From 60566981e5fd2f421d623ea92de01c31cdf071d1 Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 15 Jun 2025 15:53:25 +0200
Subject: [PATCH 01/14] WIP working encoding of a train clip to h264 mp4 video
 using gstreamer

---
 go.mod                        |   3 +
 go.sum                        |   6 ++
 internal/pkg/stitch/stitch.go | 148 +++++++++++++++++++++++++++++++++-
 3 files changed, 156 insertions(+), 1 deletion(-)

diff --git a/go.mod b/go.mod
index 9f9e06b..8e35223 100644
--- a/go.mod
+++ b/go.mod
@@ -53,6 +53,8 @@ require (
 	github.com/fatih/color v1.18.0 // indirect
 	github.com/fatih/structtag v1.2.0 // indirect
 	github.com/felixge/httpsnoop v1.0.4 // indirect
+	github.com/go-gst/go-glib v1.4.0 // indirect
+	github.com/go-gst/go-gst v1.4.0 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 // indirect
@@ -68,6 +70,7 @@ require (
 	github.com/jmespath/go-jmespath v0.4.0 // indirect
 	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/mattn/go-pointer v0.0.1 // indirect
 	github.com/mattn/go-runewidth v0.0.16 // indirect
 	github.com/mgechev/dots v0.0.0-20210922191527-e955255bf517 // indirect
 	github.com/mgechev/revive v1.9.0 // indirect
diff --git a/go.sum b/go.sum
index 5736ca1..46e00bf 100644
--- a/go.sum
+++ b/go.sum
@@ -67,6 +67,10 @@ github.com/fatih/structtag v1.2.0/go.mod h1:mBJUNpUnHmRKrKlQQlmCrh5PuhftFbNv8Ys4
 github.com/felixge/httpsnoop v1.0.4 h1:NFTV2Zj1bL4mc9sqWACXbQFVBBg2W3GPvqp8/ESS2Wg=
 github.com/felixge/httpsnoop v1.0.4/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/go-gst/go-glib v1.4.0 h1:FB2uVfB0uqz7/M6EaDdWWlBZRQpvFAbWfL7drdw8lAE=
+github.com/go-gst/go-glib v1.4.0/go.mod h1:GUIpWmkxQ1/eL+FYSjKpLDyTZx6Vgd9nNXt8dA31d5M=
+github.com/go-gst/go-gst v1.4.0 h1:EikB43u4c3wc8d2RzlFRSfIGIXYzDy6Zls2vJqrG2BU=
+github.com/go-gst/go-gst v1.4.0/go.mod h1:p8TLGtOxJLcrp6PCkTPdnanwWBxPZvYiHDbuSuwgO3c=
 github.com/go-logr/logr v0.1.0/go.mod h1:ixOQHD9gLJUVQQ2ZOR7zLEifBX6tGkNJF4QyIY7sIas=
 github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 github.com/go-logr/logr v1.4.2 h1:6pFjapn8bFcIbiKo3XT4j/BhANplGihG6tvd+8rYgrY=
@@ -143,6 +147,8 @@ github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWE
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/mattn/go-mjpeg v0.0.3 h1:0G/+KddrbI5Hnq83B11O1O4vP7Q6L9MsBu6aW71jhUM=
 github.com/mattn/go-mjpeg v0.0.3/go.mod h1:65z7Cj+u5y5K3B8Sy5NtrJFTWAhguGHs9FEkADdx6kE=
+github.com/mattn/go-pointer v0.0.1 h1:n+XhsuGeVO6MEAp7xyEukFINEa+Quek5psIR/ylA6o0=
+github.com/mattn/go-pointer v0.0.1/go.mod h1:2zXcozF6qYGgmsG+SeTZz3oAbFLdD3OWqnUbNvJZAlc=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
 github.com/mattn/go-runewidth v0.0.16 h1:E5ScNMtiwvlvB5paMFdw9p4kSQzbXFikJ5SQO6TULQc=
 github.com/mattn/go-runewidth v0.0.16/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index b5aac3d..77a343e 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -4,11 +4,16 @@ import (
 	"errors"
 	"fmt"
 	"image"
+	"image/color"
 	"image/draw"
 	"image/gif"
 	"math"
 	"time"
 
+	"github.com/go-gst/go-glib/glib"
+	"github.com/go-gst/go-gst/gst"
+	"github.com/go-gst/go-gst/gst/app"
+	"github.com/go-gst/go-gst/gst/video"
 	"github.com/mccutchen/palettor"
 	"github.com/nfnt/resize"
 	"github.com/rs/zerolog/log"
@@ -184,6 +189,146 @@ func createGIF(seq sequence, stitched image.Image) (*gif.GIF, error) {
 	return &g, nil
 }
 
