libavcodec/mpeg4video_parser.c

   1 /*
   2  * MPEG-4 video frame extraction
   3  * Copyright (c) 2003 Fabrice Bellard
   4  * Copyright (c) 2003 Michael Niedermayer
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #define UNCHECKED_BITSTREAM_READER 1
  24
  25 #include "internal.h"
  26 #include "parser.h"
  27 #include "mpegvideo.h"
  28 #include "mpeg4video.h"
  29 #include "mpeg4videodec.h"
  30 #if FF_API_FLAG_TRUNCATED
  31 /* Nuke this header when removing FF_API_FLAG_TRUNCATED */
  32 #include "mpeg4video_parser.h"
  33 #endif
  34
  35 struct Mp4vParseContext {
  36     ParseContext pc;
  37     Mpeg4DecContext dec_ctx;
  38     int first_picture;
  39 };
  40
  41 #if FF_API_FLAG_TRUNCATED
  42 int ff_mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
  43 #else
  44 /**
  45  * Find the end of the current frame in the bitstream.
  46  * @return the position of the first byte of the next frame, or -1
  47  */
  48 static int mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
  49 #endif
  50 {
  51     int vop_found, i;
  52     uint32_t state;
  53
  54     vop_found = pc->frame_start_found;
  55     state     = pc->state;
  56
  57     i = 0;
  58     if (!vop_found) {
  59         for (i = 0; i < buf_size; i++) {
  60             state = (state << 8) | buf[i];
  61             if (state == VOP_STARTCODE) {
  62                 i++;
  63                 vop_found = 1;
  64                 break;
  65             }
  66         }
  67     }
  68
  69     if (vop_found) {
  70         /* EOF considered as end of frame */
  71         if (buf_size == 0)
  72             return 0;
  73         for (; i < buf_size; i++) {
  74             state = (state << 8) | buf[i];
  75             if ((state & 0xFFFFFF00) == 0x100) {
  76                 if (state == SLICE_STARTCODE || state == EXT_STARTCODE)
  77                     continue;
  78                 pc->frame_start_found = 0;
  79                 pc->state             = -1;
  80                 return i - 3;
  81             }
  82         }
  83     }
  84     pc->frame_start_found = vop_found;
  85     pc->state             = state;
  86     return END_NOT_FOUND;
  87 }
  88
  89 /* XXX: make it use less memory */
  90 static int mpeg4_decode_header(AVCodecParserContext *s1, AVCodecContext *avctx,
  91                                const uint8_t *buf, int buf_size)
  92 {
  93     struct Mp4vParseContext *pc = s1->priv_data;
  94     Mpeg4DecContext *dec_ctx = &pc->dec_ctx;
  95     MpegEncContext *s = &dec_ctx->m;
  96     GetBitContext gb1, *gb = &gb1;
  97     int ret;
  98
  99     s->avctx               = avctx;
 100     s->current_picture_ptr = &s->current_picture;
 101
 102     if (avctx->extradata_size && pc->first_picture) {
 103         init_get_bits(gb, avctx->extradata, avctx->extradata_size * 8);
 104         ret = ff_mpeg4_decode_picture_header(dec_ctx, gb, 1, 1);
 105         if (ret < 0)
 106             av_log(avctx, AV_LOG_WARNING, "Failed to parse extradata\n");
 107     }
 108
 109     init_get_bits(gb, buf, 8 * buf_size);
 110     ret = ff_mpeg4_decode_picture_header(dec_ctx, gb, 0, 1);
 111     if (s->width && (!avctx->width || !avctx->height ||
 112                      !avctx->coded_width || !avctx->coded_height)) {
 113         ret = ff_set_dimensions(avctx, s->width, s->height);
 114         if (ret < 0)
 115             return ret;
 116     }
 117     if((s1->flags & PARSER_FLAG_USE_CODEC_TS) && s->avctx->time_base.den>0 && ret>=0){
 118         av_assert1(s1->pts == AV_NOPTS_VALUE);
 119         av_assert1(s1->dts == AV_NOPTS_VALUE);
 120
 121         s1->pts = av_rescale_q(s->time, (AVRational){1, s->avctx->time_base.den}, (AVRational){1, 1200000});
 122     }
 123
 124     s1->pict_type     = s->pict_type;
 125     pc->first_picture = 0;
 126     return ret;
 127 }
 128
 129 static av_cold int mpeg4video_parse_init(AVCodecParserContext *s)
 130 {
 131     struct Mp4vParseContext *pc = s->priv_data;
 132
 133     pc->first_picture           = 1;
 134     pc->dec_ctx.m.quant_precision     = 5;
 135     pc->dec_ctx.m.slice_context_count = 1;
 136     pc->dec_ctx.showed_packed_warning = 1;
 137     return 0;
 138 }
 139
 140 static int mpeg4video_parse(AVCodecParserContext *s,
 141                             AVCodecContext *avctx,
 142                             const uint8_t **poutbuf, int *poutbuf_size,
 143                             const uint8_t *buf, int buf_size)
 144 {
 145     ParseContext *pc = s->priv_data;
 146     int next;
 147
 148     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
 149         next = buf_size;
 150     } else {
 151 #if FF_API_FLAG_TRUNCATED
 152         next = ff_mpeg4_find_frame_end(pc, buf, buf_size);
 153 #else
 154         next = mpeg4_find_frame_end(pc, buf, buf_size);
 155 #endif
 156
 157         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 158             *poutbuf      = NULL;
 159             *poutbuf_size = 0;
 160             return buf_size;
 161         }
 162     }
 163     mpeg4_decode_header(s, avctx, buf, buf_size);
 164
 165     *poutbuf      = buf;
 166     *poutbuf_size = buf_size;
 167     return next;
 168 }
 169
 170 const AVCodecParser ff_mpeg4video_parser = {
 171     .codec_ids      = { AV_CODEC_ID_MPEG4 },
 172     .priv_data_size = sizeof(struct Mp4vParseContext),
 173     .parser_init    = mpeg4video_parse_init,
 174     .parser_parse   = mpeg4video_parse,
 175     .parser_close   = ff_parse_close,
 176 };