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jpegdec: optimise buffer scanning
Specifically, when needing more data, do not rescan from start next time around, but resume from last position. See also #583047.
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parent
761b883f2c
commit
52c71352e0
2 changed files with 45 additions and 10 deletions
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@ -414,6 +414,7 @@ gst_jpeg_dec_parse_image_data (GstJpegDec * dec)
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{
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guint8 *start, *data, *end;
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guint size;
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gboolean resync;
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size = GST_BUFFER_SIZE (dec->tempbuf);
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start = GST_BUFFER_DATA (dec->tempbuf);
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@ -424,12 +425,14 @@ gst_jpeg_dec_parse_image_data (GstJpegDec * dec)
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GST_DEBUG ("Parsing jpeg image data (%u bytes)", size);
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/* skip start marker */
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data += 2;
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GST_DEBUG ("Parse state: offset=%d, resync=%d, entropy len=%d",
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dec->parse_offset, dec->parse_resync, dec->parse_entropy_len);
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/* resume from state offset (also skips start marker) */
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data += (dec->parse_offset ? dec->parse_offset : 2);
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while (1) {
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guint frame_len;
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gboolean resync;
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/* do we need to resync? */
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resync = (*data != 0xff);
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@ -441,28 +444,33 @@ gst_jpeg_dec_parse_image_data (GstJpegDec * dec)
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++data;
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if (G_UNLIKELY (*data != 0xff)) {
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GST_DEBUG ("at end of input and no next marker found, need more data");
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return 0;
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goto need_more_data;
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}
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}
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/* may have marker, but could have been resyncng */
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resync = resync || dec->parse_resync;
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/* Skip over extra 0xff */
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while (*data == 0xff && data < end)
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++data;
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/* enough bytes left for marker? (we need 0xNN after the 0xff) */
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if (data >= end) {
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GST_DEBUG ("at end of input and no EOI marker found, need more data");
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return 0;
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goto need_more_data1;
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}
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if (*data == 0xd9) {
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GST_DEBUG ("0x%08" G_GINT64_MODIFIER "x: EOI marker",
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(gint64) (data - start));
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/* clear parse state */
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dec->parse_resync = FALSE;
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dec->parse_offset = 0;
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return (data - start + 1);
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}
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if (*data >= 0xd0 && *data <= 0xd7)
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frame_len = 0;
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else if (data >= end - 2)
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return 0;
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goto need_more_data1;
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else
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frame_len = GST_READ_UINT16_BE (data + 1);
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GST_DEBUG ("0x%08" G_GINT64_MODIFIER "x: tag %02x, frame_len=%u",
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@ -478,22 +486,26 @@ gst_jpeg_dec_parse_image_data (GstJpegDec * dec)
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/* theoretically we could have lost sync and not really need more
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* data, but that's just tough luck and a broken image then */
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GST_DEBUG ("at end of input and no EOI marker found, need more data");
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return 0;
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goto need_more_data1;
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}
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if (gst_jpeg_dec_parse_tag_has_entropy_segment (*data)) {
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guint8 *d2 = data + 1 + frame_len;
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guint eseglen = 0;
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guint eseglen = dec->parse_entropy_len;
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GST_DEBUG ("0x%08" G_GINT64_MODIFIER "x: finding entropy segment length",
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(gint64) (data - start - 1));
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while (1) {
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if (d2 + eseglen >= end - 1)
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return 0; /* need more data */
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if (d2 + eseglen >= end - 1) {
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/* need more data */
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dec->parse_entropy_len = eseglen;
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goto need_more_data1;
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}
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if (d2[eseglen] == 0xff && d2[eseglen + 1] != 0x00)
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break;
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++eseglen;
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}
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dec->parse_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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@ -511,6 +523,21 @@ gst_jpeg_dec_parse_image_data (GstJpegDec * dec)
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data += 1 + frame_len;
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}
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/* EXITS */
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need_more_data:
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{
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dec->parse_offset = data - start;
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dec->parse_resync = resync;
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return 0;
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}
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need_more_data1:
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{
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/* step back one to point at marker */
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dec->parse_offset = (data - start) - 1;
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dec->parse_resync = resync;
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return 0;
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}
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}
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/* shamelessly ripped from jpegutils.c in mjpegtools */
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@ -1605,6 +1632,9 @@ gst_jpeg_dec_change_state (GstElement * element, GstStateChange transition)
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dec->packetized = FALSE;
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dec->next_ts = 0;
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dec->discont = TRUE;
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dec->parse_offset = 0;
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dec->parse_resync = FALSE;
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dec->parse_entropy_len = FALSE;
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gst_segment_init (&dec->segment, GST_FORMAT_UNDEFINED);
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gst_jpeg_dec_reset_qos (dec);
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default:
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@ -103,6 +103,11 @@ struct _GstJpegDec {
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gint stride;
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gint inc;
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/* parse state */
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gint parse_offset;
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gint parse_entropy_len;
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gint parse_resync;
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/* properties */
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gint idct_method;
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