Re: [PATCH v2 05/10] media: v4l: Add definitions for MPEG2 frame format and header metadata

From: Paul Kocialkowski
Date: Fri May 04 2018 - 04:24:30 EST

Hi,

On Fri, 2018-04-20 at 15:57 +0200, Hans Verkuil wrote:
> On 04/19/18 17:45, Paul Kocialkowski wrote:
> > Stateless video decoding engines require both the MPEG slices and
> > associated metadata from the video stream in order to decode frames.
> >
> > This introduces definitions for a new pixel format, describing
> > buffers
> > with MPEG2 slice data, as well as a control structure for passing
> > the
> > frame header (metadata) to drivers.
> >
> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@xxxxxxxxxxx>
> > Signed-off-by: Florent Revest <florent.revest@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/media/v4l2-core/v4l2-ctrls.c | 10 ++++++++++
> > drivers/media/v4l2-core/v4l2-ioctl.c | 1 +
> > include/uapi/linux/v4l2-controls.h | 26
> > ++++++++++++++++++++++++++
> > include/uapi/linux/videodev2.h | 3 +++
> > 4 files changed, 40 insertions(+)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
> > b/drivers/media/v4l2-core/v4l2-ctrls.c
> > index ba05a8b9a095..fcdc12b9a9e0 100644
> > --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> > +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> > @@ -761,6 +761,7 @@ const char *v4l2_ctrl_get_name(u32 id)
> > case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE:
> > return "Vertical MV Search Range";
> > case V4L2_CID_MPEG_VIDEO_REPEAT_SEQ_HEADER:
> > return "Repeat Sequence Header";
> > case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME: re
> > turn "Force Key Frame";
> > + case V4L2_CID_MPEG_VIDEO_MPEG2_FRAME_HDR: re
> > turn "MPEG2 Frame Header";
> >
> > /* VPX controls */
> > case V4L2_CID_MPEG_VIDEO_VPX_NUM_PARTITIONS:
> > return "VPX Number of Partitions";
> > @@ -1152,6 +1153,9 @@ void v4l2_ctrl_fill(u32 id, const char **name,
> > enum v4l2_ctrl_type *type,
> > case V4L2_CID_RDS_TX_ALT_FREQS:
> > *type = V4L2_CTRL_TYPE_U32;
> > break;
> > + case V4L2_CID_MPEG_VIDEO_MPEG2_FRAME_HDR:
> > + *type = V4L2_CTRL_TYPE_MPEG2_FRAME_HDR;
> > + break;
> > default:
> > *type = V4L2_CTRL_TYPE_INTEGER;
> > break;
> > @@ -1472,6 +1476,9 @@ static int std_validate(const struct v4l2_ctrl
> > *ctrl, u32 idx,
> > return -ERANGE;
> > return 0;
> >
> > + case V4L2_CTRL_TYPE_MPEG2_FRAME_HDR:
> > + return 0;
> > +
> > default:
> > return -EINVAL;
> > }
> > @@ -2046,6 +2053,9 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct
> > v4l2_ctrl_handler *hdl,
> > case V4L2_CTRL_TYPE_U32:
> > elem_size = sizeof(u32);
> > break;
> > + case V4L2_CTRL_TYPE_MPEG2_FRAME_HDR:
> > + elem_size = sizeof(struct
> > v4l2_ctrl_mpeg2_frame_hdr);
> > + break;
> > default:
> > if (type < V4L2_CTRL_COMPOUND_TYPES)
> > elem_size = sizeof(s32);
> > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c
> > b/drivers/media/v4l2-core/v4l2-ioctl.c
> > index 468c3c65362d..8070203da5d2 100644
> > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > @@ -1273,6 +1273,7 @@ static void v4l_fill_fmtdesc(struct
> > v4l2_fmtdesc *fmt)
> > case V4L2_PIX_FMT_VC1_ANNEX_L: descr = "VC-1
> > (SMPTE 412M Annex L)"; break;
> > case V4L2_PIX_FMT_VP8: descr =
> > "VP8"; break;
> > case V4L2_PIX_FMT_VP9: descr =
> > "VP9"; break;
> > + case V4L2_PIX_FMT_MPEG2_FRAME: descr =
> > "MPEG2 Frame"; break;
> > case V4L2_PIX_FMT_CPIA1: descr = "GSPCA CPiA
> > YUV"; break;
> > case V4L2_PIX_FMT_WNVA: descr =
> > "WNVA"; break;
> > case V4L2_PIX_FMT_SN9C10X: descr = "GSPCA
> > SN9C10X"; break;
> > diff --git a/include/uapi/linux/v4l2-controls.h
> > b/include/uapi/linux/v4l2-controls.h
> > index cbbb750d87d1..8431b2a540c7 100644
> > --- a/include/uapi/linux/v4l2-controls.h
> > +++ b/include/uapi/linux/v4l2-controls.h
> > @@ -557,6 +557,8 @@ enum v4l2_mpeg_video_mpeg4_profile {
> > };
> > #define V4L2_CID_MPEG_VIDEO_MPEG4_QPEL (V4L2_CID_MPE
> > G_BASE+407)
> >
> > +#define
> > V4L2_CID_MPEG_VIDEO_MPEG2_FRAME_HDR (V4L2_CID_MPEG_BASE+450)
> > +
> > /* Control IDs for VP8 streams
> > * Although VP8 is not part of MPEG we add these controls to the
> > MPEG class
> > * as that class is already handling other video compression
> > standards
> > @@ -985,4 +987,28 @@ enum v4l2_detect_md_mode {
> > #define V4L2_CID_DETECT_MD_THRESHOLD_GRID (V4L2_CID_DETECT_C
> > LASS_BASE + 3)
> > #define V4L2_CID_DETECT_MD_REGION_GRID (V4L2_CID_DET
> > ECT_CLASS_BASE + 4)
> >
> > +struct v4l2_ctrl_mpeg2_frame_hdr {
> > + __u32 slice_len;
> > + __u32 slice_pos;
> > + enum { MPEG1, MPEG2 } type;
> > +
> > + __u16 width;
> > + __u16 height;
> > +
> > + enum { PCT_I = 1, PCT_P, PCT_B, PCT_D }
> > picture_coding_type;
>
> As someone else already mentioned (I believe): avoid enums. Use __u16
> instead.

