FFmpeg: Add Whip Muxer support for subsecond latency streaming

configure

@@ -3556,6 +3556,8 @@ wav_demuxer_select="riffdec"
 wav_muxer_select="riffenc"
 webm_chunk_muxer_select="webm_muxer"
 webm_dash_manifest_demuxer_select="matroska_demuxer"
+# TODO: Support libtls, mbedtls, and gnutls.
+whip_muxer_deps_any="openssl"
 wtv_demuxer_select="mpegts_demuxer riffdec"
 wtv_muxer_select="mpegts_muxer riffenc"
 xmv_demuxer_select="riffdec"
@@ -6912,6 +6914,14 @@ enabled rkmpp             && { require_pkg_config rkmpp rockchip_mpp  rockchip/r
                              }
 enabled vapoursynth       && require_pkg_config vapoursynth "vapoursynth-script >= 42" VSScript.h vsscript_init
 
+enabled openssl            && {
+    enabled whip_muxer && {
+        $pkg_config --exists --print-errors "openssl >= 1.0.1k" ||
+        require_pkg_config openssl "openssl >= 1.0.1k" openssl/ssl.h SSL_library_init ||
+        require_pkg_config openssl "openssl >= 1.0.1k" openssl/ssl.h OPENSSL_init_ssl
+    }
+}
+
 
 if enabled gcrypt; then
     GCRYPT_CONFIG="${cross_prefix}libgcrypt-config"

doc/muxers.texi

@@ -2846,4 +2846,51 @@ ffmpeg -f webm_dash_manifest -i video1.webm \
        manifest.xml
 @end example
 
+@anchor{whip}
+@section whip
+
+WebRTC (Real-Time Communication) muxer that supports sub-second latency streaming according to
+the WHIP (WebRTC-HTTP ingestion protocol) specification.
+
+It uses HTTP as a signaling protocol to exchange SDP capabilities and ICE lite candidates. Then,
+it uses STUN binding requests and responses to establish a session over UDP. Subsequently, it
+initiates a DTLS handshake to exchange the SRTP encryption keys. Lastly, it splits video and
+audio frames into RTP packets and encrypts them using SRTP.
+
+Ensure that you use H.264 without B frames and Opus for the audio codec. For example, to convert
+an input file with @command{ffmpeg} to WebRTC:
+@example
+ffmpeg -re -i input.mp4 -acodec libopus -ar 48000 -ac 2 \
+  -vcodec libx264 -profile:v baseline -tune zerolatency -threads 1 -bf 0 \
+  -f whip "http://localhost:1985/rtc/v1/whip/?app=live&stream=livestream"
+@end example
+
+For this example, we have employed low latency options, resulting in an end-to-end latency of
+approximately 150ms.
+
+@subsection Options
+
+This muxer supports the following options:
+
+@table @option
+
+@item handshake_timeout @var{integer}
+Set the timeout in milliseconds for ICE and DTLS handshake.
+Default value is 5000.
+
+@item pkt_size @var{integer}
+Set the maximum size, in bytes, of RTP packets that send out.
+Default value is 1500.
+
+@item authorization @var{string}
+The optional Bearer token for WHIP Authorization.
+
+@item cert_file @var{string}
+The optional certificate file path for DTLS.
+
+@item key_file @var{string}
+The optional private key file path for DTLS.
+
+@end table
+
 @c man end MUXERS

libavformat/Makefile

@@ -621,6 +621,7 @@ OBJS-$(CONFIG_WEBM_CHUNK_MUXER)          += webm_chunk.o
 OBJS-$(CONFIG_WEBP_MUXER)                += webpenc.o
 OBJS-$(CONFIG_WEBVTT_DEMUXER)            += webvttdec.o subtitles.o
 OBJS-$(CONFIG_WEBVTT_MUXER)              += webvttenc.o
+OBJS-$(CONFIG_WHIP_MUXER)                += whip.o dtls.o avc.o http.o srtp.o
 OBJS-$(CONFIG_WSAUD_DEMUXER)             += westwood_aud.o
 OBJS-$(CONFIG_WSAUD_MUXER)               += westwood_audenc.o
 OBJS-$(CONFIG_WSD_DEMUXER)               += wsddec.o rawdec.o

libavformat/allformats.c

@@ -504,6 +504,7 @@ extern const FFOutputFormat ff_webm_chunk_muxer;
 extern const FFOutputFormat ff_webp_muxer;
 extern const AVInputFormat  ff_webvtt_demuxer;
 extern const FFOutputFormat ff_webvtt_muxer;
+extern const FFOutputFormat ff_whip_muxer;
 extern const AVInputFormat  ff_wsaud_demuxer;
 extern const FFOutputFormat ff_wsaud_muxer;
 extern const AVInputFormat  ff_wsd_demuxer;