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Use the lame tag's encoder delay/padding to implement gapless mp3 playback

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git-svn-id: https://svn.musicpd.org/mpd/trunk@4462 09075e82-0dd4-0310-85a5-a0d7c8717e4f
This commit is contained in:
J. Alexander Treuman 2006-07-26 03:10:19 +00:00
parent bf3848ef94
commit b926dd100b
1 changed files with 53 additions and 0 deletions
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53
src/inputPlugins/mp3_plugin.c
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@ -52,6 +52,9 @@
#define MUTEFRAME_SKIP 1
#define MUTEFRAME_SEEK 2
/* the number of samples of silence the decoder inserts at start */
#define DECODERDELAY 529
/* this is stolen from mpg321! */
struct audio_dither {
mad_fixed_t error[3];
@ -131,6 +134,12 @@ typedef struct _mp3DecodeData {
long highestFrame;
long maxFrames;
long currentFrame;
int dropFramesAtStart;
int dropFramesAtEnd;
int dropSamplesAtStart;
int dropSamplesAtEnd;
int foundFirstFrame;
int decodedFirstFrame;
int flush;
unsigned long bitRate;
InputStream *inStream;
@ -148,6 +157,12 @@ static void initMp3DecodeData(mp3DecodeData * data, InputStream * inStream)
data->frameOffset = NULL;
data->times = NULL;
data->currentFrame = 0;
data->dropFramesAtStart = 0;
data->dropFramesAtEnd = 0;
data->dropSamplesAtStart = 0;
data->dropSamplesAtEnd = 0;
data->foundFirstFrame = 0;
data->decodedFirstFrame = 0;
data->flush = 1;
data->inStream = inStream;
memset(&(data->dither), 0, sizeof(struct audio_dither));
@ -625,6 +640,11 @@ static int decodeFirstFrame(mp3DecodeData * data, DecoderControl * dc,
found_xing = parse_xing(&xing, &ptr, &bitlen);
found_lame = (found_xing ? parse_lame(&lame, &ptr, &bitlen) : 0);
if (found_lame) {
data->dropSamplesAtStart = lame.encoderDelay + DECODERDELAY;
data->dropSamplesAtEnd = lame.encoderPadding;
}
if (found_xing) {
if (xing.flags & XING_FRAMES) {
mad_timer_t duration = data->frame.header.duration;
@ -707,6 +727,8 @@ static int openMp3FromInputStream(InputStream * inStream, mp3DecodeData * data,
static int mp3Read(mp3DecodeData * data, OutputBuffer * cb, DecoderControl * dc,
ReplayGainInfo ** replayGainInfo)
{
int samplesPerFrame;
int samplesLeft;
int i;
int ret;
int skip;
@ -749,6 +771,24 @@ static int mp3Read(mp3DecodeData * data, OutputBuffer * cb, DecoderControl * dc,
default:
mad_synth_frame(&data->synth, &data->frame);
if (!data->foundFirstFrame) {
samplesPerFrame = (data->synth).pcm.length;
data->dropFramesAtStart = data->dropSamplesAtStart / samplesPerFrame;
data->dropFramesAtEnd = data->dropSamplesAtEnd / samplesPerFrame;
data->dropSamplesAtStart = data->dropSamplesAtStart % samplesPerFrame;
data->dropSamplesAtEnd = data->dropSamplesAtEnd % samplesPerFrame;
data->foundFirstFrame = 1;
}
if (data->dropFramesAtStart > 0) {
data->dropFramesAtStart--;
break;
} else if ((data->dropFramesAtEnd > 0) &&
(data->currentFrame == (data->maxFrames + 1 - data->dropFramesAtEnd))) {
data->dropFramesAtEnd--;
break;
}
if (data->inStream->metaTitle) {
MpdTag *tag = newMpdTag();
if (data->inStream->metaName) {
@ -764,9 +804,20 @@ static int mp3Read(mp3DecodeData * data, OutputBuffer * cb, DecoderControl * dc,
freeMpdTag(tag);
}
samplesLeft = (data->synth).pcm.length;
for (i = 0; i < (data->synth).pcm.length; i++) {
mpd_sint16 *sample;
if (!data->decodedFirstFrame &&
(i < data->dropSamplesAtStart)) {
continue;
} else if (data->dropSamplesAtEnd &&
(data->currentFrame == (data->maxFrames - data->dropFramesAtEnd))) {
samplesLeft--;
if (samplesLeft < data->dropSamplesAtEnd) break;
}
sample = (mpd_sint16 *) data->outputPtr;
*sample = (mpd_sint16) audio_linear_dither(16,
(data->
@ -821,6 +872,8 @@ static int mp3Read(mp3DecodeData * data, OutputBuffer * cb, DecoderControl * dc,
}
}
data->decodedFirstFrame = 1;
if (dc->seek && data->inStream->seekable) {
long i = 0;
data->muteFrame = MUTEFRAME_SEEK;