1 files changed, 117 insertions, 0 deletions
diff --git a/mpeg_analyse.py b/mpeg_analyse.py
new file mode 100755
index 0000000..495e808
--- /dev/null
+++ b/mpeg_analyse.py
@@ -0,0 +1,117 @@
+#!/usr/bin/env python2
+#
+# Analyse an mp2 file for debugging
+#
+# The MIT License (MIT)
+#
+# Copyright (c) 2016 Matthias P. Braendli
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+#    The above copyright notice and this permission notice shall be included in
+#    all copies or substantial portions of the Software.
+#
+#    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+#    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+#    THE SOFTWARE.
+
+from pprint import pprint
+import sys
+import struct
+
+# Header:
+# AAAAAAAA AAABBCCD EEEEFFGH IIJJKLMM
+# see http://mpgedit.org/mpgedit/mpeg_format/mpeghdr.htm
+
+audio_version_ids = ["MPEG version 2.5", "reserved", "MPEG Version 2 (ISO/IEC 13818-3)", "MPEG Version 1 (ISO/IEC 11172-3)"]
+layer_descriptions = ["reserved", "Layer III", "Layer II", "Layer I"]
+
+# bitrate index:
+# bits	V1,L1	V1,L2	V1,L3	V2,L1	V2, L2 & L3
+# 0000	free	free	free	free	free
+# 0001	32	32	32	32	8
+# 0010	64	48	40	48	16
+# 0011	96	56	48	56	24
+# 0100	128	64	56	64	32
+# 0101	160	80	64	80	40
+# 0110	192	96	80	96	48
+# 0111	224	112	96	112	56
+# 1000	256	128	112	128	64
+# 1001	288	160	128	144	80
+# 1010	320	192	160	160	96
+# 1011	352	224	192	176	112
+# 1100	384	256	224	192	128
+# 1101	416	320	256	224	144
+# 1110	448	384	320	256	160
+# 1111	bad	bad	bad	bad	bad
+
+def analyse(fd):
+    headerdata = struct.unpack("!BBBB", fd.read(4))
+
+    sync = (headerdata[0] << 3) | (headerdata[1] >> 5)
+    print("Sync: {:x}".format(sync))
+
+    audio_version_id = (headerdata[1] >> 3) & 0x3
+    print("audio_version_id {}".format(audio_version_ids[audio_version_id]))
+
+    layer_description = (headerdata[1] >> 1) & 0x3
+    print("layer_description {}".format(layer_descriptions[layer_description]))
+
+    protection_bit = headerdata[1] & 0x1
+    if protection_bit:
+        print("Without protection")
+    else:
+        print("With protection")
+
+    bitrate_index = headerdata[2] >> 4
+    print("bitrate_index {}".format(bitrate_index))
+
+    sampling_rate = (headerdata[2] >> 2) & 0x3
+    print("sampling_rate {}".format(sampling_rate))
+
+    padding_bit = (headerdata[2] >> 1) & 0x1
+    if padding_bit:
+        print("With padding")
+    else:
+        print("Without padding")
+
+    private_bit = headerdata[2] & 0x1
+    if private_bit:
+        print("Private bit set")
+    else:
+        print("Private bit unset")
+
+    channel_mode = headerdata[3] >> 6
+    print("channel_mode {}".format(channel_mode))
+
+    mode_extension = (headerdata[3] >> 4) & 0x3
+    print("mode_extension {}".format(mode_extension))
+
+    copyright = (headerdata[3] >> 3) & 0x1
+    if copyright:
+        print("With copyright")
+    else:
+        print("Without copyright")
+
+    original = (headerdata[3] >> 2) & 0x1
+    if original:
+        print("With original")
+    else:
+        print("Without original")
+
+    emphasis = headerdata[3] & 0x3
+    print("emphasis {}".format(emphasis))
+
+
+
+fd = open(sys.argv[1], "rb")
+analyse(fd)