Buffer

Buffers are the basic unit of data transfer in GStreamer. They contain the timing and offset along with other arbitrary metadata that is associated with the #GstMemory blocks that the buffer contains.

Buffers are usually created with gst.buffer.Buffer.new_. After a buffer has been created one will typically allocate memory for it and add it to the buffer. The following example creates a buffer that can hold a given video frame with a given width, height and bits per plane.

GstBuffer *buffer;
GstMemory *memory;
gint size, width, height, bpp;
...
size = width * height * bpp;
buffer = gst_buffer_new ();
memory = gst_allocator_alloc (NULL, size, NULL);
gst_buffer_insert_memory (buffer, -1, memory);
...

Alternatively, use gst.buffer.Buffer.newAllocate to create a buffer with preallocated data of a given size.

Buffers can contain a list of #GstMemory objects. You can retrieve how many memory objects with gst.buffer.Buffer.nMemory and you can get a pointer to memory with gst.buffer.Buffer.peekMemory

A buffer will usually have timestamps, and a duration, but neither of these are guaranteed (they may be set to #GST_CLOCK_TIME_NONE). Whenever a meaningful value can be given for these, they should be set. The timestamps and duration are measured in nanoseconds (they are #GstClockTime values).

The buffer DTS refers to the timestamp when the buffer should be decoded and is usually monotonically increasing. The buffer PTS refers to the timestamp when the buffer content should be presented to the user and is not always monotonically increasing.

A buffer can also have one or both of a start and an end offset. These are media-type specific. For video buffers, the start offset will generally be the frame number. For audio buffers, it will be the number of samples produced so far. For compressed data, it could be the byte offset in a source or destination file. Likewise, the end offset will be the offset of the end of the buffer. These can only be meaningfully interpreted if you know the media type of the buffer (the preceding CAPS event). Either or both can be set to #GST_BUFFER_OFFSET_NONE.

gst_buffer_ref() is used to increase the refcount of a buffer. This must be done when you want to keep a handle to the buffer after pushing it to the next element. The buffer refcount determines the writability of the buffer, a buffer is only writable when the refcount is exactly 1, i.e. when the caller has the only reference to the buffer.

To efficiently create a smaller buffer out of an existing one, you can use gst.buffer.Buffer.copyRegion. This method tries to share the memory objects between the two buffers.

If a plug-in wants to modify the buffer data or metadata in-place, it should first obtain a buffer that is safe to modify by using gst_buffer_make_writable(). This function is optimized so that a copy will only be made when it is necessary.

Several flags of the buffer can be set and unset with the GST_BUFFER_FLAG_SET() and GST_BUFFER_FLAG_UNSET() macros. Use GST_BUFFER_FLAG_IS_SET() to test if a certain #GstBufferFlags flag is set.

Buffers can be efficiently merged into a larger buffer with gst.buffer.Buffer.append. Copying of memory will only be done when absolutely needed.

Arbitrary extra metadata can be set on a buffer with gst.buffer.Buffer.addMeta. Metadata can be retrieved with gst.buffer.Buffer.getMeta. See also #GstMeta.

An element should either unref the buffer or push it out on a src pad using gst.pad.Pad.push (see #GstPad).

Buffers are usually freed by unreffing them with gst_buffer_unref(). When the refcount drops to 0, any memory and metadata pointed to by the buffer is unreffed as well. Buffers allocated from a #GstBufferPool will be returned to the pool when the refcount drops to 0.

The #GstParentBufferMeta is a meta which can be attached to a #GstBuffer to hold a reference to another buffer that is only released when the child #GstBuffer is released.

Typically, #GstParentBufferMeta is used when the child buffer is directly using the #GstMemory of the parent buffer, and wants to prevent the parent buffer from being returned to a buffer pool until the #GstMemory is available for re-use. (Since: 1.6)

class Buffer : Boxed {

this();

static gst.buffer.Buffer newAllocate(gst.allocator.Allocator allocator, size_t size, gst.allocation_params.AllocationParams params);

static gst.buffer.Buffer newMemdup(ubyte[] data);

static gst.buffer.Buffer newWrappedBytes(glib.bytes.Bytes bytes);

static gst.buffer.Buffer newWrappedFull(gst.types.MemoryFlags flags, ubyte[] data, size_t maxsize, size_t offset, glib.types.DestroyNotify notify);

gst.custom_meta.CustomMeta addCustomMeta(string name);

gst.meta.Meta addMeta(gst.meta_info.MetaInfo info, void* params);

