[FFmpeg-devel] [PATCH v2] avformat/libsrt: add snddropdelay parameter for srt

["zhilizhao(赵志立)"]

> On Oct 10, 2021, at 11:17 AM, lance.lmwang at gmail.com wrote:
> 
> From: Limin Wang <lance.lmwang at gmail.com>
> 
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
> doc/protocols.texi   | 9 +++++++++
> libavformat/libsrt.c | 7 +++++++
> 2 files changed, 16 insertions(+)
> 
> diff --git a/doc/protocols.texi b/doc/protocols.texi
> index 726e5f1..7951abb 100644
> --- a/doc/protocols.texi
> +++ b/doc/protocols.texi
> @@ -1496,6 +1496,15 @@ 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}.
> 
> + at item snddropdelay=@var{microseconds}
> +The sender's delay before dropping packets. This delay is

snddropdelay is NOT the delay before dropping packets, it’s
an extra delay.

> +added to the default drop delay time interval value.
> +
> +Default is -2 which typically means it's unset and use the
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> +the default by libsrt(Default: 0 in Live mode, -1 in File mode).
     ^^^^^^^^^^
> +

which means using the default.

On the other hand, -2 is an implementation detail and not a real
value for snddropdelay, so it doesn’t need to be mentioned in the
doc.

> +Special value -1: Do not drop packets on the sender at all.
> +
> @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..c2e633b 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 = -2 }, -2, 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 > 0 ? s->snddropdelay / 1000 : s->snddropdelay;
>     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  >=-1 && 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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