According to the ReplayGain spec, the peak amplitude may overflow and may result
in peak amplitude values greater than 1.0 with psychoacoustically coded audio,
such as MP3. Fully compliant decoders must allow peak overflows.
Additionally, having peak values in the 0<->UINT32_MAX scale makes it more
difficult for applications to actually use the peak values (e.g. when
implementing clipping prevention) since values have to be rescaled down.
This patch corrects the peak parsing by removing the rescaling of the decoded
values between 0 and UINT32_MAX and the 1.0 upper limit.
---
Merged parse_gain() and parse_peak() into parse_value(), lavu minor version
bump, APIchanges update, better peak documentation in replaygain.h
doc/APIchanges | 4 ++++
libavformat/replaygain.c | 56 +++++++++++-------------------------------------
libavutil/replaygain.h | 4 ++--
libavutil/version.h | 2 +-
4 files changed, 20 insertions(+), 46 deletions(-)
diff --git a/doc/APIchanges b/doc/APIchanges
index d800253..e999c7e 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -13,6 +13,10 @@ libavutil: 2013-12-xx
API changes, most recent first:
+2014-03-xx - xxxxxxx - lavu 53.09.0 - replaygain.h
+ Full scale for peak values is now 100000 (instead of UINT32_MAX) and values
+ may overflow.
+
2014-02-xx - xxxxxxx - lavu 53.08.0 - frame.h
Add av_frame_remove_side_data() for removing a single side data
instance from a frame.
diff --git a/libavformat/replaygain.c b/libavformat/replaygain.c
index cf4dbf8..5e4bccd 100644
--- a/libavformat/replaygain.c
+++ b/libavformat/replaygain.c
@@ -35,19 +35,19 @@
#include "avformat.h"
#include "replaygain.h"
-static int32_t parse_gain(const char *gain)
+static int32_t parse_value(const char *value, int32_t min)
{
char *fraction;
int scale = 10000;
int32_t mb = 0;
int db;
- if (!gain)
- return INT32_MIN;
+ if (!value)
+ return min;
- gain += strspn(gain, " \t");
+ value += strspn(value, " \t");
- db = strtol(gain, &fraction, 0);
+ db = strtol(value, &fraction, 0);
if (*fraction++ == '.') {
while (av_isdigit(*fraction) && scale) {
mb += scale * (*fraction - '0');
@@ -57,41 +57,11 @@ static int32_t parse_gain(const char *gain)
}
if (abs(db) > (INT32_MAX - mb) / 100000)
- return INT32_MIN;
+ return min;
- return db * 100000 + FFSIGN(db) * mb;
-}
-
-static uint32_t parse_peak(const uint8_t *peak)
-{
- int64_t val = 0;
- int64_t scale = 1;
-
- if (!peak)
- return 0;
-
- peak += strspn(peak, " \t");
-
- if (peak[0] == '1' && peak[1] == '.')
- return UINT32_MAX;
- else if (!(peak[0] == '0' && peak[1] == '.'))
- return 0;
-
- peak += 2;
-
- while (av_isdigit(*peak)) {
- int digit = *peak - '0';
-
- if (scale > INT64_MAX / 10)
- break;
-
- val = 10 * val + digit;
- scale *= 10;
-
- peak++;
- }
-
- return av_rescale(val, UINT32_MAX, scale);
+ return (min == 0) ?
+ db * 100000 + mb :
+ db * 100000 + FFSIGN(db) * mb;
}
static int replaygain_export(AVStream *st,
@@ -104,10 +74,10 @@ static int replaygain_export(AVStream *st,
int32_t tg, ag;
uint32_t tp, ap;
- tg = parse_gain(track_gain);
- ag = parse_gain(album_gain);
- tp = parse_peak(track_peak);
- ap = parse_peak(album_peak);
+ tg = parse_value(track_gain, INT32_MIN);
+ ag = parse_value(album_gain, INT32_MIN);
+ tp = parse_value(track_peak, 0);
+ ap = parse_value(album_peak, 0);
if (tg == INT32_MIN && ag == INT32_MIN)
return 0;
diff --git a/libavutil/replaygain.h b/libavutil/replaygain.h
index 8447703..7871d2c 100644
--- a/libavutil/replaygain.h
+++ b/libavutil/replaygain.h
@@ -34,8 +34,8 @@ typedef struct AVReplayGain {
*/
int32_t track_gain;
/**
- * Peak track amplitude, with UINT32_MAX representing full scale. 0 when
- * unknown.
+ * Peak track amplitude, with 100000 representing full scale (but values
+ * may overflow). 0 when unknown.
*/
uint32_t track_peak;
/**
diff --git a/libavutil/version.h b/libavutil/version.h
index 7f439d7..f8bb447 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -54,7 +54,7 @@
*/
#define LIBAVUTIL_VERSION_MAJOR 53
-#define LIBAVUTIL_VERSION_MINOR 8
+#define LIBAVUTIL_VERSION_MINOR 9
#define LIBAVUTIL_VERSION_MICRO 0
#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
--
1.9.1
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