+func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
+	// https://github.com/go-gst/go-gst/blob/v1.4.0/examples/appsrc/main.go
+
+	// SW: x264enc
+	// HW on RPi: v4l2h264enc
+	// HW on PC AMD: va264enc
+
+	// appsrc ! x264enc ! mp4mux ! filesync location=/tmp/test.mp4
+
+	gst.Init(nil)
+
+	pipeline, err := gst.NewPipeline("")
+	if err != nil {
+		return nil, err
+	}
+
+	encoder := "x264enc"
+	elems, err := gst.NewElementMany("appsrc", "videoconvert", encoder, "h264parse", "mp4mux" /*"autovideosink"*/, "filesink")
+	//elems, err := gst.NewElementMany("appsrc", "videoconvert", "autovideosink")
+	if err != nil {
+		return nil, err
+	}
+
+	pipeline.AddMany(elems...)
+	gst.ElementLinkMany(elems...)
+
+	src := app.SrcFromElement(elems[0])
+	elems[5].SetArg("location", "/tmp/test.mp4")
+	//elems[4].SetArg("sync", "false")
+
+	// Specify the format we want to provide as application into the pipeline
+	// by creating a video info with the given format and creating caps from it for the appsrc element.
+	videoInfo := video.NewInfo().
+		WithFormat(video.FormatRGBA, 300, 300). /*uint(seq.frames[0].Bounds().Dx()), uint(seq.frames[0].Bounds().Dy()))*/
+		WithFPS(gst.Fraction(2, 1))             // FIXME
+
+	src.SetCaps(videoInfo.ToCaps())
+	src.SetProperty("format", gst.FormatTime)
+
+	// Initialize a frame counter
+	var i int
+	//palette := video.FormatRGB8P.Palette()
+
+	// Since our appsrc element operates in pull mode (it asks us to provide data),
+	// we add a handler for the need-data callback and provide new data from there.
+	// In our case, we told gstreamer that we do 2 frames per second. While the
+	// buffers of all elements of the pipeline are still empty, this will be called
+	// a couple of times until all of them are filled. After this initial period,
+	// this handler will be called (on average) twice per second.
+	src.SetCallbacks(&app.SourceCallbacks{
+		NeedDataFunc: func(self *app.Source, _ uint) {
+
+			// If we've reached the end of the palette, end the stream.
+			if i == len(seq.frames) {
+				src.EndStream()
+				return
+			}
+
+			log.Debug().Int("frame", i).Msg("Producing frame")
+
+			// Create a buffer that can hold exactly one video RGBA frame.
+			buffer := gst.NewBufferWithSize(videoInfo.Size())
+
+			// For each frame we produce, we set the timestamp when it should be displayed
+			// The autovideosink will use this information to display the frame at the right time.
+			buffer.SetPresentationTimestamp(gst.ClockTime(time.Duration(i) * 33 * time.Millisecond)) // FIXME
+
+			// Produce an image frame for this iteration.
+			pixels := seq.frames[i].(*image.RGBA).Pix
+			//pixels := produceImageFrame(palette[i])
+
+			// At this point, buffer is only a reference to an existing memory region somewhere.
+			// When we want to access its content, we have to map it while requesting the required
+			// mode of access (read, read/write).
+			// See: https://gstreamer.freedesktop.org/documentation/plugin-development/advanced/allocation.html
+			//
+			// There are convenience wrappers for building buffers directly from byte sequences as
+			// well.
+			buffer.Map(gst.MapWrite).WriteData(pixels)
+			buffer.Unmap()
+
+			//buffer := gst.NewBufferFromBytes(pixels)
+
+			// Push the buffer onto the pipeline.
+			self.PushBuffer(buffer)
+
+			log.Debug().Msg("buffer pushed")
+
+			i++
+		},
+	})
+
+	mainLoop := glib.NewMainLoop(glib.MainContextDefault(), false)
+
+	pipeline.Ref()
+	defer pipeline.Unref()
+
+	pipeline.SetState(gst.StatePlaying)
+
+	// Retrieve the bus from the pipeline and add a watch function
+	pipeline.GetPipelineBus().AddWatch(func(msg *gst.Message) bool {
+		log.Warn().Str("msg", msg.String()).Msg("gstreamer message")
+		switch msg.Type() {
+		case gst.MessageEOS:
+			//time.Sleep(5 * time.Second)
+			//pipeline.SetState(gst.StateNull)
+			//time.Sleep(5 * time.Second)
+			//mainLoop.Quit()
+			//time.Sleep(5 * time.Second)
+			//return false
+		}
+		//if err := handleMessage(msg); err != nil {
+		//	fmt.Println(err)
+		//	loop.Quit()
+		//	return false
+		//}
+		return true
+	})
+
+	mainLoop.Run()
+	//mainLoop.RunError()
+
+	return nil, errors.New("look at /tmp/test.mp4 :)")
+}
+func produceImageFrame(c color.Color) []uint8 {
+	width := 300
+	height := 300
+	upLeft := image.Point{0, 0}
+	lowRight := image.Point{width, height}
+	img := image.NewRGBA(image.Rectangle{upLeft, lowRight})
+
+	for x := 0; x < width; x++ {
+		for y := 0; y < height; y++ {
+			img.Set(x, y, c)
+		}
+	}
+
+	return img.Pix
+}
+
 // fitAndStitch tries to stitch an image from a sequence.
 // Will first try to fit a constant acceleration speed model for smoothing.
 // Might modify seq (drops leading frames with no movement).
@@ -241,7 +386,8 @@ func fitAndStitch(seq sequence, c Config) (*Train, error) {
 		return nil, fmt.Errorf("unable to assemble image: %w", err)
 	}
 
-	gif, err := createGIF(seq, img)
+	//gif, err := createGIF(seq, img)
+	gif, err := createH264(seq, img)
 	if err != nil {
 		panic(err)
 	}

From d1d51d31fa9f53938abe776c8ad6718ac916227c Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 15 Jun 2025 16:41:59 +0200
Subject: [PATCH 02/14] cleanup, still working

---
 internal/pkg/stitch/stitch.go | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index 77a343e..86256f7 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -206,8 +206,7 @@ func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
 	}
 
 	encoder := "x264enc"
-	elems, err := gst.NewElementMany("appsrc", "videoconvert", encoder, "h264parse", "mp4mux" /*"autovideosink"*/, "filesink")
-	//elems, err := gst.NewElementMany("appsrc", "videoconvert", "autovideosink")
+	elems, err := gst.NewElementMany("appsrc", "videoconvert", encoder, "h264parse", "mp4mux", "filesink")
 	if err != nil {
 		return nil, err
 	}
@@ -217,13 +216,12 @@ func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
 
 	src := app.SrcFromElement(elems[0])
 	elems[5].SetArg("location", "/tmp/test.mp4")
-	//elems[4].SetArg("sync", "false")
 
