is not flushing */
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result = GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_BLOCKING) &&
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!GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLUSHING);
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GST_OBJECT_UNLOCK (pad);
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return result;
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}
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/**
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* gst_pad_set_activate_function:
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* @pad: a #GstPad.
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@ -3141,7 +3170,7 @@ gst_ghost_pad_save_thyself (GstPad * pad, xmlNodePtr parent)
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/*
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* should be called with pad OBJECT_LOCK and STREAM_LOCK held.
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* GST_PAD_IS_BLOCK (pad) == TRUE when this function is
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* GST_PAD_IS_BLOCKED (pad) == TRUE when this function is
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* called.
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*
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* This function perform the pad blocking when an event, buffer push
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@ -3163,6 +3192,11 @@ gst_ghost_pad_save_thyself (GstPad * pad, xmlNodePtr parent)
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* - the GCond signal method, which makes any thread unblock when
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* the pad block happens.
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*
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* During the actual blocking state, the GST_PAD_BLOCKING flag is set.
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* The GST_PAD_BLOCKING flag is unset when the GST_PAD_FLUSHING flag is
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* unset. This is to know whether the pad was blocking when GST_PAD_FLUSHING
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* was set.
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*
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* MT safe.
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*/
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static GstFlowReturn
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@ -3215,6 +3249,9 @@ handle_pad_block (GstPad * pad)
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* deactivate the pad (which will also set the FLUSHING flag) or
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* when the pad is unblocked. A flushing event will also unblock
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* the pad after setting the FLUSHING flag. */
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GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
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"Waiting to be unblocked or set flushing");
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GST_OBJECT_FLAG_SET (pad, GST_PAD_BLOCKING);
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GST_PAD_BLOCK_WAIT (pad);
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/* see if we got unlocked by a flush or not */
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@ -3222,6 +3259,10 @@ handle_pad_block (GstPad * pad)
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goto flushing;
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}
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/* If we made it here we either never blocked, or were unblocked because we
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* weren't flushing, it is therefore safe to remove the BLOCKING flag */
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GST_OBJECT_FLAG_UNSET (pad, GST_PAD_BLOCKING);
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GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "got unblocked");
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/* when we get here, the pad is unblocked again and we perform
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@ -3821,9 +3862,9 @@ gst_pad_push_event (GstPad * pad, GstEvent * event)
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case GST_EVENT_FLUSH_START:
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GST_PAD_SET_FLUSHING (pad);
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if (G_UNLIKELY (GST_PAD_IS_BLOCKED (pad))) {
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if (G_UNLIKELY (GST_PAD_IS_BLOCKING (pad))) {
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/* flush start will have set the FLUSHING flag and will then
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* unlock all threads doing a GCond wait on the blocked pad. This
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* unlock all threads doing a GCond wait on the blocking pad. This
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* will typically unblock the STREAMING thread blocked on a pad. */
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GST_PAD_BLOCK_SIGNAL (pad);
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goto flushed;
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@ -3832,8 +3873,15 @@ gst_pad_push_event (GstPad * pad, GstEvent * event)
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case GST_EVENT_FLUSH_STOP:
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GST_PAD_UNSET_FLUSHING (pad);
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if (G_UNLIKELY (GST_PAD_IS_BLOCKED (pad)))
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/* If pad was blocking on something when the pad received flush-start, we
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* don't forward the flush-stop event either. */
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if (G_UNLIKELY (GST_PAD_IS_BLOCKING (pad))) {
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GST_OBJECT_FLAG_UNSET (pad, GST_PAD_BLOCKING);
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GST_LOG_OBJECT (pad,
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"Pad was previously blocking, not forwarding flush-stop");
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goto flushed;
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}
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GST_OBJECT_FLAG_UNSET (pad, GST_PAD_BLOCKING);
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break;
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default:
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if (G_UNLIKELY (GST_PAD_IS_BLOCKED (pad))) {
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@ -479,6 +479,7 @@ typedef enum {
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* @GST_PAD_FLUSHING: is pad refusing buffers
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* @GST_PAD_IN_GETCAPS: GstPadGetCapsFunction() is running now
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* @GST_PAD_IN_SETCAPS: GstPadSetCapsFunction() is running now
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* @GST_PAD_BLOCKING: is pad currently blocking on a buffer or event
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* @GST_PAD_FLAG_LAST: offset to define more flags
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*
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* Pad state flags
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@ -488,6 +489,7 @@ typedef enum {
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GST_PAD_FLUSHING = (GST_OBJECT_FLAG_LAST << 1),
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GST_PAD_IN_GETCAPS = (GST_OBJECT_FLAG_LAST << 2),
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GST_PAD_IN_SETCAPS = (GST_OBJECT_FLAG_LAST << 3),
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GST_PAD_BLOCKING = (GST_OBJECT_FLAG_LAST << 4),
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/* padding */
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GST_PAD_FLAG_LAST = (GST_OBJECT_FLAG_LAST << 8)
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} GstPadFlags;
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@ -655,6 +657,7 @@ struct _GstPadClass {
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#define GST_PAD_IS_LINKED(pad) (GST_PAD_PEER(pad) != NULL)
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#define GST_PAD_IS_BLOCKED(pad) (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_BLOCKED))
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#define GST_PAD_IS_BLOCKING(pad) (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_BLOCKING))
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#define GST_PAD_IS_FLUSHING(pad) (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_FLUSHING))
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#define GST_PAD_IS_IN_GETCAPS(pad) (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_IN_GETCAPS))
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#define GST_PAD_IS_IN_SETCAPS(pad) (GST_OBJECT_FLAG_IS_SET (pad, GST_PAD_IN_SETCAPS))
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@ -771,6 +774,7 @@ gboolean gst_pad_set_blocked (GstPad *pad, gboolean blocked);
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gboolean gst_pad_set_blocked_async (GstPad *pad, gboolean blocked,
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GstPadBlockCallback callback, gpointer user_data);
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gboolean gst_pad_is_blocked (GstPad *pad);
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gboolean gst_pad_is_blocking (GstPad *pad);
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void gst_pad_set_element_private (GstPad *pad, gpointer priv);
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gpointer gst_pad_get_element_private (GstPad *pad);
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