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-rw-r--r--gst/mpegaudioparse/gstmp3types.c254
1 files changed, 254 insertions, 0 deletions
diff --git a/gst/mpegaudioparse/gstmp3types.c b/gst/mpegaudioparse/gstmp3types.c
new file mode 100644
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+++ b/gst/mpegaudioparse/gstmp3types.c
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+/* GStreamer
+ * Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/*#define DEBUG_ENABLED */
+#include <gst/gst.h>
+#include <string.h> /* memcmp */
+
+static GstCaps* mp3_type_find(GstBuffer *buf, gpointer private);
+static GstCaps* mp3_type_find_stream(GstBuffer *buf, gpointer private);
+
+static GstTypeDefinition mp3type_definitions[] = {
+ { "mp3types_audio/mpeg", "audio/mpeg", ".mp3 .mp2 .mp1 .mpga", mp3_type_find },
+ { "mp3types_stream_audio/mpeg", "audio/mpeg", ".mp3 .mp2 .mp1 .mpga", mp3_type_find_stream },
+ { NULL, NULL, NULL, NULL },
+};
+
+static GstCaps*
+mp3_type_find(GstBuffer *buf, gpointer private)
+{
+ guint8 *data;
+ gint size, layer;
+ guint32 head;
+ GstCaps *caps;
+
+ data = GST_BUFFER_DATA (buf);
+ size = GST_BUFFER_SIZE (buf);
+
+ GST_DEBUG ("mp3typefind: typefind");
+
+ /* gracefully ripped from libid3 */
+ if (size >= 3 &&
+ data[0] == 'T' && data[1] == 'A' && data[2] == 'G') {
+ /* ID V1 tags */
+ data += 128;
+ size -= 128;
+
+ GST_DEBUG ("mp3typefind: detected ID3 Tag V1");
+ } else if (size >= 10 &&
+ (data[0] == 'I' && data[1] == 'D' && data[2] == '3') &&
+ data[3] < 0xff && data[4] < 0xff &&
+ data[6] < 0x80 && data[7] < 0x80 && data[8] < 0x80 && data[9] < 0x80)
+ {
+ guint32 skip = 0;
+
+ skip = (skip << 7) | (data[6] & 0x7f);
+ skip = (skip << 7) | (data[7] & 0x7f);
+ skip = (skip << 7) | (data[8] & 0x7f);
+ skip = (skip << 7) | (data[9] & 0x7f);
+
+ /* include size of header */
+ skip += 10;
+ /* footer present? (only available since version 4) */
+ if (data[3] > 3 && (data[5] & 0x10))
+ skip += 10;
+
+ GST_DEBUG ("mp3typefind: detected ID3 Tag V2 with %u bytes", skip);
+ size -= skip;
+ data += skip;
+ }
+
+ if (size < 4)
+ return NULL;
+
+ /* now with the right postion, do typefinding */
+ head = GUINT32_FROM_BE(*((guint32 *)data));
+ if ((head & 0xffe00000) != 0xffe00000)
+ return NULL;
+ if (!(layer = ((head >> 17) & 3)))
+ return NULL;
+ layer = 4 - layer;
+ if (((head >> 12) & 0xf) == 0xf)
+ return NULL;
+ if (!((head >> 12) & 0xf))
+ return NULL;
+ if (((head >> 10) & 0x3) == 0x3)
+ return NULL;
+
+ caps = GST_CAPS_NEW ("mp3_type_find", "audio/mpeg", "layer", GST_PROPS_INT (layer));
+
+ return caps;
+}
+static guint mp3types_bitrates[2][3][16] =
+{ { {0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, },
+ {0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, },
+ {0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, } },
+ { {0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, },
+ {0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, },
+ {0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, } },
+};
+static guint mp3types_freqs[3][3] =
+{ {44100, 48000, 32000},
+ {22050, 24000, 16000},
+ {11025, 12000, 8000}};
+static inline guint
+mp3_type_frame_length_from_header (guint32 header, guint *put_layer)
+{
+ guint length;
+ gulong samplerate, bitrate, layer, version;
+
+ /* we don't need extension, mode, copyright, original or emphasis for the frame length */
+ header >>= 9;
+ /* padding */
+ length = header & 0x1;
+ header >>= 1;
+ /* sampling frequency */
+ samplerate = header & 0x3;
+ if (samplerate == 3)
+ return 0;
+ header >>= 2;
+ /* bitrate index */
