Re: [FFmpeg-devel] [PATCH v19 02/10] avcodec/evc_parser: Added parser implementation for EVC format

[James Almer <jamrial@gmail.com>]

On 4/5/2023 4:01 AM, Dawid Kozinski wrote:
> +static int parse_nal_unit(AVCodecParserContext *s, const uint8_t *buf,
> +                          int buf_size, AVCodecContext *avctx)
> +{
> +    EVCParserContext *ev = s->priv_data;
> +    int nalu_type, nalu_size;
> +    int tid;
> +    const uint8_t *data = buf;
> +    int data_size = buf_size;
> +
> +    s->picture_structure = AV_PICTURE_STRUCTURE_FRAME;
> +    s->key_frame = -1;
> +
> +    nalu_size = buf_size;
> +    if (nalu_size <= 0) {
> +        av_log(avctx, AV_LOG_ERROR, "Invalid NAL unit size: (%d)\n", nalu_size);
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    // @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
> +    nalu_type = get_nalu_type(data, data_size, avctx);
> +    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;
> +    }
> +    ev->nalu_type = nalu_type;
> +
> +    tid = get_temporal_id(data, data_size, avctx);
> +    if (tid < 0) {
> +        av_log(avctx, AV_LOG_ERROR, "Invalid temporial id: (%d)\n", tid);
> +        return AVERROR_INVALIDDATA;
> +    }
> +    ev->nuh_temporal_id = tid;
> +
> +    if (data_size < nalu_size) {
> +        av_log(avctx, AV_LOG_ERROR, "NAL unit does not fit in the data buffer\n");
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    data += EVC_NALU_HEADER_SIZE;
> +    data_size -= EVC_NALU_HEADER_SIZE;
> +
> +    switch(nalu_type) {
> +    case EVC_SPS_NUT: {
> +        EVCParserSPS *sps;
> +        int SubGopLength;
> +
> +        sps = parse_sps(data, nalu_size, ev);
> +        if (!sps) {
> +            av_log(avctx, AV_LOG_ERROR, "SPS parsing error\n");
> +            return AVERROR_INVALIDDATA;
> +        }
> +
> +        s->coded_width         = sps->pic_width_in_luma_samples;
> +        s->coded_height        = sps->pic_height_in_luma_samples;
> +        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;
> +
> +        SubGopLength = (int)pow(2.0, sps->log2_sub_gop_length);
> +        avctx->gop_size = SubGopLength;
> +
> +        avctx->delay = (sps->sps_max_dec_pic_buffering_minus1) ? sps->sps_max_dec_pic_buffering_minus1 - 1 : SubGopLength + sps->max_num_tid0_ref_pics - 1;
> +
> +        if (sps->profile_idc == 1) avctx->profile = FF_PROFILE_EVC_MAIN;
> +        else avctx->profile = FF_PROFILE_EVC_BASELINE;
> +
> +        if (sps->vui_parameters_present_flag) {
> +            if (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);
> +            }
> +        }
> +
> +        switch (sps->chroma_format_idc) {
> +        case 0: /* YCBCR400_10LE */
> +            av_log(avctx, AV_LOG_ERROR, "YCBCR400_10LE: Not supported chroma format\n");
> +            s->format = AV_PIX_FMT_GRAY10LE;
> +            return -1;

This is a parser, and it's independent from any given decoder 
implementation. You should set it to all supported values and not abort 
on any.

> +        case 1: /* YCBCR420_10LE */
> +            s->format = AV_PIX_FMT_YUV420P10LE;
> +            break;
> +        case 2: /* YCBCR422_10LE */
> +            av_log(avctx, AV_LOG_ERROR, "YCBCR422_10LE: Not supported chroma format\n");
> +            s->format = AV_PIX_FMT_YUV422P10LE;
> +            return -1;
> +        case 3: /* YCBCR444_10LE */
> +            av_log(avctx, AV_LOG_ERROR, "YCBCR444_10LE: Not supported chroma format\n");
> +            s->format = AV_PIX_FMT_YUV444P10LE;
> +            return -1;
> +        default:
> +            s->format = AV_PIX_FMT_NONE;
> +            av_log(avctx, AV_LOG_ERROR, "Unknown supported chroma format\n");
> +            return -1;
> +        }
> +        break;
> +    }
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