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mpegvideoparse: unobfuscate frame parsing
... and add comments and debug statements. Fixes #674202. Conflicts: gst/videoparsers/gstmpegvideoparse.c
This commit is contained in:
Mark Nauwelaerts
parent
35a58df012
commit
1f0c18daf2
2 changed files with 78 additions and 46 deletions
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@ -177,7 +177,8 @@ gst_mpegv_parse_reset_frame (GstMpegvParse * mpvparse)
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{
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/* done parsing; reset state */
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mpvparse->last_sc = -1;
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mpvparse->seq_offset = G_MAXUINT;
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mpvparse->seq_size = 0;
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mpvparse->seq_offset = -1;
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mpvparse->pic_offset = -1;
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mpvparse->frame_repeat_count = 0;
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}
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@ -392,11 +393,11 @@ parse_picture_extension (GstMpegvParse * mpvparse, GstBuffer * buf, guint off)
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}
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/* caller guarantees at least start code in @buf at @off */
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/* for off == 0 initial code; returns TRUE if code starts a frame,
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/* for off == 4 initial code; returns TRUE if code starts a frame
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* otherwise returns TRUE if code terminates preceding frame */
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static gboolean
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gst_mpegv_parse_process_sc (GstMpegvParse * mpvparse,
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GstBuffer * buf, guint off, guint8 code)
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GstBuffer * buf, gint off, guint8 code)
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{
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gboolean ret = FALSE, packet = TRUE;
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@ -413,19 +414,20 @@ gst_mpegv_parse_process_sc (GstMpegvParse * mpvparse,
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if (mpvparse->pic_offset < 0)
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mpvparse->pic_offset = off;
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else
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ret = TRUE;
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ret = (off != mpvparse->pic_offset);
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/* but it's a valid starting one */
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if (off == 4)
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ret = TRUE;
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break;
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case GST_MPEG_VIDEO_PACKET_SEQUENCE:
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GST_LOG_OBJECT (mpvparse, "startcode is SEQUENCE");
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if (off < mpvparse->seq_offset)
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if (mpvparse->seq_offset < 0)
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mpvparse->seq_offset = off;
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ret = TRUE;
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break;
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case GST_MPEG_VIDEO_PACKET_GOP:
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GST_LOG_OBJECT (mpvparse, "startcode is GOP");
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if (mpvparse->seq_offset < G_MAXUINT)
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if (mpvparse->seq_offset >= 0)
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ret = mpvparse->gop_split;
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else
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ret = TRUE;
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@ -439,10 +441,11 @@ gst_mpegv_parse_process_sc (GstMpegvParse * mpvparse,
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break;
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}
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if (mpvparse->seq_offset != G_MAXUINT && off != mpvparse->seq_offset &&
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packet) {
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/* set size to avoid processing config again */
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if (mpvparse->seq_offset >= 0 && off != mpvparse->seq_offset &&
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!mpvparse->seq_size && packet) {
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gst_mpegv_parse_process_config (mpvparse, buf, off - mpvparse->seq_offset);
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mpvparse->seq_offset = G_MAXUINT;
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mpvparse->seq_size = off - mpvparse->seq_offset;
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}
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/* extract some picture info if there is any in the frame being terminated */
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@ -465,24 +468,9 @@ gst_mpegv_parse_process_sc (GstMpegvParse * mpvparse,
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return ret;
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}
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static inline gint
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get_frame_size (GstMpegvParse * mpvparse, GstBuffer * buf, GList * l_codoffsz)
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{
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GList *tmp;
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GstMpegVideoTypeOffsetSize *codoffsz;
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for (tmp = l_codoffsz; tmp; tmp = tmp->next) {
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codoffsz = tmp->data;
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GST_LOG_OBJECT (mpvparse, "next start code at %d", codoffsz->offset);
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if (gst_mpegv_parse_process_sc (mpvparse, buf, codoffsz->offset,
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codoffsz->type))
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return codoffsz->offset - 4;
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}
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return -1;
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}
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/* FIXME move into baseparse, or anything equivalent;
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* see https://bugzilla.gnome.org/show_bug.cgi?id=650093 */
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#define GST_BASE_PARSE_FRAME_FLAG_PARSING 0x10000
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static inline void
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update_frame_parsing_status (GstMpegvParse * mpvparse,
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@ -509,59 +497,102 @@ gst_mpegv_parse_handle_frame (GstBaseParse * parse,
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gint off = 0, fsize = -1;
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GstMapInfo map;
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gsize buf_size;
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GstMpegVideoTypeOffsetSize *codoffsz;
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update_frame_parsing_status (mpvparse, frame);
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if (mpvparse->last_sc >= 0)
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off = mpvparse->last_sc;
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GST_LOG_OBJECT (mpvparse, "parsing at offset %d", off);
