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jpegparse: optimize image parsing
Use adapter API for scanning and peeking to reduce buffer copying. See #583047.
This commit is contained in:
Mark Nauwelaerts
parent
12856e52fd
commit
e6cf05b114
1 changed files with 126 additions and 148 deletions
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@ -83,6 +83,7 @@ struct _GstJpegParsePrivate
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GstAdapter *adapter;
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guint last_offset;
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guint last_entropy_len;
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gboolean last_resync;
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/* negotiated state */
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gint caps_width, caps_height;
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@ -285,162 +286,138 @@ gst_jpeg_parse_parse_tag_has_entropy_segment (guint8 tag)
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return FALSE;
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}
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/*
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* gst_jpeg_parse_match_next_marker:
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* @data: data to scan (must start with 0xff)
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* @size: amount of bytes in @data (must be >=2)
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*
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* Find the next marker, based on the marker at @data.
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*
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* Returns: the offset of the next valid marker or -1 if buffer doesn't have
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* enough data.
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*/
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static guint
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gst_jpeg_parse_match_next_marker (GstJpegParse * parse, const guint8 * data,
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guint size)
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{
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guint marker_len;
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guint8 tag;
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g_return_val_if_fail (data[0] == 0xff, -1);
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g_return_val_if_fail (size >= 2, -1);
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tag = data[1];
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if (tag >= RST0 && tag <= EOI)
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marker_len = 2;
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else if (G_UNLIKELY (size < 4))
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goto need_more_data;
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else
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marker_len = GST_READ_UINT16_BE (data + 2) + 2;
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/* we log this in gst_jpeg_parse_find_end_marker() already
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GST_LOG ("Have marker %x with length %u", data[1], marker_len);
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*/
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/* Need marker_len for this marker, plus two for the next marker. */
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if (G_UNLIKELY (marker_len + 2 >= size))
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goto need_more_data;
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if (G_UNLIKELY (gst_jpeg_parse_parse_tag_has_entropy_segment (tag))) {
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if (parse->priv->last_entropy_len) {
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marker_len = parse->priv->last_entropy_len;
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GST_LOG_OBJECT (parse, "resuming entropy segment scan at len %u",
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marker_len);
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}
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while (!(data[marker_len] == 0xff && data[marker_len + 1] != 0x00)) {
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++marker_len;
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if (G_UNLIKELY (marker_len + 2 > size)) {
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parse->priv->last_entropy_len = marker_len;
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goto need_more_data;
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}
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}
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parse->priv->last_entropy_len = 0;
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}
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return marker_len;
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need_more_data:
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GST_LOG ("need more data");
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return -1;
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}
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/*
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* gst_jpeg_parse_find_end_marker:
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* @data: data to scan (must start with 0xff)
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* @size: amount of bytes in @data
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*
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* Find next position beyond end maker.
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*
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* Returns: the position, -1 if insufficient data and -2 if marker lengths are
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* inconsistent.
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*/
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static guint
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gst_jpeg_parse_find_end_marker (GstJpegParse * parse, const guint8 * data,
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guint size)
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{
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guint offset = parse->priv->last_offset;
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while (1) {
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guint marker_len;
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guint8 tag;
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if (offset + 1 >= size)
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return -1;
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/* all jpeg marker start with 0xff */
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if (data[offset] != 0xff)
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return -2;
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/* Skip over extra 0xff */
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while (G_UNLIKELY ((tag = data[offset + 1]) == 0xff)) {
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++offset;
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if (G_UNLIKELY (offset + 1 >= size))
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return -1;
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}
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/* Check for EOI */
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if (G_UNLIKELY (tag == EOI)) {
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GST_DEBUG_OBJECT (parse, "EOI at %u", offset);
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parse->priv->last_offset = offset;
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return offset;
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}
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/* Skip over this marker. */
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marker_len = gst_jpeg_parse_match_next_marker (parse, data + offset,
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size - offset);
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if (G_UNLIKELY (marker_len == -1)) {
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return -1;
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} else {
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GST_LOG_OBJECT (parse, "At offset %u: marker %02x, length %u", offset,
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tag, marker_len);
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/* remember last found marker, so that we don't rescan from begin */
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parse->priv->last_offset = offset;
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offset += marker_len;
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}
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}
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}
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/* scan until EOI, by interpreting marker + length */
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/* returns image length in bytes if parsed
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* successfully, otherwise 0 if not enough data */
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static guint
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gst_jpeg_parse_get_image_length (GstJpegParse * parse)
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{
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const guint8 *data;
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guint size, offset;
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guint size;
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gboolean resync;
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GstAdapter *adapter = parse->priv->adapter;
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gint offset, noffset;
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size = gst_adapter_available (parse->priv->adapter);
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if (size < 4) {
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GST_DEBUG_OBJECT (parse, "Insufficient data for end marker.");
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size = gst_adapter_available (adapter);
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/* we expect at least 4 bytes, first of which start marker */
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if (gst_adapter_masked_scan_uint32 (adapter, 0xffff0000, 0xffd80000, 0, 4))
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return 0;
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GST_DEBUG ("Parsing jpeg image data (%u bytes)", size);
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GST_DEBUG ("Parse state: offset=%d, resync=%d, entropy len=%d",
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parse->priv->last_offset, parse->priv->last_resync,
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parse->priv->last_entropy_len);
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/* offset is 2 less than actual offset;
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* - adapter needs at least 4 bytes for scanning,
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* - start and end marker ensure at least that much
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*/
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/* resume from state offset */
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offset = parse->priv->last_offset;
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while (1) {
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guint frame_len;
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guint32 value;
