俺とPhotoRec 〜TSファイルの救出処理を再考する〜
以前、4GB超のTSファイルについて救出処理を書いてみたが
今回はこれを改善して、汎用的に動作するコードを考えてみた。
以前のコードの問題点
改善策
- 判定するパケット数を増やす
先頭から32パケット分のsync_byte(0x47)位置を判定する処理に変更。- 何故32パケットか?
パケット数を増減させて色々試した結果、この程度かなと。
- 何故32パケットか?
- ベースをPhotoRec-6.11.3に変更。file_m2ts.c のみ、6.12-WIPのものを使用する。
- file_ts.c に書いてあった処理を、file_m2ts.c へ統合。
改善したコード
- file_m2ts.c
/* File: file_m2ts.c Copyright (C) 2008 Christophe GRENIER <grenier@cgsecurity.org> This software is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #ifdef HAVE_STRING_H #include <string.h> #endif #include <stdio.h> #include "types.h" #include "filegen.h" static void register_header_check_m2ts(file_stat_t *file_stat); /* M2TS */ static int header_check_m2ts(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new); static int data_check_m2ts(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery); /* M2T */ static int header_check_m2t(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new); static int data_check_m2t(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery); /* TS */ static int header_check_ts(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new); static int data_check_ts(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery); const file_hint_t file_hint_m2ts= { .extension="m2ts", .description="MPEG2-TS(.m2ts/.m2t/.tod/.ts)", .min_header_distance=0, .max_filesize=PHOTOREC_MAX_FILE_SIZE, .recover=1, .enable_by_default=1, .register_header_check=®ister_header_check_m2ts }; static const unsigned char hdmv_header[4] = { 'H','D','M','V'}; static const unsigned char tshv_header[4] = { 'T','S','H','V'}; static const unsigned char sdvs_header[4] = { 'S','D','V','S'}; static const unsigned char ts_header[1] = {0x47}; static void register_header_check_m2ts(file_stat_t *file_stat) { register_header_check(0xd7, hdmv_header, sizeof(hdmv_header), &header_check_m2ts, file_stat); register_header_check(0xd7, sdvs_header, sizeof(sdvs_header), &header_check_m2ts, file_stat); register_header_check(0x18b, tshv_header, sizeof(tshv_header), &header_check_m2t, file_stat); register_header_check(0, ts_header, sizeof(ts_header), &header_check_ts, file_stat); } static int header_check_m2ts(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new) { if(file_recovery!=NULL && file_recovery->file_stat!=NULL && file_recovery->file_stat->file_hint==&file_hint_m2ts) return 0; /* BDAV MPEG-2 transport stream */ /* Each frame is 192 byte long and begins by a TS_SYNC_BYTE */ if(!(buffer[4]==0x47 && buffer[4+192]==0x47 && buffer[4+2*192]==0x47)) return 0; if( memcmp(&buffer[0xd7], hdmv_header, sizeof(hdmv_header))==0 && memcmp(&buffer[0xe8], hdmv_header, sizeof(hdmv_header))==0) { reset_file_recovery(file_recovery_new); #ifdef DJGPP file_recovery_new->extension="m2t"; #else file_recovery_new->extension=file_hint_m2ts.extension; #endif file_recovery_new->min_filesize=192; file_recovery_new->calculated_file_size=192; file_recovery_new->data_check=&data_check_m2ts; file_recovery_new->file_check=&file_check_size; return 1; } if( memcmp(&buffer[0xd7], sdvs_header, sizeof(sdvs_header))==0 && memcmp(&buffer[0xe8], sdvs_header, sizeof(sdvs_header))==0) { reset_file_recovery(file_recovery_new); file_recovery_new->extension="tod"; file_recovery_new->min_filesize=192; file_recovery_new->calculated_file_size=192; file_recovery_new->data_check=&data_check_m2ts; file_recovery_new->file_check=&file_check_size; return 1; } return 0; } static int header_check_m2t(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new) { if(file_recovery!=NULL && file_recovery->file_stat!=NULL && file_recovery->file_stat->file_hint==&file_hint_m2ts && file_recovery->calculated_file_size == file_recovery->file_size) return 0; /* Each frame is 188 byte long and begins by a TS_SYNC_BYTE */ if(buffer[0]==0x47 && buffer[188]==0x47 && buffer[2*188]==0x47 && memcmp(&buffer[0x18b], tshv_header, sizeof(tshv_header))==0) { reset_file_recovery(file_recovery_new); file_recovery_new->extension="m2t"; file_recovery_new->min_filesize=188; file_recovery_new->calculated_file_size=188; file_recovery_new->data_check=&data_check_m2t; file_recovery_new->file_check=&file_check_size; return 1; } return 0; } static int header_check_ts(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new) { if(file_recovery!=NULL && file_recovery->file_stat!=NULL && file_recovery->file_stat->file_hint==&file_hint_m2ts && file_recovery->calculated_file_size == file_recovery->file_size) return 0; unsigned int i = 0; while(i < 32) { /* Each frame is 188 byte long and begins by a TS_SYNC_BYTE */ if(buffer[i*188]!=0x47) return 0; i++; } reset_file_recovery(file_recovery_new); file_recovery_new->extension="ts"; file_recovery_new->min_filesize=188; file_recovery_new->calculated_file_size=188; file_recovery_new->data_check=&data_check_m2t; file_recovery_new->file_check=&file_check_size; return 1; } static int data_check_m2ts(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery) { while(file_recovery->calculated_file_size + buffer_size/2 >= file_recovery->file_size && file_recovery->calculated_file_size + 5 < file_recovery->file_size + buffer_size/2) { unsigned int i=file_recovery->calculated_file_size - file_recovery->file_size + buffer_size/2; if(buffer[i+4]!=0x47) /* TS_SYNC_BYTE */ return 2; file_recovery->calculated_file_size+=192; } return 1; } static int data_check_m2t(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery) { while(file_recovery->calculated_file_size + 1 < file_recovery->file_size + buffer_size/2) { unsigned int i=file_recovery->calculated_file_size - file_recovery->file_size + buffer_size/2; if(buffer[i]!=0x47) /* TS_SYNC_BYTE */ return 2; file_recovery->calculated_file_size+=188; } return 1; }
結果
小さいファイルから4GB超のファイルまで救出できることを確認。
ゴミファイルは完全には無くならなかったものの、大幅に削減できたと思う。
判定するパケット数を更に増やしたり、ファイル最小サイズ(file_recovery_new->min_filesize)を大きめに設定することで
より良い処理になる可能性も。
*1:最小ファイルサイズ(4GB)に満たないゴミファイルは、最終的には自動的に削除されるけど