+ bitrate = header & 0xF;
+ if (bitrate == 15 || bitrate == 0)
+ return 0;
+ /* ignore error correction, too */
+ header >>= 5;
+ /* layer */
+ layer = 4 - (header & 0x3);
+ if (layer == 4)
+ return 0;
+ header >>= 2;
+ /* version */
+ version = header & 0x3;
+ if (version == 1)
+ return 0;
+ /* lookup */
+ bitrate = mp3types_bitrates[version == 3 ? 0 : 1][layer - 1][bitrate];
+ samplerate = mp3types_freqs[version > 0 ? version - 1 : 0][samplerate];
+ /* calculating */
+ if (layer == 1) {
+ length = ((12000 * bitrate / samplerate) + length) * 4;
+ } else {
+ length += ((layer == 3 && version == 0) ? 144000 : 72000) * bitrate / samplerate;
+ }
+
+ GST_DEBUG ("Calculated mad frame length of %u bytes", length);
+ GST_DEBUG ("samplerate = %lu - bitrate = %lu - layer = %lu - version = %lu", samplerate, bitrate, layer, version);
+ if (put_layer)
+ *put_layer = layer;
+ return length;
+}
+/* increase this value when this function finds too many false positives */
+/**
+ * The chance that random data is identified as a valid mp3 header is 63 / 2^18
+ * (0.024%) per try. This makes the function for calculating false positives
+ * 1 - (1 - ((63 / 2 ^18) ^ GST_MP3_TYPEFIND_MIN_HEADERS)) ^ buffersize)
+ * This has the following probabilities of false positives:
+ * bufsize MIN_HEADERS
+ * (bytes) 1 2 3 4
+ * 4096 62.6% 0.02% 0% 0%
+ * 16384 98% 0.09% 0% 0%
+ * 1 MiB 100% 5.88% 0% 0%
+ * 1 GiB 100% 100% 1.44% 0%
+ * 1 TiB 100% 100% 100% 0.35%
+ * This means that the current choice (3 headers by most of the time 4096 byte
+ * buffers is pretty safe for now.
+ * It is however important to note that in a worst case example a buffer of size
+ * 1440 * GST_MP3_TYPEFIND_MIN_HEADERS + 3
+ * bytes is needed to reliable find the mp3 stream in a buffer when scanning
+ * starts at a random position. This is currently (4323 bytes) slightly above
+ * the default buffer size. But you rarely hit the worst case - average mp3
+ * frames are in the 500 bytes range.
+ */
+#define GST_MP3_TYPEFIND_MIN_HEADERS 3
+static GstCaps*
+mp3_type_find_stream (GstBuffer *buf, gpointer private)
+{
+ guint8 *data;
+ guint size;
+ guint32 head;
+ gint layer = 0;
+
+ data = GST_BUFFER_DATA (buf);
+ size = GST_BUFFER_SIZE (buf);
+
+ while (size >= 4) {
+ head = GUINT32_FROM_BE(*((guint32 *)data));
+ if ((head & 0xffe00000) == 0xffe00000) {
+ guint length;
+ guint prev_layer = 0;
+ guint found = 0; /* number of valid headers found */
+ guint pos = 0;
+ do {
+ if ((length = mp3_type_frame_length_from_header (head, &layer))) {
+ if (prev_layer && prev_layer != layer)
+ break;
+ prev_layer = layer;
+ pos += length;
+ found++;
+ if (pos + 4 >= size) {
+ if (found >= GST_MP3_TYPEFIND_MIN_HEADERS) {
+ goto success;
+ } else {
+ break;
+ }
+ }
+ head = GUINT32_FROM_BE(*((guint32 *) &(data[pos])));
+ if ((head & 0xffe00000) != 0xffe00000)
+ break;
+ } else {
+ break;
+ }
+ } while (TRUE);
+ }
+ data++;
+ size--;
+ }
+
+ return NULL;
+
+success:
+ g_assert (layer);
+ return GST_CAPS_NEW ("mp3_type_find", "audio/mpeg", "layer", GST_PROPS_INT (layer));
+}
+
+static gboolean
+plugin_init (GModule *module, GstPlugin *plugin)
+{
+ gint i=0;
+
+ while (mp3type_definitions[i].name) {
+ GstTypeFactory *type;
+
+ type = gst_type_factory_new (&mp3type_definitions[i]);
+ gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (type));
+ i++;
+ }
+
+ /* gst_info("gsttypes: loaded %d mp3 types\n",i); */
+
+ return TRUE;
+}
+
+GstPluginDesc plugin_desc = {
+ GST_VERSION_MAJOR,
+ GST_VERSION_MINOR,
+ "mp3types",
+ plugin_init
+};
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