X-Git-Url: http://git.tdb.fi/?p=libs%2Fal.git;a=blobdiff_plain;f=source%2Fmp3decoder.cpp;fp=source%2Fmp3decoder.cpp;h=a717cf4b3b4dde400cac7b234d4cecf6db822c1d;hp=0000000000000000000000000000000000000000;hb=0e266d73f9aab89410c736e969eaa51ef914acf1;hpb=d035e638b940f25cb5d46a049a00b34dc60dc5e0

diff --git a/source/mp3decoder.cpp b/source/mp3decoder.cpp
new file mode 100644
index 0000000..a717cf4
--- /dev/null
+++ b/source/mp3decoder.cpp
@@ -0,0 +1,160 @@
+#include <limits>
+#include <mad.h>
+#include <msp/strings/format.h>
+#include "mp3decoder.h"
+
+using namespace std;
+
+namespace {
+
+Msp::Int16 scale(mad_fixed_t sample)
+{
+	if(sample<=-MAD_F_ONE)
+		return numeric_limits<Msp::Int16>::min();
+	else if(sample>=MAD_F_ONE)
+		return numeric_limits<Msp::Int16>::max();
+	else
+		return (sample + (1<<(MAD_F_FRACBITS-16))) >> (MAD_F_FRACBITS-15);
+}
+
+} // namespace
+
+
+namespace Msp {
+namespace AL {
+
+mp3_error::mp3_error(const std::string &func, int err):
+	runtime_error(format("%s: %s", func, get_message(err)))
+{ }
+
+string mp3_error::get_message(int err)
+{
+	return format("%d", err);
+}
+
+
+struct Mp3Decoder::Private
+{
+	mad_stream stream;
+	mad_frame frame;
+	mad_synth synth;
+};
+
+
+Mp3Decoder::Mp3Decoder(IO::Seekable &io):
+	priv(new Private),
+	in(io),
+	in_buf_size(16384),
+	in_buffer(new char[in_buf_size]),
+	read_pos(0)
+{
+	mad_stream_init(&priv->stream);
+	mad_frame_init(&priv->frame);
+	mad_synth_init(&priv->synth);
+
+	try
+	{
+		decode_frame();
+		format = (priv->frame.header.mode==MAD_MODE_SINGLE_CHANNEL ? MONO16 : STEREO16);
+		freq = priv->frame.header.samplerate;
+	}
+	catch(...)
+	{
+		delete[] in_buffer;
+		throw;
+	}
+}
+
+Mp3Decoder::~Mp3Decoder()
+{
+	delete[] in_buffer;
+	mad_synth_finish(&priv->synth);
+	mad_frame_finish(&priv->frame);
+	mad_stream_finish(&priv->stream);
+}
+
+bool Mp3Decoder::detect(const string &sig)
+{
+	if(sig.size()>=2 && sig[0]=='\xFF' && (sig[1]&0xE0)==0xE0)
+		return true;
+
+	static const char id3_sig[] = { 'I', 'D', '3' };
+	if(sig.size()<sizeof(id3_sig))
+		return false;
+	return !sig.compare(0, sizeof(id3_sig), id3_sig);
+}
+
+void Mp3Decoder::rewind()
+{
+	in.seek(0, IO::S_BEG);
+}
+
+unsigned Mp3Decoder::read(char *buf, unsigned len)
+{
+	unsigned nchan = (format==STEREO16 ? 2 : 1);
+	mad_pcm &pcm = priv->synth.pcm;
+
+	unsigned pos = 0;
+	while(pos+2*nchan<=len)
+	{
+		if(read_pos>=pcm.length)
+		{
+			if(!decode_frame())
+				break;
+		}
+
+		for(unsigned i=0; i<nchan; ++i)
+		{
+			Int16 sample = scale(pcm.samples[i][read_pos]);
+			buf[pos++] = sample;
+			buf[pos++] = sample>>8;
+		}
+
+		++read_pos;
+	}
+
+	return pos;
+}
+
+bool Mp3Decoder::fill_input()
+{
+	unsigned in_pos = 0;
+	if(priv->stream.next_frame && priv->stream.next_frame<priv->stream.bufend)
+	{
+		copy(priv->stream.next_frame, priv->stream.bufend, in_buffer);
+		in_pos = priv->stream.bufend-priv->stream.next_frame;
+	}
+
+	unsigned len = in.read(in_buffer+in_pos, in_buf_size-in_pos);
+	in_pos += len;
+
+	mad_stream_buffer(&priv->stream, reinterpret_cast<unsigned char *>(in_buffer), in_pos);
+	priv->stream.error = MAD_ERROR_NONE;
+
+	return len;
+}
+
+bool Mp3Decoder::decode_frame()
+{
+	while(1)
+	{
+		if(!priv->stream.buffer || priv->stream.error==MAD_ERROR_BUFLEN)
+			if(!fill_input())
+				return false;
+
+		if(!mad_frame_decode(&priv->frame, &priv->stream))
+		{
+			mad_synth_frame(&priv->synth, &priv->frame);
+			read_pos = 0;
+			return true;
+		}
+
+		if(priv->stream.error==MAD_ERROR_BUFLEN)
+			continue;
+		else if(!MAD_RECOVERABLE(priv->stream.error))
+			throw mp3_error("mad_frame_decode", priv->stream.error);
+	}
+}
+
+} // namespace AL
+} // namespace Msp