[FFmpeg-devel,6/6] libavformat/webrtc_mux: add WebRTC-HTTP ingestion protocol (WHIP) muxer

diff --git a/configure b/configure
index 02c6f7f2c5d..05cfbbb2376 100755
--- a/configure
+++ b/configure
@@ -3557,6 +3557,8 @@  wav_demuxer_select="riffdec"
 wav_muxer_select="riffenc"
 webm_chunk_muxer_select="webm_muxer"
 webm_dash_manifest_demuxer_select="matroska_demuxer"
+whip_muxer_deps="libdatachannel rtp_muxer"
+whip_muxer_select="http_protocol rtpenc_chain"
 whep_demuxer_deps="libdatachannel sdp_demuxer"
 whep_demuxer_select="http_protocol"
 wtv_demuxer_select="mpegts_demuxer riffdec"
diff --git a/libavformat/Makefile b/libavformat/Makefile
index f790fa8cae4..000fd308be2 100644
--- a/libavformat/Makefile
+++ b/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-$(CONFIG_WHIP_MUXER)                += webrtc.o webrtc_mux.o
 OBJS-$(CONFIG_WHEP_DEMUXER)              += webrtc.o webrtc_demux.o
 OBJS-$(CONFIG_WSAUD_DEMUXER)             += westwood_aud.o
 OBJS-$(CONFIG_WSAUD_MUXER)               += westwood_audenc.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 7acb05634c8..2ad2a6dcba2 100644
--- a/libavformat/allformats.c
+++ b/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_whep_demuxer;
 extern const AVInputFormat  ff_wsaud_demuxer;
 extern const FFOutputFormat ff_wsaud_muxer;
diff --git a/libavformat/webrtc_mux.c b/libavformat/webrtc_mux.c
new file mode 100644
index 00000000000..1fe30ecb278
--- /dev/null
+++ b/libavformat/webrtc_mux.c
@@ -0,0 +1,273 @@ 
+/*
+ * WebRTC-HTTP ingestion protocol (WHIP) muxer using libdatachannel
+ *
+ * Copyright (C) 2023 NativeWaves GmbH <contact@nativewaves.com>
+ * This work is supported by FFG project 47168763.
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avformat.h"
+#include "internal.h"
+#include "libavutil/avstring.h"
+#include "libavutil/time.h"
+#include "mux.h"
+#include "rtpenc.h"
+#include "rtpenc_chain.h"
+#include "rtsp.h"
+#include "webrtc.h"
+#include "version.h"
+
+typedef struct WHIPContext {
+    AVClass *av_class;
+    DataChannelContext data_channel;
+} WHIPContext;
+
+
+static void whip_deinit(AVFormatContext* avctx);
+static int whip_init(AVFormatContext* avctx)
+{
+    WHIPContext*const ctx = (WHIPContext*const)avctx->priv_data;
+    AVStream* stream;
+    const AVCodecParameters* codecpar;
+    int i, ret;
+    char media_stream_id[37] = { 0 };
+    rtcTrackInit track_init;
+    const AVChannelLayout supported_layout = AV_CHANNEL_LAYOUT_STEREO;
+    const RTPMuxContext* rtp_mux_ctx;
+    DataChannelTrack* track;
+    char sdp_stream[SDP_MAX_SIZE] = { 0 };
+    char* fmtp;
+
+    ctx->data_channel.avctx = avctx;
+    webrtc_init_logger();
+    ret = webrtc_init_connection(&ctx->data_channel);
+    if (ret < 0) {
+        av_log(avctx, AV_LOG_ERROR, "Failed to initialize connection\n");
+        goto fail;
+    }
+
+    if (!(ctx->data_channel.tracks = av_mallocz(sizeof(DataChannelTrack) * avctx->nb_streams))) {
+        av_log(avctx, AV_LOG_ERROR, "Failed to allocate tracks\n");
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
+
+    /* configure tracks */
+    ret = webrtc_generate_media_stream_id(media_stream_id);
+    if (ret < 0) {
+        av_log(avctx, AV_LOG_ERROR, "Failed to generate media stream id\n");
+        goto fail;
+    }
+
+    for (i = 0; i < avctx->nb_streams; ++i) {
+        stream = avctx->streams[i];
+        codecpar = stream->codecpar;
