Re: [PATCH 1/2] media: hevc: Remove RPS named flags

[John Cox]

>Le 31/08/2021 à 13:08, John Cox a écrit :
>>> Marking a picture as long-term reference is valid for DPB but not for RPS.
>>> Change flag name to match with it description in HEVC spec chapiter
>>> "8.3.2 Decoding process for reference picture set".
>>> Remove the other unused RPS flags.
>>>
>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
>>> ---
>>> Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 6 ++----
>>> drivers/staging/media/hantro/hantro_g2_hevc_dec.c         | 2 +-
>>> drivers/staging/media/sunxi/cedrus/cedrus_h265.c          | 2 +-
>>> include/media/hevc-ctrls.h                                | 4 +---
>>> 4 files changed, 5 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>>> index 3865acb9e0fd..eff33c511090 100644
>>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>>> @@ -3138,10 +3138,8 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>>> 	:c:type:`timeval` in struct :c:type:`v4l2_buffer` to a __u64.
>>>      * - __u8
>>>        - ``rps``
>>> -      - The reference set for the reference frame
>>> -        (V4L2_HEVC_DPB_ENTRY_RPS_ST_CURR_BEFORE,
>>> -        V4L2_HEVC_DPB_ENTRY_RPS_ST_CURR_AFTER or
>>> -        V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR)
>>> +      - Long term flag for the reference frame
>>> +        (V4L2_HEVC_DPB_ENTRY_LONG_TERM_REFERENCE)
>>>      * - __u8
>>>        - ``field_pic``
>>>        - Whether the reference is a field picture or a frame.
>> If you are going to remove all the RPS values except for Long Term
>> wouldn't it be better to rename the field too, either to "flags" or a
>> bool "is_long_term"?  If we have a field called RPS it really should be
>> able to have a value for any of the 5 valid Reference Picture Sets that
>> a DPB entry can belong to.
>
>I will send a v2 and rename rps into flags.

OK. I was going to say that you should merge the "field_pic" entry into
a flags bitfield, but then I remembered that H265 doesn't have the
concept of field_pics in the way that H264 does and I believe that both
it and pic_order_count[1] are redundant (i.e. can never be used). But I
guess that is the subject of yet another patch.

Regards

John Cox

>> As a side note, it is important to my code that the DPB array contains
>> all the DPB entries not just the ones that are in use in this frame.  I
>> need them so I can track which frames have left the DPB so I can
>> reuse/free the MV tables associated with them (yes I could keep one for
>> every entry in the capture Q but that is generally wasteful on memory
>> and the Pi is often memory constrained). So maybe update the docn on DPB
>> to make this explicit please? (I suspect that current code does this
>> anyway as it is generally easier to do than to not.)
>
>That should be in another patch :-)
>
>Benjamin
>
>>
>> John Cox
>>
>>> diff --git a/drivers/staging/media/hantro/hantro_g2_hevc_dec.c b/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>>> index 9ea864ca5625..be46b3c28b17 100644
>>> --- a/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>>> +++ b/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>>> @@ -503,7 +503,7 @@ static int set_ref(struct hantro_ctx *ctx)
>>> 		compress_luma_addr = luma_addr + compress_luma_offset;
>>> 		compress_chroma_addr = luma_addr + compress_chroma_offset;
>>>
>>> -		if (dpb[i].rps == V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR)
>>> +		if (dpb[i].rps == V4L2_HEVC_DPB_ENTRY_LONG_TERM_REFERENCE)
>>> 			dpb_longterm_e |= BIT(V4L2_HEVC_DPB_ENTRIES_NUM_MAX - 1 - i);
>>>
>>> 		/*
>>> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>>> index ef0311a16d01..6086cc35e8cc 100644
>>> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>>> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>>> @@ -169,7 +169,7 @@ static void cedrus_h265_ref_pic_list_write(struct cedrus_dev *dev,
>>> 		unsigned int index = list[i];
>>> 		u8 value = list[i];
>>>
>>> -		if (dpb[index].rps == V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR)
>>> +		if (dpb[index].rps == V4L2_HEVC_DPB_ENTRY_LONG_TERM_REFERENCE)
>>> 			value |= VE_DEC_H265_SRAM_REF_PIC_LIST_LT_REF;
>>>
>>> 		/* Each SRAM word gathers up to 4 references. */
>>> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
>>> index ef63bc205756..f587448ef495 100644
>>> --- a/include/media/hevc-ctrls.h
>>> +++ b/include/media/hevc-ctrls.h
>>> @@ -127,9 +127,7 @@ struct v4l2_ctrl_hevc_pps {
>>> 	__u64	flags;
>>> };
>>>
>>> -#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_ENTRY_LONG_TERM_REFERENCE	0x01
>>>
>>> #define V4L2_HEVC_DPB_ENTRIES_NUM_MAX		16
>>>