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

Benjamin Gaignard
2022-06-01T16:33:27Z

Le 01/06/2022 à 18:17, Jernej Škrabec a écrit :
> 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.

Thanks for the patch it will be in version 7.

Regards,
Benjamin

>
> 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
>>>
>>>
>>
>>
>