+        track = &ctx->data_channel.tracks[i];
+
+        switch (codecpar->codec_type)
+        {
+            case AVMEDIA_TYPE_VIDEO:
+                /* based on rtpenc */
+                avpriv_set_pts_info(stream, 32, 1, 90000);
+                break;
+            case AVMEDIA_TYPE_AUDIO:
+                if (codecpar->sample_rate != 48000) {
+                    av_log(avctx, AV_LOG_ERROR, "Unsupported sample rate. Only 48kHz is supported\n");
+                    ret = AVERROR(EINVAL);
+                    goto fail;
+                }
+                if (av_channel_layout_compare(&codecpar->ch_layout, &supported_layout) != 0) {
+                    av_log(avctx, AV_LOG_ERROR, "Unsupported channel layout. Only stereo is supported\n");
+                    ret = AVERROR(EINVAL);
+                    goto fail;
+                }
+                /* based on rtpenc */
+                avpriv_set_pts_info(stream, 32, 1, codecpar->sample_rate);
+                break;
+            default:
+                continue;
+        }
+
+        ret = webrtc_init_urlcontext(&ctx->data_channel, i);
+        if (ret < 0) {
+            av_log(avctx, AV_LOG_ERROR, "webrtc_init_urlcontext failed\n");
+            goto fail;
+        }
+
+        ret = ff_rtp_chain_mux_open(&track->rtp_ctx, avctx, stream, track->rtp_url_context, RTP_MAX_PACKET_SIZE, i);
+        if (ret < 0) {
+            av_log(avctx, AV_LOG_ERROR, "ff_rtp_chain_mux_open failed\n");
+            goto fail;
+        }
+        rtp_mux_ctx = (const RTPMuxContext*)ctx->data_channel.tracks[i].rtp_ctx->priv_data;
+
+        memset(&track_init, 0, sizeof(rtcTrackInit));
+        track_init.direction = RTC_DIRECTION_SENDONLY;
+        track_init.payloadType = rtp_mux_ctx->payload_type;
+        track_init.ssrc = rtp_mux_ctx->ssrc;
+        track_init.mid = av_asprintf("%d", i);
+        track_init.name = LIBAVFORMAT_IDENT;
+        track_init.msid = media_stream_id;
+        track_init.trackId = av_asprintf("%s-video-%d", media_stream_id, i);
+
+        ret = webrtc_convert_codec(codecpar->codec_id, &track_init.codec);
+        if (ret < 0) {
+            av_log(avctx, AV_LOG_ERROR, "Failed to convert codec\n");
+            goto fail;
+        }
+
+        /* parse fmtp from global header */
+        ret = ff_sdp_write_media(sdp_stream, sizeof(sdp_stream), stream, i, NULL, NULL, 0, 0, NULL);
+        if (ret < 0) {
+            av_log(avctx, AV_LOG_ERROR, "Failed to write sdp\n");
+            goto fail;
+        }
+        fmtp = strstr(sdp_stream, "a=fmtp:");
+        if (fmtp) {
+            track_init.profile = av_strndup(fmtp + 10, strchr(fmtp, '\r') - fmtp - 10);
+            track_init.profile = av_asprintf("%s;level-asymmetry-allowed=1", track_init.profile);
+            memset(sdp_stream, 0, sizeof(sdp_stream));
+        }
+
+        track->track_id = rtcAddTrackEx(ctx->data_channel.peer_connection, &track_init);
+        if (track->track_id < 0) {
+            av_log(avctx, AV_LOG_ERROR, "Failed to add track\n");
+            ret = AVERROR(EINVAL);
+            goto fail;
+        }
+    }
+
+    return 0;
+
+fail:
+    return ret;
+}
+
+static int whip_write_header(AVFormatContext* avctx)
+{
+    WHIPContext*const ctx = (WHIPContext*const)avctx->priv_data;
+    int ret;
+    int64_t timeout;
+
+    ret = webrtc_create_resource(&ctx->data_channel);
+    if (ret < 0) {
