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avformat/mpegts: reduce buffering during initialization 

Reduces buffering latency with low bitrate streams, where
8192 bytes can mean several seconds.

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Andriy Gelman 2019-03-08 22:20:07 -05:00 committed by Michael Niedermayer
parent 147ef1d947
commit 0a84ba2608
1 changed files with 35 additions and 22 deletions
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57
libavformat/mpegts.c
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@ -56,6 +56,9 @@
(prev_dividend) = (dividend); \ (prev_dividend) = (dividend); \
} while (0) } while (0)
#define PROBE_PACKET_MAX_BUF 8192
#define PROBE_PACKET_MARGIN 5
enum MpegTSFilterType { enum MpegTSFilterType {
MPEGTS_PES, MPEGTS_PES,
MPEGTS_SECTION, MPEGTS_SECTION,
@ -594,28 +597,42 @@ static int analyze(const uint8_t *buf, int size, int packet_size,
return best_score - FFMAX(stat_all - 10*best_score, 0)/10; return best_score - FFMAX(stat_all - 10*best_score, 0)/10;
} }
/* autodetect fec presence. Must have at least 1024 bytes */ /* autodetect fec presence */
static int get_packet_size(const uint8_t *buf, int size) static int get_packet_size(AVFormatContext* s)
{ {
int score, fec_score, dvhs_score; int score, fec_score, dvhs_score;
int margin;
int ret;
if (size < (TS_FEC_PACKET_SIZE * 5 + 1)) /*init buffer to store stream for probing */
return AVERROR_INVALIDDATA; uint8_t buf[PROBE_PACKET_MAX_BUF] = {0};
int buf_size = 0;
score = analyze(buf, size, TS_PACKET_SIZE, 0); while (buf_size < PROBE_PACKET_MAX_BUF) {
dvhs_score = analyze(buf, size, TS_DVHS_PACKET_SIZE, 0); ret = avio_read_partial(s->pb, buf + buf_size, PROBE_PACKET_MAX_BUF - buf_size);
fec_score = analyze(buf, size, TS_FEC_PACKET_SIZE, 0); if (ret < 0)
av_log(NULL, AV_LOG_TRACE, "score: %d, dvhs_score: %d, fec_score: %d \n", return AVERROR_INVALIDDATA;
score, dvhs_score, fec_score); buf_size += ret;
if (score > fec_score && score > dvhs_score) score = analyze(buf, buf_size, TS_PACKET_SIZE, 0);
return TS_PACKET_SIZE; dvhs_score = analyze(buf, buf_size, TS_DVHS_PACKET_SIZE, 0);
else if (dvhs_score > score && dvhs_score > fec_score) fec_score = analyze(buf, buf_size, TS_FEC_PACKET_SIZE, 0);
return TS_DVHS_PACKET_SIZE; av_log(s, AV_LOG_TRACE, "Probe: %d, score: %d, dvhs_score: %d, fec_score: %d \n",
else if (score < fec_score && dvhs_score < fec_score) buf_size, score, dvhs_score, fec_score);
return TS_FEC_PACKET_SIZE;
else if (buf_size < PROBE_PACKET_MAX_BUF)
return AVERROR_INVALIDDATA; margin = PROBE_PACKET_MARGIN; /*if buffer not filled */
else
margin = 0;
if (score > FFMAX(fec_score, dvhs_score) + margin)
return TS_PACKET_SIZE;
else if (dvhs_score > FFMAX(score, fec_score) + margin)
return TS_DVHS_PACKET_SIZE;
else if (fec_score > FFMAX(score, dvhs_score) + margin)
return TS_FEC_PACKET_SIZE;
}
return AVERROR_INVALIDDATA;
} }
typedef struct SectionHeader { typedef struct SectionHeader {
@ -2933,8 +2950,6 @@ static int mpegts_read_header(AVFormatContext *s)
{ {
MpegTSContext *ts = s->priv_data; MpegTSContext *ts = s->priv_data;
AVIOContext *pb = s->pb; AVIOContext *pb = s->pb;
uint8_t buf[8 * 1024] = {0};
int len;
int64_t pos, probesize = s->probesize; int64_t pos, probesize = s->probesize;
s->internal->prefer_codec_framerate = 1; s->internal->prefer_codec_framerate = 1;
@ -2942,10 +2957,8 @@ static int mpegts_read_header(AVFormatContext *s)
if (ffio_ensure_seekback(pb, probesize) < 0) if (ffio_ensure_seekback(pb, probesize) < 0)
av_log(s, AV_LOG_WARNING, "Failed to allocate buffers for seekback\n"); av_log(s, AV_LOG_WARNING, "Failed to allocate buffers for seekback\n");
/* read the first 8192 bytes to get packet size */
pos = avio_tell(pb); pos = avio_tell(pb);
len = avio_read(pb, buf, sizeof(buf)); ts->raw_packet_size = get_packet_size(s);
ts->raw_packet_size = get_packet_size(buf, len);
if (ts->raw_packet_size <= 0) { if (ts->raw_packet_size <= 0) {
av_log(s, AV_LOG_WARNING, "Could not detect TS packet size, defaulting to non-FEC/DVHS\n"); av_log(s, AV_LOG_WARNING, "Could not detect TS packet size, defaulting to non-FEC/DVHS\n");
ts->raw_packet_size = TS_PACKET_SIZE; ts->raw_packet_size = TS_PACKET_SIZE;