libavcodec/evc_parser.c - third_party/ffmpeg - Git at Google

 /*
  * EVC format parser
  *
  * Copyright (C) 2021 Dawid Kozinski <d.kozinski@samsung.com>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */

 #include "avcodec.h"
 #include "bytestream.h"
 #include "evc.h"
 #include "evc_parse.h"

 typedef struct EVCParserContext {
     EVCParamSets ps;
     EVCParserPoc poc;

     int parsed_extradata;
 } EVCParserContext;

 #define NUM_CHROMA_FORMATS      4   // @see ISO_IEC_23094-1 section 6.2 table 2

 static const enum AVPixelFormat pix_fmts_8bit[NUM_CHROMA_FORMATS] = {
     AV_PIX_FMT_GRAY8, AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV444P
 };

 static const enum AVPixelFormat pix_fmts_9bit[NUM_CHROMA_FORMATS] = {
     AV_PIX_FMT_GRAY9, AV_PIX_FMT_YUV420P9, AV_PIX_FMT_YUV422P9, AV_PIX_FMT_YUV444P9
 };

 static const enum AVPixelFormat pix_fmts_10bit[NUM_CHROMA_FORMATS] = {
     AV_PIX_FMT_GRAY10, AV_PIX_FMT_YUV420P10, AV_PIX_FMT_YUV422P10, AV_PIX_FMT_YUV444P10
 };

 static const enum AVPixelFormat pix_fmts_12bit[NUM_CHROMA_FORMATS] = {
     AV_PIX_FMT_GRAY12, AV_PIX_FMT_YUV420P12, AV_PIX_FMT_YUV422P12, AV_PIX_FMT_YUV444P12
 };

 static const enum AVPixelFormat pix_fmts_14bit[NUM_CHROMA_FORMATS] = {
     AV_PIX_FMT_GRAY14, AV_PIX_FMT_YUV420P14, AV_PIX_FMT_YUV422P14, AV_PIX_FMT_YUV444P14
 };

 static const enum AVPixelFormat pix_fmts_16bit[NUM_CHROMA_FORMATS] = {
     AV_PIX_FMT_GRAY16, AV_PIX_FMT_YUV420P16, AV_PIX_FMT_YUV422P16, AV_PIX_FMT_YUV444P16
 };

 static int parse_nal_unit(AVCodecParserContext *s, AVCodecContext *avctx,
                           const uint8_t *buf, int buf_size)
 {
     EVCParserContext *ctx = s->priv_data;
     GetBitContext gb;
     int nalu_type, tid;
     int ret;

     if (buf_size <= 0) {
         av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit size: (%d)\n", buf_size);
         return AVERROR_INVALIDDATA;
     }

     ret = init_get_bits8(&gb, buf, buf_size);
     if (ret < 0)
         return ret;

     // @see ISO_IEC_23094-1_2020, 7.4.2.2 NAL unit header semantic (Table 4 - NAL unit type codes and NAL unit type classes)
     // @see enum EVCNALUnitType in evc.h
     if (get_bits1(&gb)) {// forbidden_zero_bit
         av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit header\n");
         return AVERROR_INVALIDDATA;
     }

     nalu_type = get_bits(&gb, 6) - 1;
     if (nalu_type < EVC_NOIDR_NUT || nalu_type > EVC_UNSPEC_NUT62) {
         av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit type: (%d)\n", nalu_type);
         return AVERROR_INVALIDDATA;
     }

     tid = get_bits(&gb, 3);
     skip_bits(&gb, 5); // nuh_reserved_zero_5bits
     skip_bits1(&gb);   // nuh_extension_flag

     switch (nalu_type) {
     case EVC_SPS_NUT:
         ret = ff_evc_parse_sps(&gb, &ctx->ps);
         if (ret < 0) {
             av_log(avctx, AV_LOG_ERROR, "SPS parsing error\n");
             return ret;
         }
         break;
     case EVC_PPS_NUT:
         ret = ff_evc_parse_pps(&gb, &ctx->ps);
         if (ret < 0) {
             av_log(avctx, AV_LOG_ERROR, "PPS parsing error\n");
             return ret;
         }
         break;
     case EVC_IDR_NUT:   // Coded slice of a IDR or non-IDR picture
     case EVC_NOIDR_NUT: {
         const EVCParserPPS *pps;
         const EVCParserSPS *sps;
         EVCParserSliceHeader sh;
         int bit_depth;

