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docs: Gram and nit fixes for part-bufferpool.txt

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Reynaldo H. Verdejo Pinochet 2013-10-14 17:29:19 -07:00
parent 06a79347f3
commit 20c32ffbdf
1 changed files with 16 additions and 16 deletions
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32
docs/design/part-bufferpool.txt
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@ -4,7 +4,7 @@ Bufferpool
This document details the design of how buffers are be allocated and This document details the design of how buffers are be allocated and
managed in pools. managed in pools.
Bufferpools increases performance by reducing allocation overhead and Bufferpools increase performance by reducing allocation overhead and
improving possibilities to implement zero-copy memory transfer. improving possibilities to implement zero-copy memory transfer.
Together with the ALLOCATION query, elements can negotiate allocation properties Together with the ALLOCATION query, elements can negotiate allocation properties
@ -40,7 +40,7 @@ GstBufferPool
The bufferpool object manages a list of buffers with the same properties such The bufferpool object manages a list of buffers with the same properties such
as size, padding and alignment. as size, padding and alignment.
The bufferpool has two states: active and inactive. In the in-active The bufferpool has two states: active and inactive. In the inactive
state, the bufferpool can be configured with the required allocation state, the bufferpool can be configured with the required allocation
preferences. In the active state, buffers can be retrieved from and preferences. In the active state, buffers can be retrieved from and
returned to the pool. returned to the pool.
@ -99,13 +99,13 @@ Allocation query
guint max_buffers; guint max_buffers;
} }
use gst_query_parse_nth_allocation_pool() to get the values. Use gst_query_parse_nth_allocation_pool() to get the values.
The allocator can contain multiple pool configurations. If need-pool The allocator can contain multiple pool configurations. If need-pool
was TRUE, the pool member might contain a GstBufferPool when the was TRUE, the pool member might contain a GstBufferPool when the
downstream element can provide one. downstream element can provide one.
Size contains the size of the bufferpool 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.
@ -125,7 +125,7 @@ Allocation query
GstAllocationParams params; GstAllocationParams params;
} }
use gst_query_parse_nth_allocation_param() to get the values Use gst_query_parse_nth_allocation_param() to get the values.
The element performing the query can use the allocators and its The element performing the query can use the allocators and its
parameters to allocate memory for the downstream element. parameters to allocate memory for the downstream element.
@ -144,7 +144,7 @@ Allocation query
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
with the metadata that contains metadata specific options. with the metadata that contains metadata-specific options.
Some bufferpools have options to enable metadata on the buffers Some bufferpools have options to enable metadata on the buffers
allocated by the pool. allocated by the pool.
@ -214,7 +214,7 @@ of a caps change), alignment or number of buffers.
RECONFIGURE event upstream. This instructs upstream to renegotiate both RECONFIGURE event upstream. This instructs upstream to renegotiate both
the format and the bufferpool when needed. the format and the bufferpool when needed.
A pipeline reconfiguration is when new elements are added or removed from A pipeline reconfiguration happens when new elements are added or removed from
the pipeline or when the topology of the pipeline changes. Pipeline the pipeline or when the topology of the pipeline changes. Pipeline
reconfiguration also triggers possible renegotiation of the bufferpool and reconfiguration also triggers possible renegotiation of the bufferpool and
caps. caps.
@ -293,13 +293,13 @@ Use cases
those elements require more than that amount of buffers for temporary those elements require more than that amount of buffers for temporary
storage. storage.
