Hi
dvb_dmx_swfilter(_204) performance improvement, with packet recovery.
Remove unnecessary copying of 188 and 204 sized packets within
dvb_dmx_swfilter() and dvb_dmx_swfilter_204() functions.
Recover one packet by backtracking, when there is a short packet
with a correct SYNC byte in the middle.
------------------------------------------------------------
This patch tries to recover with backtracking one 188 / 204
sized packet if some garbage is found.
The backtracking recovery case, DVB data:
Packet Num, Packet data
1 0x47 + 99 bytes garbage
2 0x47 + 187 bytes data
3 0x47 + 187 bytes data
Recovery algorithm:
First packet 1's 0x47 is found. Process it, advance 188 bytes.
Find next SYNC byte, packet 3 found.
Check packet 3 position - 188: is there a packet?
yes, return packet 2.
Advance 188 bytes, return packet 3.
Jun 27 20:44:59 koivu kernel: demux: backtracked 137 bytes into position 442
Jun 27 20:44:59 koivu kernel: demux: backtracked 28 bytes into position 2250
Jun 27 20:45:02 koivu kernel: demux: backtracked 35 bytes into position 2634
Jun 27 20:45:02 koivu kernel: demux: backtracked 12 bytes into position 1398
Jun 27 20:45:03 koivu kernel: demux: skipped 146 bytes at position 378:
09 93 ...
Jun 27 20:45:03 koivu kernel: demux: backtracked 177 bytes into position 551
Jun 27 20:45:03 koivu kernel: demux: skipped 14 bytes at position 959:
6c 1e ...
Jun 27 20:45:03 koivu kernel: demux: backtracked 191 bytes into position 986
Regards,
Marko Ristola
diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c
b/drivers/media/dvb/dvb-core/dvb_demux.c
index 977ddba..b71d77d 100644
--- a/drivers/media/dvb/dvb-core/dvb_demux.c
+++ b/drivers/media/dvb/dvb-core/dvb_demux.c
@@ -478,97 +478,96 @@ void dvb_dmx_swfilter_packets(struct dvb_demux
*demux, const u8 *buf,
EXPORT_SYMBOL(dvb_dmx_swfilter_packets);
-void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count)
+static inline int findNextPacket(const u8 *buf, int pos, size_t count,
+ const int pktsize)
{
- int p = 0, i, j;
+ int start = pos, lost;
- spin_lock(&demux->lock);
-
- if (demux->tsbufp) {
- i = demux->tsbufp;
- j = 188 - i;
- if (count < j) {
- memcpy(&demux->tsbuf[i], buf, count);
- demux->tsbufp += count;
- goto bailout;
- }
- memcpy(&demux->tsbuf[i], buf, j);
- if (demux->tsbuf[0] == 0x47)
- dvb_dmx_swfilter_packet(demux, demux->tsbuf);
- demux->tsbufp = 0;
- p += j;
+ while(likely(pos < count)) {
+ if (likely(buf[pos] == 0x47 ||
+ (pktsize == 204 && buf[pos] == 0xB8)))
+ break;
+ pos++;
}
- while (p < count) {
- if (buf[p] == 0x47) {
- if (count - p >= 188) {
- dvb_dmx_swfilter_packet(demux, &buf[p]);
- p += 188;
- } else {
- i = count - p;
- memcpy(demux->tsbuf, &buf[p], i);
- demux->tsbufp = i;
- goto bailout;
- }
- } else
- p++;
+ if (unlikely(lost = pos - start)) {
+ /* This garbage is part of a valid packet? */
+ int backtrack = pos - pktsize;
+ if (backtrack >= 0 && (buf[backtrack] == 0x47 ||
+ (pktsize == 204 && buf[backtrack] == 0xB8))) {
+ /* printk("demux: backtracked %d bytes"
+ * "\n", start - backtrack); */
+ return backtrack;
+ }
+ /*printk("demux: skipped %d bytes at %d\n", lost, start); */
}
-bailout:
- spin_unlock(&demux->lock);
+ return pos;
}
-EXPORT_SYMBOL(dvb_dmx_swfilter);
-
-void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf,
size_t count)
+/* Filter all pktsize= 188 or 204 sized packets and skip garbage. */
+static inline void _dvb_dmx_swfilter(struct dvb_demux *demux, const u8
*buf,
+ size_t count, const int pktsize)
{
int p = 0, i, j;
- u8 tmppack[188];
+ const u8 *q;
spin_lock(&demux->lock);
- if (demux->tsbufp) {
+ if (likely(demux->tsbufp)) { /* tsbuf[0] is now 0x47. */
i = demux->tsbufp;
- j = 204 - i;
- if (count < j) {
+ j = pktsize - i;
+ if (unlikely(count < j)) {
memcpy(&demux->tsbuf[i], buf, count);
demux->tsbufp += count;
goto bailout;
}
memcpy(&demux->tsbuf[i], buf, j);
- if ((demux->tsbuf[0] == 0x47) || (demux->tsbuf[0] == 0xB8)) {
- memcpy(tmppack, demux->tsbuf, 188);
- if (tmppack[0] == 0xB8)
- tmppack[0] = 0x47;
- dvb_dmx_swfilter_packet(demux, tmppack);
- }
+ if (likely(demux->tsbuf[0] == 0x47)) /* double check */
+ dvb_dmx_swfilter_packet(demux, demux->tsbuf);
demux->tsbufp = 0;
p += j;
}
- while (p < count) {
- if ((buf[p] == 0x47) || (buf[p] == 0xB8)) {
- if (count - p >= 204) {
- memcpy(tmppack, &buf[p], 188);
- if (tmppack[0] == 0xB8)
- tmppack[0] = 0x47;
- dvb_dmx_swfilter_packet(demux, tmppack);
- p += 204;
- } else {
- i = count - p;
- memcpy(demux->tsbuf, &buf[p], i);
- demux->tsbufp = i;
- goto bailout;
- }
- } else {
- p++;
+ while (likely((p = findNextPacket(buf, p, count, pktsize)) < count)) {
+ if (unlikely(count - p < pktsize))
+ break;
+
+ q = &buf[p];
+
+ if (unlikely(pktsize == 204 && (*q == 0xB8))) {
+ memcpy(demux->tsbuf, q, 188);
+ demux->tsbuf[0] = 0x47;
+ q = demux->tsbuf;
}
+ dvb_dmx_swfilter_packet(demux, q);
+ p += pktsize;
+ }
+
+ i = count - p;
+ if (likely(i)) {
+ memcpy(demux->tsbuf, &buf[p], i);
+ demux->tsbufp = i;
+ if (unlikely(pktsize == 204 && demux->tsbuf[0] == 0xB8))
+ demux->tsbuf[0] = 0x47;
}
bailout:
spin_unlock(&demux->lock);
}
+void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count)
+{
+ _dvb_dmx_swfilter(demux, buf, count, 188);
+}
+
+EXPORT_SYMBOL(dvb_dmx_swfilter);
+
+void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf,
size_t count)
+{
+ _dvb_dmx_swfilter(demux, buf, count, 204);
+}
+
EXPORT_SYMBOL(dvb_dmx_swfilter_204);
static struct dvb_demux_filter *dvb_dmx_filter_alloc(struct dvb_demux
*demux)
--
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