On Sun, Oct 10, 2021 at 01:22:49AM +0800, "zhilizhao(赵志立)" wrote:
>
>
> > On Sep 30, 2021, at 9:14 AM, [email protected] wrote:
> >
> > From: Limin Wang <[email protected]>
> >
> > Signed-off-by: Limin Wang <[email protected]>
> > ---
> > doc/protocols.texi | 10 ++++++++++
> > libavformat/libsrt.c | 7 +++++++
> > 2 files changed, 17 insertions(+)
> >
> > diff --git a/doc/protocols.texi b/doc/protocols.texi
> > index 726e5f1..9c246f8 100644
> > --- a/doc/protocols.texi
> > +++ b/doc/protocols.texi
> > @@ -1496,6 +1496,16 @@ when the old encryption key is decommissioned.
> > Default is -1.
> > -1 means auto (0x1000 in srt library). The range for
> > this option is integers in the 0 - @code{INT_MAX}.
> >
> > +@item snddropdelay=@var{microseconds}
> > +The sender's delay before dropping packets. This delay is
> > +added to the default drop delay time interval value.
> > +Keep in mind that the longer the delay, the more probable it
> > +becomes that packets would be retransmitted uselessly because
> > +they will be dropped by the receiver anyway.
> > +
> > +Default is -1 means auto which typically means do not drop
> > +packets on the sender at all.
>
> There are two issues here:
>
> Firstly, -1 means auto for our libsrt wrapper. "typically means do not drop
> packets on the sender at all” is incorrect. The default value of libsrt is
> 0 for live mode, -1 for file mode. Live mode is the default and the file mode
> doesn’t matter much for FFmpeg, TBH.
>
> Secondly, since our wrapper and libsrt defined different sematic for -1, now
> it’s impossible to pass -1 to libsrt.
Yes, the default is misleading. I'll add -2 for auto for wrapper, it'll be
unset mode and
will be use the default value of libsrt. Then -1 can pass to libsrt.c also.
>
> And the description from libsrt doc
>
> > Keep in mind that the longer the delay, the more probable it becomes that
> > packets would be
> > retransmitted
>
> can mislead the user to set a higher value for it, which is not a good idea.
> I don’t know how to improve that.
>
> > +
> > @item payload_size=@var{bytes}
> > Sets the maximum declared size of a packet transferred
> > during the single call to the sending function in Live
> > diff --git a/libavformat/libsrt.c b/libavformat/libsrt.c
> > index c6308d1..13697d2 100644
> > --- a/libavformat/libsrt.c
> > +++ b/libavformat/libsrt.c
> > @@ -65,6 +65,7 @@ typedef struct SRTContext {
> > int enforced_encryption;
> > int kmrefreshrate;
> > int kmpreannounce;
> > + int64_t snddropdelay;
> > #endif
> > int mss;
> > int ffs;
> > @@ -111,6 +112,7 @@ static const AVOption libsrt_options[] = {
> > { "enforced_encryption", "Enforces that both connection parties have
> > the same passphrase set",
> > OFFSET(enforced_encryption), AV_OPT_TYPE_BOOL, { .i64 = -1 }, -1, 1,
> > .flags = D|E },
> > { "kmrefreshrate", "The number of packets to be transmitted after
> > which the encryption key is switched to a new key", OFFSET(kmrefreshrate),
> > AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, .flags = D|E },
> > { "kmpreannounce", "The interval between when a new encryption
> > key is sent and when switchover occurs",
> > OFFSET(kmpreannounce), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX,
> > .flags = D|E },
> > + { "snddropdelay", "The sender's delay(in microseconds) before
> > dropping packets",
> > OFFSET(snddropdelay), AV_OPT_TYPE_INT64, { .i64 = -1 }, -1,
> > INT64_MAX, .flags = D|E },
> > #endif
> > { "mss", "The Maximum Segment Size",
> > OFFSET(mss), AV_OPT_TYPE_INT, { .i64
> > = -1 }, -1, 1500, .flags = D|E },
> > { "ffs", "Flight flag size (window size) (in bytes)",
> > OFFSET(ffs), AV_OPT_TYPE_INT, { .i64
> > = -1 }, -1, INT_MAX, .flags = D|E },
> > @@ -318,6 +320,7 @@ static int libsrt_set_options_pre(URLContext *h, int fd)
> > int latency = s->latency / 1000;
> > int rcvlatency = s->rcvlatency / 1000;
> > int peerlatency = s->peerlatency / 1000;
> > + int snddropdelay = s->snddropdelay / 1000;
> > int connect_timeout = s->connect_timeout;
> >
> > if ((s->mode == SRT_MODE_RENDEZVOUS && libsrt_setsockopt(h, fd,
> > SRTO_RENDEZVOUS, "SRTO_RENDEZVOUS", &yes, sizeof(yes)) < 0) ||
> > @@ -334,6 +337,7 @@ static int libsrt_set_options_pre(URLContext *h, int fd)
> > #endif
> > (s->kmrefreshrate >= 0 && libsrt_setsockopt(h, fd,
> > SRTO_KMREFRESHRATE, "SRTO_KMREFRESHRATE", &s->kmrefreshrate,
> > sizeof(s->kmrefreshrate)) < 0) ||
> > (s->kmpreannounce >= 0 && libsrt_setsockopt(h, fd,
> > SRTO_KMPREANNOUNCE, "SRTO_KMPREANNOUNCE", &s->kmpreannounce,
> > sizeof(s->kmpreannounce)) < 0) ||
> > + (s->snddropdelay >= 0 && libsrt_setsockopt(h, fd,
> > SRTO_SNDDROPDELAY, "SRTO_SNDDROPDELAY", &snddropdelay,
> > sizeof(snddropdelay)) < 0) ||
> > #endif
> > (s->mss >= 0 && libsrt_setsockopt(h, fd, SRTO_MSS, "SRTO_MSS",
> > &s->mss, sizeof(s->mss)) < 0) ||
> > (s->ffs >= 0 && libsrt_setsockopt(h, fd, SRTO_FC, "SRTO_FC",
> > &s->ffs, sizeof(s->ffs)) < 0) ||
> > @@ -549,6 +553,9 @@ static int libsrt_open(URLContext *h, const char *uri,
> > int flags)
> > if (av_find_info_tag(buf, sizeof(buf), "kmpreannounce", p)) {
> > s->kmpreannounce = strtol(buf, NULL, 10);
> > }
> > + if (av_find_info_tag(buf, sizeof(buf), "snddropdelay", p)) {
> > + s->snddropdelay = strtoll(buf, NULL, 10);
> > + }
> > #endif
> > if (av_find_info_tag(buf, sizeof(buf), "mss", p)) {
> > s->mss = strtol(buf, NULL, 10);
> > --
> > 1.8.3.1
> >
> > _______________________________________________
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> >
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> >
>
--
Thanks,
Limin Wang
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