The bufferpool of myvideosink will then be configured with the size of the Myvideosink's bufferpool will then be configured with the size of the
buffers for the negotiated format and according to the padding and alignment buffers for the negotiated format and according to the padding and alignment
rules. When videotestsrc sets the pool to active, the 3 video rules. When videotestsrc sets the pool to active, the 3 video
buffers will be preallocated in the pool. buffers will be preallocated in the pool.
videotestsrc acquires a buffer from the configured pool on its srcpad and videotestsrc acquires a buffer from the configured pool on its srcpad and
pushes this into the queue. When the videotestsrc has acquired and pushed pushes this into the queue. When videotestsrc has acquired and pushed
3 frames, the next call to gst_buffer_pool_acquire_buffer() will block 3 frames, the next call to gst_buffer_pool_acquire_buffer() will block
(assuming the GST_BUFFER_POOL_FLAG_DONTWAIT is not specified). (assuming the GST_BUFFER_POOL_FLAG_DONTWAIT is not specified).
@ -324,9 +324,9 @@ Use cases
decoder linked to a fakesink but we will then dynamically change the decoder linked to a fakesink but we will then dynamically change the
sink to one that can provide a bufferpool. sink to one that can provide a bufferpool.
When it negotiates the size with the downstream element fakesink, it will When myvideodecoder negotiates the size with the downstream fakesink element, it will
receive a NULL bufferpool because fakesink does not provide a bufferpool. receive a NULL bufferpool because fakesink does not provide a bufferpool.
It will then select its own custom bufferpool to start the datatransfer. It will then select its own custom bufferpool to start the data transfer.
At some point we block the queue srcpad, unlink the queue from the At some point we block the queue srcpad, unlink the queue from the
fakesink, link a new sink and set the new sink to the PLAYING state. fakesink, link a new sink and set the new sink to the PLAYING state.
@ -334,7 +334,7 @@ Use cases
and, through queue, inform myvideodecoder that it should renegotiate its and, through queue, inform myvideodecoder that it should renegotiate its
bufferpool because downstream has been reconfigured. bufferpool because downstream has been reconfigured.
Before pushing the next buffer, myvideodecoder would renegotiate a new Before pushing the next buffer, myvideodecoder has to renegotiate a new
bufferpool. To do this, it performs the usual bufferpool negotiation bufferpool. To do this, it performs the usual bufferpool negotiation
algorithm. If it can obtain and configure a new bufferpool from downstream, algorithm. If it can obtain and configure a new bufferpool from downstream,
it sets its own (old) pool to inactive and unrefs it. This will eventually it sets its own (old) pool to inactive and unrefs it. This will eventually
@ -348,13 +348,13 @@ Use cases
myvideodecoder has negotiated a bufferpool with the downstream myvideosink myvideodecoder has negotiated a bufferpool with the downstream myvideosink
to handle buffers of size 320x240. It has now detected a change in the to handle buffers of size 320x240. It has now detected a change in the
video format and need to renegotiate to a resolution of 640x480. This video format and needs to renegotiate to a resolution of 640x480. This
requires it to negotiate a new bufferpool with a larger buffersize. requires it to negotiate a new bufferpool with a larger buffer size.
When myvideodecoder needs to get the bigger buffer, it starts the When myvideodecoder needs to get the bigger buffer, it starts the
negotiation of a new bufferpool. It queries a bufferpool from downstream, negotiation of a new bufferpool. It queries a bufferpool from downstream,
reconfigures it with the new configuration (which includes the bigger buffer reconfigures it with the new configuration (which includes the bigger buffer
size) and it then sets the bufferpool to active. The old pool is inactivated size) and sets the bufferpool to active. The old pool is inactivated
and unreffed, which causes the old format to drain. and unreffed, which causes the old format to drain.
It then uses the new bufferpool for allocating new buffers of the new It then uses the new bufferpool for allocating new buffers of the new
@ -371,7 +371,7 @@ Use cases
change the resolution. change the resolution.
myvideosink sends a RECONFIGURE event upstream to notify upstream that a myvideosink sends a RECONFIGURE event upstream to notify upstream that a
new format is desirable. upstream elements try to negotiate a new format new format is desirable. Upstream elements try to negotiate a new format
and bufferpool before pushing out a new buffer. The old bufferpools are and bufferpool before pushing out a new buffer. The old bufferpools are
drained in the regular way. drained in the regular way.