 	// Specify the format we want to provide as application into the pipeline
 	// by creating a video info with the given format and creating caps from it for the appsrc element.
 	videoInfo := video.NewInfo().
-		WithFormat(video.FormatRGBA, 300, 300). /*uint(seq.frames[0].Bounds().Dx()), uint(seq.frames[0].Bounds().Dy()))*/
-		WithFPS(gst.Fraction(2, 1))             // FIXME
+		WithFormat(video.FormatRGBA, uint(seq.frames[0].Bounds().Dx()), uint(seq.frames[0].Bounds().Dy())).
+		WithFPS(gst.Fraction(30, 1)) // FIXME
 
 	src.SetCaps(videoInfo.ToCaps())
 	src.SetProperty("format", gst.FormatTime)

From dc996be77777f14b54fdf3a698c0319a10013e3c Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 15 Jun 2025 22:21:46 +0200
Subject: [PATCH 03/14] UNTESTED store video clip properly

---
 cmd/trainbot/main.go          | 24 +++++++++++++++----
 internal/pkg/db/queries.go    |  6 +++++
 internal/pkg/stitch/auto.go   |  1 +
 internal/pkg/stitch/stitch.go | 45 ++++++++++++++++++++++-------------
 4 files changed, 55 insertions(+), 21 deletions(-)

diff --git a/cmd/trainbot/main.go b/cmd/trainbot/main.go
index ebe5712..0278b90 100644
--- a/cmd/trainbot/main.go
+++ b/cmd/trainbot/main.go
@@ -158,6 +158,7 @@ func detectTrainsForever(c config, trainsOut chan<- *stitch.Train) {
 		MaxSpeedKPH:         c.MaxSpeedKPH,
 		MinLengthM:          c.MinLengthM,
 		MaxFrameCountPerSeq: c.MaxFrameCountPerSeq,
+		TempDestDir:         c.DataDir,
 	})
 	defer func() {
 		train := stitcher.TryStitchAndReset()
@@ -251,12 +252,25 @@ func processTrains(store upload.DataStore, dbx *sqlx.DB, trainsIn <-chan *stitch
 		}
 
 		// Dump GIF.
-		err = imutil.DumpGIF(store.GetBlobPath(dbTrain.GIFFileName()), train.GIF)
-		if err != nil {
-			log.Err(err).Send()
-			continue
+		if train.GIF != nil {
+			err = imutil.DumpGIF(store.GetBlobPath(dbTrain.GIFFileName()), train.GIF)
+			if err != nil {
+				log.Err(err).Send()
+				continue
+			}
+			log.Debug().Str("gifFileName", dbTrain.GIFFileName()).Msg("wrote GIF")
+		}
+
+		// Move Train Clip
+		if train.TrainClip != nil {
+			filename := dbTrain.FileNameWithExt(filepath.Ext(train.TrainClip.Path))
+			err = os.Rename(train.TrainClip.Path, store.GetBlobPath(filename))
+			if err != nil {
+				log.Err(err).Send()
+				continue
+			}
+			log.Debug().Str("trainClipFileName", filename).Msg("moved train clip")
 		}
-		log.Debug().Str("gifFileName", dbTrain.GIFFileName()).Msg("wrote GIF")
 
 		id, err := db.InsertTrain(dbx, *train)
 		if err != nil {
diff --git a/internal/pkg/db/queries.go b/internal/pkg/db/queries.go
index 81710c9..fbe2104 100644
--- a/internal/pkg/db/queries.go
+++ b/internal/pkg/db/queries.go
@@ -53,6 +53,12 @@ func (t *Train) GIFFileName() string {
 	return fmt.Sprintf("train_%s.gif", tsString)
 }
 
+// FileNameWithExt returns a file name for this train with the given file extension, derived from timestamp.
+func (t Train) FileNameWithExt(extension string) string {
+	tsString := t.StartTS.Format(fileTSFormat)
+	return fmt.Sprintf("train_%s.%s", tsString, extension)
+}
+
 // ImgFileName returns the image file name for this train (derived from timestamp).
 func (t *Train) ImgFileName() string {
 	tsString := t.StartTS.Format(fileTSFormat)
diff --git a/internal/pkg/stitch/auto.go b/internal/pkg/stitch/auto.go
index e6497ed..01c020c 100644
--- a/internal/pkg/stitch/auto.go
+++ b/internal/pkg/stitch/auto.go
@@ -29,6 +29,7 @@ type Config struct {
 	MaxSpeedKPH         float64
 	MinLengthM          float64
 	MaxFrameCountPerSeq int
+	TempDestDir         string
 }
 
 func (c *Config) minPxPerFrame(framePeriodS float64) int {
diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index 86256f7..386f099 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -8,6 +8,7 @@ import (
 	"image/draw"
 	"image/gif"
 	"math"
+	"os"
 	"time"
 
 	"github.com/go-gst/go-glib/glib"
@@ -119,8 +120,9 @@ type Train struct {
 
 	Conf Config
 
-	Image *image.RGBA `json:"-"`
-	GIF   *gif.GIF    `json:"-"`
+	Image     *image.RGBA `json:"-"`
+	GIF       *gif.GIF    `json:"-"`
+	TrainClip *TrainClip  `json:"-"`
 }
 
 // LengthM returns the absolute length in m.
@@ -189,23 +191,28 @@ func createGIF(seq sequence, stitched image.Image) (*gif.GIF, error) {
 	return &g, nil
 }
 
-func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
+func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 	// https://github.com/go-gst/go-gst/blob/v1.4.0/examples/appsrc/main.go
 
-	// SW: x264enc
-	// HW on RPi: v4l2h264enc
-	// HW on PC AMD: va264enc
-
-	// appsrc ! x264enc ! mp4mux ! filesync location=/tmp/test.mp4
-
 	gst.Init(nil)
 
