1 files changed, 83 insertions, 0 deletions
diff --git a/codecs/mp3anal.h b/codecs/mp3anal.h
new file mode 100755
index 000000000..263e8520c
--- /dev/null
+++ b/codecs/mp3anal.h
@@ -0,0 +1,83 @@
+/*
+ * Asterisk -- A telephony toolkit for Linux.
+ *
+ * MP3 Header Analysis Routines.  Thanks to Robert Kaye for the logic!
+ *
+ * Copyright (C) 1999, Mark Spencer
+ *
+ * Mark Spencer <markster@linux-support.net>
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License
+ */
+
+static int bitrates1[] = { 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 };
+static int bitrates2[] = { 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 };
+
+static int samplerates1[] = { 44100, 48000, 32000 };
+static int samplerates2[] = { 22050, 24000, 16000 };
+
+static int outputsamples[] = { 576, 1152 };
+
+static int mp3_samples(unsigned char *header)
+{
+	int ver = (header[1] & 0x8) >> 3;
+	return outputsamples[ver];
+}
+
+static int mp3_bitrate(unsigned char *header)
+{
+	int ver = (header[1] & 0x8) >> 3;
+	int br = (header[2] >> 4);
+
+	if (ver > 14) {
+		ast_log(LOG_WARNING, "Invalid bit rate\n");
+		return -1;
+	}
+	if (ver)
+		return bitrates1[br];
+	else {
+		return bitrates2[br];
+	}
+}
+
+static int mp3_samplerate(unsigned char *header)
+{
+	int ver = (header[1] & 0x8) >> 3;
+	int sr = (header[2] >> 2) & 0x3;
+	
+	if (ver > 2) {
+		ast_log(LOG_WARNING, "Invalid sample rate\n");
+		return -1;
+	}
+
+	if (ver)
+		return samplerates1[sr];
+	else
+		return samplerates2[sr];
+}
+
+static int mp3_padding(unsigned char *header)
+{
+	return (header[2] >> 1) & 0x1;	
+}
+
+static int mp3_badheader(unsigned char *header)
+{
+	if ((header[0] != 0xFF) || ((header[1] & 0xF0) != 0xF0))
+		return -1;
+	return 0;
+}
+
+static int mp3_framelen(unsigned char *header)
+{
+	int br = mp3_bitrate(header);
+	int sr = mp3_samplerate(header);
+	int size;
+	
+	if ((br < 0) || (sr < 0))
+		return -1;
+	size = 144000 * br / sr + mp3_padding(header);
+	return size;
+}
+