Re: Re: [PATCH v6 16/17] media: uapi: Change data_bit_offset definition

Jernej Škrabec
2022-06-01T16:17:15Z

Dne nedelja, 29. maj 2022 ob 08:45:57 CEST je Jernej Škrabec napisal(a):
> Dne petek, 27. maj 2022 ob 16:31:33 CEST je Benjamin Gaignard napisal(a):
> > 'F.7.3.6.1 General slice segment header syntax' section of HEVC
> > specification describes that a slice header always end aligned on
> > byte boundary, therefore we only need to provide the data offset in bytes.
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> > ---
> > Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 4 ++--
> > drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 2 +-
> > include/media/hevc-ctrls.h | 4 ++--
> > 3 files changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/
> Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > index 48a8825a001b..37079581c661 100644
> > --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > @@ -3008,8 +3008,8 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
> > - ``bit_size``
> > - Size (in bits) of the current slice data.
> > * - __u32
> > - - ``data_bit_offset``
> > - - Offset (in bits) to the video data in the current slice data.
> > + - ``data_byte_offset``
> > + - Offset (in bytes) to the video data in the current slice data.
> > * - __u32
> > - ``num_entry_point_offsets``
> > - Specifies the number of entry point offset syntax elements in the
> slice header.
> > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/
> staging/media/sunxi/cedrus/cedrus_h265.c
> > index 411601975124..835454239f73 100644
> > --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > @@ -405,7 +405,7 @@ static void cedrus_h265_setup(struct cedrus_ctx *ctx,
> > /* Initialize bitstream access. */
> > cedrus_write(dev, VE_DEC_H265_TRIGGER,
> VE_DEC_H265_TRIGGER_INIT_SWDEC);
> >
> > - cedrus_h265_skip_bits(dev, slice_params->data_bit_offset);
> > + cedrus_h265_skip_bits(dev, slice_params->data_byte_offset * 8);
>
> While it's true that actual data starts on 8-bit aligned address, Cedrus for
> some reason needs offset which points at the end of the header, before
> alignment. There is very simple way to determine that, but unfortunately
this
> means reading source buffer.
>
> In short, above code won't work. I'll provide a fix.

Please include following fix http://ix.io/3Z8x otherwise Cedrus will fail to
decode slice.

Other than fix in previous e-mail and this one, code looks good and I'll be
able to add missing functionality to Cedrus without much trouble in follow up
series.

Best regards,
Jernej

>
> >
> > /* Bitstream parameters. */
> >
> > diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
> > index 9abca1a75bd4..936ff693967b 100644
> > --- a/include/media/hevc-ctrls.h
> > +++ b/include/media/hevc-ctrls.h
> > @@ -312,7 +312,7 @@ struct v4l2_hevc_pred_weight_table {
> > * V4L2_CTRL_FLAG_DYNAMIC_ARRAY flag must be set when using it.
> > *
> > * @bit_size: size (in bits) of the current slice data
> > - * @data_bit_offset: offset (in bits) to the video data in the current
slice
> data
> > + * @data_byte_offset: offset (in bytes) to the video data in the current
> slice data
> > * @num_entry_point_offsets: specifies the number of entry point offset
syntax
> > * elements in the slice header.
> > * @nal_unit_type: specifies the coding type of the slice (B, P or I)
> > @@ -356,7 +356,7 @@ struct v4l2_hevc_pred_weight_table {
> > */
> > struct v4l2_ctrl_hevc_slice_params {
> > __u32 bit_size;
> > - __u32 data_bit_offset;
> > + __u32 data_byte_offset;
> > __u32 num_entry_point_offsets;
> > /* ISO/IEC 23008-2, ITU-T Rec. H.265: NAL unit header */
> > __u8 nal_unit_type;
> > --
> > 2.32.0
> >
> >
>
>
>