gst.parent_buffer_meta.ParentBufferMeta addParentBufferMeta(gst.buffer.Buffer ref_);

gst.protection_meta.ProtectionMeta addProtectionMeta(gst.structure.Structure info);

gst.reference_timestamp_meta.ReferenceTimestampMeta addReferenceTimestampMeta(gst.caps.Caps reference, gst.types.ClockTime timestamp, gst.types.ClockTime duration);

gst.buffer.Buffer append(gst.buffer.Buffer buf2);

void appendMemory(gst.memory.Memory mem);

gst.buffer.Buffer appendRegion(gst.buffer.Buffer buf2, ptrdiff_t offset, ptrdiff_t size);

gst.buffer.Buffer copyDeep();

bool copyInto(gst.buffer.Buffer src, gst.types.BufferCopyFlags flags, size_t offset, size_t size);

gst.buffer.Buffer copyRegion(gst.types.BufferCopyFlags flags, size_t offset, size_t size);

void extractDup(size_t offset, size_t size, ubyte[] dest);

size_t fill(size_t offset, ubyte[] src);

bool findMemory(size_t offset, size_t size, uint idx, uint length, size_t skip);

bool foreachMeta(gst.types.BufferForeachMetaFunc func);

gst.memory.Memory getAllMemory();

gst.custom_meta.CustomMeta getCustomMeta(string name);

gst.types.BufferFlags getFlags();

gst.memory.Memory getMemory(uint idx);

gst.memory.Memory getMemoryRange(uint idx, int length);

gst.meta.Meta getMeta(gobject.types.GType api);

uint getNMeta(gobject.types.GType apiType);

gst.reference_timestamp_meta.ReferenceTimestampMeta getReferenceTimestampMeta(gst.caps.Caps reference);

size_t getSize();

size_t getSizes(size_t offset, size_t maxsize);

size_t getSizesRange(uint idx, int length, size_t offset, size_t maxsize);

bool hasFlags(gst.types.BufferFlags flags);

void insertMemory(int idx, gst.memory.Memory mem);

bool isAllMemoryWritable();

bool isMemoryRangeWritable(uint idx, int length);

bool map(gst.map_info.MapInfo info, gst.types.MapFlags flags);

bool mapRange(uint idx, int length, gst.map_info.MapInfo info, gst.types.MapFlags flags);

int memcmp(size_t offset, ubyte[] mem);

size_t memset(size_t offset, ubyte val, size_t size);

uint nMemory();

gst.memory.Memory peekMemory(uint idx);

void prependMemory(gst.memory.Memory mem);

void removeAllMemory();

void removeMemory(uint idx);

void removeMemoryRange(uint idx, int length);

bool removeMeta(gst.meta.Meta meta);

void replaceAllMemory(gst.memory.Memory mem);

void replaceMemory(uint idx, gst.memory.Memory mem);

void replaceMemoryRange(uint idx, int length, gst.memory.Memory mem);

void resize(ptrdiff_t offset, ptrdiff_t size);

bool resizeRange(uint idx, int length, ptrdiff_t offset, ptrdiff_t size);

bool setFlags(gst.types.BufferFlags flags);

void setSize(ptrdiff_t size);

void unmap(gst.map_info.MapInfo info);

bool unsetFlags(gst.types.BufferFlags flags);

static uint getMaxMemory();

}

Constructors

this this(): Creates a newly allocated buffer without any data.

