[−]Struct gstreamer_base::Adapter

pub struct Adapter(_, _);

This class is for elements that receive buffers in an undesired size. While for example raw video contains one image per buffer, the same is not true for a lot of other formats, especially those that come directly from a file. So if you have undefined buffer sizes and require a specific size, this object is for you.

An adapter is created with Adapter::new. It can be freed again with gobject::ObjectExt::unref.

The theory of operation is like this: All buffers received are put into the adapter using Adapter::push and the data is then read back in chunks of the desired size using Adapter::map/Adapter::unmap and/or Adapter::copy. After the data has been processed, it is freed using Adapter::unmap.

Other methods such as Adapter::take and Adapter::take_buffer combine Adapter::map and Adapter::unmap in one method and are potentially more convenient for some use cases.

For example, a sink pad's chain function that needs to pass data to a library in 512-byte chunks could be implemented like this:

static GstFlowReturn
sink_pad_chain (GstPad *pad, GstObject *parent, GstBuffer *buffer)
{
  MyElement *this;
  GstAdapter *adapter;
  GstFlowReturn ret = GST_FLOW_OK;

  this = MY_ELEMENT (parent);

  adapter = this->adapter;

  // put buffer into adapter
  gst_adapter_push (adapter, buffer);

  // while we can read out 512 bytes, process them
  while (gst_adapter_available (adapter) >= 512 && ret == GST_FLOW_OK) {
    const guint8 *data = gst_adapter_map (adapter, 512);
    // use flowreturn as an error value
    ret = my_library_foo (data);
    gst_adapter_unmap (adapter);
    gst_adapter_flush (adapter, 512);
  }
  return ret;
}

For another example, a simple element inside GStreamer that uses Adapter is the libvisual element.

An element using Adapter in its sink pad chain function should ensure that when the FLUSH_STOP event is received, that any queued data is cleared using Adapter::clear. Data should also be cleared or processed on EOS and when changing state from gst::State::Paused to gst::State::Ready.

Also check the GST_BUFFER_FLAG_DISCONT flag on the buffer. Some elements might need to clear the adapter after a discontinuity.

The adapter will keep track of the timestamps of the buffers that were pushed. The last seen timestamp before the current position can be queried with Adapter::prev_pts. This function can optionally return the number of bytes between the start of the buffer that carried the timestamp and the current adapter position. The distance is useful when dealing with, for example, raw audio samples because it allows you to calculate the timestamp of the current adapter position by using the last seen timestamp and the amount of bytes since. Additionally, the Adapter::prev_pts_at_offset can be used to determine the last seen timestamp at a particular offset in the adapter.

The adapter will also keep track of the offset of the buffers (GST_BUFFER_OFFSET) that were pushed. The last seen offset before the current position can be queried with Adapter::prev_offset. This function can optionally return the number of bytes between the start of the buffer that carried the offset and the current adapter position.

Additionally the adapter also keeps track of the PTS, DTS and buffer offset at the last discontinuity, which can be retrieved with Adapter::pts_at_discont, Adapter::dts_at_discont and Adapter::offset_at_discont. The number of bytes that were consumed since then can be queried with Adapter::distance_from_discont.

A last thing to note is that while Adapter is pretty optimized, merging buffers still might be an operation that requires a malloc and memcpy operation, and these operations are not the fastest. Because of this, some functions like Adapter::available_fast are provided to help speed up such cases should you want to. To avoid repeated memory allocations, Adapter::copy can be used to copy data into a (statically allocated) user provided buffer.

Adapter is not MT safe. All operations on an adapter must be serialized by the caller. This is not normally a problem, however, as the normal use case of Adapter is inside one pad's chain function, in which case access is serialized via the pad's STREAM_LOCK.

Note that Adapter::push takes ownership of the buffer passed. Use gst_buffer_ref before pushing it into the adapter if you still want to access the buffer later. The adapter will never modify the data in the buffer pushed in it.

Implements

glib::object::ObjectExt

Methods

`impl Adapter`[src]

`pub fn new() -> Adapter`[src]

Creates a new Adapter. Free with gobject::ObjectExt::unref.