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gst_buffer_map (buf, &map, GST_MAP_READ);
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buf_size = map.size;
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mpvparse->typeoffsize = gst_mpeg_video_parse (map.data, map.size, off);
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gst_buffer_unmap (buf, &map);
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/* No sc found */
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if (mpvparse->typeoffsize == NULL)
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goto end;
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/* Already found the start code looking for the end */
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if (mpvparse->last_sc >= 0) {
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*skipsize = 0;
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fsize = get_frame_size (mpvparse, buf, mpvparse->typeoffsize);
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if (mpvparse->typeoffsize == NULL) {
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GST_LOG_OBJECT (mpvparse, "no start code");
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*skipsize = gst_buffer_get_size (buf) - 3;
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goto end;
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}
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codoffsz = mpvparse->typeoffsize->data;
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/* if initial start code not at start, arrange to make it so */
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if (mpvparse->last_sc < 0) {
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/* check for sane start code */
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for (tmp = mpvparse->typeoffsize; tmp; tmp = g_list_next (tmp)) {
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GstMpegVideoTypeOffsetSize *codoffsz = tmp->data;
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codoffsz = tmp->data;
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g_assert (codoffsz->offset >= 4);
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off = codoffsz->offset - 4;
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GST_LOG_OBJECT (mpvparse, "checking for valid start code at %d", off);
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/* hard-code to 4 to force initial check */
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if (gst_mpegv_parse_process_sc (mpvparse, buf, 4, codoffsz->type)) {
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if (off > 0) {
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GST_LOG_OBJECT (mpvparse, "skipping to start code at offset %d", off);
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gst_mpegv_parse_reset_frame (mpvparse);
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*skipsize = off;
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goto end;
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}
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/* got starting start code where we want it now */
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GST_LOG_OBJECT (mpvparse, "got valid start code");
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mpvparse->last_sc = 0;
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break;
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}
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/* avoid hard-code hack bite */
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gst_mpegv_parse_reset_frame (mpvparse);
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}
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}
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if (mpvparse->last_sc < 0) {
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GST_LOG_OBJECT (mpvparse, "no valid start code");
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*skipsize = gst_buffer_get_size (buf) - 3;
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goto end;
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}
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/* start is fine as of now */
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*skipsize = 0;
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/* initial packet processed above */
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for (tmp = mpvparse->typeoffsize; tmp; tmp = g_list_next (tmp)) {
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codoffsz = tmp->data;
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GST_LOG_OBJECT (mpvparse, "next start code at %d", codoffsz->offset);
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if (codoffsz->offset > 4)
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ret = gst_mpegv_parse_process_sc (mpvparse, buf, codoffsz->offset,
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codoffsz->type);
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else
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ret = FALSE;
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if (ret) {
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*skipsize = 0;
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fsize = get_frame_size (mpvparse, buf, tmp->next);
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fsize = codoffsz->offset - 4;
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break;
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}
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/* start here next time around */
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mpvparse->last_sc = codoffsz->offset - 4;
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}
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end:
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if (fsize > 0) {
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ret = TRUE;
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GST_LOG_OBJECT (mpvparse, "found frame of size %d", fsize);
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} else if (mpvparse->last_sc < 0) {
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ret = FALSE;
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GST_LOG_OBJECT (mpvparse, "skipping %d", *skipsize);
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} else if (GST_BASE_PARSE_DRAINING (parse)) {
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fsize = buf_size;
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ret = TRUE;
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GST_LOG_OBJECT (mpvparse, "no more data, assuming frame size %d", fsize);
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} else {
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/* resume scan where we left it */
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if (mpvparse->typeoffsize)
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mpvparse->last_sc = buf_size - 3;
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else
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*skipsize = 0;
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/* need some more data */
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/* request best next available */
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ret = FALSE;
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GST_LOG_OBJECT (mpvparse, "obtaining more data");
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}
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g_list_foreach (mpvparse->typeoffsize, (GFunc) g_free, NULL);
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@ -54,6 +54,7 @@ struct _GstMpegvParse {
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GList *typeoffsize;
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gint last_sc;
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gint seq_offset;
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gint seq_size;
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gint pic_offset;
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gboolean update_caps;
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gboolean send_codec_tag;
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