On Mon 26 August 2013 01:02:03 Sakari Ailus wrote:
> Some devices such as the uvc produce timestamps at the beginning of the
> frame rather than at the end of it. Add a buffer flag
> (V4L2_BUF_FLAG_TIMESTAMP_SOF) to tell about this.
>
> Also document timestamp_type in struct vb2_queue.
>
> Signed-off-by: Sakari Ailus <[email protected]>
> ---
> Documentation/DocBook/media/v4l/io.xml | 17 ++++++++++++-----
> drivers/media/usb/uvc/uvc_queue.c | 3 ++-
> include/media/videobuf2-core.h | 1 +
> include/uapi/linux/videodev2.h | 10 ++++++++++
> 4 files changed, 25 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/DocBook/media/v4l/io.xml
> b/Documentation/DocBook/media/v4l/io.xml
> index b9a83bc..d3a725c 100644
> --- a/Documentation/DocBook/media/v4l/io.xml
> +++ b/Documentation/DocBook/media/v4l/io.xml
> @@ -654,11 +654,11 @@ plane, are stored in struct
> <structname>v4l2_plane</structname> instead.
> In that case, struct <structname>v4l2_buffer</structname> contains an array
> of
> plane structures.</para>
>
> - <para>On timestamp types that are sampled from the system clock
> -(V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC) it is guaranteed that the timestamp is
> -taken after the complete frame has been received (or transmitted in
> -case of video output devices). For other kinds of
> -timestamps this may vary depending on the driver.</para>
> + <para>The timestamp is taken once the complete frame has been
> +received unless <constant>V4L2_BUF_FLAG_TIMESTAMP_SOF</constant>
received -> received (or transmitted for output devices)
> +buffer flag is set. If <constant>V4L2_BUF_FLAG_TIMESTAMP_SOF</constant>
> +is set, the timestamp is taken when the first pixel of the frame is
> +received.</para>
received -> received (or transmitted)
>
> <table frame="none" pgwide="1" id="v4l2-buffer">
> <title>struct <structname>v4l2_buffer</structname></title>
> @@ -1120,6 +1120,13 @@ in which case caches have not been used.</entry>
> <entry>The CAPTURE buffer timestamp has been taken from the
> corresponding OUTPUT buffer. This flag applies only to mem2mem
> devices.</entry>
> </row>
> + <row>
> + <entry><constant>V4L2_BUF_FLAG_TIMESTAMP_SOF</constant></entry>
> + <entry>0x00010000</entry>
> + <entry>The buffer timestamp has been taken when the first
> + pixel is received. If this flag is not set, the timestamp
> + is taken when the entire frame has been received.</entry>
Ditto: received -> received (or transmitted for output devices)
> + </row>
> </tbody>
> </tgroup>
> </table>
> diff --git a/drivers/media/usb/uvc/uvc_queue.c
> b/drivers/media/usb/uvc/uvc_queue.c
> index cd962be..0d80512 100644
> --- a/drivers/media/usb/uvc/uvc_queue.c
> +++ b/drivers/media/usb/uvc/uvc_queue.c
> @@ -149,7 +149,8 @@ int uvc_queue_init(struct uvc_video_queue *queue, enum
> v4l2_buf_type type,
> queue->queue.buf_struct_size = sizeof(struct uvc_buffer);
> queue->queue.ops = &uvc_queue_qops;
> queue->queue.mem_ops = &vb2_vmalloc_memops;
> - queue->queue.timestamp_type = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> + queue->queue.timestamp_type = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC
> + | V4L2_BUF_FLAG_TIMESTAMP_SOF;
> ret = vb2_queue_init(&queue->queue);
> if (ret)
> return ret;
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 6781258..6eb2d59 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -307,6 +307,7 @@ struct v4l2_fh;
> * @buf_struct_size: size of the driver-specific buffer structure;
> * "0" indicates the driver doesn't want to use a custom buffer
> * structure type, so sizeof(struct vb2_buffer) will is used
> + * @timestamp_type: Type of the timestamp; V4L2_BUF_FLAGS_TIMESTAMP_*
> * @gfp_flags: additional gfp flags used when allocating the buffers.
> * Typically this is 0, but it may be e.g. GFP_DMA or __GFP_DMA32
> * to force the buffer allocation to a specific memory zone.
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 691077d..ca2b4fc 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -695,6 +695,16 @@ struct v4l2_buffer {
> #define V4L2_BUF_FLAG_TIMESTAMP_UNKNOWN 0x00000000
> #define V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC 0x00002000
> #define V4L2_BUF_FLAG_TIMESTAMP_COPY 0x00004000
> +/*
> + * Timestamp taken once the first pixel is received. If the flag is
received -> received (or transmitted for output devices)
> + * not set the buffer timestamp is taken at the end of the frame. This
> + * is not a timestamp type.
> + *
> + * In general drivers should not use this flag if the end-of-frame
> + * timestamps is as good quality as the start-of-frame one; the
> + * V4L2_EVENT_FRAME_SYNC event should be used in that case instead.
> + */
> +#define V4L2_BUF_FLAG_TIMESTAMP_SOF 0x00010000
>
> /**
> * struct v4l2_exportbuffer - export of video buffer as DMABUF file
> descriptor
>
Regards,
Hans
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