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More detailed mp3 frame header check

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@1383 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Björn Stenberg 2002-07-18 15:21:45 +00:00
parent c7100372e1
commit 60e7b20971
1 changed files with 24 additions and 2 deletions
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26
firmware/id3.c
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@ -34,7 +34,6 @@
#include "id3.h"
/* Some utility macros used in getsonglength() */
#define CHECKSYNC(x) (((x >> 21) & 0x07FF) == 0x7FF)
#define BYTE0(x) ((x >> 24) & 0xFF)
#define BYTE1(x) ((x >> 16) & 0xFF)
#define BYTE2(x) ((x >> 8) & 0xFF)
@ -345,6 +344,29 @@ static int getid3v1len(int fd)
return offset;
}
/* check if 'head' is a valid mp3 frame header */
static bool mp3frameheader(unsigned long head)
{
if ((head & 0xffe00000) != 0xffe00000) /* bad sync? */
return false;
if (!((head >> 17) & 3)) /* no layer? */
return false;
if (((head >> 12) & 0xf) == 0xf) /* bad bitrate? */
return false;
if (!((head >> 12) & 0xf)) /* no bitrate? */
return false;
if (((head >> 10) & 0x3) == 0x3) /* bad sample rate? */
return false;
if (((head >> 19) & 1) == 1 &&
((head >> 17) & 3) == 3 &&
((head >> 16) & 1) == 1)
return false;
if ((head & 0xffff0000) == 0xfffe0000)
return false;
return true;
}
/*
* Calculates the length (in milliseconds) of an MP3 file. Currently this code
* doesn't care about VBR (Variable BitRate) files since it would have to scan
@ -397,7 +419,7 @@ static int getsonglength(int fd, struct mp3entry *entry)
if(!read(fd, &tmp, 1))
return -1;
header |= tmp;
} while(!CHECKSYNC(header));
} while(!mp3frameheader(header));
/*
* Some files are filled with garbage in the beginning,