libavcodec/h2645_parse.c

   1 /*
   2  * H.264/HEVC common parsing code
   3  *
   4  * This file is part of Libav.
   5  *
   6  * Libav is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * Libav is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with Libav; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include <string.h>
  22
  23 #include "config.h"
  24
  25 #include "libavutil/intmath.h"
  26 #include "libavutil/intreadwrite.h"
  27 #include "libavutil/mem.h"
  28
  29 #include "bytestream.h"
  30 #include "h2645_parse.h"
  31
  32 int ff_h2645_extract_rbsp(const uint8_t *src, int length,
  33                           H2645NAL *nal)
  34 {
  35     int i, si, di;
  36     uint8_t *dst;
  37
  38 #define STARTCODE_TEST                                                  \
  39         if (i + 2 < length && src[i + 1] == 0 && src[i + 2] <= 3) {     \
  40             if (src[i + 2] != 3) {                                      \
  41                 /* startcode, so we must be past the end */             \
  42                 length = i;                                             \
  43             }                                                           \
  44             break;                                                      \
  45         }
  46 #if HAVE_FAST_UNALIGNED
  47 #define FIND_FIRST_ZERO                                                 \
  48         if (i > 0 && !src[i])                                           \
  49             i--;                                                        \
  50         while (src[i])                                                  \
  51             i++
  52 #if HAVE_FAST_64BIT
  53     for (i = 0; i + 1 < length; i += 9) {
  54         if (!((~AV_RN64A(src + i) &
  55                (AV_RN64A(src + i) - 0x0100010001000101ULL)) &
  56               0x8000800080008080ULL))
  57             continue;
  58         FIND_FIRST_ZERO;
  59         STARTCODE_TEST;
  60         i -= 7;
  61     }
  62 #else
  63     for (i = 0; i + 1 < length; i += 5) {
  64         if (!((~AV_RN32A(src + i) &
  65                (AV_RN32A(src + i) - 0x01000101U)) &
  66               0x80008080U))
  67             continue;
  68         FIND_FIRST_ZERO;
  69         STARTCODE_TEST;
  70         i -= 3;
  71     }
  72 #endif /* HAVE_FAST_64BIT */
  73 #else
  74     for (i = 0; i + 1 < length; i += 2) {
  75         if (src[i])
  76             continue;
  77         if (i > 0 && src[i - 1] == 0)
  78             i--;
  79         STARTCODE_TEST;
  80     }
  81 #endif /* HAVE_FAST_UNALIGNED */
  82
  83     if (i >= length - 1) { // no escaped 0
  84         nal->data     =
  85         nal->raw_data = src;
  86         nal->size     =
  87         nal->raw_size = length;
  88         return length;
  89     }
  90
  91     av_fast_malloc(&nal->rbsp_buffer, &nal->rbsp_buffer_size,
  92                    length + AV_INPUT_BUFFER_PADDING_SIZE);
  93     if (!nal->rbsp_buffer)
  94         return AVERROR(ENOMEM);
  95
  96     dst = nal->rbsp_buffer;
  97
  98     memcpy(dst, src, i);
  99     si = di = i;
 100     while (si + 2 < length) {
 101         // remove escapes (very rare 1:2^22)
 102         if (src[si + 2] > 3) {
 103             dst[di++] = src[si++];
 104             dst[di++] = src[si++];
 105         } else if (src[si] == 0 && src[si + 1] == 0) {
 106             if (src[si + 2] == 3) { // escape
 107                 dst[di++] = 0;
 108                 dst[di++] = 0;
 109                 si       += 3;
 110
 111                 continue;
 112             } else // next start code
 113                 goto nsc;
 114         }
 115
