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.