Re: [FFmpeg-devel] [PATCH] cbs_h266: add range extension support

[James Almer <jamrial@gmail.com>]

On 7/5/2023 8:38 AM, Nuo Mi wrote:
> From: frankplow <post@frankplowman.com>
> 
> ---
>   libavcodec/cbs_h266.h                 | 18 ++++++
>   libavcodec/cbs_h266_syntax_template.c | 79 +++++++++++++++++++++++++--
>   2 files changed, 93 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/cbs_h266.h b/libavcodec/cbs_h266.h
> index e33d08a0f5..40aba9eb13 100644
> --- a/libavcodec/cbs_h266.h
> +++ b/libavcodec/cbs_h266.h
> @@ -120,6 +120,13 @@ typedef struct H266GeneralConstraintsInfo {
>       uint8_t gci_no_virtual_boundaries_constraint_flag;
>       uint8_t gci_num_reserved_bits;
>       uint8_t gci_reserved_zero_bit[255];
> +
> +    uint8_t gci_all_rap_pictures_constraint_flag;
> +    uint8_t gci_no_extended_precision_processing_constraint_flag;
> +    uint8_t gci_no_ts_residual_coding_rice_constraint_flag;
> +    uint8_t gci_no_rrc_rice_extension_constraint_flag;
> +    uint8_t gci_no_persistent_rice_adaptation_constraint_flag;
> +    uint8_t gci_no_reverse_last_sig_coeff_constraint_flag;
>   } H266GeneralConstraintsInfo;
>   
>   typedef struct H266RawProfileTierLevel {
> @@ -451,6 +458,15 @@ typedef struct H266RawSPS {
>   
>       uint8_t  sps_extension_flag;
>   
> +    uint8_t  sps_range_extension_flag;
> +    uint8_t  sps_extension_7bits;
> +
> +    uint8_t  sps_extended_precision_flag;
> +    uint8_t  sps_ts_residual_coding_rice_present_in_sh_flag;
> +    uint8_t  sps_rrc_rice_extension_flag;
> +    uint8_t  sps_persistent_rice_adaptation_enabled_flag;
> +    uint8_t  sps_reverse_last_sig_coeff_enabled_flag;
> +
>       H266RawExtensionData extension_data;
>   
>   } H266RawSPS;
> @@ -734,6 +750,8 @@ typedef struct  H266RawSliceHeader {
>   
>       uint8_t  sh_sign_data_hiding_used_flag;
>       uint8_t  sh_ts_residual_coding_disabled_flag;
> +    uint8_t  sh_ts_residual_coding_rice_idx_minus1;
> +    uint8_t  sh_reverse_last_sig_coeff_flag;
>       uint16_t sh_slice_header_extension_length;
>       uint8_t  sh_slice_header_extension_data_byte[256];
>   
> diff --git a/libavcodec/cbs_h266_syntax_template.c b/libavcodec/cbs_h266_syntax_template.c
> index 485c02f590..893fa55369 100644
> --- a/libavcodec/cbs_h266_syntax_template.c
> +++ b/libavcodec/cbs_h266_syntax_template.c
> @@ -61,7 +61,7 @@ static int FUNC(general_constraints_info) (CodedBitstreamContext *ctx,
>                                              RWContext *rw,
>                                              H266GeneralConstraintsInfo *current)
>   {
> -    int err, i;
> +    int err, i, num_additional_bits_used;
>   
>       flag(gci_present_flag);
>       if (current->gci_present_flag) {
> @@ -149,7 +149,25 @@ static int FUNC(general_constraints_info) (CodedBitstreamContext *ctx,
>           flag(gci_no_ladf_constraint_flag);
>           flag(gci_no_virtual_boundaries_constraint_flag);
>           ub(8, gci_num_reserved_bits);

This should be renamed to gci_num_additional_bits while at it.

