LCOV - code coverage report
Current view: top level - libavcodec - mpeg4_unpack_bframes_bsf.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 73 81 90.1 %
Date: 2018-05-20 11:54:08 Functions: 5 5 100.0 %

          Line data    Source code
       1             : /*
       2             :  * Bitstream filter for unpacking DivX-style packed B-frames in MPEG-4 (divx_packed)
       3             :  * Copyright (c) 2015 Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
       4             :  *
       5             :  * This file is part of FFmpeg.
       6             :  *
       7             :  * FFmpeg is free software; you can redistribute it and/or
       8             :  * modify it under the terms of the GNU Lesser General Public
       9             :  * License as published by the Free Software Foundation; either
      10             :  * version 2.1 of the License, or (at your option) any later version.
      11             :  *
      12             :  * FFmpeg is distributed in the hope that it will be useful,
      13             :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      14             :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      15             :  * Lesser General Public License for more details.
      16             :  *
      17             :  * You should have received a copy of the GNU Lesser General Public
      18             :  * License along with FFmpeg; if not, write to the Free Software
      19             :  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
      20             :  */
      21             : 
      22             : #include "avcodec.h"
      23             : #include "bsf.h"
      24             : #include "mpeg4video.h"
      25             : 
      26             : typedef struct UnpackBFramesBSFContext {
      27             :     AVPacket *b_frame;
      28             : } UnpackBFramesBSFContext;
      29             : 
      30             : /* search next start code */
      31          48 : static unsigned int find_startcode(const uint8_t *buf, int buf_size, int *pos)
      32             : {
      33          48 :     unsigned int startcode = 0xFF;
      34             : 
      35       56413 :     for (; *pos < buf_size;) {
      36       56349 :         startcode = ((startcode << 8) | buf[*pos]) & 0xFFFFFFFF;
      37       56349 :         *pos +=1;
      38       56349 :         if ((startcode & 0xFFFFFF00) != 0x100)
      39       56317 :             continue;  /* no startcode */
      40          32 :         return startcode;
      41             :     }
      42             : 
      43          16 :     return 0;
      44             : }
      45             : 
      46             : /* determine the position of the packed marker in the userdata,
      47             :  * the number of VOPs and the position of the second VOP */
      48          16 : static void scan_buffer(const uint8_t *buf, int buf_size,
      49             :                         int *pos_p, int *nb_vop, int *pos_vop2) {
      50             :     unsigned int startcode;
      51             :     int pos, i;
      52             : 
      53          80 :     for (pos = 0; pos < buf_size;) {
      54          48 :         startcode = find_startcode(buf, buf_size, &pos);
      55             : 
      56          52 :         if (startcode == USER_DATA_STARTCODE && pos_p) {
      57             :             /* check if the (DivX) userdata string ends with 'p' (packed) */
      58         288 :             for (i = 0; i < 255 && pos + i + 1 < buf_size; i++) {
      59         286 :                 if (buf[pos + i] == 'p' && buf[pos + i + 1] == '\0') {
      60           2 :                     *pos_p = pos + i;
      61           2 :                     break;
      62             :                 }
      63             :             }
      64          44 :         } else if (startcode == VOP_STARTCODE && nb_vop) {
      65          20 :             *nb_vop += 1;
      66          20 :             if (*nb_vop == 2 && pos_vop2) {
      67           5 :                 *pos_vop2 = pos - 4; /* subtract 4 bytes startcode */
      68             :             }
      69             :         }
      70             :     }
      71          16 : }
      72             : 
      73          30 : static int mpeg4_unpack_bframes_filter(AVBSFContext *ctx, AVPacket *out)
      74             : {
      75          30 :     UnpackBFramesBSFContext *s = ctx->priv_data;
      76          30 :     int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0;
      77             :     AVPacket *in;
      78             : 
      79          30 :     ret = ff_bsf_get_packet(ctx, &in);
      80          30 :     if (ret < 0)
      81          15 :         return ret;
      82             : 
      83          15 :     scan_buffer(in->data, in->size, &pos_p, &nb_vop, &pos_vop2);
      84          15 :     av_log(ctx, AV_LOG_DEBUG, "Found %d VOP startcode(s) in this packet.\n", nb_vop);
      85             : 
      86          15 :     if (pos_vop2 >= 0) {
      87           5 :         if (s->b_frame->data) {
      88           0 :             av_log(ctx, AV_LOG_WARNING,