 116         dst[di++] = src[si++];
 117     }
 118     while (si < length)
 119         dst[di++] = src[si++];
 120
 121 nsc:
 122     memset(dst + di, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 123
 124     nal->data = dst;
 125     nal->size = di;
 126     nal->raw_data = src;
 127     nal->raw_size = si;
 128     return si;
 129 }
 130
 131 static int get_bit_length(H2645NAL *nal, int skip_trailing_zeros)
 132 {
 133     int size = nal->size;
 134     int v;
 135
 136     while (skip_trailing_zeros && size > 0 && nal->data[size - 1] == 0)
 137         size--;
 138
 139     if (!size)
 140         return 0;
 141
 142     v = nal->data[size - 1];
 143
 144     if (size > INT_MAX / 8)
 145         return AVERROR(ERANGE);
 146     size *= 8;
 147
 148     /* remove the stop bit and following trailing zeros,
 149      * or nothing for damaged bitstreams */
 150     if (v)
 151         size -= av_ctz(v) + 1;
 152
 153     return size;
 154 }
 155
 156 /**
 157  * @return AVERROR_INVALIDDATA if the packet is not a valid NAL unit,
 158  * 0 if the unit should be skipped, 1 otherwise
 159  */
 160 static int hevc_parse_nal_header(H2645NAL *nal, void *logctx)
 161 {
 162     GetBitContext *gb = &nal->gb;
 163     int nuh_layer_id;
 164
 165     if (get_bits1(gb) != 0)
 166         return AVERROR_INVALIDDATA;
 167
 168     nal->type = get_bits(gb, 6);
 169
 170     nuh_layer_id   = get_bits(gb, 6);
 171     nal->temporal_id = get_bits(gb, 3) - 1;
 172     if (nal->temporal_id < 0)
 173         return AVERROR_INVALIDDATA;
 174
 175     av_log(logctx, AV_LOG_DEBUG,
 176            "nal_unit_type: %d, nuh_layer_id: %dtemporal_id: %d\n",
 177            nal->type, nuh_layer_id, nal->temporal_id);
 178
 179     return nuh_layer_id == 0;
 180 }
 181
 182 static int h264_parse_nal_header(H2645NAL *nal, void *logctx)
 183 {
 184     GetBitContext *gb = &nal->gb;
 185
 186     if (get_bits1(gb) != 0)
 187         return AVERROR_INVALIDDATA;
 188
 189     nal->ref_idc = get_bits(gb, 2);
 190     nal->type    = get_bits(gb, 5);
 191
 192     av_log(logctx, AV_LOG_DEBUG,
 193            "nal_unit_type: %d, nal_ref_idc: %d\n",
 194            nal->type, nal->ref_idc);
 195
 196     return 1;
 197 }
 198
 199 static int find_next_start_code(const uint8_t *buf, const uint8_t *next_avc)
 200 {
 201     int i = 0;
 202
 203     if (buf + 3 >= next_avc)
 204         return next_avc - buf;
 205
 206     while (buf + i + 3 < next_avc) {
 207         if (buf[i] == 0 && buf[i + 1] == 0 && buf[i + 2] == 1)
 208             break;
 209         i++;
 210     }
 211     return i + 3;
 212 }
 213
 214 int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
 215                           void *logctx, int is_nalff, int nal_length_size,
 216                           enum AVCodecID codec_id)
 217 {
 218     GetByteContext bc;
 219     int consumed, ret = 0;
 220     size_t next_avc = is_nalff ? 0 : length;
 221
 222     bytestream2_init(&bc, buf, length);
 223
 224     pkt->nb_nals = 0;
 225     while (bytestream2_get_bytes_left(&bc) >= 4) {
 226         H2645NAL *nal;
 227         int extract_length = 0;
 228         int skip_trailing_zeros = 1;
 229
 230         /*
 231          * Only parse an AVC1 length field if one is expected at the current
 232          * buffer position. There are unfortunately streams with multiple
 233          * NAL units covered by the length field. Those NAL units are delimited
 234          * by Annex B start code prefixes. ff_h2645_extract_rbsp() detects it
 235          * correctly and consumes only the first NAL unit. The additional NAL
 236          * units are handled here in the Annex B parsing code.
