created new script for converting bilingual captions to monolingual c…

…aption (#399)

subtitles/README.md

@@ -26,4 +26,17 @@ Some languages like Simplified Chinese have a different YouTube language code (`
 python utils/generate_subtitles.py --language zh-CN --youtube_language_code zh-Hans
 ```
 
-Once you have the `.srt` files you can manually fix any translation errors and then open a pull request with the new files.
+Once you have the `.srt` files you can manually fix any translation errors and then open a pull request with the new files.
+
+# How to convert bilingual subtitle to monolingual subtitle
+
+# Logic
+
+The english caption line is conventionally placed at the last line of each subtitle block in srt files. So removing the last line of each subtitle block would make the bilingual subtitle a monolingual subtitle. 
+
+# Usage
+> python3 convert_bilingual_monolingual.py -i \<input_file\> -o \<output_file\>
+
+**Example**
+* For instance, the input file name is "test.cn.en.srt", and you name your output file as "output_test.cn.srt" *
+> python3 convert_bilingual_monolingual.py -i test.cn.en.srt -o output_test.cn.srt

utils/convert_bilingual_monolingual.py

@@ -0,0 +1,61 @@
+#!/usr/bin/python3
+import getopt
+import re
+import sys
+
+PATTERN_TIMESTAMP = re.compile('^[0-9][0-9]:[0-9][0-9]:[0-9][0-9],[0-9][0-9][0-9] --> [0-9][0-9]:[0-9][0-9]:[0-9][0-9],[0-9][0-9][0-9]')
+PATTERN_NUM = re.compile('\\d+')
+
+
+def main(argv):
+    inputfile = ''
+    outputfile = ''
+    try:
+        opts, args = getopt.getopt(argv, "hi:o:", ["ifile=", "ofile="])
+    except getopt.GetoptError:
+        print('srt_worker.py -i <inputfile> -o <outputfile>')
+        sys.exit(2)
+    for opt, arg in opts:
+          if opt == '-h':
+             print( 'Usage: convert_bilingual_monolingual.py -i <inputfile> -o <outputfile>')
+             sys.exit(-2)
+          elif opt in ("-i", "--ifile"):
+             inputfile = arg
+          elif opt in ("-o", "--ofile"):
+             outputfile = arg
+
+    if not inputfile:
+        print('no input file is specified.\nUsage: convert_bilingual_monolingual.py -i <inputfile> -o <outputfile>')
+    elif not outputfile:
+        print('no output file is specified.\nUsage: convert_bilingual_monolingual.py -i <inputfile> -o <outputfile>')
+    else:
+        process(inputfile, outputfile)
+
+
+def process(input_file, output):
+    """
+    Convert bilingual caption file to monolingual caption, supported caption file type is srt.
+    """
+    line_count = 0
+    with open(input_file) as file:
+        with open(output, 'a') as output:
+            for line in file:
+                if line_count == 0:
+                    line_count += 1
+                    output.write(line)
+                elif PATTERN_TIMESTAMP.match(line):
+                    line_count += 1
+                    output.write(line)
+                elif line == '\n':
+                    line_count = 0
+                    output.write(line)
+                else:
+                    if line_count == 2:
+                        output.write(line)
+                    line_count += 1
+        output.close()
+        print('conversion completed!')
+
+
+if __name__ == "__main__":
+    main(sys.argv[1:])