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Parse lame tag for encoder delay/padding so we can later implement gapless

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git-svn-id: https://svn.musicpd.org/mpd/trunk@4460 09075e82-0dd4-0310-85a5-a0d7c8717e4f
This commit is contained in:
J. Alexander Treuman 2006-07-25 22:49:10 +00:00
parent a686436c77
commit 1523e8a842
1 changed files with 67 additions and 0 deletions
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67
src/inputPlugins/mp3_plugin.c
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@ -455,6 +455,18 @@ enum {
XING_SCALE = 0x00000008L,
};
struct lame {
char encoder[10]; /* 9 byte encoder name/version ("LAME3.97b") */
#if 0
/* See related comment in parse_lame() */
float peak; /* replaygain peak */
float trackGain; /* replaygain track gain */
float albumGain; /* replaygain album gain */
#endif
int encoderDelay; /* # of added samples at start of mp3 */
int encoderPadding; /* # of added samples at end of mp3 */
};
static int parse_xing(struct xing *xing, struct mad_bitptr *ptr, int *oldbitlen)
{
unsigned long bits;
@ -528,13 +540,67 @@ static int parse_xing(struct xing *xing, struct mad_bitptr *ptr, int *oldbitlen)
return 0;
}
static int parse_lame(struct lame *lame, struct mad_bitptr *ptr, int *bitlen)
{
int i;
/* Unlike the xing header, the lame tag has a fixed length. Fail if
* not all 36 bytes (288 bits) are there. */
if (*bitlen < 288) return 0;
for (i = 0; i < 9; i++) lame->encoder[i] = (char)mad_bit_read(ptr, 8);
lame->encoder[9] = '\0';
/* This is technically incorrect, since the encoder might not be lame.
* But there's no other way to determine if this is a lame tag, and we
* wouldn't want to go reading a tag that's not there. */
if (strncmp(lame->encoder, "LAME", 4) != 0) return 0;
#if 0
/* Apparently lame versions <3.97b1 do not calculate replaygain. I'm
* using lame 3.97b2, and while it does calculate replaygain, it's
* setting the values to 0. Using --replaygain-(fast|accurate) doesn't
* make any difference. Leaving this code unused until we have a way
* of testing it. -- jat */
mad_bit_read(ptr, 16);
mad_bit_read(ptr, 32); /* peak */
mad_bit_read(ptr, 6); /* header */
bits = mad_bit_read(ptr, 1); /* sign bit */
lame->trackGain = mad_bit_read(ptr, 9); /* gain*10 */
lame->trackGain = (bits ? -lame->trackGain : lame->trackGain) / 10;
mad_bit_read(ptr, 6); /* header */
bits = mad_bit_read(ptr, 1); /* sign bit */
lame->albumGain = mad_bit_read(ptr, 9); /* gain*10 */
lame->albumGain = (bits ? -lame->albumGain : lame->albumGain) / 10;
mad_bit_read(ptr, 16);
#else
mad_bit_read(ptr, 96);
#endif
lame->encoderDelay = mad_bit_read(ptr, 12);
lame->encoderPadding = mad_bit_read(ptr, 12);
mad_bit_read(ptr, 96);
*bitlen -= 288;
return 1;
}
static int decodeFirstFrame(mp3DecodeData * data, DecoderControl * dc,
MpdTag ** tag, ReplayGainInfo ** replayGainInfo)
{
struct xing xing;
struct lame lame;
struct mad_bitptr ptr;
int bitlen;
int found_xing;
int found_lame;
int ret;
int skip;
@ -557,6 +623,7 @@ static int decodeFirstFrame(mp3DecodeData * data, DecoderControl * dc,
bitlen = data->stream.anc_bitlen;
found_xing = parse_xing(&xing, &ptr, &bitlen);
found_lame = (found_xing ? parse_lame(&lame, &ptr, &bitlen) : 0);
if (found_xing) {
if (xing.flags & XING_FRAMES) {