[−]Struct gstreamer_base::Adapter

Methods

impl Adapter[src]

pub fn new() -> Adapter[src]

pub fn available(&self) -> usize[src]

pub fn available_fast(&self) -> usize[src]

pub fn clear(&self)[src]

pub fn copy_bytes(&self, offset: usize, size: usize) -> Result<Bytes, BoolError>[src]

pub fn distance_from_discont(&self) -> u64[src]

pub fn dts_at_discont(&self) -> ClockTime[src]

pub fn flush(&self, flush: usize)[src]

pub fn get_buffer(&self, nbytes: usize) -> Result<Buffer, BoolError>[src]

pub fn get_buffer_fast(&self, nbytes: usize) -> Result<Buffer, BoolError>[src]

pub fn get_buffer_list(&self, nbytes: usize) -> Result<BufferList, BoolError>[src]

pub fn get_list(&self, nbytes: usize) -> Vec<Buffer>[src]

pub fn masked_scan_uint32( &self, mask: u32, pattern: u32, offset: usize, size: usize) -> isize[src]

pub fn masked_scan_uint32_peek( &self, mask: u32, pattern: u32, offset: usize, size: usize) -> (isize, u32)[src]

pub fn offset_at_discont(&self) -> u64[src]

pub fn prev_dts(&self) -> (ClockTime, u64)[src]

pub fn prev_dts_at_offset(&self, offset: usize) -> (ClockTime, u64)[src]

pub fn prev_offset(&self) -> (u64, u64)[src]

pub fn prev_pts(&self) -> (ClockTime, u64)[src]

pub fn prev_pts_at_offset(&self, offset: usize) -> (ClockTime, u64)[src]

pub fn pts_at_discont(&self) -> ClockTime[src]

pub fn take_buffer(&self, nbytes: usize) -> Result<Buffer, BoolError>[src]

pub fn take_buffer_fast(&self, nbytes: usize) -> Result<Buffer, BoolError>[src]

pub fn take_buffer_list(&self, nbytes: usize) -> Result<BufferList, BoolError>[src]

pub fn take_list(&self, nbytes: usize) -> Vec<Buffer>[src]

impl Adapter[src]

pub fn copy(&self, offset: usize, dest: &mut [u8])[src]

pub fn push(&self, buf: Buffer)[src]

Trait Implementations

impl Clone for Adapter

fn clone(&self) -> Adapter

fn clone_from(&mut self, source: &Self)1.0.0[src]

impl Debug for Adapter

fn fmt(&self, f: &mut Formatter) -> Result

impl Default for Adapter[src]

fn default() -> Self[src]

impl Eq for Adapter

impl Hash for Adapter

fn hash<__H: Hasher>(&self, state: &mut __H)

fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher, 1.3.0[src]

impl Ord for Adapter

fn cmp(&self, other: &Adapter) -> Ordering

#[must_use] fn max(self, other: Self) -> Self1.21.0[src]

#[must_use] fn min(self, other: Self) -> Self1.21.0[src]

#[must_use] fn clamp(self, min: Self, max: Self) -> Self[src]

impl<T: ObjectType> PartialEq<T> for Adapter

fn eq(&self, other: &T) -> bool

#[must_use] fn ne(&self, other: &Rhs) -> bool1.0.0[src]

impl<T: ObjectType> PartialOrd<T> for Adapter

fn partial_cmp(&self, other: &T) -> Option<Ordering>

#[must_use] fn lt(&self, other: &Rhs) -> bool1.0.0[src]

#[must_use] fn le(&self, other: &Rhs) -> bool1.0.0[src]

#[must_use] fn gt(&self, other: &Rhs) -> bool1.0.0[src]

#[must_use] fn ge(&self, other: &Rhs) -> bool1.0.0[src]

impl Read for Adapter[src]

fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error>[src]

fn read_vectored(&mut self, bufs: &mut [IoSliceMut]) -> Result<usize, Error>1.36.0[src]

unsafe fn initializer(&self) -> Initializer[src]

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>1.0.0[src]

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>1.0.0[src]

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>1.6.0[src]

fn by_ref(&mut self) -> &mut Self1.0.0[src]

fn bytes(self) -> Bytes<Self>1.0.0[src]

fn chain<R>(self, next: R) -> Chain<Self, R> where R: Read, 1.0.0[src]

fn take(self, limit: u64) -> Take<Self>1.0.0[src]

impl SendUnique for Adapter[src]

fn is_unique(&self) -> bool[src]

impl StaticType for Adapter

fn static_type() -> Type

Auto Trait Implementations

impl RefUnwindSafe for Adapter

impl !Send for Adapter

impl !Sync for Adapter

impl Unpin for Adapter

impl UnwindSafe for Adapter

Blanket Implementations

impl<T> Any for T where T: 'static + ?Sized, [src]

`impl Adapter`[src]

`pub fn new() -> Adapter`[src]

`pub fn available(&self) -> usize`[src]

`pub fn available_fast(&self) -> usize`[src]

`pub fn clear(&self)`[src]

`pub fn copy_bytes(&self, offset: usize, size: usize) -> Result<Bytes, BoolError>`[src]

`pub fn distance_from_discont(&self) -> u64`[src]

`pub fn dts_at_discont(&self) -> ClockTime`[src]

`pub fn flush(&self, flush: usize)`[src]

`pub fn get_buffer(&self, nbytes: usize) -> Result<Buffer, BoolError>`[src]