+	dest_file, err := os.CreateTemp(dest_dir, ".temp-createH264.mp4.*")
+	if err != nil {
+		return nil, err
+	}
+	dest_file.Close()
+	dest_path := dest_file.Name()
+
 	pipeline, err := gst.NewPipeline("")
 	if err != nil {
 		return nil, err
 	}
 
+	// SW: x264enc
+	// HW on RPi: v4l2h264enc
+	// HW on PC AMD: va264enc
 	encoder := "x264enc"
+
 	elems, err := gst.NewElementMany("appsrc", "videoconvert", encoder, "h264parse", "mp4mux", "filesink")
 	if err != nil {
 		return nil, err
@@ -215,7 +222,7 @@ func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
 	gst.ElementLinkMany(elems...)
 
 	src := app.SrcFromElement(elems[0])
-	elems[5].SetArg("location", "/tmp/test.mp4")
+	elems[5].SetArg("location", dest_path)
 
 	// Specify the format we want to provide as application into the pipeline
 	// by creating a video info with the given format and creating caps from it for the appsrc element.
@@ -241,11 +248,12 @@ func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
 
 			// If we've reached the end of the palette, end the stream.
 			if i == len(seq.frames) {
+				log.Debug().Msg("all frames pushed to gstreamer appsrc")
 				src.EndStream()
 				return
 			}
 
-			log.Debug().Int("frame", i).Msg("Producing frame")
+			log.Trace().Int("frame", i).Msg("Producing frame")
 
 			// Create a buffer that can hold exactly one video RGBA frame.
 			buffer := gst.NewBufferWithSize(videoInfo.Size())
@@ -273,7 +281,7 @@ func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
 			// Push the buffer onto the pipeline.
 			self.PushBuffer(buffer)
 
-			log.Debug().Msg("buffer pushed")
+			log.Trace().Msg("buffer pushed")
 
 			i++
 		},
@@ -288,7 +296,7 @@ func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
 
 	// Retrieve the bus from the pipeline and add a watch function
 	pipeline.GetPipelineBus().AddWatch(func(msg *gst.Message) bool {
-		log.Warn().Str("msg", msg.String()).Msg("gstreamer message")
+		log.Debug().Str("msg", msg.String()).Msg("gstreamer message")
 		switch msg.Type() {
 		case gst.MessageEOS:
 			//time.Sleep(5 * time.Second)
@@ -309,7 +317,7 @@ func createH264(seq sequence, stitched image.Image) (*gif.GIF, error) {
 	mainLoop.Run()
 	//mainLoop.RunError()
 
-	return nil, errors.New("look at /tmp/test.mp4 :)")
+	return &TrainClip{Path: dest_path}, nil
 }
 func produceImageFrame(c color.Color) []uint8 {
 	width := 300
@@ -327,6 +335,10 @@ func produceImageFrame(c color.Color) []uint8 {
 	return img.Pix
 }
 
+type TrainClip struct {
+	Path string
+}
+
 // fitAndStitch tries to stitch an image from a sequence.
 // Will first try to fit a constant acceleration speed model for smoothing.
 // Might modify seq (drops leading frames with no movement).
@@ -385,7 +397,7 @@ func fitAndStitch(seq sequence, c Config) (*Train, error) {
 	}
 
 	//gif, err := createGIF(seq, img)
-	gif, err := createH264(seq, img)
+	trainClip, err := createH264(seq, c.TempDestDir)
 	if err != nil {
 		panic(err)
 	}
@@ -399,6 +411,7 @@ func fitAndStitch(seq sequence, c Config) (*Train, error) {
 		-a,
 		c,
 		img,
-		gif,
+		nil,
+		trainClip,
 	}, nil
 }

From cf4bf47af350c999ff32b5c813a814bcacb5aebf Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Tue, 17 Jun 2025 19:41:48 +0200
Subject: [PATCH 04/14] UNTESTED correct frame timestamps

---
 internal/pkg/stitch/stitch.go | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index 386f099..53737e8 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -233,9 +233,7 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 	src.SetCaps(videoInfo.ToCaps())
 	src.SetProperty("format", gst.FormatTime)
 
-	// Initialize a frame counter
-	var i int
-	//palette := video.FormatRGB8P.Palette()
+	frame_no := 0
 
 	// Since our appsrc element operates in pull mode (it asks us to provide data),
 	// we add a handler for the need-data callback and provide new data from there.
@@ -247,23 +245,23 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 		NeedDataFunc: func(self *app.Source, _ uint) {
 
 			// If we've reached the end of the palette, end the stream.
-			if i == len(seq.frames) {
+			if frame_no == len(seq.frames) {
 				log.Debug().Msg("all frames pushed to gstreamer appsrc")
 				src.EndStream()
 				return
 			}
 
-			log.Trace().Int("frame", i).Msg("Producing frame")
+			log.Trace().Int("frame", frame_no).Msg("Producing frame")
 
 			// Create a buffer that can hold exactly one video RGBA frame.
 			buffer := gst.NewBufferWithSize(videoInfo.Size())
 
 			// For each frame we produce, we set the timestamp when it should be displayed
 			// The autovideosink will use this information to display the frame at the right time.
-			buffer.SetPresentationTimestamp(gst.ClockTime(time.Duration(i) * 33 * time.Millisecond)) // FIXME
+			buffer.SetPresentationTimestamp(gst.ClockTime(seq.startTS.Sub(seq.ts[frame_no])))
 
 			// Produce an image frame for this iteration.
-			pixels := seq.frames[i].(*image.RGBA).Pix
+			pixels := seq.frames[frame_no].(*image.RGBA).Pix
 			//pixels := produceImageFrame(palette[i])
 
 			// At this point, buffer is only a reference to an existing memory region somewhere.
@@ -283,7 +281,7 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 
 			log.Trace().Msg("buffer pushed")
 
-			i++
+			frame_no++
 		},
 	})
 

