Pause/Resume and flush for V4L2 codec drivers.

Pause/Resume and flush for V4L2 codec drivers.

[vkalia]

Hi

I am trying to implement v4l2 driver for video decoders. The problem I am
facing is how to send pause/resume and flush commands from user-space to
v4l2 driver. I am thinking of using controls for this. Has anyone done
this before or if anyone has any ideas please let me know. Appreciate your
help.

Thanks
Vinay

Re: Pause/Resume and flush for V4L2 codec drivers.

[Hans Verkuil]

On Friday, January 06, 2012 03:31:37 vkalia@codeaurora.org wrote:
> Hi
> 
> I am trying to implement v4l2 driver for video decoders. The problem I am
> facing is how to send pause/resume and flush commands from user-space to
> v4l2 driver. I am thinking of using controls for this. Has anyone done
> this before or if anyone has any ideas please let me know. Appreciate your
> help.

See this patch series:

http://www.mail-archive.com/linux-media@vger.kernel.org/msg40516.html

Does this give you what you need?

Regards,

	Hans

> 
> Thanks
> Vinay
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: Pause/Resume and flush for V4L2 codec drivers.

[vkalia]

Thanks Hans.

Yes it does solve a part of my problem - Pause/Resume. But I dont see any
command defined for Flush yet. Do you think we should add one more command
to Flush. Also, I see two more commands

#define V4L2_DEC_CMD_START       (0)
#define V4L2_DEC_CMD_STOP        (1)

How should I use the above two commands for an encoding/decoding session?
I was calling start/stop to hardware in streamon/streamoff earlier.

Thanks
Vinay

> On Friday, January 06, 2012 03:31:37 vkalia@codeaurora.org wrote:
>> Hi
>>
>> I am trying to implement v4l2 driver for video decoders. The problem I
>> am
>> facing is how to send pause/resume and flush commands from user-space to
>> v4l2 driver. I am thinking of using controls for this. Has anyone done
>> this before or if anyone has any ideas please let me know. Appreciate
>> your
>> help.
>
> See this patch series:
>
> http://www.mail-archive.com/linux-media@vger.kernel.org/msg40516.html
>
> Does this give you what you need?
>
> Regards,
>
> 	Hans
>
>>
>> Thanks
>> Vinay
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-media"
>> in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: Pause/Resume and flush for V4L2 codec drivers.

[Hans Verkuil]

On Saturday 07 January 2012 02:55:08 vkalia@codeaurora.org wrote:
> Thanks Hans.
> 
> Yes it does solve a part of my problem - Pause/Resume. But I dont see any
> command defined for Flush yet. Do you think we should add one more command
> to Flush.

What exactly does flush do? Is it the equivalent of an immediate stop?

> Also, I see two more commands
> 
> #define V4L2_DEC_CMD_START       (0)
> #define V4L2_DEC_CMD_STOP        (1)
> 
> How should I use the above two commands for an encoding/decoding session?
> I was calling start/stop to hardware in streamon/streamoff earlier.

See the documentation of these commands in patch 2/8: a write() or streamon
does an implicit decoder start, and close/streamoff() does an implicit 
immediate stop.

For hardware codecs that handle a compressed stream (as opposed to separate 
compressed frames) it is often very useful to implement the read/write API. 
That tends to be a natural API to use. E.g. you can just do:

	cat test.mpg >/dev/videoX

Regards,

	Hans

> 
> Thanks
> Vinay
> 
> > On Friday, January 06, 2012 03:31:37 vkalia@codeaurora.org wrote:
> >> Hi
> >> 
> >> I am trying to implement v4l2 driver for video decoders. The problem I
> >> am
> >> facing is how to send pause/resume and flush commands from user-space to
> >> v4l2 driver. I am thinking of using controls for this. Has anyone done
> >> this before or if anyone has any ideas please let me know. Appreciate
> >> your
> >> help.
> > 
> > See this patch series:
> > 
> > http://www.mail-archive.com/linux-media@vger.kernel.org/msg40516.html
> > 
> > Does this give you what you need?
> > 
> > Regards,
> > 
> > 	Hans
> > 	
> >> Thanks
> >> Vinay
> >> 
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-media"
> >> in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-media" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Pause/Resume and flush for V4L2 codec drivers.

[Laurent Pinchart]

Hi Vinay,

On Friday 06 January 2012 03:31:37 vkalia@codeaurora.org wrote:
> Hi
> 
> I am trying to implement v4l2 driver for video decoders. The problem I am
> facing is how to send pause/resume and flush commands from user-space to
> v4l2 driver. I am thinking of using controls for this. Has anyone done
> this before or if anyone has any ideas please let me know. Appreciate your
> help.

Is this a memory-to-memory device, or a live stream decoder ?

-- 
Regards,

Laurent Pinchart