Re: [FFmpeg-devel] [PATCH v1 14/19] avcodec/cbs_sei_syntax_template: add sei message frame_field_information

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

James Almer:
> On 4/25/2025 7:55 PM, Andreas Rheinhardt wrote:
>> James Almer:
>>> On 4/25/2025 7:08 PM, Andreas Rheinhardt wrote:
>>>> toqsxw@gmail.com:
>>>>> From: Wu Jianhua <toqsxw@outlook.com>
>>>>>
>>>>> Signed-off-by: Wu Jianhua <toqsxw@outlook.com>
>>>>> ---
>>>>>    libavcodec/cbs_h2645.c               |  6 ++++++
>>>>>    libavcodec/cbs_sei.h                 | 12 ++++++++++++
>>>>>    libavcodec/cbs_sei_syntax_template.c | 26 ++++++++++++++++++++++
>>>>> ++++
>>>>>    3 files changed, 44 insertions(+)
>>>>>
>>>>> diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
>>>>> index c868770209..6677134d77 100644
>>>>> --- a/libavcodec/cbs_h2645.c
>>>>> +++ b/libavcodec/cbs_h2645.c
>>>>> @@ -2199,6 +2199,12 @@ static const SEIMessageTypeDescriptor
>>>>> cbs_sei_common_types[] = {
>>>>>            sizeof(SEIRawDisplayOrientation),
>>>>>            SEI_MESSAGE_RW(sei, display_orientation)
>>>>>        },
>>>>> +    {
>>>>> +        SEI_TYPE_FRAME_FIELD_INFO,
>>>>> +        1, 0,
>>>>> +        sizeof(SEIRawFrameFieldInformation),
>>>>> +        SEI_MESSAGE_RW(sei, frame_field_information)
>>>>> +    },
>>>>>        SEI_MESSAGE_TYPE_END,
>>>>>    };
>>>>>    diff --git a/libavcodec/cbs_sei.h b/libavcodec/cbs_sei.h
>>>>> index 7be12e33e0..81867b79a7 100644
>>>>> --- a/libavcodec/cbs_sei.h
>>>>> +++ b/libavcodec/cbs_sei.h
>>>>> @@ -125,6 +125,18 @@ typedef struct SEIRawDisplayOrientation {
>>>>>        uint8_t      display_orientation_reserved_zero_3bits;
>>>>>    } SEIRawDisplayOrientation;
>>>>>    +typedef struct SEIRawFrameFieldInformation {
>>>>> +    uint8_t      ffi_field_pic_flag;
>>>>> +    uint8_t      ffi_bottom_field_flag;
>>>>> +    uint8_t      ffi_pairing_indicated_flag;
>>>>> +    uint8_t      ffi_paired_with_next_field_flag;
>>>>> +    uint8_t      ffi_display_fields_from_frame_flag;
>>>>> +    uint8_t      ffi_top_field_first_flag;
>>>>> +    uint8_t      ffi_display_elemental_periods_minus1;
>>>>> +    uint8_t      ffi_source_scan_type;
>>>>> +    uint8_t      ffi_duplicate_flag;
>>>>> +} SEIRawFrameFieldInformation;
>>>>> +
>>>>>    typedef struct SEIRawMessage {
>>>>>        uint32_t     payload_type;
>>>>>        uint32_t     payload_size;
>>>>> diff --git a/libavcodec/cbs_sei_syntax_template.c b/libavcodec/
>>>>> cbs_sei_syntax_template.c
>>>>> index fb19f6ee42..e6863a0fd7 100644
>>>>> --- a/libavcodec/cbs_sei_syntax_template.c
>>>>> +++ b/libavcodec/cbs_sei_syntax_template.c
>>>>> @@ -295,6 +295,32 @@ SEI_FUNC(display_orientation,
>>>>> (CodedBitstreamContext *ctx, RWContext *rw,
>>>>>        return 0;
>>>>>    }
>>>>>    +SEI_FUNC(frame_field_information, (CodedBitstreamContext *ctx,
>>>>> RWContext *rw,
>>>>> +                                       SEIRawFrameFieldInformation
>>>>> *current,
>>>>> +                                       SEIMessageState *state))
>>>>> +{
>>>>> +    int err;
>>>>> +
>>>>> +    HEADER("Frame-field information");
>>>>> +
>>>>> +    flag(ffi_field_pic_flag);
>>>>> +    if (current->ffi_field_pic_flag) {
>>>>> +        flag(ffi_bottom_field_flag);
>>>>> +        flag(ffi_pairing_indicated_flag);
>>>>> +        if (current->ffi_pairing_indicated_flag)
>>>>> +            flag(ffi_paired_with_next_field_flag);
>>>>> +    } else {
>>>>> +        flag(ffi_display_fields_from_frame_flag);
>>>>> +        if (current->ffi_display_fields_from_frame_flag)
>>>>> +            flag(ffi_top_field_first_flag);
>>>>> +        u(8, ffi_display_elemental_periods_minus1, 0, 0xff);
>>>>> +    }
>>>>> +    u(2, ffi_source_scan_type, 0, 3);
>>>>> +    flag(ffi_duplicate_flag);
>>>>> +
>>>>> +    return 0;
>>>>> +}
>>>>> +
>>>>>    static int FUNC(message)(CodedBitstreamContext *ctx, RWContext *rw,
>>>>>                             SEIRawMessage *current)
>>>>>    {
>>>>
>>>> This does really not seem like a common SEI, yet you add it to the
>>>> common ones.
>>>
>>> It's in ITU-T H.274, which is what the common list contains. It's used
>>> as fallback if a SEI type is not a H.26x specific one.
>>>
>>
>> I know and this makes it wrong. It will e.g. be used for H.264 SEI type
>> 168, although this SEI does not exist in H.264 (unless I am mistaken
>> about the last point, but I don't think I am).
> 
> Then maybe ff_cbs_sei_find_type() should not look at
> cbs_sei_common_types for H.264 and H.265, given that those don't
> reference H.274, unlike H.266 which does (while not defining any SEI
> type at all).
> 

Common types just means types that are common to all codecs; it is not
equal to H.274. Instead a new list for H.274 should be added.

- Andreas

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