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docs/design/part-element-transform.txt: Added some docs about the design of tranform elements.

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Original commit message from CVS:
* docs/design/part-element-transform.txt:
Added some docs about the design of tranform elements.
* libs/gst/base/gstbasesrc.c: (gst_base_src_perform_seek),
(gst_base_src_loop), (gst_base_src_change_state):
Mark buffers with the DISCONT flag.
This commit is contained in:
Wim Taymans 2006-03-08 13:44:55 +00:00
parent 81cc6d92ba
commit 3f3536bf73
3 changed files with 56 additions and 0 deletions
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9
ChangeLog
View file

@ -1,3 +1,12 @@
2006-03-08 Wim Taymans <wim@fluendo.com>
* docs/design/part-element-transform.txt:
Added some docs about the design of tranform elements.
* libs/gst/base/gstbasesrc.c: (gst_base_src_perform_seek),
(gst_base_src_loop), (gst_base_src_change_state):
Mark buffers with the DISCONT flag.
2006-03-08 Michael Smith <msmith@fluendo.com>
* gst/gstregistry.h:

38
docs/design/part-element-transform.txt Normal file
View file

@ -0,0 +1,38 @@
Transform elements
------------------
Transform elements transform input buffers to output buffers based
on the sink and source caps.
typical transform elements include:
- audio convertors (audioconvert, ...)
- video convertors (colorspace, videoscale, audioconvert, ...)
- filters (capfilter, colorbalance,
The implementation of the transform element has to take care of
the following things:
- efficient negotiation both up and downstream
- efficient buffer alloc and other buffer management
Some transform elements can operate in different modes:
- passthrough (no changes to buffers)
- in-place (changes made to incomming buffer)
- metadata changes only
Depending on the mode of operation the buffer allocation strategy might change.
Negotiation
-----------
The transform element is configured to perform a specific transform in these
two situations:
- new caps are received on the sink pad.
- new caps are received on the source pad when allocating an output buffer and
we can transform to these caps with the current input buffer.

9
libs/gst/base/gstbasesrc.c
View file

@ -207,6 +207,7 @@ struct _GstBaseSrcPrivate
{
gboolean last_sent_eos; /* last thing we did was send an EOS (we set this
* to avoid the sending of two EOS in some cases) */
gboolean discont;
};
static GstElementClass *parent_class = NULL;
@ -850,6 +851,7 @@ gst_base_src_perform_seek (GstBaseSrc * src, GstEvent * event, gboolean unlock)
src->segment.last_stop, stop, src->segment.time));
}
src->priv->discont = TRUE;
src->data.ABI.running = TRUE;
/* and restart the task in case it got paused explicitely or by
* the FLUSH_START event we pushed out. */
@ -1370,6 +1372,12 @@ gst_base_src_loop (GstPad * pad)
if (position != -1)
gst_segment_set_last_stop (&src->segment, src->segment.format, position);
if (G_UNLIKELY (src->priv->discont)) {
buf = gst_buffer_make_metadata_writable (buf);
GST_BUFFER_FLAG_SET (buf, GST_BUFFER_FLAG_DISCONT);
src->priv->discont = FALSE;
}
ret = gst_pad_push (pad, buf);
if (G_UNLIKELY (ret != GST_FLOW_OK))
goto pause;
@ -1787,6 +1795,7 @@ gst_base_src_change_state (GstElement * element, GstStateChange transition)
basesrc->live_running = FALSE;
}
basesrc->priv->last_sent_eos = FALSE;
basesrc->priv->discont = TRUE;
GST_LIVE_UNLOCK (element);
break;
case GST_STATE_CHANGE_PAUSED_TO_PLAYING: