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design: bufferpool: assorted formatting improvements

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Reynaldo H. Verdejo Pinochet 2017-01-24 13:28:41 -08:00
parent 730ed0da1e
commit 3570418527
1 changed files with 14 additions and 14 deletions
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markdown/design/bufferpool.md
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@ -103,7 +103,7 @@ downstream element can provide one.
Size contains the size of the bufferpool's buffers and is never 0. Size contains the size of the bufferpool's buffers and is never 0.
min_buffers and max_buffers contain the suggested min and max amount of `min_buffers` and `max_buffers` contain the suggested min and max amount of
buffers that should be managed by the pool. buffers that should be managed by the pool.
The upstream element can choose to use the provided pool or make its own The upstream element can choose to use the provided pool or make its own
@ -138,7 +138,7 @@ It is also possible to configure the allocator in a provided pool.
} }
``` ```
Use `gst_query_parse_nth_allocation_meta(`) to get the values. Use `gst_query_parse_nth_allocation_meta()` to get the values.
These metadata items can be accepted by the downstream element when These metadata items can be accepted by the downstream element when
placed on buffers. There is also an arbitrary `GstStructure` associated placed on buffers. There is also an arbitrary `GstStructure` associated
@ -205,7 +205,7 @@ The element that wants to renegotiate a new bufferpool uses exactly the same
algorithm as when it first started. It will negotiate caps first then use the algorithm as when it first started. It will negotiate caps first then use the
ALLOCATION query to get and configure the new pool. ALLOCATION query to get and configure the new pool.
### upstream ### Upstream
When a downstream element wants to negotiate a new format, it will send a When a downstream element wants to negotiate a new format, it will send a
RECONFIGURE event upstream. This instructs upstream to renegotiate both RECONFIGURE event upstream. This instructs upstream to renegotiate both
@ -234,20 +234,20 @@ automatically be freed by the pool and new allocations will fail.
## Use cases ## Use cases
### - `videotestsrc ! xvimagesink` ### `videotestsrc ! xvimagesink`
* Before videotestsrc can output a buffer, it needs to negotiate caps and * Before videotestsrc can output a buffer, it needs to negotiate caps and
a bufferpool with the downstream peer pad. a bufferpool with the downstream peer pad.
* First it will negotiate a suitable format with downstream according to the * First it will negotiate a suitable format with downstream according to the
normal rules. It will send a CAPS event downstream with the negotiated normal rules. It will send a `CAPS` event downstream with the negotiated
configuration. configuration.
* Then it does an ALLOCATION query. It will use the returned bufferpool or * Then it does an `ALLOCATION` query. It will use the returned bufferpool or
configures its own bufferpool with the returned parameters. The bufferpool is configures its own bufferpool with the returned parameters. The bufferpool is
initially in the inactive state. initially in the inactive state.
* The ALLOCATION query lists the desired configuration of the downstream * The `ALLOCATION` query lists the desired configuration of the downstream
xvimagesink, which can have specific alignment and/or min/max amount of xvimagesink, which can have specific alignment and/or min/max amount of
buffers. buffers.
@ -271,16 +271,16 @@ the pool member.
this will cause further allocations to fail and currently allocated buffers to this will cause further allocations to fail and currently allocated buffers to
be freed. videotestsrc will then free the pool and stop streaming. be freed. videotestsrc will then free the pool and stop streaming.
### - ``videotestsrc ! queue ! myvideosink`` ### `videotestsrc ! queue ! myvideosink`
* In this second use case we have a videosink that can at most allocate 3 video * In this second use case we have a videosink that can at most allocate 3 video
buffers. buffers.
* Again videotestsrc will have to negotiate a bufferpool with the peer element. * Again videotestsrc will have to negotiate a bufferpool with the peer element.
For this it will perform the ALLOCATION query which queue will proxy to its For this it will perform the `ALLOCATION` query which queue will proxy to its
downstream peer element. downstream peer element.
* The bufferpool returned from myvideosink will have a max_buffers set to 3. * The bufferpool returned from myvideosink will have a `max_buffers` set to 3.
queue and videotestsrc can operate with this upper limit because none of those queue and videotestsrc can operate with this upper limit because none of those
elements require more than that amount of buffers for temporary storage. elements require more than that amount of buffers for temporary storage.
@ -307,7 +307,7 @@ bufferpool.
to inactive. This causes any pending (blocked) acquire to return with to inactive. This causes any pending (blocked) acquire to return with
a FLUSHING result and causes the streaming thread to pause. a FLUSHING result and causes the streaming thread to pause.
### - `.. ! myvideodecoder ! queue ! fakesink` ### `.. ! myvideodecoder ! queue ! fakesink`
* In this case, the myvideodecoder requires buffers to be aligned to 128 bytes * In this case, the myvideodecoder requires buffers to be aligned to 128 bytes
and padded with 4096 bytes. The pipeline starts out with the decoder linked to and padded with 4096 bytes. The pipeline starts out with the decoder linked to
@ -334,7 +334,7 @@ the old bufferpool.
* The new bufferpool is set as the new bufferpool for the srcpad and sinkpad of * The new bufferpool is set as the new bufferpool for the srcpad and sinkpad of
the queue and set to the active state. the queue and set to the active state.
### - `.. ! myvideodecoder ! queue ! myvideosink ` ### `.. ! myvideodecoder ! queue ! myvideosink`
* myvideodecoder has negotiated a bufferpool with the downstream myvideosink to * myvideodecoder has negotiated a bufferpool with the downstream myvideosink to
handle buffers of size 320x240. It has now detected a change in the video handle buffers of size 320x240. It has now detected a change in the video
@ -354,12 +354,12 @@ dimension.
can choose to use the current pool (which has buffers that are larger than the can choose to use the current pool (which has buffers that are larger than the
required size) or it can choose to renegotiate a new bufferpool. required size) or it can choose to renegotiate a new bufferpool.
### - `.. ! myvideodecoder ! videoscale ! myvideosink` ### `.. ! myvideodecoder ! videoscale ! myvideosink`
* myvideosink is providing a bufferpool for upstream elements and wants to * myvideosink is providing a bufferpool for upstream elements and wants to
change the resolution. change the resolution.
* myvideosink sends a RECONFIGURE event upstream to notify upstream that a new * myvideosink sends a `RECONFIGURE` event upstream to notify upstream that a new
format is desirable. Upstream elements try to negotiate a new format and format is desirable. Upstream elements try to negotiate a new format and
bufferpool before pushing out a new buffer. The old bufferpools are drained in bufferpool before pushing out a new buffer. The old bufferpools are drained in
the regular way. the regular way.