From 21f53154489b9e948c2e04edce21fbdd298ee980 Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Fri, 10 Nov 2023 22:54:08 +0100
Subject: [PATCH 05/14] allow higher resolution

---
 cmd/trainbot/main.go          | 2 +-
 internal/pkg/stitch/stitch.go | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/cmd/trainbot/main.go b/cmd/trainbot/main.go
index 0278b90..1fdddb1 100644
--- a/cmd/trainbot/main.go
+++ b/cmd/trainbot/main.go
@@ -77,7 +77,7 @@ func (c *config) mustOpenDB() *sqlx.DB {
 
 const (
 	rectSizeMin = 100
-	rectSizeMax = 500
+	rectSizeMax = 1000
 
 	failedFramesMax = 50
 
diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index 53737e8..1410a16 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -22,7 +22,7 @@ import (
 )
 
 const (
-	maxMemoryMB = 1024 * 1024 * 50
+	maxMemoryMB = 1024 * 1024 * 50 * 10
 )
 
 func isign(x int) int {

From ef8380b4a410e4e0db8db5088342a21f327036bd Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 22 Jun 2025 20:26:15 +0200
Subject: [PATCH 06/14] fix segfault, image sometimes was a SubImage

---
 internal/pkg/stitch/stitch.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index 1410a16..eb18b30 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -19,6 +19,7 @@ import (
 	"github.com/nfnt/resize"
 	"github.com/rs/zerolog/log"
 	"jo-m.ch/go/trainbot/internal/pkg/prometheus"
+	"jo-m.ch/go/trainbot/pkg/imutil"
 )
 
 const (
@@ -261,7 +262,9 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 			buffer.SetPresentationTimestamp(gst.ClockTime(seq.startTS.Sub(seq.ts[frame_no])))
 
 			// Produce an image frame for this iteration.
-			pixels := seq.frames[frame_no].(*image.RGBA).Pix
+			// We can't write the pixels from image directly, since it may be a SubImage
+			frameRGBA := imutil.ToRGBA(seq.frames[frame_no])
+			pixels := frameRGBA.Pix
 			//pixels := produceImageFrame(palette[i])
 
 			// At this point, buffer is only a reference to an existing memory region somewhere.
@@ -271,6 +274,10 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 			//
 			// There are convenience wrappers for building buffers directly from byte sequences as
 			// well.
+			if len(pixels) > len(buffer.Bytes()) {
+				imutil.Dump("too_long.png", seq.frames[frame_no])
+				panic(fmt.Errorf("image frame pixels are too long for gstreamer buffer: %v > %v", len(pixels), len(buffer.Bytes())))
+			}
 			buffer.Map(gst.MapWrite).WriteData(pixels)
 			buffer.Unmap()
 

From e28094da1b9548d24bc048102d727a6375c0bc6e Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 22 Jun 2025 20:27:11 +0200
Subject: [PATCH 07/14] start video at t=0

---
 internal/pkg/stitch/stitch.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index eb18b30..e11efb6 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -235,6 +235,7 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 	src.SetProperty("format", gst.FormatTime)
 
 	frame_no := 0
+	startTS := seq.ts[0]
 
 	// Since our appsrc element operates in pull mode (it asks us to provide data),
 	// we add a handler for the need-data callback and provide new data from there.
@@ -259,7 +260,7 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 
 			// For each frame we produce, we set the timestamp when it should be displayed
 			// The autovideosink will use this information to display the frame at the right time.
-			buffer.SetPresentationTimestamp(gst.ClockTime(seq.startTS.Sub(seq.ts[frame_no])))
+			buffer.SetPresentationTimestamp(gst.ClockTime(startTS.Sub(seq.ts[frame_no])))
 
 			// Produce an image frame for this iteration.
 			// We can't write the pixels from image directly, since it may be a SubImage

From 0464acaac50972e15f12ebf0cad7dcfbeab980da Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 22 Jun 2025 20:31:28 +0200
Subject: [PATCH 08/14] fix negative PTS d'oh!

---
 internal/pkg/stitch/stitch.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index e11efb6..1712048 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -260,7 +260,7 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 
 			// For each frame we produce, we set the timestamp when it should be displayed
 			// The autovideosink will use this information to display the frame at the right time.
-			buffer.SetPresentationTimestamp(gst.ClockTime(startTS.Sub(seq.ts[frame_no])))
+			buffer.SetPresentationTimestamp(gst.ClockTime(seq.ts[frame_no].Sub(startTS)))
 
 			// Produce an image frame for this iteration.
 			// We can't write the pixels from image directly, since it may be a SubImage

From 6f53110378790c40812c248105e075265736c978 Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 22 Jun 2025 20:41:07 +0200
Subject: [PATCH 09/14] handle multiple trains in one input video

---
 internal/pkg/stitch/stitch.go | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index 1712048..bbf0649 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -305,13 +305,11 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 		log.Debug().Str("msg", msg.String()).Msg("gstreamer message")
 		switch msg.Type() {
 		case gst.MessageEOS:
-			//time.Sleep(5 * time.Second)
-			//pipeline.SetState(gst.StateNull)
-			//time.Sleep(5 * time.Second)
-			//mainLoop.Quit()
-			//time.Sleep(5 * time.Second)
-			//return false
+			pipeline.SetState(gst.StateNull)
+			mainLoop.Quit()
+			return false
 		}
+		// FIXME: abort on gstreamer errors
 		//if err := handleMessage(msg); err != nil {
 		//	fmt.Println(err)
 		//	loop.Quit()

From 9ed9182665a9a3447bdf0e0a3bf081b519a25bae Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 22 Jun 2025 20:56:27 +0200
Subject: [PATCH 10/14] create both .mp4 and .gif for now

---
 internal/pkg/stitch/stitch.go | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index bbf0649..c1e782a 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -400,7 +400,11 @@ func fitAndStitch(seq sequence, c Config) (*Train, error) {
 		return nil, fmt.Errorf("unable to assemble image: %w", err)
 	}
 