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noffset =
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gst_adapter_masked_scan_uint32_peek (adapter, 0x0000ff00, 0x0000ff00,
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offset, size - offset, &value);
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/* lost sync if 0xff marker not where expected */
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if ((resync = (noffset != offset))) {
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GST_DEBUG ("Lost sync at 0x%08x, resyncing", offset + 2);
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}
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/* may have marker, but could have been resyncng */
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resync = resync || parse->priv->last_resync;
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/* Skip over extra 0xff */
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while ((noffset > 0) && ((value & 0xff) == 0xff)) {
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noffset++;
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noffset =
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gst_adapter_masked_scan_uint32_peek (adapter, 0x0000ff00, 0x0000ff00,
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noffset, size - noffset, &value);
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}
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/* enough bytes left for marker? (we need 0xNN after the 0xff) */
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if (noffset < 0) {
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GST_DEBUG ("at end of input and no EOI marker found, need more data");
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goto need_more_data;
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}
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/* now lock on the marker we found */
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offset = noffset;
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value = value & 0xff;
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if (value == 0xd9) {
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GST_DEBUG ("0x%08x: EOI marker", offset + 2);
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/* clear parse state */
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parse->priv->last_resync = FALSE;
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parse->priv->last_offset = 0;
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return (offset + 4);
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}
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if (value >= 0xd0 && value <= 0xd7)
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frame_len = 0;
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else {
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/* peek tag and subsequent length */
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if (offset + 2 + 4 > size)
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goto need_more_data;
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else
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gst_adapter_masked_scan_uint32_peek (adapter, 0x0, 0x0, offset + 2, 4,
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&frame_len);
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frame_len = frame_len & 0xffff;
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}
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GST_DEBUG ("0x%08x: tag %02x, frame_len=%u", offset + 2, value, frame_len);
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/* the frame length includes the 2 bytes for the length; here we want at
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* least 2 more bytes at the end for an end marker */
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if (offset + 2 + 2 + frame_len + 2 > size) {
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goto need_more_data;
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}
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if (gst_jpeg_parse_parse_tag_has_entropy_segment (value)) {
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guint eseglen = parse->priv->last_entropy_len;
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GST_DEBUG ("0x%08x: finding entropy segment length", offset + 2);
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noffset = offset + 2 + frame_len + eseglen;
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while (1) {
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noffset = gst_adapter_masked_scan_uint32_peek (adapter, 0x0000ff00,
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0x0000ff00, noffset, size - noffset, &value);
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if (noffset < 0) {
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/* need more data */
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parse->priv->last_entropy_len = size - offset - 4 - frame_len - 2;
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goto need_more_data;
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}
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if ((value & 0xff) != 0x00) {
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eseglen = noffset - offset - frame_len - 2;
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break;
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}
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noffset++;
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}
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parse->priv->last_entropy_len = 0;
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frame_len += eseglen;
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GST_DEBUG ("entropy segment length=%u => frame_len=%u", eseglen,
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frame_len);
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}
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if (resync) {
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/* check if we will still be in sync if we interpret
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* this as a sync point and skip this frame */
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noffset = offset + frame_len + 2;
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noffset = gst_adapter_masked_scan_uint32 (adapter, 0x0000ff00, 0x0000ff00,
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noffset, 4);
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if (noffset < 0) {
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/* ignore and continue resyncing until we hit the end
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* of our data or find a sync point that looks okay */
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continue;
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}
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GST_DEBUG ("found sync at 0x%x", offset + 2);
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}
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offset += frame_len + 2;
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}
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/* EXITS */
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need_more_data:
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{
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parse->priv->last_offset = offset;
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parse->priv->last_resync = resync;
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return 0;
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}
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data = gst_adapter_peek (parse->priv->adapter, size);
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g_return_val_if_fail (data[0] == 0xff && data[1] == SOI, 0);
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offset = gst_jpeg_parse_find_end_marker (parse, data, size);
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if (offset == -1) {
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GST_LOG_OBJECT (parse, "Insufficient data.");
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return 0;
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} else if (G_UNLIKELY (offset == -2)) {
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guint start = parse->priv->last_offset;
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GST_DEBUG_OBJECT (parse, "Lost sync, resyncing.");
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/* FIXME does this make sense at all? This can only happen for broken
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* images, and the most likely breakage is that it's truncated. In that
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* case, however, we should be looking for a new start marker... */
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while (offset == -2 || offset == -1) {
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start++;
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/* scan for 0xff */
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while (start + 1 < size && data[start] != 0xff)
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start++;
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if (G_UNLIKELY (start + 1 >= size)) {
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GST_DEBUG_OBJECT (parse, "Insufficient data while resyncing.");
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return 0;
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}
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GST_LOG_OBJECT (parse, "Resyncing from offset %u (size %u).",
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start, size);
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parse->priv->last_offset = start;
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offset = gst_jpeg_parse_find_end_marker (parse, data, size);
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}
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}
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/* position of EOI + the length of the marker */
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return offset + 2;
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}
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static gboolean
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@ -774,7 +751,7 @@ gst_jpeg_parse_push_buffer (GstJpegParse * parse, guint len)
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gboolean header_ok;
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/* reset the offset (only when we flushed) */
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parse->priv->last_offset = 2;
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parse->priv->last_offset = 0;
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parse->priv->last_entropy_len = 0;
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outbuf = gst_adapter_take_buffer (parse->priv->adapter, len);
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@ -924,8 +901,9 @@ gst_jpeg_parse_change_state (GstElement * element, GstStateChange transition)
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parse->priv->next_ts = GST_CLOCK_TIME_NONE;
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parse->priv->last_offset = 2;
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parse->priv->last_offset = 0;
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parse->priv->last_entropy_len = 0;
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parse->priv->last_resync = FALSE;
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default:
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break;
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}
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