Members

Functions

addCustomMeta gst.custom_meta.CustomMeta addCustomMeta(string name): Creates and adds a #GstCustomMeta for the desired name. name must have been successfully registered with gst.meta.Meta.registerCustom.
addMeta gst.meta.Meta addMeta(gst.meta_info.MetaInfo info, void* params): Adds metadata for info to buffer using the parameters in params.
addParentBufferMeta gst.parent_buffer_meta.ParentBufferMeta addParentBufferMeta(gst.buffer.Buffer ref_): Adds a #GstParentBufferMeta to buffer that holds a reference on ref until the buffer is freed.
addProtectionMeta gst.protection_meta.ProtectionMeta addProtectionMeta(gst.structure.Structure info): Attaches protection metadata to a #GstBuffer.
addReferenceTimestampMeta gst.reference_timestamp_meta.ReferenceTimestampMeta addReferenceTimestampMeta(gst.caps.Caps reference, gst.types.ClockTime timestamp, gst.types.ClockTime duration): Adds a #GstReferenceTimestampMeta to buffer that holds a timestamp and optionally duration based on a specific timestamp reference. See the documentation of #GstReferenceTimestampMeta for details.
append gst.buffer.Buffer append(gst.buffer.Buffer buf2): Appends all the memory from buf2 to buf1. The result buffer will contain a concatenation of the memory of buf1 and buf2.
appendMemory void appendMemory(gst.memory.Memory mem): Appends the memory block mem to buffer. This function takes ownership of mem and thus doesn't increase its refcount.
appendRegion gst.buffer.Buffer appendRegion(gst.buffer.Buffer buf2, ptrdiff_t offset, ptrdiff_t size): Appends size bytes at offset from buf2 to buf1. The result buffer will contain a concatenation of the memory of buf1 and the requested region of buf2.
copyDeep gst.buffer.Buffer copyDeep(): Creates a copy of the given buffer. This will make a newly allocated copy of the data the source buffer contains.
copyInto bool copyInto(gst.buffer.Buffer src, gst.types.BufferCopyFlags flags, size_t offset, size_t size): Copies the information from src into dest.
copyRegion gst.buffer.Buffer copyRegion(gst.types.BufferCopyFlags flags, size_t offset, size_t size): Creates a sub-buffer from parent at offset and size. This sub-buffer uses the actual memory space of the parent buffer. This function will copy the offset and timestamp fields when the offset is 0. If not, they will be set to #GST_CLOCK_TIME_NONE and #GST_BUFFER_OFFSET_NONE. If offset equals 0 and size equals the total size of buffer, the duration and offset end fields are also copied. If not they will be set to #GST_CLOCK_TIME_NONE and #GST_BUFFER_OFFSET_NONE.
extractDup void extractDup(size_t offset, size_t size, ubyte[] dest): Extracts a copy of at most size bytes the data at offset into newly-allocated memory. dest must be freed using glib.global.gfree when done.
fill size_t fill(size_t offset, ubyte[] src): Copies size bytes from src to buffer at offset.
findMemory bool findMemory(size_t offset, size_t size, uint idx, uint length, size_t skip): Finds the memory blocks that span size bytes starting from offset in buffer.
foreachMeta bool foreachMeta(gst.types.BufferForeachMetaFunc func): Calls func with user_data for each meta in buffer.
getAllMemory gst.memory.Memory getAllMemory(): Gets all the memory blocks in buffer. The memory blocks will be merged into one large #GstMemory.
getCustomMeta gst.custom_meta.CustomMeta getCustomMeta(string name): Finds the first #GstCustomMeta on buffer for the desired name.
getFlags gst.types.BufferFlags getFlags(): Gets the #GstBufferFlags flags set on this buffer.
getMemory gst.memory.Memory getMemory(uint idx): Gets the memory block at index idx in buffer.
getMemoryRange gst.memory.Memory getMemoryRange(uint idx, int length): Gets length memory blocks in buffer starting at idx. The memory blocks will be merged into one large #GstMemory.
getMeta gst.meta.Meta getMeta(gobject.types.GType api): Gets the metadata for api on buffer. When there is no such metadata, null is returned. If multiple metadata with the given api are attached to this buffer only the first one is returned. To handle multiple metadata with a given API use gst.buffer.Buffer.iterateMeta or gst.buffer.Buffer.foreachMeta instead and check the meta->info.api member for the API type.
getNMeta uint getNMeta(gobject.types.GType apiType)
getReferenceTimestampMeta gst.reference_timestamp_meta.ReferenceTimestampMeta getReferenceTimestampMeta(gst.caps.Caps reference): Finds the first #GstReferenceTimestampMeta on buffer that conforms to reference. Conformance is tested by checking if the meta's reference is a subset of reference.
getSize size_t getSize(): Gets the total size of the memory blocks in buffer.
getSizes size_t getSizes(size_t offset, size_t maxsize): Gets the total size of the memory blocks in buffer.
getSizesRange size_t getSizesRange(uint idx, int length, size_t offset, size_t maxsize): Gets the total size of length memory blocks stating from idx in buffer.
hasFlags bool hasFlags(gst.types.BufferFlags flags): Gives the status of a specific flag on a buffer.
insertMemory void insertMemory(int idx, gst.memory.Memory mem): Inserts the memory block mem into buffer at idx. This function takes ownership of mem and thus doesn't increase its refcount.
isAllMemoryWritable bool isAllMemoryWritable(): Checks if all memory blocks in buffer are writable.
isMemoryRangeWritable bool isMemoryRangeWritable(uint idx, int length): Checks if length memory blocks in buffer starting from idx are writable.
map bool map(gst.map_info.MapInfo info, gst.types.MapFlags flags): Fills info with the #GstMapInfo of all merged memory blocks in buffer.
mapRange bool mapRange(uint idx, int length, gst.map_info.MapInfo info, gst.types.MapFlags flags): Fills info with the #GstMapInfo of length merged memory blocks starting at idx in buffer. When length is -1, all memory blocks starting from idx are merged and mapped.
memcmp int memcmp(size_t offset, ubyte[] mem): Compares size bytes starting from offset in buffer with the memory in mem.
memset size_t memset(size_t offset, ubyte val, size_t size): Fills buf with size bytes with val starting from offset.
nMemory uint nMemory(): Gets the amount of memory blocks that this buffer has. This amount is never larger than what gst.buffer.Buffer.getMaxMemory returns.
peekMemory gst.memory.Memory peekMemory(uint idx): Gets the memory block at idx in buffer. The memory block stays valid until the memory block in buffer is removed, replaced or merged, typically with any call that modifies the memory in buffer.
prependMemory void prependMemory(gst.memory.Memory mem): Prepends the memory block mem to buffer. This function takes ownership of mem and thus doesn't increase its refcount.
removeAllMemory void removeAllMemory(): Removes all the memory blocks in buffer.
removeMemory void removeMemory(uint idx): Removes the memory block in b at index i.
removeMemoryRange void removeMemoryRange(uint idx, int length): Removes length memory blocks in buffer starting from idx.
removeMeta bool removeMeta(gst.meta.Meta meta): Removes the metadata for meta on buffer.
replaceAllMemory void replaceAllMemory(gst.memory.Memory mem): Replaces all memory in buffer with mem.
replaceMemory void replaceMemory(uint idx, gst.memory.Memory mem): Replaces the memory block at index idx in buffer with mem.
replaceMemoryRange void replaceMemoryRange(uint idx, int length, gst.memory.Memory mem): Replaces length memory blocks in buffer starting at idx with mem.
resize void resize(ptrdiff_t offset, ptrdiff_t size): Sets the offset and total size of the memory blocks in buffer.
resizeRange bool resizeRange(uint idx, int length, ptrdiff_t offset, ptrdiff_t size): Sets the total size of the length memory blocks starting at idx in buffer
setFlags bool setFlags(gst.types.BufferFlags flags): Sets one or more buffer flags on a buffer.
setSize void setSize(ptrdiff_t size): Sets the total size of the memory blocks in buffer.
unmap void unmap(gst.map_info.MapInfo info): Releases the memory previously mapped with gst.buffer.Buffer.map.
unsetFlags bool unsetFlags(gst.types.BufferFlags flags): Clears one or more buffer flags.

