/*----------------------------------------------------------------------
|   IsIFrame
+---------------------------------------------------------------------*/
static bool
IsIFrame(AP4_Sample& sample, AP4_AvcSampleDescription* avc_desc) {
    AP4_DataBuffer sample_data;
    if (AP4_FAILED(sample.ReadData(sample_data))) {
        return false;
    }

    const unsigned char* data = sample_data.GetData();
    AP4_Size             size = sample_data.GetDataSize();

    while (size >= avc_desc->GetNaluLengthSize()) {
        unsigned int nalu_length = 0;
        if (avc_desc->GetNaluLengthSize() == 1) {
            nalu_length = *data++;
            --size;
        } else if (avc_desc->GetNaluLengthSize() == 2) {
            nalu_length = AP4_BytesToUInt16BE(data);
            data += 2;
            size -= 2;
        } else if (avc_desc->GetNaluLengthSize() == 4) {
            nalu_length = AP4_BytesToUInt32BE(data);
            data += 4;
            size -= 4;
        } else {
            return false;
        }
        if (nalu_length <= size) {
            size -= nalu_length;
        } else {
            size = 0;
        }
        
        switch (*data & 0x1F) {
            case 1: {
                AP4_BitStream bits;
                bits.WriteBytes(data+1, 8);
                ReadGolomb(bits);
                unsigned int slice_type = ReadGolomb(bits);
                if (slice_type == 2 || slice_type == 7) {
                    return true;
                } else {
                    return false; // only show first slice type
                }
            }
            
            case 5: 
                return true;
        }
        
        data += nalu_length;
    }
 
    return false;
}
Beispiel #2
0
/*----------------------------------------------------------------------
|   PrintSliceInfo
+---------------------------------------------------------------------*/
static void
PrintSliceInfo(const unsigned char* data)
{
    AP4_BitStream bits;
    bits.WriteBytes(data, 8);
    ReadGolomb(bits);
    
    unsigned int slice_type = ReadGolomb(bits);
    const char* slice_type_name = AP4_AvcNalParser::SliceTypeName(slice_type);
    if (slice_type_name == NULL) slice_type_name = "?";
    printf(" slice=%d (%s)", slice_type, slice_type_name);
}
/*----------------------------------------------------------------------
|   ReadGolomb
+---------------------------------------------------------------------*/
static unsigned int
ReadGolomb(AP4_BitStream& bits)
{
    unsigned int leading_zeros = 0;
    while (bits.ReadBit() == 0) {
        leading_zeros++;
    }
    if (leading_zeros) {
        return (1<<leading_zeros)-1+bits.ReadBits(leading_zeros);
    } else {
        return 0;
    }
}