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typefinding: improve jpeg typefinder

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Make jpeg typefinder check more than just the first two bytes
plus Exif or JFIF marker. This allows us to report MAXIMUM
probability in cases where there's no Exif or JFIF marker,
making typefinding stop early. Also extract width and height,
because we can.
This commit is contained in:
Tim-Philipp Müller 2010-05-19 15:40:30 +01:00
parent 2c989ef3a7
commit 95b4de4ed7
1 changed files with 103 additions and 8 deletions
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111
gst/typefind/gsttypefindfunctions.c
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@ -111,6 +111,16 @@ data_scan_ctx_ensure_data (GstTypeFind * tf, DataScanCtx * c, gint min_len)
return FALSE;
}
static inline gboolean
data_scan_ctx_memcmp (GstTypeFind * tf, DataScanCtx * c, guint offset,
const gchar * data, guint len)
{
if (!data_scan_ctx_ensure_data (tf, c, offset + len))
return FALSE;
return (memcmp (c->data + offset, data, len) == 0);
}
/*** text/plain ***/
static gboolean xml_check_first_element (GstTypeFind * tf,
const gchar * element, guint elen, gboolean strict);
@ -2568,24 +2578,109 @@ swf_type_find (GstTypeFind * tf, gpointer unused)
/*** image/jpeg ***/
#define JPEG_MARKER_IS_START_OF_FRAME(x) \
((x)>=0xc0 && (x) <= 0xcf && (x)!=0xc4 && (x)!=0xc8 && (x)!=0xcc)
static GstStaticCaps jpeg_caps = GST_STATIC_CAPS ("image/jpeg");
#define JPEG_CAPS (gst_static_caps_get(&jpeg_caps))
static void
jpeg_type_find (GstTypeFind * tf, gpointer unused)
{
guint8 *data = gst_type_find_peek (tf, 0, 10);
guint8 header[2] = { 0xFF, 0xD8 };
GstTypeFindProbability prob = GST_TYPE_FIND_POSSIBLE;
DataScanCtx c = { 0, NULL, 0 };
GstCaps *caps;
guint num_markers;
if (data && memcmp (data, header, 2) == 0) {
if (memcmp (data + 6, "JFIF", 4) == 0) {
gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, JPEG_CAPS);
} else if (memcmp (data + 6, "Exif", 4) == 0) {
gst_type_find_suggest (tf, GST_TYPE_FIND_MAXIMUM, JPEG_CAPS);
if (G_UNLIKELY (!data_scan_ctx_ensure_data (tf, &c, 2)))
return;
if (c.data[0] != 0xff || c.data[1] != 0xd8)
return;
num_markers = 1;
data_scan_ctx_advance (tf, &c, 2);
caps = gst_caps_copy (JPEG_CAPS);
while (data_scan_ctx_ensure_data (tf, &c, 4) && c.offset < (200 * 1024)) {
guint16 len;
guint8 marker;
if (c.data[0] != 0xff)
break;
marker = c.data[1];
if (G_UNLIKELY (marker == 0xff)) {
data_scan_ctx_advance (tf, &c, 1);
continue;
}
data_scan_ctx_advance (tf, &c, 2);
/* we assume all markers we'll see before SOF have a payload length; if
* that's not the case we'll just detect a false sync and bail out, but
* still report POSSIBLE probability */
len = GST_READ_UINT16_BE (c.data);
GST_LOG ("possible JPEG marker 0x%02x (@0x%04x), segment length %u",
marker, c.offset, len);
if (!data_scan_ctx_ensure_data (tf, &c, len))
break;
if (marker == 0xc4 || /* DEFINE_HUFFMAN_TABLES */
marker == 0xcc || /* DEFINE_ARITHMETIC_CONDITIONING */
marker == 0xdb || /* DEFINE_QUANTIZATION_TABLES */
marker == 0xdd || /* DEFINE_RESTART_INTERVAL */
marker == 0xfe) { /* COMMENT */
data_scan_ctx_advance (tf, &c, len);
++num_markers;
} else if (marker == 0xe0 && len >= (2 + 4) && /* APP0 */
data_scan_ctx_memcmp (tf, &c, 2, "JFIF", 4)) {
GST_LOG ("found JFIF tag");
prob = GST_TYPE_FIND_MAXIMUM;
data_scan_ctx_advance (tf, &c, len);
++num_markers;
/* we continue until we find a start of frame marker */
} else if (marker == 0xe1 && len >= (2 + 4) && /* APP1 */
data_scan_ctx_memcmp (tf, &c, 2, "Exif", 4)) {
GST_LOG ("found Exif tag");
prob = GST_TYPE_FIND_MAXIMUM;
data_scan_ctx_advance (tf, &c, len);
++num_markers;
/* we continue until we find a start of frame marker */
} else if (marker >= 0xe0 && marker <= 0xef) { /* APPn */
data_scan_ctx_advance (tf, &c, len);
++num_markers;
} else if (JPEG_MARKER_IS_START_OF_FRAME (marker) && len >= (2 + 8)) {
int h, w;
h = GST_READ_UINT16_BE (c.data + 2 + 1);
w = GST_READ_UINT16_BE (c.data + 2 + 1 + 2);
if (h == 0 || w == 0) {
GST_WARNING ("bad width %u and/or height %u in SOF header", w, h);
break;
}
GST_LOG ("SOF at offset %" G_GUINT64_FORMAT ", num_markers=%d, "
"WxH=%dx%d", c.offset - 2, num_markers, w, h);
if (num_markers >= 5 || prob == GST_TYPE_FIND_MAXIMUM)
prob = GST_TYPE_FIND_MAXIMUM;
else
prob = GST_TYPE_FIND_LIKELY;
gst_caps_set_simple (caps, "width", G_TYPE_INT, w,
"height", G_TYPE_INT, h, NULL);
} else {
gst_type_find_suggest (tf, GST_TYPE_FIND_POSSIBLE, JPEG_CAPS);
GST_WARNING ("bad length or unexpected JPEG marker 0xff 0x%02x", marker);
break;
}
}
gst_type_find_suggest (tf, prob, caps);
gst_caps_unref (caps);
}
/*** image/bmp ***/