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;

    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

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

    si = h->rbsp_buffer_size[bufidx];
    av_fast_padded_malloc(&h->rbsp_buffer[bufidx], &h->rbsp_buffer_size[bufidx], length+MAX_MBPAIR_SIZE);
    dst = h->rbsp_buffer[bufidx];

    if (dst == NULL)
        return NULL;

    if(i>=length-1){ //no escaped 0
        *dst_length= length;
        *consumed= length+1; //+1 for the header
        if(h->avctx->flags2 & CODEC_FLAG2_FAST){
            return src;
        }else{
            memcpy(dst, src, length);
            return dst;
        }
    }

    memcpy(dst, src, i);
    si = di = i;
    while (si + 2 < length) {
        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;
}

Unknown