 237          */
 238         if (bytestream2_tell(&bc) == next_avc) {
 239             int i;
 240             for (i = 0; i < nal_length_size; i++)
 241                 extract_length = (extract_length << 8) | bytestream2_get_byte(&bc);
 242
 243             if (extract_length > bytestream2_get_bytes_left(&bc)) {
 244                 av_log(logctx, AV_LOG_ERROR,
 245                        "Invalid NAL unit size (%d > %d).\n",
 246                        extract_length, bytestream2_get_bytes_left(&bc));
 247                 return AVERROR_INVALIDDATA;
 248             }
 249             // keep track of the next AVC1 length field
 250             next_avc = bytestream2_tell(&bc) + extract_length;
 251         } else {
 252             /*
 253              * expected to return immediately except for streams with mixed
 254              * NAL unit coding
 255              */
 256             int buf_index = find_next_start_code(bc.buffer, buf + next_avc);
 257
 258             bytestream2_skip(&bc, buf_index);
 259
 260             /*
 261              * break if an AVC1 length field is expected at the current buffer
 262              * position
 263              */
 264             if (bytestream2_tell(&bc) == next_avc)
 265                 continue;
 266
 267             if (bytestream2_get_bytes_left(&bc) > 0) {
 268                 extract_length = bytestream2_get_bytes_left(&bc);
 269             } else if (pkt->nb_nals == 0) {
 270                 av_log(logctx, AV_LOG_ERROR, "No NAL unit found\n");
 271                 return AVERROR_INVALIDDATA;
 272             } else {
 273                 break;
 274             }
 275         }
 276
 277         if (pkt->nals_allocated < pkt->nb_nals + 1) {
 278             int new_size = pkt->nals_allocated + 1;
 279             H2645NAL *tmp = av_realloc_array(pkt->nals, new_size, sizeof(*tmp));
 280             if (!tmp)
 281                 return AVERROR(ENOMEM);
 282
 283             pkt->nals = tmp;
 284             memset(pkt->nals + pkt->nals_allocated, 0,
 285                    (new_size - pkt->nals_allocated) * sizeof(*tmp));
 286             pkt->nals_allocated = new_size;
 287         }
 288         nal = &pkt->nals[pkt->nb_nals++];
 289
 290         consumed = ff_h2645_extract_rbsp(bc.buffer, extract_length, nal);
 291         if (consumed < 0)
 292             return consumed;
 293
 294         bytestream2_skip(&bc, consumed);
 295
 296         /* see commit 3566042a0 */
 297         if (bytestream2_get_bytes_left(&bc) >= 4 &&
 298             bytestream2_peek_be32(&bc) == 0x000001E0)
 299             skip_trailing_zeros = 0;
 300
 301         nal->size_bits = get_bit_length(nal, skip_trailing_zeros);
 302
 303         ret = init_get_bits(&nal->gb, nal->data, nal->size_bits);
 304         if (ret < 0)
 305             return ret;
 306
 307         if (codec_id == AV_CODEC_ID_HEVC)
 308             ret = hevc_parse_nal_header(nal, logctx);
 309         else
 310             ret = h264_parse_nal_header(nal, logctx);
 311         if (ret <= 0) {
 312             if (ret < 0) {
 313                 av_log(logctx, AV_LOG_ERROR, "Invalid NAL unit %d, skipping.\n",
 314                        nal->type);
 315             }
 316             pkt->nb_nals--;
 317         }
 318     }
 319
 320     return 0;
 321 }
 322
 323 void ff_h2645_packet_uninit(H2645Packet *pkt)
 324 {
 325     int i;
 326     for (i = 0; i < pkt->nals_allocated; i++)
 327         av_freep(&pkt->nals[i].rbsp_buffer);
 328     av_freep(&pkt->nals);
 329     pkt->nals_allocated = 0;
 330 }