         ret = ff_evc_parse_slice_header(&gb, &sh, &ctx->ps, nalu_type);
         if (ret < 0) {
             av_log(avctx, AV_LOG_ERROR, "Slice header parsing error\n");
             return ret;
         }

         pps = ctx->ps.pps[sh.slice_pic_parameter_set_id];
         sps = ctx->ps.sps[pps->pps_seq_parameter_set_id];
         av_assert0(sps && pps);

         s->coded_width  = sps->pic_width_in_luma_samples;
         s->coded_height = sps->pic_height_in_luma_samples;

         if (sps->picture_cropping_flag) {
             s->width    = sps->pic_width_in_luma_samples  - sps->picture_crop_left_offset - sps->picture_crop_right_offset;
             s->height   = sps->pic_height_in_luma_samples - sps->picture_crop_top_offset  - sps->picture_crop_bottom_offset;
         } else {
             s->width    = sps->pic_width_in_luma_samples;
             s->height   = sps->pic_height_in_luma_samples;
         }

         switch (sh.slice_type) {
         case EVC_SLICE_TYPE_B: {
             s->pict_type =  AV_PICTURE_TYPE_B;
             break;
         }
         case EVC_SLICE_TYPE_P: {
             s->pict_type =  AV_PICTURE_TYPE_P;
             break;
         }
         case EVC_SLICE_TYPE_I: {
             s->pict_type =  AV_PICTURE_TYPE_I;
             break;
         }
         default: {
             s->pict_type =  AV_PICTURE_TYPE_NONE;
         }
         }

         avctx->profile = sps->profile_idc;

         if (sps->vui_parameters_present_flag && sps->vui_parameters.timing_info_present_flag) {
             int64_t num = sps->vui_parameters.num_units_in_tick;
             int64_t den = sps->vui_parameters.time_scale;
             if (num != 0 && den != 0)
                 av_reduce(&avctx->framerate.den, &avctx->framerate.num, num, den, 1 << 30);
         } else
             avctx->framerate = (AVRational) { 0, 1 };

         bit_depth = sps->bit_depth_chroma_minus8 + 8;
         s->format = AV_PIX_FMT_NONE;

         switch (bit_depth) {
         case 8:
             s->format = pix_fmts_8bit[sps->chroma_format_idc];
             break;
         case 9:
             s->format = pix_fmts_9bit[sps->chroma_format_idc];
             break;
         case 10:
             s->format = pix_fmts_10bit[sps->chroma_format_idc];
             break;
         case 12:
             s->format = pix_fmts_12bit[sps->chroma_format_idc];
             break;
         case 14:
             s->format = pix_fmts_14bit[sps->chroma_format_idc];
             break;
         case 16:
             s->format = pix_fmts_16bit[sps->chroma_format_idc];
             break;
         }

         s->key_frame = (nalu_type == EVC_IDR_NUT) ? 1 : 0;

         // POC (picture order count of the current picture) derivation
         // @see ISO/IEC 23094-1:2020(E) 8.3.1 Decoding process for picture order count
         ret = ff_evc_derive_poc(&ctx->ps, &sh, &ctx->poc, nalu_type, tid);
         if (ret < 0)
             return ret;

         s->output_picture_number = ctx->poc.PicOrderCntVal;

         break;
     }
     case EVC_SEI_NUT:   // Supplemental Enhancement Information
     case EVC_APS_NUT:   // Adaptation parameter set
     case EVC_FD_NUT:    // Filler data
     default:
         break;
     }

     return 0;
 }

 /**
  * Parse NAL units of found picture and decode some basic information.
  *
  * @param s codec parser context
  * @param avctx codec context
  * @param buf buffer with field/frame data
  * @param buf_size size of the buffer
  */
 static int parse_nal_units(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t *buf, int buf_size)
 {
     const uint8_t *data = buf;
     int data_size = buf_size;

     while (data_size > 0) {
         int nalu_size = 0;
         int ret;

