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; }