From b926dd100b89baa23cb62d24c56c4a1f793ac55e Mon Sep 17 00:00:00 2001
From: "J. Alexander Treuman" <jat@spatialrift.net>
Date: Wed, 26 Jul 2006 03:10:19 +0000
Subject: Use the lame tag's encoder delay/padding to implement gapless mp3
playback
git-svn-id: https://svn.musicpd.org/mpd/trunk@4462 09075e82-0dd4-0310-85a5-a0d7c8717e4f
---
src/inputPlugins/mp3_plugin.c | 53 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
(limited to 'src/inputPlugins')
diff --git a/src/inputPlugins/mp3_plugin.c b/src/inputPlugins/mp3_plugin.c
index 549e62af3..86c3742bb 100644
--- a/src/inputPlugins/mp3_plugin.c
+++ b/src/inputPlugins/mp3_plugin.c
@@ -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;
--
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