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tag_rva2: add struct rva2_data

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.. and several accessor inline functions, to simplify the calling
code.
This commit is contained in:
Max Kellermann 2010-07-20 18:39:57 +02:00
parent 2f16f8e9f7
commit 43a840552f
1 changed files with 39 additions and 18 deletions
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57
src/tag_rva2.c
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@ -21,6 +21,7 @@
#include "tag_rva2.h"
#include "replay_gain_info.h"
#include <stdint.h>
#include <glib.h>
#include <id3tag.h>
@ -36,6 +37,40 @@ enum rva2_channel {
CHANNEL_SUBWOOFER = 0x08
};
struct rva2_data {
uint8_t type;
uint8_t volume_adjustment[2];
uint8_t peak_bits;
};
static inline id3_length_t
rva2_peak_bytes(const struct rva2_data *data)
{
return (data->peak_bits + 7) / 8;
}
static inline int
rva2_fixed_volume_adjustment(const struct rva2_data *data)
{
signed int voladj_fixed;
voladj_fixed = (data->volume_adjustment[0] << 8) |
data->volume_adjustment[1];
voladj_fixed |= -(voladj_fixed & 0x8000);
return voladj_fixed;
}
static inline float
rva2_float_volume_adjustment(const struct rva2_data *data)
{
/*
* "The volume adjustment is encoded as a fixed point decibel
* value, 16 bit signed integer representing (adjustment*512),
* giving +/- 64 dB with a precision of 0.001953125 dB."
*/
return (float)rva2_fixed_volume_adjustment(data) / (float)512;
}
bool
tag_rva2_parse(struct id3_tag *tag, struct replay_gain_info *replay_gain_info)
{
@ -70,27 +105,13 @@ tag_rva2_parse(struct id3_tag *tag, struct replay_gain_info *replay_gain_info)
*/
while (length >= 4) {
unsigned int peak_bytes;
peak_bytes = (data[3] + 7) / 8;
const struct rva2_data *d = (const struct rva2_data *)data;
unsigned int peak_bytes = rva2_peak_bytes(d);
if (4 + peak_bytes > length)
break;
if (data[0] == CHANNEL_MASTER_VOLUME) {
signed int voladj_fixed;
double voladj_float;
/*
* "The volume adjustment is encoded as a fixed
* point decibel value, 16 bit signed integer
* representing (adjustment*512), giving +/- 64
* dB with a precision of 0.001953125 dB."
*/
voladj_fixed = (data[1] << 8) | (data[2] << 0);
voladj_fixed |= -(voladj_fixed & 0x8000);
voladj_float = (double) voladj_fixed / 512;
if (d->type == CHANNEL_MASTER_VOLUME) {
double voladj_float = rva2_float_volume_adjustment(d);
replay_gain_info->tuples[REPLAY_GAIN_TRACK].gain = voladj_float;
replay_gain_info->tuples[REPLAY_GAIN_ALBUM].gain = voladj_float;