revid/pipeline.go: improved handling of undefined pipeline permutations

We no longer panic for undefined pipeline permutations that have got past config package validation i.e. it's not possible to crash revid from setting things remotely incorrectly

revid/pipeline.go

@@ -69,7 +69,7 @@ func (r *Revid) reset(c config.Config) error {
 	r.cfg.Logger.Log(logger.Debug, "setting config")
 	err := r.setConfig(c)
 	if err != nil {
-		return err
+		return fmt.Errorf("could not set config: %w",err)
 	}
 	r.cfg.Logger.Log(logger.Info, "config set")
 
@@ -85,7 +85,7 @@ func (r *Revid) reset(c config.Config) error {
 				switch r.cfg.InputCodec {
 				case codecutil.H265:
 					if r.cfg.Input != config.InputRTSP {
-						panic("H265 codec valid only for InputRTSP")
+						return nil, errors.New("h.265 codec valid only for InputRTSP")
 					}
 					st = mts.EncodeH265
 				case codecutil.H264:
@@ -94,8 +94,10 @@ func (r *Revid) reset(c config.Config) error {
 					st = mts.EncodeMJPEG
 					encOptions = append(encOptions, mts.TimeBasedPSI(time.Duration(r.cfg.PSITime)*time.Second))
 					r.cfg.CBR = true
+				case codecutil.PCM, codecutil.ADPCM:
+					return nil, errors.New(fmt.Sprintf("invalid input codec: %v for input: %v",r.cfg.InputCodec,r.cfg.Input))
 				default:
-					panic("unknown input codec for Raspivid, File, V4l or RTSP input")
+					panic("unknown input codec")
 				}
 			case config.InputAudio:
 				st = mts.EncodeAudio
@@ -115,7 +117,7 @@ func (r *Revid) reset(c config.Config) error {
 	r.cfg.Logger.Log(logger.Info, "finished setting pipeline")
 
 	if err != nil {
-		return err
+		return fmt.Errorf("could not set up pipeline: %w",err)
 	}
 
 	return nil
@@ -246,46 +248,47 @@ func (r *Revid) setupPipeline(mtsEnc func(dst io.WriteCloser, rate float64) (io.
 				r.cfg.Logger.Log(logger.Debug, "using go difference filter")
 				r.filters[i] = filter.NewBasic(dst, r.cfg)
 			default:
-				panic("Undefined Filter")
+				panic("unknown filter")
 			}
 			dst = r.filters[i]
 		}
 		r.cfg.Logger.Log(logger.Info, "filters set up")
 	}
 
+	var err error
 	switch r.cfg.Input {
 	case config.InputRaspivid:
 		r.cfg.Logger.Log(logger.Debug, "using raspivid input")
 		r.input = raspivid.New(r.cfg.Logger)
-		r.setLexer(r.cfg.InputCodec, false)
+		err = r.setLexer(r.cfg.InputCodec, false)
 
 	case config.InputV4L:
 		r.cfg.Logger.Log(logger.Debug, "using V4L input")
 		r.input = webcam.New(r.cfg.Logger)
-		r.setLexer(r.cfg.InputCodec, false)
+		err = r.setLexer(r.cfg.InputCodec, false)
 
 	case config.InputFile:
 		r.cfg.Logger.Log(logger.Debug, "using file input")
 		r.input = file.New()
-		r.setLexer(r.cfg.InputCodec, false)
+		err = r.setLexer(r.cfg.InputCodec, false)
 
 	case config.InputRTSP:
 		r.cfg.Logger.Log(logger.Debug, "using RTSP input")
 		r.input = geovision.New(r.cfg.Logger)
-		r.setLexer(r.cfg.InputCodec, true)
+		err = r.setLexer(r.cfg.InputCodec, true)
 
 	case config.InputAudio:
 		r.cfg.Logger.Log(logger.Debug, "using audio input")
-		err := r.setupAudio()
+		err = r.setupAudio()
-		if err != nil {
-			return err
 	}
+	if err != nil {
+		return fmt.Errorf("could not set lexer: %w",err)
 	}
 
 	// Configure the input device. We know that defaults are set, so no need to
 	// return error, but we should log.
 	r.cfg.Logger.Log(logger.Debug, "configuring input device")
-	err := r.input.Set(r.cfg)
+	err = r.input.Set(r.cfg)
 	if err != nil {
 		r.cfg.Logger.Log(logger.Warning, "errors from configuring input device", "errors", err)
 	}
@@ -296,7 +299,7 @@ func (r *Revid) setupPipeline(mtsEnc func(dst io.WriteCloser, rate float64) (io.
 
 // setLexer sets the revid input lexer based on input codec and whether input
 // is RTSP or not, in which case an RTP/<codec> extractor is used.
-func (r *Revid) setLexer(c uint8, isRTSP bool) {
+func (r *Revid) setLexer(c uint8, isRTSP bool) error {
 	switch c {
 	case codecutil.H264:
 		r.cfg.Logger.Log(logger.Debug, "using H.264 codec")
@@ -308,7 +311,7 @@ func (r *Revid) setLexer(c uint8, isRTSP bool) {
 		r.cfg.Logger.Log(logger.Debug, "using H.265 codec")
 		r.lexTo = h265.NewExtractor(false).Extract
 		if !isRTSP {
-			panic("byte stream H.265 lexing not implemented")
+			return errors.New("byte stream h.265 lexing not implemented")
 		}
 	case codecutil.MJPEG:
 		r.cfg.Logger.Log(logger.Debug, "using MJPEG codec")
@@ -316,9 +319,12 @@ func (r *Revid) setLexer(c uint8, isRTSP bool) {
 		if isRTSP {
 			r.lexTo = mjpeg.NewExtractor().Extract
 		}
+	case codecutil.PCM, codecutil.ADPCM:
+		return errors.New("invalid codec for this selected input")
 	default:
 		panic("unrecognised codec")
 	}
+	return nil
 }
 
 // processFrom is run as a routine to read from a input data source, lex and