Hi Sakari,
On Tuesday 26 July 2011 20:49:43 Sakari Ailus wrote:
> Define a frame start event to tell user space when the reception of a frame
> starts.
You might want to rename 'frame start' to 'frame sync' in the subject and
commit message as well.
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxx>
> ---
> Documentation/DocBook/media/v4l/vidioc-dqevent.xml | 23
> ++++++++++++++++++++ .../DocBook/media/v4l/vidioc-subscribe-event.xml |
> 18 +++++++++++++++ include/linux/videodev2.h |
> 12 +++++++-- 3 files changed, 50 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/DocBook/media/v4l/vidioc-dqevent.xml
> b/Documentation/DocBook/media/v4l/vidioc-dqevent.xml index
> 5200b68..1d03313 100644
> --- a/Documentation/DocBook/media/v4l/vidioc-dqevent.xml
> +++ b/Documentation/DocBook/media/v4l/vidioc-dqevent.xml
> @@ -88,6 +88,12 @@
> </row>
> <row>
> <entry></entry>
> + <entry>&v4l2-event-frame-sync;</entry>
> + <entry><structfield>frame</structfield></entry>
> + <entry>Event data for event V4L2_EVENT_FRAME_SYNC.</entry>
> + </row>
> + <row>
> + <entry></entry>
> <entry>__u8</entry>
> <entry><structfield>data</structfield>[64]</entry>
> <entry>Event data. Defined by the event type. The union
> @@ -220,6 +226,23 @@
> </tgroup>
> </table>
>
> + <table frame="none" pgwide="1" id="v4l2-event-frame-sync">
> + <title>struct <structname>v4l2_event_frame_sync</structname></title>
> + <tgroup cols="3">
> + &cs-str;
> + <tbody valign="top">
> + <row>
> + <entry>__u32</entry>
> + <entry><structfield>buffer_sequence</structfield></entry>
> + <entry>
> + The sequence number of the buffer to be handled next or
> + currently handled by the driver.
What happens if a particular piece of hardware can capture two (or more)
simultaneous streams from the same video source (an unscaled compressed stream
and a scaled down uncompressed stream for instance) ? Applications don't need
to start both streams at the same time, what buffer sequence number should be
reported in that case ?
> + </entry>
> + </row>
> + </tbody>
> + </tgroup>
> + </table>
> +
> <table pgwide="1" frame="none" id="changes-flags">
> <title>Changes</title>
> <tgroup cols="3">
> diff --git a/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
> b/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml index
> 275be96..812b63c 100644
> --- a/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
> +++ b/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
> @@ -139,6 +139,24 @@
> </entry>
> </row>
> <row>
> + <entry><constant>V4L2_EVENT_FRAME_SYNC</constant></entry>
> + <entry>4</entry>
> + <entry>
> + <para>Triggered immediately when the reception of a
> + frame has begun. This event has a
> + &v4l2-event-frame-sync; associated with it.</para>
> +
> + <para>A driver will only generate this event when the
> + hardware can generate it. This might not be the case
> + e.g. when the hardware has no DMA buffer to write the
> + image data to. In such cases the
> + <structfield>buffer_sequence</structfield> field in
> + &v4l2-event-frame-sync; will not be incremented either.
> + This causes two consecutive buffer sequence numbers to
> + have n times frame interval in between them.</para>
I don't think that's correct. Don't many drivers still increment the sequence
number in that case, to make it possible for applications to detect frame loss
?
> + </entry>
> + </row>
> + <row>
> <entry><constant>V4L2_EVENT_PRIVATE_START</constant></entry>
> <entry>0x08000000</entry>
> <entry>Base event number for driver-private events.</entry>
> diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> index fca24cc..056a49e 100644
> --- a/include/linux/videodev2.h
> +++ b/include/linux/videodev2.h
> @@ -2006,6 +2006,7 @@ struct v4l2_streamparm {
> #define V4L2_EVENT_VSYNC 1
> #define V4L2_EVENT_EOS 2
> #define V4L2_EVENT_CTRL 3
> +#define V4L2_EVENT_FRAME_SYNC 4
> #define V4L2_EVENT_PRIVATE_START 0x08000000
>
> /* Payload for V4L2_EVENT_VSYNC */
> @@ -2032,12 +2033,17 @@ struct v4l2_event_ctrl {
> __s32 default_value;
> };
>
> +struct v4l2_event_frame_sync {
> + __u32 buffer_sequence;
> +};
> +
> struct v4l2_event {
> __u32 type;
> union {
> - struct v4l2_event_vsync vsync;
> - struct v4l2_event_ctrl ctrl;
> - __u8 data[64];
> + struct v4l2_event_vsync vsync;
> + struct v4l2_event_ctrl ctrl;
> + struct v4l2_event_frame_sync frame_sync;
> + __u8 data[64];
> } u;
> __u32 pending;
> __u32 sequence;
--
Regards,
Laurent Pinchart
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