Snapshot continuously generates pictures by video frame

[aFog]

Hello! I'd like to ask about the snapshot example about generating pictures. I plan to save every frame of the video stream from the camera to a directory on the server. Do I just need to use io. Writer writes bytes to os. File object is fine. Delete the return code below:
`// Encode to (RGB) jpeg
buffer := new(bytes.Buffer)
if err = jpeg.Encode(buffer, img, nil); err != nil {
panic(err)
}

            // Serve image
            w.Header().Set("Content-Type", "image/jpeg")
            w.Header().Set("Content-Length", strconv.Itoa(len(buffer.Bytes())))

            // Write jpeg as HTTP Response
            if _, err = w.Write(buffer.Bytes()); err != nil {
                    panic(err)
            }
            return`

[aFog]

`func (t *TrackWriter) start() {
for {
pkt, _, err := t.track.ReadRTP()
if err != nil {
log.Println("read rtp error: ", err)
break
}
t.sb.Push(pkt)
// Use SampleBuilder to generate full picture from many RTP Packets
sample := t.sb.Pop()
if sample == nil {
log.Println("sample is nil")
continue
}

	// Read VP8 header.
	videoKeyframe := (sample.Data[0]&0x1 == 0)
	if !videoKeyframe {
		log.Println("not video keyframe")
		continue
	}
	// Begin VP8-to-image decode: Init->DecodeFrameHeader->DecodeFrame
	t.decoder.Init(bytes.NewReader(sample.Data), len(sample.Data))

	// Decode header
	if _, err := t.decoder.DecodeFrameHeader(); err != nil {
		log.Println("decode frame header error: ", err)
		continue
	}

	// Decode Frame
	img, err := t.decoder.DecodeFrame()
	if err != nil {
		log.Println("decode frame error: ", err)
		continue
	}

	// Encode to (RGB) jpeg
	buffer := new(bytes.Buffer)
	if err = jpeg.Encode(buffer, img, &jpeg.Options{Quality: 100}); err != nil {
		log.Println("encode jpeg error: ", err)
		continue
	}
	// write to file
	fileName := fmt.Sprintf("%s-%s.jpg", t.track.Kind().String(), time.Now().Format("2006-01-02-15-04-05"))
	if err = os.WriteFile(fileName, buffer.Bytes(), 0644); err != nil {
		log.Println("write file error: ", err)
		continue
	}
}

}`

The above code can only get one picture, and then it will be judged that the keyframe is unsuccessful.
My encoder is vp8 encoder

[aFog]

can anyone help