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updates
This commit is contained in:
Wim Taymans
parent
023cada1f4
commit
8e4ab802f9
2 changed files with 74 additions and 11 deletions
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@ -39,6 +39,20 @@ Requirements
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- We should be able to attach statically allocated metadata to a buffer. This
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is for metadata that does not change much.
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Use cases
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---------
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* DSP vs CPU caches
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Both DSP and CPU have separate MMUs and memory caches. When we exchange buffers
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between two subsystems we need to flush caches so that one CPU can see the
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modifications done by the other CPU. These cashes must only be flushed when one
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CPU performed a write and the other CPU needs to do a read.
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In order to implement this we need to be able to mark our read and write
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operations on the buffer data.
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GstMiniObject
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~~~~~~~~~~~~~
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@ -90,6 +104,9 @@ struct _GstBuffer {
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GstCaps *caps;
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GstBuffer *parent;
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GstBufferDataMap mmap_func;
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GstBufferDataUnmap munmap_func;
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gpointer _gst_padding[10];
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};
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@ -103,6 +120,24 @@ region of the buffer. The size of the free region is kept in the free_size field
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Buffers point to a GstCaps structure that contains the caps of the buffer data.
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We add two functions, map and unmap. We introduce explicit read and write transactions
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on the buffer data in order to be able to implement flushing of the data between
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different caches and mapping between different MMUs.
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typedef enum {
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GST_BUFFER_MAP_NONE,
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GST_BUFFER_MAP_READ,
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GST_BUFFER_MAP_WRITE,
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} GstBufferMapFlags
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gpointer gst_buffer_map (GstBuffer *, guint offset, guint *size, GstBufferMapFlags);
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gboolean gst_buffer_unmap (GstBuffer *, gpointer data, guint size);
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The map functions always create a contiguous memory space for the requested
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area of the buffer. This might involve memcpy and other expensive operations. It
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is assumed that more specialized elements can deal with the different memory
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metadata structures in order to optimize access to the memory.
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GstBufferMeta
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~~~~~~~~~~~~~
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@ -110,9 +145,8 @@ GstBufferMeta
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A GstBufferMeta is a structure as follows:
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struct _GstBufferMeta {
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GstBufferMetaInfo *info; /* tag and info for the meta item */
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GstBufferMeta *next; /* pointer to the next item */
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}
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GstBufferMetaInfo *info; /* tag and info for the meta item */
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};
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The purpose of the this structure is to serve as a common header for all metadata
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information that we can attach to a buffer. Specific metadata, such as timing metadata,
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@ -133,9 +167,9 @@ Or another example for the buffer memory region
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GstBufferMeta meta;
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/* pointer to data and its size */
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guint8 *data;
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gpointer *data;
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guint size;
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guint8 *malloc_data;
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gpointer *data_orig;
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GFreeFunc data_free;
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gpointer data_user;
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};
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@ -146,6 +180,7 @@ GstBufferMetaInfo will point to more information about the metadata and looks li
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GQuark api; /* api name */
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GQuark impl; /* implementation name */
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gsize size; /* size of the structure */
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GstBufferMetaInfo *parent /* parent info */
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GstMetaInitFunction init_func;
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GstMetaFreeFunction free_func;
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@ -154,7 +189,7 @@ GstBufferMetaInfo will point to more information about the metadata and looks li
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GstMetaSerializeFunction serialize_func
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GstMetaDeserializeFunction deserialize_func
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GstMetaConvFunction conv_func;
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}
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};
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Tag will contain a GQuark of the metadata name. We will be able to refer to specific
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metadata by name or by its (cached) GQuark. A repository of registered MetaInfo
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@ -189,16 +224,18 @@ GstMiniObject | GType (GstBuffer) |
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+-------------------------------------+
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GstBuffer | caps, parent, subfunc |
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+.....................................+
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| next ---+
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| parent ------> NULL
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+- | info ------> GstBufferMetaInfo
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GstBufferMetaTiming | | next ---+
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| | | |
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GstBufferMetaTiming | | | |
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| | dts | |
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| | pts | |
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| | duration | |
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+- | clock_rate | |
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+ . . . . . . . . . . . . . . . . . . + |
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+- | info <--+ -> GstBufferMetaInfo
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GstBufferMetaMemory | | next ---+
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| next <--+
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| parent ------> NULL
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GstBufferMetaMemory +- | info ------> GstBufferMetaInfo
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| | | |
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| | data | |
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| | size | |
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@ -208,6 +245,7 @@ GstBufferMetaMemory | | next ---+
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+ . . . . . . . . . . . . . . . . . . + .
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. .
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API examples
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~~~~~~~~~~~~
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@ -453,4 +491,29 @@ allows us to define all use cases.
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Video Buffers
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-------------
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#define GST_VIDEO_MAX_PLANES 4
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struct GstVideoPlane {
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guint8 *data;
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guint size;
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guint stride;
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guint8 *data_orig;
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guint size_orig;
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GFreeFunc data_free;
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gpointer data_user;
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};
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struct GstBufferVideoMeta {
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GstBufferMeta meta
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GstBufferVideoFlags flags
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guint n_planes;
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GstVideoPlane plane[GST_VIDEO_MAX_PLANES];
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};
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@ -114,7 +114,7 @@ typedef gboolean (*GstMetaDeserializeFunction) (GstBufferMeta *meta,
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* @serialize_func: function for serializing
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* @deserialize_func: function for deserializing
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*
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* The #GstBufferMetaInfo provides infomation about a specific metadata
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* The #GstBufferMetaInfo provides information about a specific metadata
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* structure.
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*/
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struct _GstBufferMetaInfo {
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