         // Buffer size is not enough for buffer to store NAL unit 4-bytes prefix (length)
         if (data_size < EVC_NALU_LENGTH_PREFIX_SIZE)
             return AVERROR_INVALIDDATA;

         nalu_size = evc_read_nal_unit_length(data, data_size, avctx);


         data += EVC_NALU_LENGTH_PREFIX_SIZE;
         data_size -= EVC_NALU_LENGTH_PREFIX_SIZE;

         if (data_size < nalu_size)
             return AVERROR_INVALIDDATA;

         ret = parse_nal_unit(s, avctx, data, nalu_size);
         if (ret < 0) {
             av_log(avctx, AV_LOG_ERROR, "Parsing of NAL unit failed\n");
             return AVERROR_INVALIDDATA;
         }

         data += nalu_size;
         data_size -= nalu_size;
     }
     return 0;
 }

 // Decoding nal units from evcC (EVCDecoderConfigurationRecord)
 // @see @see ISO/IEC 14496-15:2021 Coding of audio-visual objects - Part 15: section 12.3.3.2
 static int decode_extradata(AVCodecParserContext *s, AVCodecContext *avctx)
 {
     const uint8_t *data = avctx->extradata;
     int size = avctx->extradata_size;
     int ret = 0;
     GetByteContext gb;

     bytestream2_init(&gb, data, size);

     if (!data || size <= 0)
         return -1;

     // extradata is encoded as evcC format.
     if (data[0] == 1) {
         int num_of_arrays;  // indicates the number of arrays of NAL units of the indicated type(s)

         int nalu_length_field_size; // indicates the length in bytes of the NALUnitLenght field in EVC video stream sample in the stream
         // The value of this field shall be one of 0, 1, or 3 corresponding to a length encoded with 1, 2, or 4 bytes, respectively.

         if (bytestream2_get_bytes_left(&gb) < 18) {
             av_log(avctx, AV_LOG_ERROR, "evcC %d too short\n", size);
             return AVERROR_INVALIDDATA;
         }

         bytestream2_skip(&gb, 16);

         // @see ISO/IEC 14496-15:2021 Coding of audio-visual objects - Part 15: section 12.3.3.3
         // LengthSizeMinusOne plus 1 indicates the length in bytes of the NALUnitLength field in a EVC video stream sample in the stream to which this configuration record applies. For example, a size of one byte is indicated with a value of 0.
         // The value of this field shall be one of 0, 1, or 3 corresponding to a length encoded with 1, 2, or 4 bytes, respectively.
         nalu_length_field_size = (bytestream2_get_byte(&gb) & 3) + 1;
         if( nalu_length_field_size != 1 &&
             nalu_length_field_size != 2 &&
             nalu_length_field_size != 4 ) {
             av_log(avctx, AV_LOG_ERROR, "The length in bytes of the NALUnitLenght field in a EVC video stream has unsupported value of %d\n", nalu_length_field_size);
             return AVERROR_INVALIDDATA;
         }

         num_of_arrays = bytestream2_get_byte(&gb);

         /* Decode nal units from evcC. */
         for (int i = 0; i < num_of_arrays; i++) {

             // @see ISO/IEC 14496-15:2021 Coding of audio-visual objects - Part 15: section 12.3.3.3
             // NAL_unit_type indicates the type of the NAL units in the following array (which shall be all of that type);
             // - it takes a value as defined in ISO/IEC 23094-1;
             // - it is restricted to take one of the values indicating a SPS, PPS, APS, or SEI NAL unit.
             int nal_unit_type = bytestream2_get_byte(&gb) & 0x3f;
             int num_nalus  = bytestream2_get_be16(&gb);

             for (int j = 0; j < num_nalus; j++) {

                 int nal_unit_length = bytestream2_get_be16(&gb);

                 if (bytestream2_get_bytes_left(&gb) < nal_unit_length) {
                     av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit size in extradata.\n");
                     return AVERROR_INVALIDDATA;
                 }

