>Le 26/08/2021 à 18:09, Nicolas Dufresne a écrit : >> Le lundi 23 août 2021 à 12:35 +0100, John Cox a écrit : >>> Hi >>> >>>> Le 23/08/2021 à 11:50, John Cox a écrit : >>>>>> The lists embedded Picture Order Count values which are s32 so their type >>>>>> most be s32 and not u8. >>>>> I'm not convinced that you can't calculate all of those lists from the >>>>> info already contained in the DPB array so this is probably redundant >>>>> info though I grant that having the list pre-calced might make your life >>>>> easier, and the userland side will have calculated the lists to >>>>> calculate other required things so it isn't much extra work for it. >>>> Yes the userland have already compute these lists and the number of items >>>> in each of them. >>>> Build them in the kernel would means to also compute the values of NumPocStCurrBefore, >>>> NumPocStCurrAfter, NumPocLtCurr, NumPocStCurrAfter, NumPocStCurrBefore and NumPocLtCurr >>>> and that requires information (NumNegativePics, NumPositivePics...) not provided to the kernel. >>>> Since it have to be done in userland anyway, I'm reluctant to modify the API to redo in the kernel. >>> Well, fair enough, I'm not going to argue >>> >>>>> Even if you do need the lists wouldn't it be a better idea to have them >>>>> as indices into the DPB (you can't have a frame in any of those lists >>>>> that isn't in the DPB) which already contains POCs then it will still >>>>> fit into u8 and be smaller? >>>> Hantro HW works with indexes but I think it is more simple to send PoC rather than indexes. >>> I'd disagree but as I don't use the info I'm not concerned. Though I >>> think I should point out that when Hantro converts the POCs to indicies >>> it compares the now s32 POC in these lists with the u16 POC in the DPB >>> so you might need to fix that too; by std (8.3.1) no POC diff can be >>> outside s16 so you can mask & compare or use u16 POCs in the lists or >>> s32 in the DPB. >> Fun fact, my interpretation with the API when I drafted GStreamer support was >> that it was DPB indexes: >> >> https://gitlab.freedesktop.org/ndufresne/gst-plugins-bad/-/blob/hevc_wip/sys/v4l2codecs/gstv4l2codech265dec.c#L850 >> >> It felt quite natural to be, since this is also how we pass references for l0/l1 >> (unused by hantro I guess). >> >> Looking at old rkvdec code as a refresher: >> >> for (j = 0; j < run->num_slices; j++) { >> sl_params = &run->slices_params[j]; >> dpb = sl_params->dpb; >> >> hw_ps = &priv_tbl->rps[j]; >> memset(hw_ps, 0, sizeof(*hw_ps)); >> >> for (i = 0; i <= sl_params->num_ref_idx_l0_active_minus1; i++) { >> WRITE_RPS(!!(dpb[sl_params->ref_idx_l0[i]].rps == V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR), >> REF_PIC_LONG_TERM_L0(i)); >> WRITE_RPS(sl_params->ref_idx_l0[i], REF_PIC_IDX_L0(i)); >> } >> >> for (i = 0; i <= sl_params->num_ref_idx_l1_active_minus1; i++) { >> WRITE_RPS(!!(dpb[sl_params->ref_idx_l1[i]].rps == V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR), >> REF_PIC_LONG_TERM_L1(i)); >> WRITE_RPS(sl_params->ref_idx_l1[i], REF_PIC_IDX_L1(i)); >> } >> >> >> This is code is clearly unsafe, but now I remember that dpb_entry has a flag >> "rps". So we know from the DPB in which of the list the reference lives, if any. >> In the case of RKVDEC the HW only cares to know if this is long term or not. >> >> So without looking at the spec, is that dpb represention enough to reconstruct >> these array ? If we pass these array, shall we keep the rps flag ? I think a >> little step back and cleanup will be needed. I doubt there is a single answer, >> perhaps list what others do (VA, DXVA, NVDEC, Khronos, etc) and we can >> collectively decide were we want V4L2 to sit ? > >I have done some tests with Hantro driver and look at the spec, the order of the PoC >in the reference lists matters. You can deducted the order for DPB rps flags. >I would suggest to remove rps flags to avoid information duplication. I want the DPB rps member for long term reference marking. I don't care about before / after, but LTR can't be deduced from PoC and if you are going to keep the member you might as well keep before / after. John Cox >Benjamin > >> >>> Regards >>> >>> John Cox >>> >>>> Benjamin >>>> >>>>> Full disclosure: Pi decode doesn't use this info at all so I'm only >>>>> arguing from a theoretical point of view - I think it is only relevant >>>>> if your h/w is parsing the reference list setups. >>>>> >>>>> Regards >>>>> >>>>> John Cox >>>>> >>>>>> Reported-by: John Cox <jc@xxxxxxxxxxxxx> >>>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx> >>>>>> --- >>>>>> Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 6 +++--- >>>>>> include/media/hevc-ctrls.h | 6 +++--- >>>>>> 2 files changed, 6 insertions(+), 6 deletions(-) >>>>>> >>>>>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst >>>>>> index 976d34445a24..db9859ddc8b2 100644 >>>>>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst >>>>>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst >>>>>> @@ -3323,15 +3323,15 @@ enum v4l2_mpeg_video_hevc_size_of_length_field - >>>>>> * - __u8 >>>>>> - ``num_poc_lt_curr`` >>>>>> - The number of reference pictures in the long-term set. >>>>>> - * - __u8 >>>>>> + * - __s32 >>>>>> - ``poc_st_curr_before[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]`` >>>>>> - PocStCurrBefore as described in section 8.3.2 "Decoding process for reference >>>>>> picture set. >>>>>> - * - __u8 >>>>>> + * - __s32 >>>>>> - ``poc_st_curr_after[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]`` >>>>>> - PocStCurrAfter as described in section 8.3.2 "Decoding process for reference >>>>>> picture set. >>>>>> - * - __u8 >>>>>> + * - __s32 >>>>>> - ``poc_lt_curr[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]`` >>>>>> - PocLtCurr as described in section 8.3.2 "Decoding process for reference >>>>>> picture set. >>>>>> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h >>>>>> index 781371bff2ad..04cd62e77f25 100644 >>>>>> --- a/include/media/hevc-ctrls.h >>>>>> +++ b/include/media/hevc-ctrls.h >>>>>> @@ -219,9 +219,9 @@ struct v4l2_ctrl_hevc_decode_params { >>>>>> __u8 num_poc_st_curr_before; >>>>>> __u8 num_poc_st_curr_after; >>>>>> __u8 num_poc_lt_curr; >>>>>> - __u8 poc_st_curr_before[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]; >>>>>> - __u8 poc_st_curr_after[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]; >>>>>> - __u8 poc_lt_curr[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]; >>>>>> + __s32 poc_st_curr_before[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]; >>>>>> + __s32 poc_st_curr_after[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]; >>>>>> + __s32 poc_lt_curr[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]; >>>>>> __u64 flags; >>>>>> }; >>>>>> >>