> -        for (i = 0; i < current->gci_num_reserved_bits; i++) {
> +        if (current->gci_num_reserved_bits > 5) {
> +            flag(gci_all_rap_pictures_constraint_flag);
> +            flag(gci_no_extended_precision_processing_constraint_flag);
> +            flag(gci_no_ts_residual_coding_rice_constraint_flag);
> +            flag(gci_no_rrc_rice_extension_constraint_flag);
> +            flag(gci_no_persistent_rice_adaptation_constraint_flag);
> +            flag(gci_no_reverse_last_sig_coeff_constraint_flag);
> +            num_additional_bits_used = 6;
> +        } else {
> +            infer(gci_all_rap_pictures_constraint_flag, 0);
> +            infer(gci_no_extended_precision_processing_constraint_flag, 0);
> +            infer(gci_no_ts_residual_coding_rice_constraint_flag, 0);
> +            infer(gci_no_rrc_rice_extension_constraint_flag, 0);
> +            infer(gci_no_persistent_rice_adaptation_constraint_flag, 0);
> +            infer(gci_no_reverse_last_sig_coeff_constraint_flag, 0);
> +            num_additional_bits_used = 0;
> +        }
> +
> +        for (i = 0; i < current->gci_num_reserved_bits - num_additional_bits_used; i++) {
>               flags(gci_reserved_zero_bit[i], 1, i);
>           }
>       }
> @@ -963,6 +981,23 @@ static int FUNC(vps) (CodedBitstreamContext *ctx, RWContext *rw,
>       return 0;
>   }
>   
> +static int FUNC(sps_range_extension)(CodedBitstreamContext *ctx, RWContext *rw,
> +                                     H266RawSPS *current)
> +{
> +    int err;
> +
> +    flag(sps_extended_precision_flag);
> +    if (current->sps_transform_skip_enabled_flag) {
> +        flag(sps_ts_residual_coding_rice_present_in_sh_flag);
> +    } else {
> +        infer(sps_ts_residual_coding_rice_present_in_sh_flag, 0);
> +    }
> +    flag(sps_rrc_rice_extension_flag);
> +    flag(sps_persistent_rice_adaptation_enabled_flag);
> +    flag(sps_reverse_last_sig_coeff_enabled_flag);
> +
> +    return 0;
> +}
>   
>   static int FUNC(sps)(CodedBitstreamContext *ctx, RWContext *rw,
>                        H266RawSPS *current)
> @@ -1518,9 +1553,33 @@ static int FUNC(sps)(CodedBitstreamContext *ctx, RWContext *rw,
>       } else {
>           CHECK(FUNC(vui_parameters_default) (ctx, rw, &current->vui));
>       }
> +
>       flag(sps_extension_flag);
> -    if (current->sps_extension_flag)
> -        CHECK(FUNC(extension_data) (ctx, rw, &current->extension_data));
> +    if (current->sps_extension_flag) {
> +        flag(sps_range_extension_flag);
> +        ub(7, sps_extension_7bits);
> +
> +        if (current->sps_range_extension_flag) {
> +            CHECK(FUNC(sps_range_extension)(ctx, rw, current));
> +        } else {
> +            infer(sps_extended_precision_flag, 0);
> +            infer(sps_ts_residual_coding_rice_present_in_sh_flag, 0);
> +            infer(sps_rrc_rice_extension_flag, 0);
> +            infer(sps_persistent_rice_adaptation_enabled_flag, 0);
> +            infer(sps_reverse_last_sig_coeff_enabled_flag, 0);
> +        }
> +    } else {
> +        infer(sps_range_extension_flag, 0);
> +        infer(sps_extension_7bits, 0);
> +        infer(sps_extended_precision_flag, 0);
> +        infer(sps_ts_residual_coding_rice_present_in_sh_flag, 0);
> +        infer(sps_rrc_rice_extension_flag, 0);
> +        infer(sps_persistent_rice_adaptation_enabled_flag, 0);
> +        infer(sps_reverse_last_sig_coeff_enabled_flag, 0);
> +    }
> +
> +    if (current->sps_extension_7bits)
> +        CHECK(FUNC(extension_data)(ctx, rw, &current->extension_data));
>   
>       CHECK(FUNC(rbsp_trailing_bits) (ctx, rw));
>   
> @@ -3005,6 +3064,18 @@ static int FUNC(slice_header) (CodedBitstreamContext *ctx, RWContext *rw,
>           flag(sh_ts_residual_coding_disabled_flag);
>       else
>           infer(sh_ts_residual_coding_disabled_flag, 0);
> +
> +    if (!current->sh_ts_residual_coding_disabled_flag &&
> +        sps->sps_ts_residual_coding_rice_present_in_sh_flag)
> +        ub(3, sh_ts_residual_coding_rice_idx_minus1);
> +    else
> +        infer(sh_ts_residual_coding_rice_idx_minus1, 0);
> +
> +    if (sps->sps_reverse_last_sig_coeff_enabled_flag)
> +        flag(sh_reverse_last_sig_coeff_flag);
> +    else
> +        infer(sh_reverse_last_sig_coeff_flag, 0);

Do you know what sample if any in the conformance suite covers this?

> +
>       if (pps->pps_slice_header_extension_present_flag) {
>           ue(sh_slice_header_extension_length, 0, 256);
>           for (i = 0; i < current->sh_slice_header_extension_length; i++)
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