Re: How can I feed more data to a stream after I stream on?

[Hans Verkuil <hverkuil@xs4all.nl>]

On 03/19/2014 12:18 AM, m silverstri wrote:
> I am using v4l2 m2m framework to develop a resize driver. I have an
> image , pass it to the driver and it generated a resize output image.
> 
> My v4l2 sequence is
> 1. qbuf OUTPUT, CAPTURE
> 2. stream on OUTPUT, CAPTURE
> 3. dqbuf OUTPUT, CAPTURE
> 4. stream off OUTPUT, CAPTURE
> 
> this works if i have a full frame of image before i start streaming.
> 
> But what I only have partial buffers when I start streaming, how can I
> qbuf more buffer after I 'stream on' OUTPUT,

You can't. Each buffer passed to the driver must contain a full image.
So your application needs some logic to keep filling a buffer until it
is complete and only then do you issue the QBUF.

Regards,

	Hans

> 
> I try this, but this fail
> 1. qbuf OUTPUT, CAPTURE (I qbuf only partial OUTPUT)
> 2. stream on OUTPUT, CAPTURE
> 
> // do this in a loop:
> 3. dqbuf OUTPUT (I want to queue more OUTPUT as they become available)
> 4. qbuf OUTPUT
> 
> // now I am done, I want to dqbuf my output
> 5. dqbuf CAPTURE
> 6. stream off OUTPUT, CAPTURE
> 
> I try to do dqbuf/qbuf OUTPUT in step #3, #4 above, but it just stuck
> in dqbuf OUTPUT.
> 
> How can I queue more of my input data after I stream on?
> 
> Thank you.
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