RE: using MFC memory to memery encoder, start stream and queue order problem

[Kamil Debski <k.debski@samsung.com>]

Hi Randy,

> From: randy [mailto:lxr1234@hotmail.com]
> Sent: Friday, January 03, 2014 4:17 PM
> 
> I rewrite my program, it takes the order as below 1.request buffer.
> 2.mmap input buffer with OUTPUT
> 3.output buffer with CAPTURE.
> 4.filled input buffer with the first frame.
> 5.enqueue the first frame in the input buffer in OUTPUT side 6.enqueue
> the output buffer in CAPTURE side 7.start stream 8.dequeue CAPTURE
> buffer and make output buffer pointer to data of it.
> 9.get output data from output buffer
> /* the buffer get size is 22 below */
> 10.dequeue OUTPUT
> /* timed out, it will never end */
> Is there any problem with the order? I don't do any thing
> simultaneously below, it seems to difficult to me to understand and not
> easy to debug.
> I am not sure whether the mmap is correct, but I think it it as I don't
> get segment fault.

Please have a look at the V4L2_CID_MPEG_VIDEO_HEADER_MODE control.
>From your description it seems that it is in its default state - 
V4L2_MPEG_VIDEO_HEADER_MODE_SEPARATE. This means that the header for a
newly encoded stream is returned after init. Then in another buffer you will
find the encoded picture.

So after point 9 please enqueue the CAPTURE buffer again and see what
happens. I think that you should get the first frame encoded.

You can also try to set the V4L2_CID_MPEG_VIDEO_HEADER_MODE control to
V4L2_MPEG_VIDEO_HEADER_MODE_JOINED_WITH_1ST_FRAME and see if it works.
(instead of enqueueing the CAPTURE buffer again after receiving the header).

In addition I would recommend you to use more than one buffer per queue.
 
> 
> And the thing in the next is like this I think 11.filled input buffer
> with the next frame 12.enqueue the next frame in the input buffer in
> OUTPUT side 13.dequeue CAPTURE buffer and make output buffer pointer to
> data of it.
> 14.dequeue OUTPUT
> goto 11
> Is it correct
> 
> I doubt the REAME
> 5. Request CAPTURE and OUTPUT buffers. Due to hardware limitations of
> MFC on
>    some platforms it is recommended to use V4L2_MEMORY_MMAP buffers.
> 6. Enqueue CAPTURE buffers.
> 7. Enqueue OUTPUT buffer with first frame.
> 8. Start streaming (VIDIOC_STREAMON) on both ends.
> 9. Simultaneously:
> I don't need to dequeue the OUTPUT buffer which is with first frame?
>    - enqueue buffers with next frames,
>    - dequeue used OUTPUT buffers (blocking operation),
>    - dequeue buffers with encoded stream (blocking operation),
>    - enqueue free CAPTURE buffers.
> 
> 
> 							Thank you.

Best wishes,
Kamil