org.gstreamer.Buffer Maven / Gradle / Ivy
Show all versions of gstreamer-java Show documentation
/*
* Copyright (C) 2007 Wayne Meissner
* Copyright (C) 1999,2000 Erik Walthinsen
* 2000 Wim Taymans
*
* This file is part of gstreamer-java.
*
* This code is free software: you can redistribute it and/or modify it under
* the terms of the GNU Lesser General Public License version 3 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* version 3 for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* version 3 along with this work. If not, see
* Buffers are the basic unit of data transfer in GStreamer. The Buffer
* type provides all the state necessary to define a region of memory as part
* of a stream. Sub-buffers are also supported, allowing a smaller region of a
* buffer to become its own buffer, with mechanisms in place to ensure that
* neither memory space goes away prematurely.
*
* Non-plugins will usually not need to allocate buffers, but they can be allocated
* using new {@link #Buffer(int)} to create a buffer with preallocated data of a given size.
*
* The data pointed to by the buffer can be accessed with the {@link #getByteBuffer}
* method. For buffers of size 0, the data pointer is undefined (usually NULL)
* and should never be used.
*
* If an element knows what pad you will push the buffer out on, it should use
* gst_pad_alloc_buffer() instead to create a buffer. This allows downstream
* elements to provide special buffers to write in, like hardware buffers.
*
* A buffer has a pointer to a {@link Caps} describing the media type of the data
* in the buffer. Attach caps to the buffer with {@link #setCaps}; this
* is typically done before pushing out a buffer using gst_pad_push() so that
* the downstream element knows the type of the buffer.
*
* A buffer will usually have a timestamp, and a duration, but neither of these
* are guaranteed (they may be set to -1). Whenever a
* meaningful value can be given for these, they should be set. The timestamp
* and duration are measured in nanoseconds (they are long values).
*
* 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 #GstCaps set on it). Either or both
* can be set to -1.
*
* To efficiently create a smaller buffer out of an existing one, you can
* use {@link #createSubBuffer}.
*
* If a plug-in wants to modify the buffer data in-place, it should first obtain
* a buffer that is safe to modify by using {@link #makeWritable}. This
* function is optimized so that a copy will only be made when it is necessary.
*
* A plugin that only wishes to modify the metadata of a buffer, such as the
* offset, timestamp or caps, should use gst_buffer_make_metadata_writable(),
* which will create a subbuffer of the original buffer to ensure the caller
* has sole ownership, and not copy the buffer data.
*
* Buffers can be efficiently merged into a larger buffer with
* gst_buffer_merge() and gst_buffer_span() if the gst_buffer_is_span_fast()
* function returns TRUE.
*
*/
public class Buffer extends MiniObject {
private static interface API extends GstBufferAPI, GstMiniObjectAPI {
@CallerOwnsReturn Pointer ptr_gst_buffer_new();
@CallerOwnsReturn Pointer ptr_gst_buffer_new_and_alloc(int size);
}
private static final API gst = GstNative.load(API.class);
public Buffer(Initializer init) {
super(init);
struct = new BufferStruct(handle());
}
/**
* Creates a newly allocated buffer without any data.
*/
public Buffer() {
this(initializer(gst.ptr_gst_buffer_new()));
}
/**
* Creates a newly allocated buffer with data of the given size.
* The buffer memory is not cleared. If the requested amount of
* memory cannot be allocated, an exception will be thrown.
*
* Note that when size == 0, the buffer data pointer will be NULL.
*
* @param size
*/
public Buffer(int size) {
this(initializer(allocBuffer(size)));
}
private static Pointer allocBuffer(int size) {
Pointer ptr = gst.ptr_gst_buffer_new_and_alloc(size);
if (ptr == null) {
throw new OutOfMemoryError("Could not allocate Buffer of size "+ size);
}
return ptr;
}
/**
* Gets the native address of this Buffer
*
* @return a pointer
*/
public Pointer getAddress() {
return handle();
}
/**
* Creates a sub-buffer from this buffer 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 both be set to -1.
*
* 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 -1.
*
* @param offset The offset into parent Buffer at which the new sub-buffer begins.
* @param size the size of the new Buffer sub-buffer, in bytes.
* @return The new Buffer, or null if the arguments were invalid.