-	//gif, err := createGIF(seq, img)
+	gif, err := createGIF(seq, img)
+	if err != nil {
+		panic(err)
+	}
+
 	trainClip, err := createH264(seq, c.TempDestDir)
 	if err != nil {
 		panic(err)
@@ -415,7 +419,7 @@ func fitAndStitch(seq sequence, c Config) (*Train, error) {
 		-a,
 		c,
 		img,
-		nil,
+		gif,
 		trainClip,
 	}, nil
 }

From 2a918da6e0a45bcd0bcf9590fefb4a9c9428f151 Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 22 Jun 2025 20:59:35 +0200
Subject: [PATCH 11/14] fixup! UNTESTED store video clip properly

---
 internal/pkg/db/queries.go | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/internal/pkg/db/queries.go b/internal/pkg/db/queries.go
index fbe2104..e32b601 100644
--- a/internal/pkg/db/queries.go
+++ b/internal/pkg/db/queries.go
@@ -49,8 +49,12 @@ type Train struct {
 
 // GIFFileName returns the GIF file name for this train (derived from timestamp).
 func (t *Train) GIFFileName() string {
-	tsString := t.StartTS.Format(fileTSFormat)
-	return fmt.Sprintf("train_%s.gif", tsString)
+	return t.FileNameWithExt("gif")
+}
+
+// ImgFileName returns the image file name for this train (derived from timestamp).
+func (t *Train) ImgFileName() string {
+	return t.FileNameWithExt("jpg")
 }
 
 // FileNameWithExt returns a file name for this train with the given file extension, derived from timestamp.
@@ -59,12 +63,6 @@ func (t Train) FileNameWithExt(extension string) string {
 	return fmt.Sprintf("train_%s.%s", tsString, extension)
 }
 
-// ImgFileName returns the image file name for this train (derived from timestamp).
-func (t *Train) ImgFileName() string {
-	tsString := t.StartTS.Format(fileTSFormat)
-	return fmt.Sprintf("train_%s.jpg", tsString)
-}
-
 // GetNextUpload returns the next train sighting to upload from the database.
 func GetNextUpload(db *sqlx.DB) (*Train, error) {
 	const q = `

From 25e152f29bdb577e6717ad83ea664e2776afc37c Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 22 Jun 2025 21:07:22 +0200
Subject: [PATCH 12/14] fix .mp4 file names

---
 cmd/trainbot/main.go          | 2 +-
 internal/pkg/stitch/stitch.go | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/cmd/trainbot/main.go b/cmd/trainbot/main.go
index 1fdddb1..9e4f2df 100644
--- a/cmd/trainbot/main.go
+++ b/cmd/trainbot/main.go
@@ -263,7 +263,7 @@ func processTrains(store upload.DataStore, dbx *sqlx.DB, trainsIn <-chan *stitch
 
 		// Move Train Clip
 		if train.TrainClip != nil {
-			filename := dbTrain.FileNameWithExt(filepath.Ext(train.TrainClip.Path))
+			filename := dbTrain.FileNameWithExt(train.TrainClip.Ext)
 			err = os.Rename(train.TrainClip.Path, store.GetBlobPath(filename))
 			if err != nil {
 				log.Err(err).Send()
diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index c1e782a..ff55cb1 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -197,7 +197,8 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 
 	gst.Init(nil)
 
-	dest_file, err := os.CreateTemp(dest_dir, ".temp-createH264.mp4.*")
+	file_extension := "mp4"
+	dest_file, err := os.CreateTemp(dest_dir, fmt.Sprintf(".temp-createH264.%s.*", file_extension))
 	if err != nil {
 		return nil, err
 	}
@@ -321,7 +322,7 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 	mainLoop.Run()
 	//mainLoop.RunError()
 
-	return &TrainClip{Path: dest_path}, nil
+	return &TrainClip{Path: dest_path, Ext: "mp4"}, nil
 }
 func produceImageFrame(c color.Color) []uint8 {
 	width := 300
@@ -341,6 +342,7 @@ func produceImageFrame(c color.Color) []uint8 {
 
 type TrainClip struct {
 	Path string
+	Ext  string
 }
 
 // fitAndStitch tries to stitch an image from a sequence.

From 812d8d82db6d5ec394199af9547e0cb87e773a4b Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 22 Jun 2025 21:12:58 +0200
Subject: [PATCH 13/14] gstreamer debugging hint

---
 internal/pkg/stitch/stitch.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index ff55cb1..06d5550 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -194,6 +194,8 @@ func createGIF(seq sequence, stitched image.Image) (*gif.GIF, error) {
 
 func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 	// https://github.com/go-gst/go-gst/blob/v1.4.0/examples/appsrc/main.go
+	//
+	// to debug gstreamer, use the GST_DEBUG and (optionally) GST_DEBUG_FILE env vars
 
 	gst.Init(nil)
 

From c35bf71ee06ce39d53681eaa2de6a60104b86eb9 Mon Sep 17 00:00:00 2001
From: clonejo <clonejo@shakik.de>
Date: Sun, 13 Jul 2025 01:44:50 +0200
Subject: [PATCH 14/14] reimplement with ffmpeg

no per-frame PTS yet
---
 go.mod                        |   3 -
 go.sum                        |   6 --
 internal/pkg/stitch/stitch.go | 152 +++++++++-------------------------
 3 files changed, 39 insertions(+), 122 deletions(-)

