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gst/typefind/gsttypefindfunctions.c: Replace AC3 typefinder with one that isn't terrible, and actually works usefully.

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Original commit message from CVS:
* gst/typefind/gsttypefindfunctions.c: (ac3_type_find):
Replace AC3 typefinder with one that isn't terrible, and actually
works usefully.
This commit is contained in:
Michael Smith 2007-03-09 13:05:04 +00:00
parent e81b9ec719
commit c9cd89bbab
2 changed files with 89 additions and 5 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2007-03-09 Michael Smith <msmith@fluendo.com>
* gst/typefind/gsttypefindfunctions.c: (ac3_type_find):
Replace AC3 typefinder with one that isn't terrible, and actually
works usefully.
2007-03-09 Thomas Vander Stichele <thomas at apestaart dot org>
* gst/audioconvert/gstaudioconvert.c:

88
gst/typefind/gsttypefindfunctions.c
View file

@ -871,21 +871,99 @@ musepack_type_find (GstTypeFind * tf, gpointer unused)
}
/*** audio/x-ac3 ***/
/* This should be audio/ac3, but isn't for backwards compatibility */
static GstStaticCaps ac3_caps = GST_STATIC_CAPS ("audio/x-ac3");
#define AC3_CAPS (gst_static_caps_get(&ac3_caps))
struct ac3_frmsize
{
unsigned short bit_rate;
unsigned short frm_size[3];
};
static const struct ac3_frmsize ac3_frmsizecod_tbl[] = {
{32, {64, 69, 96}},
{32, {64, 70, 96}},
{40, {80, 87, 120}},
{40, {80, 88, 120}},
{48, {96, 104, 144}},
{48, {96, 105, 144}},
{56, {112, 121, 168}},
{56, {112, 122, 168}},
{64, {128, 139, 192}},
{64, {128, 140, 192}},
{80, {160, 174, 240}},
{80, {160, 175, 240}},
{96, {192, 208, 288}},
{96, {192, 209, 288}},
{112, {224, 243, 336}},
{112, {224, 244, 336}},
{128, {256, 278, 384}},
{128, {256, 279, 384}},
{160, {320, 348, 480}},
{160, {320, 349, 480}},
{192, {384, 417, 576}},
{192, {384, 418, 576}},
{224, {448, 487, 672}},
{224, {448, 488, 672}},
{256, {512, 557, 768}},
{256, {512, 558, 768}},
{320, {640, 696, 960}},
{320, {640, 697, 960}},
{384, {768, 835, 1152}},
{384, {768, 836, 1152}},
{448, {896, 975, 1344}},
{448, {896, 976, 1344}},
{512, {1024, 1114, 1536}},
{512, {1024, 1115, 1536}},
{576, {1152, 1253, 1728}},
{576, {1152, 1254, 1728}},
{640, {1280, 1393, 1920}},
{640, {1280, 1394, 1920}}
};
static void
ac3_type_find (GstTypeFind * tf, gpointer unused)
{
guint8 *data = gst_type_find_peek (tf, 0, 2);
guint8 *data = gst_type_find_peek (tf, 0, 5);
gint offset = 0;
if (data) {
/* pretty lame method... */
/* Search for an ac3 frame; not neccesarily right at the start, but give it
* a lower probability if not found right at the start. Check that the
* frame is followed by a second frame at the expected offset.
* We could also check the two ac3 CRCs, but we don't do that right now */
while (data && offset < 1024) {
if (data[0] == 0x0b && data[1] == 0x77) {
gst_type_find_suggest (tf, GST_TYPE_FIND_POSSIBLE, AC3_CAPS);
return;
guint fscod = (data[4] >> 6) & 0x03;
guint frmsizecod = data[4] & 0x3f;
if (fscod < 3 && frmsizecod < 38) {
guint frame_size = ac3_frmsizecod_tbl[frmsizecod].frm_size[fscod];
data = gst_type_find_peek (tf, offset + frame_size * 2, 5);
if (data) {
if (data[0] == 0x0b && data[1] == 0x77) {
guint fscod2 = (data[4] >> 6) & 0x03;
guint frmsizecod2 = data[4] & 0x3f;
if (fscod == fscod2 && frmsizecod == frmsizecod2) {
int prob;
if (offset == 0)
prob = GST_TYPE_FIND_MAXIMUM;
else
prob = GST_TYPE_FIND_NEARLY_CERTAIN;
gst_type_find_suggest (tf, prob, AC3_CAPS);
}
}
}
}
}
offset++;
data = gst_type_find_peek (tf, offset, 5);
}
}