diff options
Diffstat (limited to 'wsutil')
| -rw-r--r-- | wsutil/mpeg-audio.c | 27 | ||||
| -rw-r--r-- | wsutil/mpeg-audio.h | 3 |
2 files changed, 30 insertions, 0 deletions
diff --git a/wsutil/mpeg-audio.c b/wsutil/mpeg-audio.c index 00ac78d8bd..e22bef38c8 100644 --- a/wsutil/mpeg-audio.c +++ b/wsutil/mpeg-audio.c @@ -81,6 +81,33 @@ mpa_padding(const struct mpa *mpa) return(mpa->padding ? mpa_padding_data[mpa_layers[mpa->layer]] : 0); } +/* Decode an ID3v2 synchsafe integer. + * See https://id3.org/id3v2.4.0-structure section 6.2. + */ +guint32 +decode_synchsafe_int(guint32 input) +{ + guint32 value; + + /* High-order byte */ + value = (input >> 24) & 0x7f; + /* Shift the result left to make room for the next 7 bits */ + value <<= 7; + + /* Now OR in the 2nd byte */ + value |= (input >> 16) & 0x7f; + value <<= 7; + + /* ... and the 3rd */ + value |= (input >> 8) & 0x7f; + value <<= 7; + + /* For the 4th byte don't do the shift */ + value |= input & 0x7f; + + return value; +} + /* * Editor modelines - https://www.wireshark.org/tools/modelines.html * diff --git a/wsutil/mpeg-audio.h b/wsutil/mpeg-audio.h index ced51ff745..e496a9b10d 100644 --- a/wsutil/mpeg-audio.h +++ b/wsutil/mpeg-audio.h @@ -11,6 +11,7 @@ #ifndef MPA_H #define MPA_H 1 +#include <glib.h> #include "ws_symbol_export.h" struct mpa { @@ -71,6 +72,8 @@ WS_DLL_PUBLIC unsigned int mpa_frequency(const struct mpa *); WS_DLL_PUBLIC unsigned int mpa_padding(const struct mpa *); +WS_DLL_PUBLIC +guint32 decode_synchsafe_int(guint32); #define MPA_DATA_BYTES(mpa) (mpa_bitrate(mpa) * mpa_samples(mpa) \ / mpa_frequency(mpa) / 8) |