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Subject: Re: [linux-sunxi] [PATCH v2 1/2] media: v4l: Add definitions for the
 HEVC slice format and controls
From:   ayaka <ayaka@soulik.info>
To:     Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Cc:     Randy Li <randy.li@rock-chips.com>,
        =?UTF-8?Q?Jernej_=c5=a0krabec?= <jernej.skrabec@gmail.com>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        devel@driverdev.osuosl.org, linux-arm-kernel@lists.infradead.org,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Hans Verkuil <hverkuil@xs4all.nl>,
        Ezequiel Garcia <ezequiel@collabora.com>,
        Tomasz Figa <tfiga@chromium.org>,
        Alexandre Courbot <acourbot@chromium.org>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        linux-rockchip@lists.infradead.org
References: <20181123130209.11696-1-paul.kocialkowski@bootlin.com>
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 <5515174.7lFZcYkk85@jernej-laptop>
 <ffe9c81db34b599f675ca5bbf02de360bf0a1608.camel@bootlin.com>
 <776e63c9-d4a5-342a-e0f7-200ef144ffc4@rock-chips.com>
 <64c793e08d61181b78125b3956ec38623fa5d261.camel@bootlin.com>
 <D8005130-F7FD-4CBD-8396-1BB08BB08E81@soulik.info>
 <f982ef378a8ade075bc7077b93640e20ecebf9f4.camel@bootlin.com>
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Date:   Thu, 10 Jan 2019 21:32:35 +0800
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I forget a important thing, for the rkvdec and rk hevc decoder, it would 
requests cabac table, scaling list, picture parameter set and reference 
picture storing in one or various of DMA buffers. I am not talking about 
the data been parsed, the decoder would requests a raw data.

For the pps and rps, it is possible to reuse the slice header, just let 
the decoder know the offset from the bitstream bufer, I would suggest to 
add three properties(with sps) for them. But I think we need a method to 
mark a OUTPUT side buffer for those aux data.

On 1/8/19 6:00 PM, Ayaka wrote:
>
> Sent from my iPad
>
>> On Jan 8, 2019, at 4:38 PM, Paul Kocialkowski <paul.kocialkowski@bootlin.com> wrote:
>>
>> Hi,
>>
>>> On Tue, 2019-01-08 at 09:16 +0800, Ayaka wrote:
>>>
>>> Sent from my iPad
>>>
>>>> On Jan 7, 2019, at 5:57 PM, Paul Kocialkowski <paul.kocialkowski@bootlin.com> wrote:
>>>>
>>>> Hi,
>>>>
>>>>>> On Mon, 2019-01-07 at 11:49 +0800, Randy Li wrote:
>>>>>> On 12/12/18 8:51 PM, Paul Kocialkowski wrote:
>>>>>> Hi,
>>>>>>
>>>>>> On Wed, 2018-12-05 at 21:59 +0100, Jernej Škrabec wrote:
>>>>>>
>>>>>>>> +
>>>>>>>> +#define V4L2_HEVC_DPB_ENTRY_RPS_ST_CURR_BEFORE    0x01
>>>>>>>> +#define V4L2_HEVC_DPB_ENTRY_RPS_ST_CURR_AFTER    0x02
>>>>>>>> +#define V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR        0x03
>>>>>>>> +
>>>>>>>> +#define V4L2_HEVC_DPB_ENTRIES_NUM_MAX        16
>>>>>>>> +
>>>>>>>> +struct v4l2_hevc_dpb_entry {
>>>>>>>> +    __u32    buffer_tag;
>>>>>>>> +    __u8    rps;
>>>>>>>> +    __u8    field_pic;
>>>>>>>> +    __u16    pic_order_cnt[2];
>>>>>>>> +};
>>>>> Please add a property for reference index, if that rps is not used for
>>>>> this, some device would request that(not the rockchip one). And
>>>>> Rockchip's VDPU1 and VDPU2 for AVC would request a similar property.
