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gstbin: Remove mentions of duration caching

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This was effectively disabled in 1.0 with the intent of maybe re-enabling it.

The problem is that caching duration at a bin level doesn't make much sense
since there might be queueing/buffering taking place internally and therefore
the duration reported might have no correlation to what is actually being
outputted.

Remove commented code and fixmes, and update documentation

Fixes #4

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/489>
This commit is contained in:
Edward Hervey 2020-05-18 10:46:04 +02:00 committed by Edward Hervey
parent 24d789a9b5
commit 7f068512ec
1 changed files with 10 additions and 83 deletions
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93
gst/gstbin.c
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@ -73,12 +73,15 @@
* a SEGMENT_START have posted a SEGMENT_DONE.
*
* * GST_MESSAGE_DURATION_CHANGED: Is posted by an element that detected a change
* in the stream duration. The default bin behaviour is to clear any
* cached duration values so that the next duration query will perform
* a full duration recalculation. The duration change is posted to the
* in the stream duration. The duration change is posted to the
* application so that it can refetch the new duration with a duration
* query. Note that these messages can be posted before the bin is
* prerolled, in which case the duration query might fail.
* prerolled, in which case the duration query might fail. Note also that
* there might be a discrepancy (due to internal buffering/queueing) between the
* stream being currently displayed and the returned duration query.
* Applications might want to also query for duration (and changes) by
* listening to the GST_MESSAGE_STREAM_START message, signaling the active start
* of a (new) stream.
*
* * GST_MESSAGE_CLOCK_LOST: This message is posted by an element when it
* can no longer provide a clock. The default bin behaviour is to
@ -103,11 +106,8 @@
* A #GstBin implements the following default behaviour for answering to a
* #GstQuery:
*
* * GST_QUERY_DURATION:If the query has been asked before with the same format
* and the bin is a toplevel bin (ie. has no parent),
* use the cached previous value. If no previous value was cached, the
* query is sent to all sink elements in the bin and the MAXIMUM of all
* values is returned. If the bin is a toplevel bin the value is cached.
* * GST_QUERY_DURATION: The bin will forward the query to all sink
* elements contained within and will return the maximum value.
* If no sinks are available in the bin, the query fails.
*
* * GST_QUERY_POSITION:The query is sent to all sink elements in the bin and the
@ -3678,14 +3678,6 @@ gst_bin_update_context_unlocked (GstBin * bin, GstContext * context)
* with the segment_done message. If there are no more segment_start
* messages, post segment_done message upwards.
*
* GST_MESSAGE_DURATION_CHANGED: clear any cached durations.
* Whenever someone performs a duration query on the bin, we store the
* result so we can answer it quicker the next time. Any element that
* changes its duration marks our cached values invalid.
* This message is also posted upwards. This is currently disabled
* because too many elements don't post DURATION_CHANGED messages when
* the duration changes.
*
* GST_MESSAGE_CLOCK_LOST: This message is posted by an element when it
* can no longer provide a clock. The default bin behaviour is to
* check if the lost clock was the one provided by the bin. If so and
@ -3843,17 +3835,6 @@ gst_bin_handle_message_func (GstBin * bin, GstMessage * message)
}
break;
}
case GST_MESSAGE_DURATION_CHANGED:
{
/* FIXME: remove all cached durations, next time somebody asks
* for duration, we will recalculate. */
#if 0
GST_OBJECT_LOCK (bin);
bin_remove_messages (bin, NULL, GST_MESSAGE_DURATION_CHANGED);
GST_OBJECT_UNLOCK (bin);
#endif
goto forward;
}
case GST_MESSAGE_CLOCK_LOST:
{
GstClock **provided_clock_p;
@ -4142,15 +4123,6 @@ bin_query_duration_done (GstBin * bin, QueryFold * fold)
gst_query_set_duration (fold->query, format, fold->max);
GST_DEBUG_OBJECT (bin, "max duration %" G_GINT64_FORMAT, fold->max);
/* FIXME: re-implement duration caching */
#if 0
/* and cache now */
GST_OBJECT_LOCK (bin);
bin->messages = g_list_prepend (bin->messages,
gst_message_new_duration (GST_OBJECT_CAST (bin), format, fold->max));
GST_OBJECT_UNLOCK (bin);
#endif
}
static gboolean
@ -4318,52 +4290,7 @@ gst_bin_query (GstElement * element, GstQuery * query)
switch (GST_QUERY_TYPE (query)) {
case GST_QUERY_DURATION:
{
/* FIXME: implement duration caching in GstBin again */
#if 0
GList *cached;
GstFormat qformat;
gst_query_parse_duration (query, &qformat, NULL);
/* find cached duration query */
GST_OBJECT_LOCK (bin);
for (cached = bin->messages; cached; cached = g_list_next (cached)) {
GstMessage *message = (GstMessage *) cached->data;
if (GST_MESSAGE_TYPE (message) == GST_MESSAGE_DURATION_CHANGED &&
GST_MESSAGE_SRC (message) == GST_OBJECT_CAST (bin)) {
GstFormat format;
gint64 duration;
gst_message_parse_duration (message, &format, &duration);
/* if cached same format, copy duration in query result */
if (format == qformat) {
GST_DEBUG_OBJECT (bin, "return cached duration %" G_GINT64_FORMAT,
duration);
GST_OBJECT_UNLOCK (bin);
gst_query_set_duration (query, qformat, duration);
res = TRUE;
goto exit;
}
}
}
GST_OBJECT_UNLOCK (bin);
#else
#ifndef GST_DISABLE_GST_DEBUG
G_STMT_START {
/* Quieten this particularly annoying FIXME a bit: */
static gboolean printed_fixme = FALSE;
if (!printed_fixme) {
GST_FIXME ("implement duration caching in GstBin again");
printed_fixme = TRUE;
}
}
G_STMT_END;
#endif
#endif
/* no cached value found, iterate and collect durations */
/* iterate and collect durations */
fold_func = (GstIteratorFoldFunction) bin_query_duration_fold;
fold_init = bin_query_min_max_init;
fold_done = bin_query_duration_done;