Indeed. I have taken a note of that.

> > + __u8 f_code[2][2];
> > +
> > + __u8 intra_dc_precision;
> > + __u8 picture_structure;
> > + __u8 top_field_first;
> > + __u8 frame_pred_frame_dct;
> > + __u8 concealment_motion_vectors;
> > + __u8 q_scale_type;
> > + __u8 intra_vlc_format;
> > + __u8 alternate_scan;
> > +
> > + __u8 backward_ref_index;
> > + __u8 forward_ref_index;
> > +};
>
> Please test that the layout and size of this structure is identical
> for 32 and 64 bit
> architectures, both on Intel and ARM.
>
> It looks good, but it doesn't hurt to check.

Right, I'll keep that in mind and make sure this is the case.

Cheers and thanks for the review!

Paul

> Regards,
>
> Hans
>
> > +
> > #endif
> > diff --git a/include/uapi/linux/videodev2.h
> > b/include/uapi/linux/videodev2.h
> > index 31b5728b56e9..4b8336f7bcf0 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -635,6 +635,7 @@ struct v4l2_pix_format {
> > #define V4L2_PIX_FMT_VC1_ANNEX_L v4l2_fourcc('V', 'C', '1', 'L') /*
> > SMPTE 421M Annex L compliant stream */
> > #define V4L2_PIX_FMT_VP8 v4l2_fourcc('V', 'P', '8', '0') /*
> > VP8 */
> > #define V4L2_PIX_FMT_VP9 v4l2_fourcc('V', 'P', '9', '0') /*
> > VP9 */
> > +#define V4L2_PIX_FMT_MPEG2_FRAME v4l2_fourcc('M', 'G', '2', 'F') /*
> > MPEG2 frame */
> >
> > /* Vendor-specific formats */
> > #define V4L2_PIX_FMT_CPIA1 v4l2_fourcc('C', 'P', 'I', 'A') /*
> > cpia1 YUV */
> > @@ -1586,6 +1587,7 @@ struct v4l2_ext_control {
> > __u8 __user *p_u8;
> > __u16 __user *p_u16;
> > __u32 __user *p_u32;
> > + struct v4l2_ctrl_mpeg2_frame_hdr __user
> > *p_mpeg2_frame_hdr;
> > void __user *ptr;
> > };
> > } __attribute__ ((packed));
> > @@ -1631,6 +1633,7 @@ enum v4l2_ctrl_type {
> > V4L2_CTRL_TYPE_U8 = 0x0100,
> > V4L2_CTRL_TYPE_U16 = 0x0101,
> > V4L2_CTRL_TYPE_U32 = 0x0102,
> > + V4L2_CTRL_TYPE_MPEG2_FRAME_HDR = 0x0109,
> > };
> >
> > /* Used in the VIDIOC_QUERYCTRL ioctl for querying controls */
> >
>
>
--
Paul Kocialkowski, Bootlin (formerly Free Electrons)
Embedded Linux and kernel engineering
https://bootlin.com

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