From 8a7712a4c807ad4af1f3dde73618da050c322c8f Mon Sep 17 00:00:00 2001
From: Alex X <alexey.khit@gmail.com>
Date: Wed, 22 May 2024 18:49:43 +0300
Subject: [PATCH] Add ffmpeg auto codec selection logic

---
 internal/ffmpeg/ffmpeg.go   |  12 ++--
 internal/ffmpeg/producer.go | 112 ++++++++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+), 4 deletions(-)
 create mode 100644 internal/ffmpeg/producer.go

diff --git a/internal/ffmpeg/ffmpeg.go b/internal/ffmpeg/ffmpeg.go
index ff66c835..48172bcb 100644
--- a/internal/ffmpeg/ffmpeg.go
+++ b/internal/ffmpeg/ffmpeg.go
@@ -2,6 +2,7 @@ package ffmpeg
 
 import (
 	"net/url"
+	"slices"
 	"strings"
 
 	"github.com/AlexxIT/go2rtc/internal/app"
@@ -28,9 +29,14 @@ func Init() {
 
 	streams.RedirectFunc("ffmpeg", func(url string) (string, error) {
 		args := parseArgs(url[7:])
+		if slices.Contains(args.Codecs, "auto") {
+			return "", nil // force call streams.HandleFunc("ffmpeg")
+		}
 		return "exec:" + args.String(), nil
 	})
 
+	streams.HandleFunc("ffmpeg", NewProducer)
+
 	device.Init(defaults["bin"])
 	hardware.Init(defaults["bin"])
 }
@@ -85,6 +91,8 @@ var defaults = map[string]string{
 	"pcml/8000":  "-c:a pcm_s16le -ar:a 8000 -ac:a 1",
 	"pcml/44100": "-c:a pcm_s16le -ar:a 44100 -ac:a 1",
 
+	"opus/48000/2": "-c:a libopus -application:a lowdelay -min_comp 0 -ar:a 48000 -ac:a 2",
+
 	// hardware Intel and AMD on Linux
 	// better not to set `-async_depth:v 1` like for QSV, because framedrops
 	// `-bf 0` - disable B-frames is very important
@@ -202,10 +210,6 @@ func parseArgs(s string) *ffmpeg.Args {
 		args.Input = inputTemplate("file", s, query)
 	}
 
-	if args.Input == "" {
-		return nil
-	}
-
 	if query["async"] != nil {
 		args.Input = "-use_wallclock_as_timestamps 1 -async 1 " + args.Input
 	}
diff --git a/internal/ffmpeg/producer.go b/internal/ffmpeg/producer.go
new file mode 100644
index 00000000..8cb3cb10
--- /dev/null
+++ b/internal/ffmpeg/producer.go
@@ -0,0 +1,112 @@
+package ffmpeg
+
+import (
+	"encoding/json"
+	"errors"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/AlexxIT/go2rtc/internal/streams"
+	"github.com/AlexxIT/go2rtc/pkg/aac"
+	"github.com/AlexxIT/go2rtc/pkg/core"
+)
+
+type Producer struct {
+	core.SuperProducer
+	url    string
+	query  url.Values
+	ffmpeg core.Producer
+}
+
+// NewProducer - FFmpeg producer with auto selection video/audio codec based on client capabilities
+func NewProducer(url string) (core.Producer, error) {
+	p := &Producer{}
+
+	i := strings.IndexByte(url, '#')
+	p.url, p.query = url[:i], streams.ParseQuery(url[i+1:])
+
+	// ffmpeg.NewProducer support only one audio
+	if len(p.query["video"]) != 0 || len(p.query["audio"]) != 1 {
+		return nil, errors.New("ffmpeg: unsupported params: " + url[i:])
+	}
+
+	p.Type = "FFmpeg producer"
+	p.Medias = []*core.Media{
+		{
+			Kind:      core.KindAudio,
+			Direction: core.DirectionRecvonly,
+			Codecs: []*core.Codec{
+				{Name: core.CodecOpus, ClockRate: 48000, Channels: 2},
+				{Name: core.CodecAAC, ClockRate: 16000, FmtpLine: aac.FMTP + "1408"},
+				{Name: core.CodecPCM, ClockRate: 16000},
+				{Name: core.CodecPCM, ClockRate: 8000},
+				{Name: core.CodecPCMA, ClockRate: 16000},
+				{Name: core.CodecPCMA, ClockRate: 8000},
+				{Name: core.CodecPCMU, ClockRate: 16000},
+				{Name: core.CodecPCMU, ClockRate: 8000},
+			},
+		},
+	}
+	return p, nil
+}
+
+func (p *Producer) Start() error {
+	var err error
+	if p.ffmpeg, err = streams.GetProducer(p.newURL()); err != nil {
+		return err
+	}
+
+	for i, media := range p.ffmpeg.GetMedias() {
+		track, err := p.ffmpeg.GetTrack(media, media.Codecs[0])
+		if err != nil {
+			return err
+		}
+		p.Receivers[i].Replace(track)
+	}
+
+	return p.ffmpeg.Start()
+}
+
+func (p *Producer) Stop() error {
+	if p.ffmpeg == nil {
+		return nil
+	}
+	return p.ffmpeg.Stop()
+}
+
+func (p *Producer) MarshalJSON() ([]byte, error) {
+	if p.ffmpeg == nil {
+		return json.Marshal(p.SuperProducer)
+	}
+	return json.Marshal(p.ffmpeg)
+}
+
+func (p *Producer) newURL() string {
+	s := p.url
+	// rewrite codecs in url from auto to known presets from defaults
+	for _, receiver := range p.Receivers {
+		codec := receiver.Codec
+		switch codec.Name {
+		case core.CodecPCMU, core.CodecPCMA:
+			s += "#audio=" + strings.ToLower(codec.Name)
+			if codec.ClockRate != 0 {
+				s += "/" + strconv.Itoa(int(codec.ClockRate))
+			}
+		case core.CodecAAC:
+			s += "#audio=aac/16000"
+		case core.CodecOpus:
+			s += "#audio=opus/48000/2"
+		}
+	}
+	// add other params
+	for key, values := range p.query {
+		if key != "audio" {
+			for _, value := range values {
+				s += "#" + key + "=" + value
+			}
+		}
+	}
+
+	return s
+}