[FFmpeg-devel] [PATCH 1/2] avformat/hevc: add support for writing alpha layer
James Almer
jamrial at gmail.com
Tue Dec 10 21:21:58 EET 2024
On 12/10/2024 4:16 PM, Timo Rothenpieler wrote:
> ---
> libavformat/hevc.c | 138 ++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 123 insertions(+), 15 deletions(-)
>
> diff --git a/libavformat/hevc.c b/libavformat/hevc.c
> index 7cf0b0ffb2..50e7f91bd2 100644
> --- a/libavformat/hevc.c
> +++ b/libavformat/hevc.c
> @@ -82,6 +82,8 @@ typedef struct HEVCDecoderConfigurationRecord {
> uint8_t lengthSizeMinusOne;
> uint8_t numOfArrays;
> HVCCNALUnitArray arrays[NB_ARRAYS];
> +
> + uint8_t alpha_layer_nuh_id;
> } HEVCDecoderConfigurationRecord;
>
> typedef struct HVCCProfileTierLevel {
> @@ -149,6 +151,7 @@ static void hvcc_update_ptl(HEVCDecoderConfigurationRecord *hvcc,
>
> static void hvcc_parse_ptl(GetBitContext *gb,
> HEVCDecoderConfigurationRecord *hvcc,
> + int profile_present_flag,
> unsigned int max_sub_layers_minus1)
> {
> unsigned int i;
> @@ -156,13 +159,17 @@ static void hvcc_parse_ptl(GetBitContext *gb,
> uint8_t sub_layer_profile_present_flag[HEVC_MAX_SUB_LAYERS];
> uint8_t sub_layer_level_present_flag[HEVC_MAX_SUB_LAYERS];
>
> - general_ptl.profile_space = get_bits(gb, 2);
> - general_ptl.tier_flag = get_bits1(gb);
> - general_ptl.profile_idc = get_bits(gb, 5);
> - general_ptl.profile_compatibility_flags = get_bits_long(gb, 32);
> - general_ptl.constraint_indicator_flags = get_bits64(gb, 48);
> - general_ptl.level_idc = get_bits(gb, 8);
> - hvcc_update_ptl(hvcc, &general_ptl);
> + if (profile_present_flag) {
> + general_ptl.profile_space = get_bits(gb, 2);
> + general_ptl.tier_flag = get_bits1(gb);
> + general_ptl.profile_idc = get_bits(gb, 5);
> + general_ptl.profile_compatibility_flags = get_bits_long(gb, 32);
> + general_ptl.constraint_indicator_flags = get_bits64(gb, 48);
> + general_ptl.level_idc = get_bits(gb, 8);
> + hvcc_update_ptl(hvcc, &general_ptl);
> + } else {
Nit: unnecesary brackets.
> + skip_bits(gb, 8); // general_level_idc
> + }
>
> for (i = 0; i < max_sub_layers_minus1; i++) {
> sub_layer_profile_present_flag[i] = get_bits1(gb);
> @@ -387,12 +394,16 @@ static void skip_sub_layer_ordering_info(GetBitContext *gb)
> static int hvcc_parse_vps(GetBitContext *gb, HVCCNALUnit *nal,
> HEVCDecoderConfigurationRecord *hvcc)
> {
> + uint8_t vps_base_layer_internal_flag, vps_max_layers_minus1;
> + uint8_t vps_sub_layer_ordering_info_present_flag, vps_max_layer_id;
> + int vps_num_layer_sets_minus1;
> + int i, j;
> +
> nal->parameter_set_id = get_bits(gb, 4);
> - /*
> - * vps_reserved_three_2bits u(2)
> - * vps_max_layers_minus1 u(6)
> - */
> - skip_bits(gb, 8);
> +
> + vps_base_layer_internal_flag = get_bits(gb, 1);
> + skip_bits(gb, 1); // vps_base_layer_available_flag
> + vps_max_layers_minus1 = get_bits(gb, 6);
>
> nal->vps_max_sub_layers_minus1 = get_bits(gb, 3);
>
> @@ -413,7 +424,104 @@ static int hvcc_parse_vps(GetBitContext *gb, HVCCNALUnit *nal,
> */
> skip_bits(gb, 17);
>
> - hvcc_parse_ptl(gb, hvcc, nal->vps_max_sub_layers_minus1);
> + hvcc_parse_ptl(gb, hvcc, 1, nal->vps_max_sub_layers_minus1);
> +
> + vps_sub_layer_ordering_info_present_flag = get_bits(gb, 1);
> + for (i = (vps_sub_layer_ordering_info_present_flag ? 0 : nal->vps_max_sub_layers_minus1);
> + i <= nal->vps_max_sub_layers_minus1; i++) {
> + get_ue_golomb(gb); // vps_max_dec_pic_buffering_minus1
> + get_ue_golomb(gb); // vps_max_num_reorder_pics
> + get_ue_golomb(gb); // vps_max_latency_increase_plus1
> + }
> +
> + vps_max_layer_id = get_bits(gb, 6);
> + vps_num_layer_sets_minus1 = get_ue_golomb(gb);
> + skip_bits_long(gb, (vps_max_layer_id + 1) * vps_num_layer_sets_minus1); // layer_id_included_flag[i][j]
> +
> + if (get_bits(gb, 1)) { // vps_timing_info_present_flag
> + int vps_num_hrd_parameters;
> +
> + skip_bits_long(gb, 64); // vps_num_units_in_tick, vps_time_scale
> +
> + if (get_bits(gb, 1)) // vps_poc_proportional_to_timing_flag
> + get_ue_golomb(gb); // vps_num_ticks_poc_diff_one_minus1
> +
> + vps_num_hrd_parameters = get_ue_golomb(gb); // vps_num_hrd_parameters
> +
> + for (i = 0; i < vps_num_hrd_parameters; i++) {
> + int cprms_present_flag;
> +
> + get_ue_golomb(gb); // hrd_layer_set_idx[i]
> + if (i > 0)
> + cprms_present_flag = get_bits(gb, 1);
> + else
> + cprms_present_flag = 1;
> +
> + skip_hrd_parameters(gb, cprms_present_flag, nal->vps_max_sub_layers_minus1);
> + }
> + }
> +
> + if (get_bits(gb, 1)) { // vps_extension_flag
Maybe move this to its own function, following the syntax in the spec.