>>>> What exactly is that reference index? Is it a bitstream element or
>>>> something deduced from the bitstream?
>>>>
>>> picture order count(POC) for HEVC and frame_num in AVC. I think it is
>>> the number used in list0(P slice and B slice) and list1(B slice).
>> The picture order count is already the last field of the DPB entry
>> structure. There is one for each field picture.
> As we are not sure whether there is a field coded slice or CTU, I would hold this part and else about the field.
>>>>> Adding another buffer_tag for referring the memory of the motion vectors
>>>>> for each frames. Or a better method is add a meta data to echo picture
>>>>> buffer,  since the picture output is just the same as the original,
>>>>> display won't care whether the motion vectors are written the button of
>>>>> picture or somewhere else.
>>>> The motion vectors are passed as part of the raw bitstream data, in the
>>>> slices. Is there a case where the motion vectors are coded differently?
>>> No, it is an additional cache for decoder, even FFmpeg having such
>>> data, I think allwinner must output it into somewhere.
>> Ah yes I see what you mean! This is handled internally by our driver
>> and not exposed to userspace. I don't think it would be a good idea to
>> expose this cache or request that userspace allocates it like a video
>> buffer.
>>
> No, usually the driver should allocate, as the user space have no idea on size of each devices.
> But for advantage user, application can fix a broken picture with a proper data or analysis a object motion from that.
> So I would suggest attaching this information to a picture buffer as a meta data.
>>>>>>>> +
>>>>>>>> +struct v4l2_hevc_pred_weight_table {
>>>>>>>> +    __u8    luma_log2_weight_denom;
>>>>>>>> +    __s8    delta_chroma_log2_weight_denom;
>>>>>>>> +
>>>>>>>> +    __s8    delta_luma_weight_l0[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>>>>>>>> +    __s8    luma_offset_l0[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>>>>>>>> +    __s8    delta_chroma_weight_l0[V4L2_HEVC_DPB_ENTRIES_NUM_MAX][2];
>>>>>>>> +    __s8    chroma_offset_l0[V4L2_HEVC_DPB_ENTRIES_NUM_MAX][2];
>>>>>>>> +
>>>>>>>> +    __s8    delta_luma_weight_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>>>>>>>> +    __s8    luma_offset_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>>>>>>>> +    __s8    delta_chroma_weight_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX][2];
>>>>>>>> +    __s8    chroma_offset_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX][2];
>>>>>>>> +};
>>>>>>>> +
>>>>> Those properties I think are not necessary are applying for the
>>>>> Rockchip's device, may not work for the others.
>>>> Yes, it's possible that some of the elements are not necessary for some
>>>> decoders. What we want is to cover all the elements that might be
>>>> required for a decoder.
>>> I wonder whether allwinner need that, those sao flag usually ignored
>>> by decoder in design. But more is better than less, it is hard to
>>> extend a v4l2 structure  in the future, maybe a new HEVC profile
>>> would bring a new property, it is still too early for HEVC.
>> Yes this is used by our decoder. The idea is to have all the basic
>> bitstream elements in the structures (even if some decoders don't use
>> them all) and add others for extension as separate controls later.
>>
>>>>>>>> +struct v4l2_ctrl_hevc_slice_params {
>>>>>>>> +    __u32    bit_size;
>>>>>>>> +    __u32    data_bit_offset;
>>>>>>>> +
>>>>>>>> +    /* ISO/IEC 23008-2, ITU-T Rec. H.265: NAL unit header */
>>>>>>>> +    __u8    nal_unit_type;
>>>>>>>> +    __u8    nuh_temporal_id_plus1;
>>>>>>>> +
>>>>>>>> +    /* ISO/IEC 23008-2, ITU-T Rec. H.265: General slice segment header */
>>>>>>>> +    __u8    slice_type;
>>>>>>>> +    __u8    colour_plane_id;
>>>>> ----------------------------------------------------------------------------
>>>>>>>> +    __u16    slice_pic_order_cnt;
>>>>>>>> +    __u8    slice_sao_luma_flag;
>>>>>>>> +    __u8    slice_sao_chroma_flag;
>>>>>>>> +    __u8    slice_temporal_mvp_enabled_flag;
>>>>>>>> +    __u8    num_ref_idx_l0_active_minus1;
>>>>>>>> +    __u8    num_ref_idx_l1_active_minus1;
>>>>> Rockchip's decoder doesn't use this part.