diff --git a/go.mod b/go.mod
index 8e35223..9f9e06b 100644
--- a/go.mod
+++ b/go.mod
@@ -53,8 +53,6 @@ require (
 	github.com/fatih/color v1.18.0 // indirect
 	github.com/fatih/structtag v1.2.0 // indirect
 	github.com/felixge/httpsnoop v1.0.4 // indirect
-	github.com/go-gst/go-glib v1.4.0 // indirect
-	github.com/go-gst/go-gst v1.4.0 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 // indirect
@@ -70,7 +68,6 @@ require (
 	github.com/jmespath/go-jmespath v0.4.0 // indirect
 	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/mattn/go-pointer v0.0.1 // indirect
 	github.com/mattn/go-runewidth v0.0.16 // indirect
 	github.com/mgechev/dots v0.0.0-20210922191527-e955255bf517 // indirect
 	github.com/mgechev/revive v1.9.0 // indirect
diff --git a/go.sum b/go.sum
index 46e00bf..5736ca1 100644
--- a/go.sum
+++ b/go.sum
@@ -67,10 +67,6 @@ github.com/fatih/structtag v1.2.0/go.mod h1:mBJUNpUnHmRKrKlQQlmCrh5PuhftFbNv8Ys4
 github.com/felixge/httpsnoop v1.0.4 h1:NFTV2Zj1bL4mc9sqWACXbQFVBBg2W3GPvqp8/ESS2Wg=
 github.com/felixge/httpsnoop v1.0.4/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
-github.com/go-gst/go-glib v1.4.0 h1:FB2uVfB0uqz7/M6EaDdWWlBZRQpvFAbWfL7drdw8lAE=
-github.com/go-gst/go-glib v1.4.0/go.mod h1:GUIpWmkxQ1/eL+FYSjKpLDyTZx6Vgd9nNXt8dA31d5M=
-github.com/go-gst/go-gst v1.4.0 h1:EikB43u4c3wc8d2RzlFRSfIGIXYzDy6Zls2vJqrG2BU=
-github.com/go-gst/go-gst v1.4.0/go.mod h1:p8TLGtOxJLcrp6PCkTPdnanwWBxPZvYiHDbuSuwgO3c=
 github.com/go-logr/logr v0.1.0/go.mod h1:ixOQHD9gLJUVQQ2ZOR7zLEifBX6tGkNJF4QyIY7sIas=
 github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 github.com/go-logr/logr v1.4.2 h1:6pFjapn8bFcIbiKo3XT4j/BhANplGihG6tvd+8rYgrY=
@@ -147,8 +143,6 @@ github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWE
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/mattn/go-mjpeg v0.0.3 h1:0G/+KddrbI5Hnq83B11O1O4vP7Q6L9MsBu6aW71jhUM=
 github.com/mattn/go-mjpeg v0.0.3/go.mod h1:65z7Cj+u5y5K3B8Sy5NtrJFTWAhguGHs9FEkADdx6kE=
-github.com/mattn/go-pointer v0.0.1 h1:n+XhsuGeVO6MEAp7xyEukFINEa+Quek5psIR/ylA6o0=
-github.com/mattn/go-pointer v0.0.1/go.mod h1:2zXcozF6qYGgmsG+SeTZz3oAbFLdD3OWqnUbNvJZAlc=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
 github.com/mattn/go-runewidth v0.0.16 h1:E5ScNMtiwvlvB5paMFdw9p4kSQzbXFikJ5SQO6TULQc=
 github.com/mattn/go-runewidth v0.0.16/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
diff --git a/internal/pkg/stitch/stitch.go b/internal/pkg/stitch/stitch.go
index 06d5550..6b464fb 100644
--- a/internal/pkg/stitch/stitch.go
+++ b/internal/pkg/stitch/stitch.go
@@ -7,17 +7,15 @@ import (
 	"image/color"
 	"image/draw"
 	"image/gif"
+	"io"
 	"math"
 	"os"
 	"time"
 
-	"github.com/go-gst/go-glib/glib"
-	"github.com/go-gst/go-gst/gst"
-	"github.com/go-gst/go-gst/gst/app"
-	"github.com/go-gst/go-gst/gst/video"
 	"github.com/mccutchen/palettor"
 	"github.com/nfnt/resize"
 	"github.com/rs/zerolog/log"
+	ffmpeg "github.com/u2takey/ffmpeg-go"
 	"jo-m.ch/go/trainbot/internal/pkg/prometheus"
 	"jo-m.ch/go/trainbot/pkg/imutil"
 )
@@ -193,12 +191,6 @@ func createGIF(seq sequence, stitched image.Image) (*gif.GIF, error) {
 }
 
 func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
-	// https://github.com/go-gst/go-gst/blob/v1.4.0/examples/appsrc/main.go
-	//
-	// to debug gstreamer, use the GST_DEBUG and (optionally) GST_DEBUG_FILE env vars
-
-	gst.Init(nil)
-
 	file_extension := "mp4"
 	dest_file, err := os.CreateTemp(dest_dir, fmt.Sprintf(".temp-createH264.%s.*", file_extension))
 	if err != nil {
@@ -207,124 +199,58 @@ func createH264(seq sequence, dest_dir string) (*TrainClip, error) {
 	dest_file.Close()
 	dest_path := dest_file.Name()
 
-	pipeline, err := gst.NewPipeline("")
-	if err != nil {
-		return nil, err
-	}
+	//// SW: x264enc
+	//// HW on RPi: v4l2h264enc
+	//// HW on PC AMD: va264enc
+	//encoder := "x264enc"
 
-	// SW: x264enc
-	// HW on RPi: v4l2h264enc
-	// HW on PC AMD: va264enc
-	encoder := "x264enc"
+	//	WithFPS(gst.Fraction(30, 1)) // FIXME
 
-	elems, err := gst.NewElementMany("appsrc", "videoconvert", encoder, "h264parse", "mp4mux", "filesink")
-	if err != nil {
-		return nil, err
-	}
+	reader, writer := io.Pipe()
+	input_args := ffmpeg.KwArgs{"format": "rawvideo", "pix_fmt": "rgba", "video_size": fmt.Sprintf("%dx%d", uint(seq.frames[0].Bounds().Dx()), uint(seq.frames[0].Bounds().Dy()))}
+	input := ffmpeg.Input("pipe:", input_args).WithInput(reader)
+	output := input.Output(dest_path, ffmpeg.KwArgs{"format": "mp4"}).OverWriteOutput()
 
