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06f6935107
Add a query to request allocation parameters and optionally a bufferpool as well. This should allow elements to discover downstream capabilities and also use the downstream allocators.
51 lines
1.4 KiB
Text
51 lines
1.4 KiB
Text
Allocation
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----------
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This document outlines the requirements for determining how memory and buffers
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will be allocated between to pads.
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Overview
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~~~~~~~~
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After a particular media format has been negotiated between two pads, they must
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agree on how to allocate buffers.
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The srcpad will always take the initiative to negotiate the allocation
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properties. It starts with creating a GST_QUERY_ALLOCATION with the negotiated
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caps.
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The srcpad can set the need-pool flag to TRUE in the query to optionally make the
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peer pad allocate a bufferpool.
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It will then inspect the returned results and configure the returned pool or
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create a new pool when needed.
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Buffers are then allocated by the srcpad from the negotiated pool.
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Allocation query
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~~~~~~~~~~~~~~~~
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(in) "caps", GST_TYPE_CAPS
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- the caps that was negotiated
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(in) "need-pool", G_TYPE_BOOLEAN
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- if a GstBufferPool is requested
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(out) "prefix", G_TYPE_UINT
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- the prefix of the buffer memory
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(out) "align", G_TYPE_UINT
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- the aligment of the memory in the buffers, the alignment will be applied
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to the prefix.
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(out) "size", G_TYPE_UINT
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- the total size of the buffer memory
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(out) "pool", GST_TYPE_BUFFER_POOL
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- a buffer pool when need-pool was TRUE and the peer can provide a pool
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(out) "metadata", G_TYPE_VALUE_ARRAY of G_TYPE_STRING
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- an array of metadata API strings that can be accepted.
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