*/
public Buffer createSubBuffer(int offset, int size) {
return gst.gst_buffer_create_sub(this, offset, size);
}
/**
* Tests if you can safely write data into a buffer's data array or validly
* modify the caps and timestamp metadata. Metadata in a GstBuffer is always
* writable, but it is only safe to change it when there is only one owner
* of the buffer - ie, the refcount is 1.
*
* @return true if the Buffer is writable.
*/
@Override
public boolean isWritable() {
return super.isWritable();
}
/**
* Makes a writable buffer from this buffer. If the this buffer is
* already writable, this will simply return the same buffer. A copy will
* otherwise be made and returned.
*
* @return A writable Buffer referring to the same memory as this one.
*/
public Buffer makeWritable() {
Buffer buf = (Buffer) gst.gst_mini_object_make_writable(this);
if (buf == null) {
throw new NullPointerException("Could not make Buffer writable");
}
return buf;
}
public boolean isMetadataWritable() {
return false;
}
/**
* Gets the size of the buffer data
*
* @return the size of the buffer data in bytes.
*/
public int getSize() {
return (Integer) struct.readField("size");
}
/**
* Gets the duration in time of the buffer data, can be {@link ClockTime#NONE}
* when the duration is not known or relevant.
*
* @return a ClockTime representing the duration.
*/
public ClockTime getDuration() {
return (ClockTime) struct.readField("duration");
}
public void setDuration(ClockTime dur) {
struct.duration = dur;
struct.writeField("duration");
}
/**
* Gets the timestamp in time of the buffer data, can be {@link ClockTime#NONE}
* when the timestamp is not known or relevant.
*
* @return a ClockTime representing the timestamp.
*/
public ClockTime getTimestamp() {
return (ClockTime) struct.readField("timestamp");
}
/**
* Sets the timestamp in time of the buffer data, can be {@link ClockTime#NONE}
* when the timestamp is not known or relevant.
*/
public void setTimestamp(ClockTime timestamp) {
struct.timestamp = timestamp;
struct.writeField("timestamp");
}
/**
* Gets the media type of the buffer. This can be null if there
* is no media type attached to this buffer.
*
* @return a {@link Caps} describing the media type, or null if there was no
* media type associated with the buffer.
*/
public Caps getCaps() {
return gst.gst_buffer_get_caps(this);
}
/**
* Sets the media type on the buffer.
* @param caps the {@link Caps} describing the media type.
*/
public void setCaps(Caps caps) {
gst.gst_buffer_set_caps(this, caps);
}
/**
* Gets a {@link java.nio.ByteBuffer} that can access the native memory
* associated with this Buffer.
*
* @return A {@link java.nio.ByteBuffer} that can access this Buffer's data.
*/
public synchronized ByteBuffer getByteBuffer() {
if (byteBuffer == null) {
int size = getSize();
Pointer data = (Pointer) struct.readField("data");
if (data != null && size > 0) {
byteBuffer = data.getByteBuffer(0, size);
}
}
return byteBuffer;
}
/**
* Gets the offset for the buffer data in the stream.
*
*
The offset is a media specific offset for the buffer data.
* For video frames, this is the frame number of this buffer.
* For audio samples, this is the offset of the first sample in this buffer.
* For file data or compressed data this is the byte offset of the first
* byte in this buffer.
*
* @return the offset
*/
public long getOffset() {
return (Long) struct.readField("offset");
}
/**
* Sets the offset of the buffer in the media stream.
*
* @param offset
* @see #getOffset
*/
public void setOffset(long offset) {
struct.offset = offset;
struct.writeField("offset");
}
/**
* Gets the last offset contained in this buffer.
*
It has the same format as {@link #getOffset getOffset}
*
* @return the last offset
*/
public long getLastOffset() {
return (Long) struct.readField("offset_end");
}
/**
* Sets the last offset contained in this buffer.
*
It has the same format as {@link #getOffset getOffset}
*
*/
public void setLastOffset(long offset) {
struct.offset_end = offset;
struct.writeField("offset_end");
}
/**
* Gets GstBuffer flags
*
* @return an integer value containing flags
*/
public int getFlags() {
return struct.mini_object.flags;
}
private final BufferStruct struct;
private ByteBuffer byteBuffer;
}