解析hevc的nal数据，判断是I帧P帧还是B帧的c代码

下面是一个简单的C代码示例，用于解析HEVC的NAL数据并确定其类型，包括I帧，P帧和B帧：

#include <stdio.h>
#include <stdlib.h>

#define NAL_TYPE_SLICE 1
#define NAL_TYPE_SLICE_DPA 2
#define NAL_TYPE_SLICE_DPB 3
#define NAL_TYPE_SLICE_DPC 4
#define NAL_TYPE_IDR 5
#define NAL_TYPE_SEI 6
#define NAL_TYPE_SPS 7
#define NAL_TYPE_PPS 8
#define NAL_TYPE_AUD 9
#define NAL_TYPE_EOSEQ 10
#define NAL_TYPE_EOSTREAM 11
#define NAL_TYPE_FILLER 12

int get_nal_type(unsigned char* nal_data)
{
    return (nal_data[0] & 0x7E) >> 1;
}

int get_nal_unit_size(unsigned char* nal_data)
{
    return (nal_data[0] << 24) | (nal_data[1] << 16) | (nal_data[2] << 8) | (nal_data[3]);
}

int is_I_frame(unsigned char* nal_data)
{
    int nal_type = get_nal_type(nal_data);
    if (nal_type == NAL_TYPE_IDR)
        return 1;
    else if (nal_type == NAL_TYPE_SLICE)
    {
        int nal_ref_idc = nal_data[0] & 0x60;
        if (nal_ref_idc == 0x00)
            return 1;
    }
    return 0;
}

int is_B_frame(unsigned char* nal_data)
{
    int nal_type = get_nal_type(nal_data);
    if (nal_type == NAL_TYPE_SLICE_DPB)
        return 1;
    return 0;
}

int is_P_frame(unsigned char* nal_data)
{
    int nal_type = get_nal_type(nal_data);
    if (nal_type == NAL_TYPE_SLICE || nal_type == NAL_TYPE_SLICE_DPA || nal_type == NAL_TYPE_SLICE_DPC)
    {
        int nal_ref_idc = nal_data[0] & 0x60;
        if (nal_ref_idc == 0x40 || nal_ref_idc == 0x60)
            return 1;
    }
    return 0;
}

int main(int argc, char** argv)
{
    if (argc < 2)
    {
        printf("Usage: %s filename\n", argv[0]);
        return -1;
    }

    FILE* fp = fopen(argv[1], "rb");
    if (fp == NULL)
    {
        printf("Failed to open file %s\n", argv[1]);
        return -1;
    }

    unsigned char nal_data[1024];
    while (!feof(fp))
    {
        int nal_unit_size = 0;
        if (fread(&nal_unit_size, sizeof(int), 1, fp) == 0)
            break;

        nal_unit_size = get_nal_unit_size(nal_data);
        if (fread(nal_data, sizeof(unsigned char), nal_unit_size, fp) != nal_unit_size)
            break;

        int nal_type = get_nal_type(nal_data);
        if (is_I_frame(nal_data))
            printf("NAL unit is I frame\n");
        else if (is_P_frame(nal_data))
            printf("NAL unit is P frame\n");
        else if (is_B_frame(nal_data))
            printf("NAL unit is B frame\n");
        else
            printf("NAL unit is unknown frame type\n");
    }

    fclose(fp);
    return 0;
}

该代码从文件中读取HEVC NAL数据，检测每个NAL单元的类型，并使用is_I_frame，is_P_frame和is_B_frame函数来确定帧类型。请注意，这只是一个简单的示例，对于更复杂的HEVC流，需要更复杂和严格的解析器。