[gst-devel] How to control pipeline frame rate when my camera needs some time to get one frame data

[thiagossantos at gmail.com]

On Tue, Nov 17, 2009 at 8:11 PM, Zhao, Halley <halley.zhao at intel.com> wrote:

>  Hi all:
>
> My camera needs ~20ms to get one frame of data, and a video sink in the
> pipeline needs ~4ms to render it.
>
> But when I set pipeline fps to 35, I only got 20 fps (calculate by GST
> CLOCK). CPU is not busy at this time, only 60%.
>
>
>
> I guess the reason is following:
>
> When we got nth frame at time 0, gst framework schedule to get next frame
> after 30ms (1000/35), and when the camera src element got scheduled to
> create one frame, it needs 20ms to get the data.
>
> Then the time between n frame and n+1 frame is 30+20=50ms, so I just got 20
> fps.
>
> Is my assumption right?
>
> If yes, is there any way to adjust it?
>
You can speed it up by adding a queue right after your source element. It
will create another thread to push data after it, the thread used to request
a frame from the camera will quickly return to the source and it will
request another one.


>
>
> I had though to create another thread inside camera source, and prepare the
> frame data in a buffer before it is schedule.
>
> However, I think it is hack, and make timestamp differ. I think it’s better
> settled inside gst framework.
>
>
>
>
>
> *ZHAO, Halley (Aihua)*
>
> Email: halley.zhao at intel.com
>
> Tel: +86(21)61166476
>
> iNet: 8821-6476
>
> SSG/OTC/Moblin 3W038 Pole: F4
>
>
>
>
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-- 
Thiago Sousa Santos
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