                 if( nal_unit_type == EVC_SPS_NUT ||
                     nal_unit_type == EVC_PPS_NUT ||
                     nal_unit_type == EVC_APS_NUT ||
                     nal_unit_type == EVC_SEI_NUT ) {
                     if (parse_nal_unit(s, avctx, gb.buffer, nal_unit_length) != 0) {
                         av_log(avctx, AV_LOG_ERROR, "Parsing of NAL unit failed\n");
                         return AVERROR_INVALIDDATA;
                     }
                 }

                 bytestream2_skip(&gb, nal_unit_length);
             }
         }
     } else
         return -1;

     return ret;
 }

 static int evc_parse(AVCodecParserContext *s, AVCodecContext *avctx,
                      const uint8_t **poutbuf, int *poutbuf_size,
                      const uint8_t *buf, int buf_size)
 {
     int next;
     int ret;
     EVCParserContext *ctx = s->priv_data;

     s->picture_structure = AV_PICTURE_STRUCTURE_FRAME;
     s->key_frame = 0;

     if (avctx->extradata && !ctx->parsed_extradata) {
         decode_extradata(s, avctx);
         ctx->parsed_extradata = 1;
     }

     next = buf_size;

     ret = parse_nal_units(s, avctx, buf, buf_size);
     if(ret < 0) {
         *poutbuf      = NULL;
         *poutbuf_size = 0;
         return buf_size;
     }

     // poutbuf contains just one Access Unit
     *poutbuf      = buf;
     *poutbuf_size = buf_size;

     return next;
 }

 static void evc_parser_close(AVCodecParserContext *s)
 {
     EVCParserContext *ctx = s->priv_data;

     ff_evc_ps_free(&ctx->ps);
 }

 const AVCodecParser ff_evc_parser = {
     .codec_ids      = { AV_CODEC_ID_EVC },
     .priv_data_size = sizeof(EVCParserContext),
     .parser_parse   = evc_parse,
     .parser_close   = evc_parser_close,
 };
	/*
	* EVC format parser
	*
	* Copyright (C) 2021 Dawid Kozinski <d.kozinski@samsung.com>
	*
	* This file is part of FFmpeg.
	*
	* FFmpeg is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* FFmpeg is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with FFmpeg; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	#include "avcodec.h"
	#include "bytestream.h"
	#include "evc.h"
	#include "evc_parse.h"

	typedef struct EVCParserContext {
	EVCParamSets ps;
	EVCParserPoc poc;

	int parsed_extradata;
	} EVCParserContext;

	#define NUM_CHROMA_FORMATS 4 // @see ISO_IEC_23094-1 section 6.2 table 2

	static const enum AVPixelFormat pix_fmts_8bit[NUM_CHROMA_FORMATS] = {
	AV_PIX_FMT_GRAY8, AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV444P
	};

	static const enum AVPixelFormat pix_fmts_9bit[NUM_CHROMA_FORMATS] = {
	AV_PIX_FMT_GRAY9, AV_PIX_FMT_YUV420P9, AV_PIX_FMT_YUV422P9, AV_PIX_FMT_YUV444P9
	};

	static const enum AVPixelFormat pix_fmts_10bit[NUM_CHROMA_FORMATS] = {
	AV_PIX_FMT_GRAY10, AV_PIX_FMT_YUV420P10, AV_PIX_FMT_YUV422P10, AV_PIX_FMT_YUV444P10
	};

	static const enum AVPixelFormat pix_fmts_12bit[NUM_CHROMA_FORMATS] = {
	AV_PIX_FMT_GRAY12, AV_PIX_FMT_YUV420P12, AV_PIX_FMT_YUV422P12, AV_PIX_FMT_YUV444P12
	};

	static const enum AVPixelFormat pix_fmts_14bit[NUM_CHROMA_FORMATS] = {
	AV_PIX_FMT_GRAY14, AV_PIX_FMT_YUV420P14, AV_PIX_FMT_YUV422P14, AV_PIX_FMT_YUV444P14
	};