      89             :                    "Missing one N-VOP packet, discarding one B-frame.\n");
      90           0 :             av_packet_unref(s->b_frame);
      91             :         }
      92             :         /* store the packed B-frame in the BSFContext */
      93           5 :         ret = av_packet_ref(s->b_frame, in);
      94           5 :         if (ret < 0) {
      95           0 :             goto fail;
      96             :         }
      97           5 :         s->b_frame->size -= pos_vop2;
      98           5 :         s->b_frame->data += pos_vop2;
      99             :     }
     100             : 
     101          15 :     if (nb_vop > 2) {
     102           0 :         av_log(ctx, AV_LOG_WARNING,
     103             :        "Found %d VOP headers in one packet, only unpacking one.\n", nb_vop);
     104             :     }
     105             : 
     106          15 :     if (nb_vop == 1 && s->b_frame->data) {
     107             :         /* use frame from BSFContext */
     108           7 :         av_packet_move_ref(out, s->b_frame);
     109             : 
     110             :         /* use properties from current input packet */
     111           7 :         ret = av_packet_copy_props(out, in);
     112           7 :         if (ret < 0) {
     113           0 :             goto fail;
     114             :         }
     115             : 
     116          14 :         if (in->size <= MAX_NVOP_SIZE) {
     117             :             /* N-VOP */
     118           4 :             av_log(ctx, AV_LOG_DEBUG, "Skipping N-VOP.\n");
     119             :         } else {
     120             :             /* copy packet into BSFContext */
     121           3 :             av_packet_move_ref(s->b_frame, in);
     122             :         }
     123           8 :     } else if (nb_vop >= 2) {
     124             :         /* use first frame of the packet */
     125           5 :         av_packet_move_ref(out, in);
     126           5 :         out->size = pos_vop2;
     127           3 :     } else if (pos_p >= 0) {
     128           1 :         ret = av_packet_make_writable(in);
     129           1 :         if (ret < 0)
     130           0 :             goto fail;
     131           1 :         av_log(ctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n");
     132           1 :         av_packet_move_ref(out, in);
     133             :         /* remove 'p' (packed) from the end of the (DivX) userdata string */
     134           1 :         out->data[pos_p] = '\0';
     135             :     } else {
     136             :         /* copy packet */
     137           2 :         av_packet_move_ref(out, in);
     138             :     }
     139             : 
     140          15 : fail:
     141          15 :     if (ret < 0)
     142           0 :         av_packet_unref(out);
     143          15 :     av_packet_free(&in);
     144             : 
     145          15 :     return ret;
     146             : }
     147             : 
     148           1 : static int mpeg4_unpack_bframes_init(AVBSFContext *ctx)
     149             : {
     150           1 :     UnpackBFramesBSFContext *s = ctx->priv_data;
     151             : 
     152           1 :     s->b_frame = av_packet_alloc();
     153           1 :     if (!s->b_frame)
     154           0 :         return AVERROR(ENOMEM);
     155             : 
     156           1 :     if (ctx->par_in->extradata) {
     157           1 :         int pos_p_ext = -1;
     158           1 :         scan_buffer(ctx->par_in->extradata, ctx->par_in->extradata_size, &pos_p_ext, NULL, NULL);
     159           1 :         if (pos_p_ext >= 0) {
     160           1 :             av_log(ctx, AV_LOG_DEBUG,
     161             :                    "Updating DivX userdata (remove trailing 'p') in extradata.\n");
     162           1 :             ctx->par_out->extradata[pos_p_ext] = '\0';
     163             :         }
     164             :     }
     165             : 
     166           1 :     return 0;
     167             : }
     168             : 
     169           1 : static void mpeg4_unpack_bframes_close(AVBSFContext *bsfc)
     170             : {
     171           1 :     UnpackBFramesBSFContext *ctx = bsfc->priv_data;
     172           1 :     av_packet_free(&ctx->b_frame);
     173           1 : }
     174             : 
     175             : static const enum AVCodecID codec_ids[] = {
     176             :     AV_CODEC_ID_MPEG4, AV_CODEC_ID_NONE,
     177             : };
     178             : 
     179             : const AVBitStreamFilter ff_mpeg4_unpack_bframes_bsf = {
     180             :     .name           = "mpeg4_unpack_bframes",
     181             :     .priv_data_size = sizeof(UnpackBFramesBSFContext),
     182             :     .init           = mpeg4_unpack_bframes_init,
     183             :     .filter         = mpeg4_unpack_bframes_filter,
     184             :     .close          = mpeg4_unpack_bframes_close,
     185             :     .codec_ids      = codec_ids,
     186             : };

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