const uint8_t *ff_h264_decode_nal(H264Context *h, const uint8_t *src,

                                  int *dst_length, int *consumed, int length)

{

    int i, si, di;

    uint8_t *dst;

    int bufidx;



    // src[0]&0x80; // forbidden bit

    h->nal_ref_idc   = src[0] >> 5;

    h->nal_unit_type = src[0] & 0x1F;



    src++;

    length--;



#define STARTCODE_TEST                                                  \

    if (i + 2 < length && src[i + 1] == 0 && src[i + 2] <= 3) {         \

        if (src[i + 2] != 3) {                                          \

            /* startcode, so we must be past the end */                 \

            length = i;                                                 \

        }                                                               \

        break;                                                          \

    }



#if HAVE_FAST_UNALIGNED

#define FIND_FIRST_ZERO                                                 \

    if (i > 0 && !src[i])                                               \

        i--;                                                            \

    while (src[i])                                                      \

        i++



#if HAVE_FAST_64BIT

    for (i = 0; i + 1 < length; i += 9) {

        if (!((~AV_RN64A(src + i) &

               (AV_RN64A(src + i) - 0x0100010001000101ULL)) &

              0x8000800080008080ULL))

            continue;

        FIND_FIRST_ZERO;

        STARTCODE_TEST;

        i -= 7;

    }

#else

    for (i = 0; i + 1 < length; i += 5) {

        if (!((~AV_RN32A(src + i) &

               (AV_RN32A(src + i) - 0x01000101U)) &

              0x80008080U))

            continue;

        FIND_FIRST_ZERO;

        STARTCODE_TEST;

        i -= 3;

    }

#endif

#else

    for (i = 0; i + 1 < length; i += 2) {

        if (src[i])

            continue;

        if (i > 0 && src[i - 1] == 0)

            i--;

        STARTCODE_TEST;

    }

#endif



    if (i >= length - 1) { // no escaped 0

        *dst_length = length;

        *consumed   = length + 1; // +1 for the header

        return src;

    }



    // use second escape buffer for inter data

    bufidx = h->nal_unit_type == NAL_DPC ? 1 : 0;

    av_fast_malloc(&h->rbsp_buffer[bufidx], &h->rbsp_buffer_size[bufidx],

                   length + FF_INPUT_BUFFER_PADDING_SIZE);

    dst = h->rbsp_buffer[bufidx];



    if (dst == NULL)

        return NULL;



    memcpy(dst, src, i);

    si = di = i;

    while (si + 2 < length) {

        // remove escapes (very rare 1:2^22)

        if (src[si + 2] > 3) {

            dst[di++] = src[si++];

            dst[di++] = src[si++];

        } else if (src[si] == 0 && src[si + 1] == 0) {

            if (src[si + 2] == 3) { // escape

                dst[di++]  = 0;

                dst[di++]  = 0;

                si        += 3;

                continue;

            } else // next start code

                goto nsc;

        }



        dst[di++] = src[si++];

    }

    while (si < length)

        dst[di++] = src[si++];



nsc:

    memset(dst + di, 0, FF_INPUT_BUFFER_PADDING_SIZE);



    *dst_length = di;

    *consumed   = si + 1; // +1 for the header

    /* FIXME store exact number of bits in the getbitcontext

     * (it is needed for decoding) */

    return dst;

}
