Add in-memory screenshot generation for sprites and phash (#1316)

pkg/ffmpeg/encoder.go

@@ -1,7 +1,7 @@
 package ffmpeg
 
 import (
-	"fmt"
+	"bytes"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -62,7 +62,7 @@ func KillRunningEncoders(path string) {
 
 	for _, process := range processes {
 		// assume it worked, don't check for error
-		fmt.Printf("Killing encoder process for file: %s", path)
+		logger.Infof("Killing encoder process for file: %s", path)
 		process.Kill()
 
 		// wait for the process to die before returning
@@ -82,7 +82,8 @@ func KillRunningEncoders(path string) {
 	}
 }
 
-func (e *Encoder) run(probeResult VideoFile, args []string) (string, error) {
+// FFmpeg runner with progress output, used for transcodes
+func (e *Encoder) runTranscode(probeResult VideoFile, args []string) (string, error) {
 	cmd := exec.Command(e.Path, args...)
 
 	stderr, err := cmd.StderrPipe()
@@ -137,3 +138,26 @@ func (e *Encoder) run(probeResult VideoFile, args []string) (string, error) {
 
 	return stdoutString, nil
 }
+
+func (e *Encoder) run(probeResult VideoFile, args []string) (string, error) {
+	cmd := exec.Command(e.Path, args...)
+
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	if err := cmd.Start(); err != nil {
+		return "", err
+	}
+
+	registerRunningEncoder(probeResult.Path, cmd.Process)
+	err := waitAndDeregister(probeResult.Path, cmd)
+
+	if err != nil {
+		// error message should be in the stderr stream
+		logger.Errorf("ffmpeg error when running command <%s>: %s", strings.Join(cmd.Args, " "), stderr.String())
+		return stdout.String(), err
+	}
+
+	return stdout.String(), nil
+}

pkg/ffmpeg/encoder_sprite_screenshot.go

@@ -0,0 +1,38 @@
+package ffmpeg
+
+import (
+	"fmt"
+	"image"
+	"strings"
+)
+
+type SpriteScreenshotOptions struct {
+	Time  float64
+	Width int
+}
+
+func (e *Encoder) SpriteScreenshot(probeResult VideoFile, options SpriteScreenshotOptions) (image.Image, error) {
+	args := []string{
+		"-v", "error",
+		"-ss", fmt.Sprintf("%v", options.Time),
+		"-i", probeResult.Path,
+		"-vframes", "1",
+		"-vf", fmt.Sprintf("scale=%v:-1", options.Width),
+		"-c:v", "bmp",
+		"-f", "rawvideo",
+		"-",
+	}
+	data, err := e.run(probeResult, args)
+	if err != nil {
+		return nil, err
+	}
+
+	reader := strings.NewReader(data)
+
+	img, _, err := image.Decode(reader)
+	if err != nil {
+		return nil, err
+	}
+
+	return img, err
+}

pkg/ffmpeg/encoder_transcode.go

@@ -64,7 +64,7 @@ func (e *Encoder) Transcode(probeResult VideoFile, options TranscodeOptions) {
 		"-strict", "-2",
 		options.OutputPath,
 	}
-	_, _ = e.run(probeResult, args)
+	_, _ = e.runTranscode(probeResult, args)
 }
 
 //transcode the video, remove the audio
@@ -84,7 +84,7 @@ func (e *Encoder) TranscodeVideo(probeResult VideoFile, options TranscodeOptions
 		"-vf", "scale=" + scale,
 		options.OutputPath,
 	}
-	_, _ = e.run(probeResult, args)
+	_, _ = e.runTranscode(probeResult, args)
 }
 
 //copy the video stream as is, transcode audio
@@ -96,7 +96,7 @@ func (e *Encoder) TranscodeAudio(probeResult VideoFile, options TranscodeOptions
 		"-strict", "-2",
 		options.OutputPath,
 	}
-	_, _ = e.run(probeResult, args)
+	_, _ = e.runTranscode(probeResult, args)
 }
 
 //copy the video stream as is, drop audio
@@ -107,5 +107,5 @@ func (e *Encoder) CopyVideo(probeResult VideoFile, options TranscodeOptions) {
 		"-c:v", "copy",
 		options.OutputPath,
 	}
-	_, _ = e.run(probeResult, args)
+	_, _ = e.runTranscode(probeResult, args)
 }