	static const enum AVPixelFormat pix_fmts_16bit[NUM_CHROMA_FORMATS] = {
	AV_PIX_FMT_GRAY16, AV_PIX_FMT_YUV420P16, AV_PIX_FMT_YUV422P16, AV_PIX_FMT_YUV444P16
	};

	static int parse_nal_unit(AVCodecParserContext s, AVCodecContext avctx,
	const uint8_t *buf, int buf_size)
	{
	EVCParserContext *ctx = s->priv_data;
	GetBitContext gb;
	int nalu_type, tid;
	int ret;

	if (buf_size <= 0) {
	av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit size: (%d)\n", buf_size);
	return AVERROR_INVALIDDATA;
	}

	ret = init_get_bits8(&gb, buf, buf_size);
	if (ret < 0)
	return ret;

	// @see ISO_IEC_23094-1_2020, 7.4.2.2 NAL unit header semantic (Table 4 - NAL unit type codes and NAL unit type classes)
	// @see enum EVCNALUnitType in evc.h
	if (get_bits1(&gb)) {// forbidden_zero_bit
	av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit header\n");
	return AVERROR_INVALIDDATA;
	}

	nalu_type = get_bits(&gb, 6) - 1;
	if (nalu_type < EVC_NOIDR_NUT \|\| nalu_type > EVC_UNSPEC_NUT62) {
	av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit type: (%d)\n", nalu_type);
	return AVERROR_INVALIDDATA;
	}

	tid = get_bits(&gb, 3);
	skip_bits(&gb, 5); // nuh_reserved_zero_5bits
	skip_bits1(&gb); // nuh_extension_flag

	switch (nalu_type) {
	case EVC_SPS_NUT:
	ret = ff_evc_parse_sps(&gb, &ctx->ps);
	if (ret < 0) {
	av_log(avctx, AV_LOG_ERROR, "SPS parsing error\n");
	return ret;
	}
	break;
	case EVC_PPS_NUT:
	ret = ff_evc_parse_pps(&gb, &ctx->ps);
	if (ret < 0) {
	av_log(avctx, AV_LOG_ERROR, "PPS parsing error\n");
	return ret;
	}
	break;
	case EVC_IDR_NUT: // Coded slice of a IDR or non-IDR picture
	case EVC_NOIDR_NUT: {
	const EVCParserPPS *pps;
	const EVCParserSPS *sps;
	EVCParserSliceHeader sh;
	int bit_depth;

	ret = ff_evc_parse_slice_header(&gb, &sh, &ctx->ps, nalu_type);
	if (ret < 0) {
	av_log(avctx, AV_LOG_ERROR, "Slice header parsing error\n");
	return ret;
	}

	pps = ctx->ps.pps[sh.slice_pic_parameter_set_id];
	sps = ctx->ps.sps[pps->pps_seq_parameter_set_id];
	av_assert0(sps && pps);

	s->coded_width = sps->pic_width_in_luma_samples;
	s->coded_height = sps->pic_height_in_luma_samples;

	if (sps->picture_cropping_flag) {
	s->width = sps->pic_width_in_luma_samples - sps->picture_crop_left_offset - sps->picture_crop_right_offset;
	s->height = sps->pic_height_in_luma_samples - sps->picture_crop_top_offset - sps->picture_crop_bottom_offset;
	} else {
	s->width = sps->pic_width_in_luma_samples;
	s->height = sps->pic_height_in_luma_samples;
	}

	switch (sh.slice_type) {
	case EVC_SLICE_TYPE_B: {
	s->pict_type = AV_PICTURE_TYPE_B;
	break;
	}
	case EVC_SLICE_TYPE_P: {
	s->pict_type = AV_PICTURE_TYPE_P;
	break;
	}
	case EVC_SLICE_TYPE_I: {
	s->pict_type = AV_PICTURE_TYPE_I;
	break;
	}
	default: {
	s->pict_type = AV_PICTURE_TYPE_NONE;
	}
	}

	avctx->profile = sps->profile_idc;