`pub fn get_buffer_fast(&self, nbytes: usize) -> Result<Buffer, BoolError>`[src]

`pub fn get_buffer_list(&self, nbytes: usize) -> Result<BufferList, BoolError>`[src]

`pub fn get_list(&self, nbytes: usize) -> Vec<Buffer>`[src]

`pub fn masked_scan_uint32( &self, mask: u32, pattern: u32, offset: usize, size: usize ) -> isize`[src]

`pub fn masked_scan_uint32_peek( &self, mask: u32, pattern: u32, offset: usize, size: usize ) -> (isize, u32)`[src]

`pub fn offset_at_discont(&self) -> u64`[src]

`pub fn prev_dts(&self) -> (ClockTime, u64)`[src]

`pub fn prev_dts_at_offset(&self, offset: usize) -> (ClockTime, u64)`[src]

`pub fn prev_offset(&self) -> (u64, u64)`[src]

`pub fn prev_pts(&self) -> (ClockTime, u64)`[src]

`pub fn prev_pts_at_offset(&self, offset: usize) -> (ClockTime, u64)`[src]

`pub fn pts_at_discont(&self) -> ClockTime`[src]

`pub fn take_buffer(&self, nbytes: usize) -> Result<Buffer, BoolError>`[src]

`pub fn take_buffer_fast(&self, nbytes: usize) -> Result<Buffer, BoolError>`[src]

`pub fn take_buffer_list(&self, nbytes: usize) -> Result<BufferList, BoolError>`[src]

`pub fn take_list(&self, nbytes: usize) -> Vec<Buffer>`[src]

`impl Adapter`[src]

`pub fn copy(&self, offset: usize, dest: &mut [u8])`[src]

`pub fn push(&self, buf: Buffer)`[src]

`impl Clone for Adapter`

`fn clone(&self) -> Adapter`

`fn clone_from(&mut self, source: &Self)`1.0.0[src]

`impl Debug for Adapter`

`fn fmt(&self, f: &mut Formatter) -> Result`

`impl Default for Adapter`[src]

`fn default() -> Self`[src]

`impl Eq for Adapter`

`impl Hash for Adapter`

`fn hash<H: Hasher>(&self, state: &mut H)`

`fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher,` 1.3.0[src]

`impl Ord for Adapter`

`fn cmp(&self, other: &Adapter) -> Ordering`

`#[must_use] fn max(self, other: Self) -> Self`1.21.0[src]

`#[must_use] fn min(self, other: Self) -> Self`1.21.0[src]

`#[must_use] fn clamp(self, min: Self, max: Self) -> Self`[src]

`impl<T: ObjectType> PartialEq<T> for Adapter`

`fn eq(&self, other: &T) -> bool`

`#[must_use] fn ne(&self, other: &Rhs) -> bool`1.0.0[src]

`impl<T: ObjectType> PartialOrd<T> for Adapter`

`fn partial_cmp(&self, other: &T) -> Option<Ordering>`

`#[must_use] fn lt(&self, other: &Rhs) -> bool`1.0.0[src]

`#[must_use] fn le(&self, other: &Rhs) -> bool`1.0.0[src]

`#[must_use] fn gt(&self, other: &Rhs) -> bool`1.0.0[src]

`#[must_use] fn ge(&self, other: &Rhs) -> bool`1.0.0[src]

`impl Read for Adapter`[src]

`fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error>`[src]

`fn read_vectored(&mut self, bufs: &mut [IoSliceMut]) -> Result<usize, Error>`1.36.0[src]

`unsafe fn initializer(&self) -> Initializer`[src]

`fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>`1.0.0[src]

`fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>`1.0.0[src]

`fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>`1.6.0[src]

`fn by_ref(&mut self) -> &mut Self`1.0.0[src]

`fn bytes(self) -> Bytes<Self>`1.0.0[src]

`fn chain<R>(self, next: R) -> Chain<Self, R> where R: Read,` 1.0.0[src]

`fn take(self, limit: u64) -> Take<Self>`1.0.0[src]

`impl SendUnique for Adapter`[src]

`fn is_unique(&self) -> bool`[src]

`impl StaticType for Adapter`

`fn static_type() -> Type`

`impl RefUnwindSafe for Adapter`

`impl !Send for Adapter`

`impl !Sync for Adapter`

`impl Unpin for Adapter`

`impl UnwindSafe for Adapter`

`impl<T> Any for T where T: 'static + ?Sized,` [src]

`fn type_id(&self) -> TypeId`[src]

`impl<T> Borrow<T> for T where T: ?Sized,` [src]

`fn borrow(&self) -> &T`[src]

`impl<T> BorrowMut<T> for T where T: ?Sized,` [src]

`fn borrow_mut(&mut self) -> &mut T`[src]