> + uint8_t num_scalability_types = 0;
> + uint8_t max_layers_minus_1 = FFMIN(62, vps_max_layers_minus1);
> + uint8_t splitting_flag, vps_nuh_layer_id_present_flag;
> + uint8_t scalability_mask_flag[16] = { 0 };
> + uint8_t dimension_id_len[16] = { 0 };
> + uint8_t layer_id_in_nuh[64] = { 0 };
> +
> + align_get_bits(gb);
> +
> + if (vps_max_layers_minus1 > 0 && vps_base_layer_internal_flag)
> + hvcc_parse_ptl(gb, hvcc, 0, nal->vps_max_sub_layers_minus1);
> +
> + splitting_flag = get_bits(gb, 1);
> +
> + for (i = 0; i < 16; i++)
> + if (get_bits(gb, 1))
> + scalability_mask_flag[num_scalability_types++] = i;
> +
> + for (j = 0; j < (num_scalability_types - splitting_flag); j++)
> + dimension_id_len[j] = get_bits(gb, 3) + 1;
> +
> + vps_nuh_layer_id_present_flag = get_bits(gb, 1);
> +
> + for (i = 1; i <= max_layers_minus_1; i++) {
> + if (vps_nuh_layer_id_present_flag)
> + layer_id_in_nuh[i] = get_bits(gb, 6);
> + else
> + layer_id_in_nuh[i] = i;
> +
> + if (!splitting_flag) {
> + for (j = 0; j < num_scalability_types; j++) {
> + int dimension_id = get_bits(gb, dimension_id_len[j]);
> +
> + if (dimension_id == 1 /* AUX_ALPHA */ && scalability_mask_flag[j] == 3 /* AuxId */)
> + hvcc->alpha_layer_nuh_id = layer_id_in_nuh[i];
> + }
> + }
> + }
> +
> + if (splitting_flag) {
> + uint8_t dim_bit_offset[17] = { 0 };
> +
> + dim_bit_offset[0] = 0;
> + for (j = 1; j < num_scalability_types; j++)
> + dim_bit_offset[j] = dim_bit_offset[j-1] + dimension_id_len[j-1];
> + dim_bit_offset[num_scalability_types] = 6;
> +
> + if (num_scalability_types > 0 && dim_bit_offset[num_scalability_types - 1] >= 6)
> + return 0; // invalid bitstream
> +
> + for (i = 1; i <= max_layers_minus_1; i++) {
> + for (j = 0; j < num_scalability_types; j++) {
> + int dimension_id = (layer_id_in_nuh[i] & ((1 << dim_bit_offset[j+1]) - 1)) >> dim_bit_offset[j];
> +
> + if (dimension_id == 1 /* AUX_ALPHA */ && scalability_mask_flag[j] == 3 /* AuxId */)
> + hvcc->alpha_layer_nuh_id = layer_id_in_nuh[i];
> + }
> + }
> + }
> + }
>
> /* nothing useful for hvcC past this point */
> return 0;
> @@ -551,7 +659,7 @@ static int hvcc_parse_sps(GetBitContext *gb, HVCCNALUnit *nal,
>
> if (!multi_layer_ext_sps_flag) {
> hvcc->temporalIdNested = get_bits1(gb);
> - hvcc_parse_ptl(gb, hvcc, sps_max_sub_layers_minus1);
> + hvcc_parse_ptl(gb, hvcc, 1, sps_max_sub_layers_minus1);
> }
>
> nal->parameter_set_id = get_ue_golomb_long(gb);
> @@ -762,7 +870,7 @@ static int hvcc_add_nal_unit(const uint8_t *nal_buf, uint32_t nal_size,
> goto end;
>
> nal_unit_parse_header(&gbc, &nal_type, &nuh_layer_id);
> - if (!is_lhvc && nuh_layer_id > 0)
> + if (!is_lhvc && nuh_layer_id > 0 && nuh_layer_id != hvcc->alpha_layer_nuh_id)
> goto end;
>
> /*
Confirmed working (in that the PS nalus are not filtered when the checks
succeed and alpha_layer_nuh_id is set), so LGTM.
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