+        av_log(avctx, AV_LOG_ERROR, "Failed to create resource\n");
+        goto fail;
+    }
+
+    /* wait for connection to be established */
+    timeout = av_gettime_relative() + ctx->data_channel.connection_timeout;
+    while (ctx->data_channel.state != RTC_CONNECTED) {
+        if (ctx->data_channel.state == RTC_FAILED || ctx->data_channel.state == RTC_CLOSED || av_gettime_relative() > timeout) {
+            av_log(avctx, AV_LOG_ERROR, "Failed to open connection\n");
+            ret = AVERROR_EXTERNAL;
+            goto fail;
+        }
+
+        av_log(avctx, AV_LOG_VERBOSE, "Waiting for PeerConnection to open\n");
+        av_usleep(1000);
+    }
+
+    return 0;
+
+fail:
+    return ret;
+}
+
+static int whip_write_packet(AVFormatContext* avctx, AVPacket* pkt)
+{
+    WHIPContext*const ctx = (WHIPContext*const)avctx->priv_data;
+    AVFormatContext* rtpctx = ctx->data_channel.tracks[pkt->stream_index].rtp_ctx;
+    pkt->stream_index = 0;
+
+    if (ctx->data_channel.state != RTC_CONNECTED) {
+        av_log(avctx, AV_LOG_ERROR, "Connection is not open\n");
+        return AVERROR(EINVAL);
+    }
+
+    return av_write_frame(rtpctx, pkt);
+}
+
+static int whip_write_trailer(AVFormatContext* avctx)
+{
+    WHIPContext*const ctx = (WHIPContext*const)avctx->priv_data;
+    return webrtc_close_resource(&ctx->data_channel);
+}
+
+static void whip_deinit(AVFormatContext* avctx)
+{
+    WHIPContext*const ctx = (WHIPContext*const)avctx->priv_data;
+    webrtc_deinit(&ctx->data_channel);
+}
+
+static int whip_check_bitstream(AVFormatContext *s, AVStream *st, const AVPacket *pkt)
+{
+    /* insert SPS/PPS into every keyframe otherwise browsers won't play the stream */
+    if (st->codecpar->extradata_size && st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
+        return ff_stream_add_bitstream_filter(st, "dump_extra", "freq=keyframe");
+    return 1;
+}
+
+static int whip_query_codec(enum AVCodecID codec_id, int std_compliance)
+{
+    switch (codec_id)
+    {
+        case AV_CODEC_ID_OPUS:
+        case AV_CODEC_ID_AAC:
+        case AV_CODEC_ID_PCM_MULAW:
+        case AV_CODEC_ID_PCM_ALAW:
+        case AV_CODEC_ID_H264:
+        case AV_CODEC_ID_HEVC:
+        case AV_CODEC_ID_AV1:
+        case AV_CODEC_ID_VP9:
+            return 1;
+        default:
+            return 0;
+    }
+}
+
+#define OFFSET(x) offsetof(WHIPContext, x)
+#define ENC AV_OPT_FLAG_ENCODING_PARAM
+static const AVOption options[] = {
+    WEBRTC_OPTIONS(ENC, OFFSET(data_channel)),
+    { NULL },
+};
+
+static const AVClass whip_muxer_class = {
+    .class_name = "WHIP muxer",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+const FFOutputFormat ff_whip_muxer = {
+    .p.name             = "whip",
+    .p.long_name        = NULL_IF_CONFIG_SMALL("WebRTC-HTTP ingestion protocol (WHIP) muxer"),
+    .p.audio_codec      = AV_CODEC_ID_OPUS, // supported by major browsers
+    .p.video_codec      = AV_CODEC_ID_H264,
+    .p.flags            = AVFMT_NOFILE | AVFMT_GLOBALHEADER | AVFMT_EXPERIMENTAL,
+    .p.priv_class       = &whip_muxer_class,
+    .priv_data_size     = sizeof(WHIPContext),
+    .write_packet       = whip_write_packet,
+    .write_header       = whip_write_header,
+    .write_trailer      = whip_write_trailer,
+    .init               = whip_init,
+    .deinit             = whip_deinit,
+    .query_codec        = whip_query_codec,
+    .check_bitstream    = whip_check_bitstream,
+};