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mpegvideoparse: look beyond start code before leaping

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In case more data than a start code alone is needed to decide whether
it ends a frame, arrange for more input data and decide when available.

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=711627
This commit is contained in:
Mark Nauwelaerts 2013-11-11 16:15:00 +01:00
parent 58be5ce16d
commit 830a4aa7f4
1 changed files with 33 additions and 17 deletions
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50
gst/videoparsers/gstmpegvideoparse.c
View file

@ -461,18 +461,21 @@ parse_packet_extension (GstMpegvParse * mpvparse, GstMapInfo * info, guint off)
}
}
/* caller guarantees at least start code in @buf at @off */
/* caller guarantees at least start code in @buf at @off ( - 4)*/
/* for off == 4 initial code; returns TRUE if code starts a frame
* otherwise returns TRUE if code terminates preceding frame */
static gboolean
gst_mpegv_parse_process_sc (GstMpegvParse * mpvparse,
GstMapInfo * info, gint off, GstMpegVideoPacket * packet)
GstMapInfo * info, gint off, GstMpegVideoPacket * packet,
gboolean * need_more)
{
gboolean ret = FALSE, checkconfig = TRUE;
GST_LOG_OBJECT (mpvparse, "process startcode %x (%s) offset:%d", packet->type,
picture_start_code_name (packet->type), off);
*need_more = FALSE;
switch (packet->type) {
case GST_MPEG_VIDEO_PACKET_PICTURE:
GST_LOG_OBJECT (mpvparse, "startcode is PICTURE");
@ -553,6 +556,7 @@ gst_mpegv_parse_process_sc (GstMpegvParse * mpvparse,
&& (mpvparse->config_flags & FLAG_SEQUENCE_EXT)
&& !mpvparse->sequenceext.progressive) {
if (info->size - off < 2) { /* we need at least two bytes to read the TSN */
*need_more = TRUE;
ret = FALSE;
} else {
/* TSN is stored in first 10 bits */
@ -596,6 +600,7 @@ gst_mpegv_parse_handle_frame (GstBaseParse * parse,
GstMpegVideoPacket packet;
guint8 *data;
gint size;
gboolean need_more = FALSE;
GstMapInfo map;
update_frame_parsing_status (mpvparse, frame);
@ -635,7 +640,7 @@ retry:
/* note: initial start code is assumed at offset 0 by subsequent code */
/* examine start code, see if it looks like an initial start code */
if (gst_mpegv_parse_process_sc (mpvparse, &map, 4, &packet)) {
if (gst_mpegv_parse_process_sc (mpvparse, &map, 4, &packet, &need_more)) {
/* found sc */
GST_LOG_OBJECT (mpvparse, "valid start code found");
mpvparse->last_sc = 0;
@ -665,22 +670,18 @@ next:
GST_LOG_OBJECT (mpvparse, "next start code at %d", off);
if (off < 0) {
/* if draining, take all */
if (GST_BASE_PARSE_DRAINING (parse)) {
GST_LOG_OBJECT (mpvparse, "draining, accepting all data");
off = size;
ret = TRUE;
} else {
GST_LOG_OBJECT (mpvparse, "need more data");
/* resume scan where we left it */
mpvparse->last_sc = size - 3;
/* request best next available */
off = G_MAXUINT;
goto exit;
}
off = size - 3;
goto need_more;
} else {
/* decide whether this startcode ends a frame */
ret = gst_mpegv_parse_process_sc (mpvparse, &map, off + 4, &packet);
ret = gst_mpegv_parse_process_sc (mpvparse, &map, off + 4, &packet,
&need_more);
/* in rare cases, might need to peek past start code */
if (need_more) {
GST_LOG_OBJECT (mpvparse, "need more data (past start code");
ret = FALSE;
goto need_more;
}
}
if (!ret)
@ -707,6 +708,21 @@ exit:
}
return flowret;
need_more:
/* if draining, take all */
if (GST_BASE_PARSE_DRAINING (parse)) {
GST_LOG_OBJECT (mpvparse, "draining, accepting all data");
off = size;
ret = TRUE;
} else {
GST_LOG_OBJECT (mpvparse, "need more data");
/* resume scan where we left it */
mpvparse->last_sc = off;
/* request best next available */
off = G_MAXUINT;
}
goto exit;
}
static void