Not able to use downstream (kmssink) bufferpool in omx decoder component

[Víctor M. Jáquez L.]

On 01/15/17 at 05:06am, Devarsh Thakkar wrote:
> Hi,
> 
> I am using below pipeline :
> 
> /gst-launch-1.0 ! filesrc <input_file> ! h264parse ! omxh264dec ! kmssink/
> 
> After inserting some debug messages (after gst_is_kms_memory() in kmssink
> code) i got to know that omxh264dec doesn't use downstream i.e kmssink
> bufferpool, 
> 
> however when I use below pipeline, kmssink bufferpool is used  :
> /gst-launch-1.0 videotestsrc ! 'video/x-raw, format=(string)NV12, width=176,
> height=144, framerate=30/1' ! kmssink/
> 
> QUESTIONS :
> Any ideas on what changes need to be done in gst-omx so that it uses kmssink
> buffer pool?
> Any examples of omxh264dec using downstream bufferpool would also be
> helpful.

I guess, if I recall correctly, that will depend on you hardware/platform: if
the decoding subsystem can use an external memory area (in the case of
kmssink, a DRM's dumb buffer). Normally it is not the case, and the media
subsystem needs a special memory area, hence a memcopy is unavoidable.

The special case, if you see the gst-omx code, is the EGL, the video decoder
will export a EGL if downstream supports GstGLMemory (EGL).

You could add another special case: DMABuf. If your platform can export
DMABUf, you could use GstDMABufAllocator, and kmssink can import DMABufs.

vmjl

> 
> I think if downstream element is able to provide a buffer pool and omx
> component uses it than it should increase the performance of overall
> pipeline, isn't omxvideodec code designed such a way to handle this or am I
> missing something?
> 
> Kindly let me know if there is anything wrong with my understanding as I am
> a gstreamer newbie.
> Thanks in advance.
> 
> Best Regards,
> Devarsh
> 
> 
> 
> --
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