	if (sps->vui_parameters_present_flag && sps->vui_parameters.timing_info_present_flag) {
	int64_t num = sps->vui_parameters.num_units_in_tick;
	int64_t den = sps->vui_parameters.time_scale;
	if (num != 0 && den != 0)
	av_reduce(&avctx->framerate.den, &avctx->framerate.num, num, den, 1 << 30);
	} else
	avctx->framerate = (AVRational) { 0, 1 };

	bit_depth = sps->bit_depth_chroma_minus8 + 8;
	s->format = AV_PIX_FMT_NONE;

	switch (bit_depth) {
	case 8:
	s->format = pix_fmts_8bit[sps->chroma_format_idc];
	break;
	case 9:
	s->format = pix_fmts_9bit[sps->chroma_format_idc];
	break;
	case 10:
	s->format = pix_fmts_10bit[sps->chroma_format_idc];
	break;
	case 12:
	s->format = pix_fmts_12bit[sps->chroma_format_idc];
	break;
	case 14:
	s->format = pix_fmts_14bit[sps->chroma_format_idc];
	break;
	case 16:
	s->format = pix_fmts_16bit[sps->chroma_format_idc];
	break;
	}

	s->key_frame = (nalu_type == EVC_IDR_NUT) ? 1 : 0;

	// POC (picture order count of the current picture) derivation
	// @see ISO/IEC 23094-1:2020(E) 8.3.1 Decoding process for picture order count
	ret = ff_evc_derive_poc(&ctx->ps, &sh, &ctx->poc, nalu_type, tid);
	if (ret < 0)
	return ret;

	s->output_picture_number = ctx->poc.PicOrderCntVal;

	break;
	}
	case EVC_SEI_NUT: // Supplemental Enhancement Information
	case EVC_APS_NUT: // Adaptation parameter set
	case EVC_FD_NUT: // Filler data
	default:
	break;
	}

	return 0;
	}

	/**
	* Parse NAL units of found picture and decode some basic information.
	*
	* @param s codec parser context
	* @param avctx codec context
	* @param buf buffer with field/frame data
	* @param buf_size size of the buffer
	*/
	static int parse_nal_units(AVCodecParserContext s, AVCodecContext avctx, const uint8_t *buf, int buf_size)
	{
	const uint8_t *data = buf;
	int data_size = buf_size;

	while (data_size > 0) {
	int nalu_size = 0;
	int ret;

	// Buffer size is not enough for buffer to store NAL unit 4-bytes prefix (length)
	if (data_size < EVC_NALU_LENGTH_PREFIX_SIZE)
	return AVERROR_INVALIDDATA;

	nalu_size = evc_read_nal_unit_length(data, data_size, avctx);


	data += EVC_NALU_LENGTH_PREFIX_SIZE;
	data_size -= EVC_NALU_LENGTH_PREFIX_SIZE;

	if (data_size < nalu_size)
	return AVERROR_INVALIDDATA;

	ret = parse_nal_unit(s, avctx, data, nalu_size);
	if (ret < 0) {
	av_log(avctx, AV_LOG_ERROR, "Parsing of NAL unit failed\n");
	return AVERROR_INVALIDDATA;
	}

	data += nalu_size;
	data_size -= nalu_size;
	}
	return 0;
	}

	// Decoding nal units from evcC (EVCDecoderConfigurationRecord)
	// @see @see ISO/IEC 14496-15:2021 Coding of audio-visual objects - Part 15: section 12.3.3.2
	static int decode_extradata(AVCodecParserContext s, AVCodecContext avctx)
	{
	const uint8_t *data = avctx->extradata;
	int size = avctx->extradata_size;
	int ret = 0;
	GetByteContext gb;

	bytestream2_init(&gb, data, size);

	if (!data \|\| size <= 0)
	return -1;

	// extradata is encoded as evcC format.
	if (data[0] == 1) {
	int num_of_arrays; // indicates the number of arrays of NAL units of the indicated type(s)

	int nalu_length_field_size; // indicates the length in bytes of the NALUnitLenght field in EVC video stream sample in the stream
	// The value of this field shall be one of 0, 1, or 3 corresponding to a length encoded with 1, 2, or 4 bytes, respectively.

