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typefinding: optimise AC-3 typefinder a bit

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Make AC-3 typefinder use the DataScanCtx stuff so we don't have to
do gst_type_find_peek() in the inner loop all the time. Also return
when we've suggested AC3 caps, instead of continuing with the loop.
This commit is contained in:
Tim-Philipp Müller 2010-01-23 15:25:42 +00:00
parent ca7ba91e5b
commit eef885cf86
1 changed files with 22 additions and 18 deletions
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40
gst/typefind/gsttypefindfunctions.c
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@ -1090,7 +1090,7 @@ musepack_type_find (GstTypeFind * tf, gpointer unused)
}
/*** audio/x-ac3 ***/
/* This should be audio/ac3, but isn't for backwards compatibility */
/* FIXME 0.11: 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))
@ -1142,47 +1142,51 @@ static const struct ac3_frmsize ac3_frmsizecod_tbl[] = {
{640, {1280, 1394, 1920}}
};
static void
ac3_type_find (GstTypeFind * tf, gpointer unused)
{
guint8 *data = gst_type_find_peek (tf, 0, 5);
gint offset = 0;
DataScanCtx c = { 0, NULL, 0 };
/* 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) {
guint fscod = (data[4] >> 6) & 0x03;
guint frmsizecod = data[4] & 0x3f;
while (c.offset < 1024) {
if (G_UNLIKELY (!data_scan_ctx_ensure_data (tf, &c, 5)))
break;
if (c.data[0] == 0x0b && c.data[1] == 0x77) {
guint fscod = (c.data[4] >> 6) & 0x03;
guint frmsizecod = c.data[4] & 0x3f;
if (fscod < 3 && frmsizecod < 38) {
guint frame_size = ac3_frmsizecod_tbl[frmsizecod].frm_size[fscod];
DataScanCtx c_next = c;
guint frame_size;
data = gst_type_find_peek (tf, offset + frame_size * 2, 5);
frame_size = ac3_frmsizecod_tbl[frmsizecod].frm_size[fscod];
if (data_scan_ctx_ensure_data (tf, &c_next, (frame_size * 2) + 5)) {
data_scan_ctx_advance (tf, &c, frame_size * 2);
if (data) {
if (data[0] == 0x0b && data[1] == 0x77) {
guint fscod2 = (data[4] >> 6) & 0x03;
guint frmsizecod2 = data[4] & 0x3f;
if (c_next.data[0] == 0x0b && c_next.data[1] == 0x77) {
guint fscod2 = (c_next.data[4] >> 6) & 0x03;
guint frmsizecod2 = c_next.data[4] & 0x3f;
if (fscod == fscod2 && frmsizecod == frmsizecod2) {
int prob;
GstTypeFindProbability prob;
if (offset == 0)
if (c.offset == 0)
prob = GST_TYPE_FIND_MAXIMUM;
else
prob = GST_TYPE_FIND_NEARLY_CERTAIN;
gst_type_find_suggest (tf, prob, AC3_CAPS);
return;
}
}
}
}
}
offset++;
data = gst_type_find_peek (tf, offset, 5);
data_scan_ctx_advance (tf, &c, 1);
}
}