>>>>>>>> +    __u8    mvd_l1_zero_flag;
>>>>>>>> +    __u8    cabac_init_flag;
>>>>>>>> +    __u8    collocated_from_l0_flag;
>>>>>>>> +    __u8    collocated_ref_idx;
>>>>>>>> +    __u8    five_minus_max_num_merge_cand;
>>>>>>>> +    __u8    use_integer_mv_flag;
>>>>>>>> +    __s8    slice_qp_delta;
>>>>>>>> +    __s8    slice_cb_qp_offset;
>>>>>>>> +    __s8    slice_cr_qp_offset;
>>>>>>>> +    __s8    slice_act_y_qp_offset;
>>>>>>>> +    __s8    slice_act_cb_qp_offset;
>>>>>>>> +    __s8    slice_act_cr_qp_offset;
>>>>>>>> +    __u8    slice_deblocking_filter_disabled_flag;
>>>>>>>> +    __s8    slice_beta_offset_div2;
>>>>>>>> +    __s8    slice_tc_offset_div2;
>>>>>>>> +    __u8    slice_loop_filter_across_slices_enabled_flag;
>>>>>>>> +
>>>>>>>> +    /* ISO/IEC 23008-2, ITU-T Rec. H.265: Picture timing SEI message */
>>>>>>>> +    __u8    pic_struct;
>>>>> I think the decoder doesn't care about this, it is used for display.
>>>> The purpose of this field is to indicate whether the current picture is
>>>> a progressive frame or an interlaced field picture, which is useful for
>>>> decoding.
>>>>
>>>> At least our decoder has a register field to indicate frame/top
>>>> field/bottom field, so we certainly need to keep the info around.
>>>> Looking at the spec and the ffmpeg implementation, it looks like this
>>>> flag of the bitstream is the usual way to report field coding.
>>> It depends whether the decoder cares about scan type or more, I
>>> wonder prefer general_interlaced_source_flag for just scan type, it
>>> would be better than reading another SEL.
>> Well we still need a way to indicate if the current data is top or
>> bottom field for interlaced. I don't think that knowing that the whole
>> video is interlaced would be precise enough.
>>
>> Cheers,
>>
>> Paul
>>
>>>>>>>> +
>>>>>>>> +    /* ISO/IEC 23008-2, ITU-T Rec. H.265: General slice segment header */
>>>>>>>> +    struct v4l2_hevc_dpb_entry dpb[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>>>>>>>> +    __u8    num_active_dpb_entries;
>>>>>>>> +    __u8    ref_idx_l0[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>>>>>>>> +    __u8    ref_idx_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>>>>>>>> +
>>>>>>>> +    __u8    num_rps_poc_st_curr_before;
>>>>>>>> +    __u8    num_rps_poc_st_curr_after;
>>>>>>>> +    __u8    num_rps_poc_lt_curr;
>>>>>>>> +
>>>>>>>> +    /* ISO/IEC 23008-2, ITU-T Rec. H.265: Weighted prediction parameter */
>>>>>>>> +    struct v4l2_hevc_pred_weight_table pred_weight_table;
>>>>>>>> +};
>>>>>>>> +
>>>>>>>> #endif
>>>> -- 
>>>> Paul Kocialkowski, Bootlin (formerly Free Electrons)
>>>> Embedded Linux and kernel engineering
>>>> https://bootlin.com
>>>>
>> -- 
>> Paul Kocialkowski, Bootlin (formerly Free Electrons)
>> Embedded Linux and kernel engineering
>> https://bootlin.com
>>