int avcodec_parameters_to_context(AVCodecContext *codec,
                                  const AVCodecParameters *par)
{
    codec->codec_type = par->codec_type;
    codec->codec_id   = par->codec_id;
    codec->codec_tag  = par->codec_tag;

    codec->bit_rate              = par->bit_rate;
    codec->bits_per_coded_sample = par->bits_per_coded_sample;
    codec->bits_per_raw_sample   = par->bits_per_raw_sample;
    codec->profile               = par->profile;
    codec->level                 = par->level;

    switch (par->codec_type) {
    case AVMEDIA_TYPE_VIDEO:
        codec->pix_fmt                = par->format;
        codec->width                  = par->width;
        codec->height                 = par->height;
        codec->field_order            = par->field_order;
        codec->color_range            = par->color_range;
        codec->color_primaries        = par->color_primaries;
        codec->color_trc              = par->color_trc;
        codec->colorspace             = par->color_space;
        codec->chroma_sample_location = par->chroma_location;
        codec->sample_aspect_ratio    = par->sample_aspect_ratio;
        codec->has_b_frames           = par->video_delay;
        break;
    case AVMEDIA_TYPE_AUDIO:
        codec->sample_fmt       = par->format;
        codec->channel_layout   = par->channel_layout;
        codec->channels         = par->channels;
        codec->sample_rate      = par->sample_rate;
        codec->block_align      = par->block_align;
        codec->frame_size       = par->frame_size;
        codec->delay            =
        codec->initial_padding  = par->initial_padding;
        codec->trailing_padding = par->trailing_padding;
        codec->seek_preroll     = par->seek_preroll;
        break;
    case AVMEDIA_TYPE_SUBTITLE:
        codec->width  = par->width;
        codec->height = par->height;
        break;
    }

    if (par->extradata) {
        av_freep(&codec->extradata);
        codec->extradata = av_mallocz(par->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
        if (!codec->extradata)
            return AVERROR(ENOMEM);
        memcpy(codec->extradata, par->extradata, par->extradata_size);
        codec->extradata_size = par->extradata_size;
    }

    return 0;
}

The product writes data past the end, or before the beginning, of the intended buffer.