[FFmpeg-cvslog] mpegts: Remove one memcpy per packet
Ben Avison
git at videolan.org
Tue Aug 6 15:16:12 CEST 2013
ffmpeg | branch: master | Ben Avison <bavison at riscosopen.org> | Wed Jul 31 23:46:08 2013 +0100| [cabb1681697555e2c319c37c1f30f149207e9434] | committer: Martin Storsjö
mpegts: Remove one memcpy per packet
This was being performed to ensure that a complete packet was held in
contiguous memory, prior to parsing the packet. However, the source buffer
is typically large enough that the packet was already contiguous, so it is
beneficial to return the packet by reference in most cases.
Before After
Mean StdDev Mean StdDev Change
memcpy 720.7 32.7 649.8 25.1 +10.9%
Overall 2372.7 46.1 2291.7 21.8 +3.5%
Signed-off-by: Martin Storsjö <martin at martin.st>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=cabb1681697555e2c319c37c1f30f149207e9434
---
libavformat/mpegts.c | 41 ++++++++++++++++++++++++++++-------------
1 file changed, 28 insertions(+), 13 deletions(-)
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 1540a8d..2def573 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -1743,17 +1743,17 @@ static int mpegts_resync(AVFormatContext *s)
}
/* return -1 if error or EOF. Return 0 if OK. */
-static int read_packet(AVFormatContext *s, uint8_t *buf, int raw_packet_size)
+static int read_packet(AVFormatContext *s, uint8_t *buf, int raw_packet_size, uint8_t **data)
{
AVIOContext *pb = s->pb;
- int skip, len;
+ int len;
for(;;) {
- len = avio_read(pb, buf, TS_PACKET_SIZE);
+ len = ffio_read_indirect(pb, buf, TS_PACKET_SIZE, data);
if (len != TS_PACKET_SIZE)
return len < 0 ? len : AVERROR_EOF;
/* check packet sync byte */
- if (buf[0] != 0x47) {
+ if ((*data)[0] != 0x47) {
/* find a new packet start */
avio_seek(pb, -TS_PACKET_SIZE, SEEK_CUR);
if (mpegts_resync(s) < 0)
@@ -1761,19 +1761,25 @@ static int read_packet(AVFormatContext *s, uint8_t *buf, int raw_packet_size)
else
continue;
} else {
- skip = raw_packet_size - TS_PACKET_SIZE;
- if (skip > 0)
- avio_skip(pb, skip);
break;
}
}
return 0;
}
+static void finished_reading_packet(AVFormatContext *s, int raw_packet_size)
+{
+ AVIOContext *pb = s->pb;
+ int skip = raw_packet_size - TS_PACKET_SIZE;
+ if (skip > 0)
+ avio_skip(pb, skip);
+}
+
static int handle_packets(MpegTSContext *ts, int nb_packets)
{
AVFormatContext *s = ts->stream;
uint8_t packet[TS_PACKET_SIZE+FF_INPUT_BUFFER_PADDING_SIZE];
+ uint8_t *data;
int packet_num, ret = 0;
if (avio_tell(s->pb) != ts->last_pos) {
@@ -1802,10 +1808,11 @@ static int handle_packets(MpegTSContext *ts, int nb_packets)
packet_num++;
if (nb_packets != 0 && packet_num >= nb_packets)
break;
- ret = read_packet(s, packet, ts->raw_packet_size);
+ ret = read_packet(s, packet, ts->raw_packet_size, &data);
if (ret != 0)
break;
- ret = handle_packet(ts, packet);
+ ret = handle_packet(ts, data);
+ finished_reading_packet(s, ts->raw_packet_size);
if (ret != 0)
break;
}
@@ -1909,6 +1916,7 @@ static int mpegts_read_header(AVFormatContext *s)
int64_t pcrs[2], pcr_h;
int packet_count[2];
uint8_t packet[TS_PACKET_SIZE];
+ uint8_t *data;
/* only read packets */
@@ -1924,18 +1932,21 @@ static int mpegts_read_header(AVFormatContext *s)
nb_pcrs = 0;
nb_packets = 0;
for(;;) {
- ret = read_packet(s, packet, ts->raw_packet_size);
+ ret = read_packet(s, packet, ts->raw_packet_size, &data);
if (ret < 0)
return -1;
- pid = AV_RB16(packet + 1) & 0x1fff;
+ pid = AV_RB16(data + 1) & 0x1fff;
if ((pcr_pid == -1 || pcr_pid == pid) &&
- parse_pcr(&pcr_h, &pcr_l, packet) == 0) {
+ parse_pcr(&pcr_h, &pcr_l, data) == 0) {
+ finished_reading_packet(s, ts->raw_packet_size);
pcr_pid = pid;
packet_count[nb_pcrs] = nb_packets;
pcrs[nb_pcrs] = pcr_h * 300 + pcr_l;
nb_pcrs++;
if (nb_pcrs >= 2)
break;
+ } else {
+ finished_reading_packet(s, ts->raw_packet_size);
}
nb_packets++;
}
@@ -1967,15 +1978,19 @@ static int mpegts_raw_read_packet(AVFormatContext *s,
int64_t pcr_h, next_pcr_h, pos;
int pcr_l, next_pcr_l;
uint8_t pcr_buf[12];
+ uint8_t *data;
if (av_new_packet(pkt, TS_PACKET_SIZE) < 0)
return AVERROR(ENOMEM);
pkt->pos= avio_tell(s->pb);
- ret = read_packet(s, pkt->data, ts->raw_packet_size);
+ ret = read_packet(s, pkt->data, ts->raw_packet_size, &data);
if (ret < 0) {
av_free_packet(pkt);
return ret;
}
+ if (data != pkt->data)
+ memcpy(pkt->data, data, ts->raw_packet_size);
+ finished_reading_packet(s, ts->raw_packet_size);
if (ts->mpeg2ts_compute_pcr) {
/* compute exact PCR for each packet */
if (parse_pcr(&pcr_h, &pcr_l, pkt->data) == 0) {
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