Static functions

getMaxMemory uint getMaxMemory(): Gets the maximum amount of memory blocks that a buffer can hold. This is a compile time constant that can be queried with the function.
newAllocate gst.buffer.Buffer newAllocate(gst.allocator.Allocator allocator, size_t size, gst.allocation_params.AllocationParams params): Tries to create a newly allocated buffer with data of the given size and extra parameters from allocator. If the requested amount of memory can't be allocated, null will be returned. The allocated buffer memory is not cleared.
newMemdup gst.buffer.Buffer newMemdup(ubyte[] data): Creates a new buffer of size size and fills it with a copy of data.
newWrappedBytes gst.buffer.Buffer newWrappedBytes(glib.bytes.Bytes bytes): Creates a new #GstBuffer that wraps the given bytes. The data inside bytes cannot be null and the resulting buffer will be marked as read only.
newWrappedFull gst.buffer.Buffer newWrappedFull(gst.types.MemoryFlags flags, ubyte[] data, size_t maxsize, size_t offset, glib.types.DestroyNotify notify): Allocates a new buffer that wraps the given memory. data must point to maxsize of memory, the wrapped buffer will have the region from offset and size visible.

Inherited Members

From Boxed

cInstancePtr void* cInstancePtr;: Pointer to the C boxed value
getType GType getType(): Get the GType of this boxed type.
gType GType gType [@property getter]: Boxed GType property.
self Boxed self(): Convenience method to return this cast to a type. For use in D with statements.
copy_ void* copy_(): Make a copy of the wrapped C boxed data.
boxedCopy void* boxedCopy(void* cBoxed): Copy a C boxed value using g_boxed_copy.
boxedFree void boxedFree(void* cBoxed): Free a C boxed value using g_boxed_free.

gst buffer classes

Buffer