Re: [linux-sunxi] [PATCH v2 1/2] media: v4l: Add definitions for the HEVC slice format and controls

From: Ayaka
Date: Thu Jan 24 2019 - 07:19:23 EST



Sent from my iPad

> On Jan 24, 2019, at 6:36 PM, Paul Kocialkowski <paul.kocialkowski@xxxxxxxxxxx> wrote:
>
> Hi,
>
>> On Tue, 2019-01-08 at 18:00 +0800, Ayaka wrote:
>>
>> Sent from my iPad
>>
>>> On Jan 8, 2019, at 4:38 PM, Paul Kocialkowski <paul.kocialkowski@xxxxxxxxxxx> 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@xxxxxxxxxxx> 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 Åkrabec 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.
>
> I'm not sure what you meant here, sorry.
As we talked in IRC, I am not sure the field coded picture is supported in HEVC.
And I donât why there would be two pic order cnt, a picture can only be used a short term or a long term reference at one picture decoding
>
>>>>>> 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.
>
> Right, the driver will allocate chunks of memory for the decoding
> metadata used by the hardware decoder.
>
> Well, I don't think V4L2 has any mechanism to expose this data for now
> and since it's very specific to the hardware implementation, I guess
> the interest in having that is generally pretty low.
>
> That's maybe something that could be added later if someone wants to
> work on it, but I think we are better off keeping this metadata hidden
> by the driver for now.
I am writing a V4l2 driver for rockchip based on the previous vendor driver I sent to mail list. I think I would offer a better way to describe the meta after that. But it need both work in derives and userspace, it would cost some times.
>
>>>>>>>>> +
>>>>>>>>> +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
>>>
> --
> Paul Kocialkowski, Bootlin
> Embedded Linux and kernel engineering
> https://bootlin.com
>