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Acorn Pooley
Acorn Pooley, NVIDIA (apooley 'at'
Copyright (c) 2011-2013 The Khronos Group Inc. Copyright terms at
Approved by the Khronos Board of Promoters on December 2, 2011.
Version 4, October 4, 2011
EGL Extension #35
Requires EGL 1.2 or later.
Requires OpenMAX AL 1.1 or later.
Requires the EGL_KHR_stream extension.
Requires the OpenMAX_AL_EGLStream_DataLocator extension.
This extension (in conjunction with the
OpenMAX_AL_EGLStream_DataLocator extension to OpenMAX AL)
allows an OpenMAX AL MediaPlayer object to be connected as the
producer of an EGLStream.
After the EGLStream is created and connected to a consumer, the
OpenMAX AL MediaPlayer object is created by calling <pEngine>'s
CreateMediaPlayer() method. The <pImageVideoSnk> argument points
to an XADataLocator_EGLStream containing the EGLStreamKHR handle
of the stream. The CreateMediaPlayer() method creates a
MediaPlayer object and connects it as the producer of the
EGLStream. (Note that the pFormat member of the XADataSink
structure is ignored in this case and may be NULL.)
Once connected the MediaPlayer inserts image frames into the
Replace section " No way to connect producer to EGLStream" in
the EGL_KHR_stream extension with this: OpenMAX AL Stream Producer
An OpenMAX AL MediaPlayer object can act as a producer for an
EGLStream. First create the EGLStream and connect a consumer to
it so that the EGLStream is in EGL_STREAM_STATE_CONNECTING_KHR
At this point the application can create an OpenMAX AL MediaPlayer
object as described in the OpenMAX AL specification and the
OpenMAX_AL_EGLStream_DataLocator extension. The application
should create an XADataSink structure with pLocator pointing to an
XADataLocator_EGLStream structure referencing the EGLStream (in
the pEGLStream member) and the EGLDisplay used to create the
EGLStream (in the pEGLDisplay member). The pFormat field of the
XADataSink is ignored and should be NULL. This XADataSink
structure is passed as the <pImageVideoSnk> argument to
<pEngine>'s CreateMediaPlayer() method.
If the OpenMAX AL implementation is unable to convert image frames
to a format usable by <stream>'s consumer then CreateMediaPlayer
will fail with a XA_RESULT_CONTENT_UNSUPPORTED error.
After CreateMediaPlayer() has returned successfully, <stream>'s
state will be one of
and the OpenMAX AL MediaPlayer object returned in <pPlayer> will
be connected as the producer of <stream>. If the MediaPlayer
object is destroyed then <stream>'s state will become
Image and video frame data generated by the OpenMAX AL object (as
described in the OpenMAX AL spec) are inserted into <stream> (as
described in section "3.10.5 EGLStream operation" of the
EGL_KHR_stream extension).
The OpenMAX AL object will use the value of the
EGL_CONSUMER_LATENCY_USEC_KHR attribute of <stream> to determine
when to insert each image frame. If the
EGL_CONSUMER_LATENCY_USEC_KHR attribute is modified (by the
consumer and/or by the application) then OpenMAX AL object
will adjust its timing within 500 milliseconds of the change. If
an image frame is intended to appear to the user at time T (e.g.
so that it is synchronized with audio) then the OpenMAX AL object
must insert the image frame at time
1. How many image frame buffers should be used?
RESOLVED: This is left up to the OpenMAX AL implementation.
2. How is the image frame size determined?
Could also expose EGL_WIDTH and EGL_HEIGHT in the attrib_list
as a hint (or as a requirement) as to what size should be
used. However, a MediaPlayer object typically knows what size
to decode based on the source of the data. So this is
probably not necessary. If needed it can be added with a
layered extension.
RESOLVED: Leave this up to the OpenMAX AL MediaPlayer object.
3. What image frame format should be used?
RESOLVED: This is a negotiation between the consumer and
producer, but ultimately the producer must convert to the
format that the consumer requests, or fail if that is not
Details of any such communication is implementation dependent
and outside the scope of this specification.
4. Should this extension create an XADataSink structure rather
than making the application create its own as described in
RESOLVED: NO no need to do this.
5. (This issue no longer applies)
Should this extension allow the application to ignore the
XADataSink structure returned by eglStreamProducerALDataSource
and instead use its own?
RESOLVED: This issue no longer applies
6. (This issue no longer applies)
Should eglStreamProducerALDataSource check that <ppDataSink>
is not NULL and that <ppDataSink> points to a pointer that is
RESOLVED: This issue no longer applies
Revision History
#4 (October 4, 2011) Acorn Pooley
- Convert from an NV extension to a KHR extension
#3 (September 23, 2011) Acorn Pooley
- Eliminate the eglStreamProducerALDataSource function.
- Rename AL0124b_EGLImageStream_DataLocator_Nokia to
OpenMAX_AL_EGLStream_DataLocator and point to new link.
- Resolve issue 2
#2 (July 6, 2011) Acorn Pooley
- remove the creation of the XADataSink by
#1 (June 30, 2011) Acorn Pooley
- initial draft
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