Speech Recognition - Subtitles
The amount of knowledge necessary to develop such a large scale multi-language, speaker-independent, large-vocabulary speech recognition system is spread well over hundreds of papers; and each individual brick of the system (say the feature extraction front-end, the FST decoding library, the language model store) is developed by world-class expert in this specific field. Some of Google's research scientists have published papers on these topics, this might be a good place to start if you want to understand what's behind the scenes... But maybe  you should start with a smaller goal - like building a system that has a vocabulary of a dozen different words from the same speaker - using a library like HTK or Sphinx (using the "canonical" approach with the hierarchy GMM->phone->word->language model), and once you have all the basics right, explore deeper in one direction (try more complex feature extraction methods to handle noise, grow the vocabulary and the complexity of the grammar, try speaker adaptation).