|
@@ -0,0 +1,54 @@
|
|
|
|
|
+# decoder_owner
|
|
|
|
|
+
|
|
|
|
|
+During playback, decoder behaviour is handled by a decoder_owner.
|
|
|
|
|
+This owner controls play/pause, flush, drain, waiting, and decoding.
|
|
|
|
|
+
|
|
|
|
|
+The decoder behaviour with resources can be quite confusing because resources
|
|
|
|
|
+are sometimes allocated from **vout** memory and sometimes from decoder memory.
|
|
|
|
|
+Indeed, when the decoder behind the scene is a harware decoder, and especially
|
|
|
|
|
+when it is able to directly render the decoded picture with the correct timing
|
|
|
|
|
+on the video output, the picture is likely to be allocated by the API
|
|
|
|
|
+controlling this hardware decoder. This mecanism is called
|
|
|
|
|
+**inflight pictures** or **direct rendering** in VLC.
|
|
|
|
|
+
|
|
|
|
|
+Some examples of this can be found in the omxil/mediacodec decoder.
|
|
|
|
|
+
|
|
|
|
|
+# decoder
|
|
|
|
|
+
|
|
|
|
|
+## General architecture
|
|
|
|
|
+
|
|
|
|
|
+In VLC, a decoder is a special structure containing the following functions:
|
|
|
|
|
+
|
|
|
|
|
++ ``int pf_decode (decoder_t *, block_t *)``: used by audio and video decoder
|
|
|
|
|
+ to push the block into the actual decoder.
|
|
|
|
|
++ ``block_t *pf_packetize (decoder_t *, block_t ***)``: used by the different
|
|
|
|
|
+ packetizer, which are ``decoder_t`` objects too, to transform a list of
|
|
|
|
|
+ blocks into new blocks.
|
|
|
|
|
++ ``void pf_flush (decoder_t *)``: used by all decoder to perform a flush
|
|
|
|
|
+ operation so as to clean up the real decoder module.
|
|
|
|
|
++ ``block_t pf_get_cc (decoder_t *, decoder_cc_desc_t *)``: used by spu decoder
|
|
|
|
|
+ so as to // TODO
|
|
|
|
|
+
|
|
|
|
|
+When a block is decoded and direct rendering is disabled, the
|
|
|
|
|
+``decoder_QueueVideo`` is called and allows the ``decoder_owner`` to collect
|
|
|
|
|
+the picture.
|
|
|
|
|
+
|
|
|
|
|
+## Push-event architecture
|
|
|
|
|
+
|
|
|
|
|
+What we may want is a push-event architecture but some obstacles prevents an
|
|
|
|
|
+easy implementation:
|
|
|
|
|
+
|
|
|
|
|
+First, in the situation where only one event queue exists and because of the
|
|
|
|
|
+**direct rendering** feature, if a _pause_ order is made, it will be pushed
|
|
|
|
|
+after the decoding block order. This is great in the general case because you
|
|
|
|
|
+get full control of the pipeline behaviour but it leads to an unexpected
|
|
|
|
|
+playback of the queues block before pausing in the case of harware decoder.
|
|
|
|
|
+
|
|
|
|
|
+Then, we could argue that the decoder might need to be paused as soon as
|
|
|
|
|
+possible or flushed as soon as possible, for instance because we seeked in the
|
|
|
|
|
+video. As a consequence, we would need a way to push out of band order with a
|
|
|
|
|
+higher priority than usual data.
|
|
|
|
|
+
|
|
|
|
|
+## Memory allocation
|
|
|
|
|
+
|
|
|
|
|
+## Date, tick and timestamp
|