	if (bytestream2_get_bytes_left(&gb) < 18) {
	av_log(avctx, AV_LOG_ERROR, "evcC %d too short\n", size);
	return AVERROR_INVALIDDATA;
	}

	bytestream2_skip(&gb, 16);

	// @see ISO/IEC 14496-15:2021 Coding of audio-visual objects - Part 15: section 12.3.3.3
	// LengthSizeMinusOne plus 1 indicates the length in bytes of the NALUnitLength field in a EVC video stream sample in the stream to which this configuration record applies. For example, a size of one byte is indicated with a value of 0.
	// The value of this field shall be one of 0, 1, or 3 corresponding to a length encoded with 1, 2, or 4 bytes, respectively.
	nalu_length_field_size = (bytestream2_get_byte(&gb) & 3) + 1;
	if( nalu_length_field_size != 1 &&
	nalu_length_field_size != 2 &&
	nalu_length_field_size != 4 ) {
	av_log(avctx, AV_LOG_ERROR, "The length in bytes of the NALUnitLenght field in a EVC video stream has unsupported value of %d\n", nalu_length_field_size);
	return AVERROR_INVALIDDATA;
	}

	num_of_arrays = bytestream2_get_byte(&gb);

	/* Decode nal units from evcC. */
	for (int i = 0; i < num_of_arrays; i++) {

	// @see ISO/IEC 14496-15:2021 Coding of audio-visual objects - Part 15: section 12.3.3.3
	// NAL_unit_type indicates the type of the NAL units in the following array (which shall be all of that type);
	// - it takes a value as defined in ISO/IEC 23094-1;
	// - it is restricted to take one of the values indicating a SPS, PPS, APS, or SEI NAL unit.
	int nal_unit_type = bytestream2_get_byte(&gb) & 0x3f;
	int num_nalus = bytestream2_get_be16(&gb);

	for (int j = 0; j < num_nalus; j++) {

	int nal_unit_length = bytestream2_get_be16(&gb);

	if (bytestream2_get_bytes_left(&gb) < nal_unit_length) {
	av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit size in extradata.\n");
	return AVERROR_INVALIDDATA;
	}

	if( nal_unit_type == EVC_SPS_NUT \|\|
	nal_unit_type == EVC_PPS_NUT \|\|
	nal_unit_type == EVC_APS_NUT \|\|
	nal_unit_type == EVC_SEI_NUT ) {
	if (parse_nal_unit(s, avctx, gb.buffer, nal_unit_length) != 0) {
	av_log(avctx, AV_LOG_ERROR, "Parsing of NAL unit failed\n");
	return AVERROR_INVALIDDATA;
	}
	}

	bytestream2_skip(&gb, nal_unit_length);
	}
	}
	} else
	return -1;

	return ret;
	}

	static int evc_parse(AVCodecParserContext s, AVCodecContext avctx,
	const uint8_t *poutbuf, int poutbuf_size,
	const uint8_t *buf, int buf_size)
	{
	int next;
	int ret;
	EVCParserContext *ctx = s->priv_data;

	s->picture_structure = AV_PICTURE_STRUCTURE_FRAME;
	s->key_frame = 0;

	if (avctx->extradata && !ctx->parsed_extradata) {
	decode_extradata(s, avctx);
	ctx->parsed_extradata = 1;
	}

	next = buf_size;

	ret = parse_nal_units(s, avctx, buf, buf_size);
	if(ret < 0) {
	*poutbuf = NULL;
	*poutbuf_size = 0;
	return buf_size;
	}

	// poutbuf contains just one Access Unit
	*poutbuf = buf;
	*poutbuf_size = buf_size;

	return next;
	}

	static void evc_parser_close(AVCodecParserContext *s)
	{
	EVCParserContext *ctx = s->priv_data;

	ff_evc_ps_free(&ctx->ps);
	}

	const AVCodecParser ff_evc_parser = {
	.codec_ids = { AV_CODEC_ID_EVC },
	.priv_data_size = sizeof(EVCParserContext),
	.parser_parse = evc_parse,
	.parser_close = evc_parser_close,
	};