-	pipeline.AddMany(elems...)
-	gst.ElementLinkMany(elems...)
-
-	src := app.SrcFromElement(elems[0])
-	elems[5].SetArg("location", dest_path)
-
-	// Specify the format we want to provide as application into the pipeline
-	// by creating a video info with the given format and creating caps from it for the appsrc element.
-	videoInfo := video.NewInfo().
-		WithFormat(video.FormatRGBA, uint(seq.frames[0].Bounds().Dx()), uint(seq.frames[0].Bounds().Dy())).
-		WithFPS(gst.Fraction(30, 1)) // FIXME
-
-	src.SetCaps(videoInfo.ToCaps())
-	src.SetProperty("format", gst.FormatTime)
-
-	frame_no := 0
-	startTS := seq.ts[0]
-
-	// Since our appsrc element operates in pull mode (it asks us to provide data),
-	// we add a handler for the need-data callback and provide new data from there.
-	// In our case, we told gstreamer that we do 2 frames per second. While the
-	// buffers of all elements of the pipeline are still empty, this will be called
-	// a couple of times until all of them are filled. After this initial period,
-	// this handler will be called (on average) twice per second.
-	src.SetCallbacks(&app.SourceCallbacks{
-		NeedDataFunc: func(self *app.Source, _ uint) {
-
-			// If we've reached the end of the palette, end the stream.
-			if frame_no == len(seq.frames) {
-				log.Debug().Msg("all frames pushed to gstreamer appsrc")
-				src.EndStream()
-				return
-			}
+	//startTS := seq.ts[0]
 
+	errChan := make(chan error)
+	go func() {
+		for frame_no := range len(seq.frames) {
 			log.Trace().Int("frame", frame_no).Msg("Producing frame")
 
-			// Create a buffer that can hold exactly one video RGBA frame.
-			buffer := gst.NewBufferWithSize(videoInfo.Size())
-
-			// For each frame we produce, we set the timestamp when it should be displayed
-			// The autovideosink will use this information to display the frame at the right time.
-			buffer.SetPresentationTimestamp(gst.ClockTime(seq.ts[frame_no].Sub(startTS)))
+			//		// For each frame we produce, we set the timestamp when it should be displayed
+			//		// The autovideosink will use this information to display the frame at the right time.
+			//		buffer.SetPresentationTimestamp(gst.ClockTime(seq.ts[frame_no].Sub(startTS)))
 
 			// Produce an image frame for this iteration.
 			// We can't write the pixels from image directly, since it may be a SubImage
+			// TODO: we could skip this copy, by writing from the SubImage directly to the writer
 			frameRGBA := imutil.ToRGBA(seq.frames[frame_no])
 			pixels := frameRGBA.Pix
-			//pixels := produceImageFrame(palette[i])
-
-			// At this point, buffer is only a reference to an existing memory region somewhere.
-			// When we want to access its content, we have to map it while requesting the required
-			// mode of access (read, read/write).
-			// See: https://gstreamer.freedesktop.org/documentation/plugin-development/advanced/allocation.html
-			//
-			// There are convenience wrappers for building buffers directly from byte sequences as
-			// well.
-			if len(pixels) > len(buffer.Bytes()) {
-				imutil.Dump("too_long.png", seq.frames[frame_no])
-				panic(fmt.Errorf("image frame pixels are too long for gstreamer buffer: %v > %v", len(pixels), len(buffer.Bytes())))
-			}
-			buffer.Map(gst.MapWrite).WriteData(pixels)
-			buffer.Unmap()
-
-			//buffer := gst.NewBufferFromBytes(pixels)
-
-			// Push the buffer onto the pipeline.
-			self.PushBuffer(buffer)
 
+			_, err = writer.Write(pixels)
+			if err != nil {
+				errChan <- err
+			}
 			log.Trace().Msg("buffer pushed")
+		}
+		log.Debug().Msg("all frames pushed to ffmpeg pipe")
+		writer.Close()
+		errChan <- nil
+	}()
 
-			frame_no++
-		},
-	})
-
-	mainLoop := glib.NewMainLoop(glib.MainContextDefault(), false)
-
-	pipeline.Ref()
-	defer pipeline.Unref()
-
-	pipeline.SetState(gst.StatePlaying)
+	log.Trace().Msg("Waiting for ffmpeg to finish ...")
+	err = output.WithErrorOutput(os.Stderr).Run()
+	if err != nil {
+		return nil, err
+	}
+	log.Trace().Msg("Waiting for raw frame writer to return ...")
+	err = <-errChan
+	if err != nil {
+		return nil, err
+	}
 
-	// Retrieve the bus from the pipeline and add a watch function
-	pipeline.GetPipelineBus().AddWatch(func(msg *gst.Message) bool {
-		log.Debug().Str("msg", msg.String()).Msg("gstreamer message")
-		switch msg.Type() {
-		case gst.MessageEOS:
-			pipeline.SetState(gst.StateNull)
-			mainLoop.Quit()
-			return false
-		}
-		// FIXME: abort on gstreamer errors
-		//if err := handleMessage(msg); err != nil {
-		//	fmt.Println(err)
-		//	loop.Quit()
-		//	return false
-		//}
-		return true
-	})
-
-	mainLoop.Run()
-	//mainLoop.RunError()
-
-	return &TrainClip{Path: dest_path, Ext: "mp4"}, nil
+	return &TrainClip{Path: dest_path, Ext: file_extension}, nil
 }
 func produceImageFrame(c color.Color) []uint8 {
 	width := 300