fix datatype crop

bin/ffx.py

@@ -92,8 +92,8 @@ if dtsTokens:
 if not dtsBandwidth.endswith('k'):
     dtsBandwidth += "k"
 
-cropStart = -1
-cropLength = -1
+cropStart = ''
+cropLength = ''
 cropTokens = [c for c in sys.argv if c.startswith('crop=')]
 if cropTokens:
   cropString = cropTokens[0].split('=')[1]
@@ -167,7 +167,7 @@ for quality in qualities:
         else:
             commandSequence += generateOutputTokens(outputFilename)
     
-        if cropStart > -1:
+        if cropStart:
             commandSequence += generateCropTokens(cropStart, cropLength)
 
 
@@ -181,7 +181,7 @@ for quality in qualities:
         commandSequence1 = commandTokens + generateVP9Pass1Tokens(quality) + nullTokens
 
 
-        if cropStart > -1:
+        if cropStart:
             commandSequence += generateCropTokens(cropStart, cropLength)
 
 
@@ -192,7 +192,7 @@ for quality in qualities:
         commandSequence2 = commandTokens + mappingTokens + generateVP9Pass2Tokens(quality) + audioTokens
 
 
-        if cropStart > -1:
+        if cropStart:
             commandSequence += generateCropTokens(cropStart, cropLength)