A computer system for adaptively transcoding a source audio stream of an audio/video hosting service, the system comprising: a computer processor configured to execute computer modules comprising: an audio stream metadata extraction module configured to extract metadata of the source audio stream, the metadata of the source audio stream describing audio content characteristics of the source audio stream, the metadata of the source audio stream comprising a confidence score of the source audio stream, the confidence score of a source audio stream ranging from 0 to 10 and representing a probability of the source audio stream being a type of audio stream; an audio stream classification module configured to classify the source audio stream into one of a plurality of audio content categories based on a comparison of the confidence score of the source audio stream with a confidence score threshold, the audio stream classification module coupled to the audio stream metadata extraction module; an adaptive audio encoder configured to determine one or more transcoding parameters based on the metadata and classification of the source audio stream, the adaptive audio encoder coupled to the audio stream metadata extraction module and the audio stream classification module; and an adaptive audio transcoder configured to transcode the source audio stream to an output audio stream using the transcoding parameters, and the adaptive audio transcoder coupled to the adaptive audio encoder. a computer processor configured to execute computer modules comprising: an audio stream metadata extraction module configured to extract metadata of the source audio stream, the metadata of the source audio stream describing audio content characteristics of the source audio stream, the metadata of the source audio stream comprising a confidence score of the source audio stream, the confidence score of a source audio stream ranging from 0 to 10 and representing a probability of the source audio stream being a type of audio stream; an audio stream classification module configured to classify the source audio stream into one of a plurality of audio content categories based on a comparison of the confidence score of the source audio stream with a confidence score threshold, the audio stream classification module coupled to the audio stream metadata extraction module; an adaptive audio encoder configured to determine one or more transcoding parameters based on the metadata and classification of the source audio stream, the adaptive audio encoder coupled to the audio stream metadata extraction module and the audio stream classification module; and an adaptive audio transcoder configured to transcode the source audio stream to an output audio stream using the transcoding parameters, and the adaptive audio transcoder coupled to the adaptive audio encoder. an audio stream metadata extraction module configured to extract metadata of the source audio stream, the metadata of the source audio stream describing audio content characteristics of the source audio stream, the metadata of the source audio stream comprising a confidence score of the source audio stream, the confidence score of a source audio stream ranging from 0 to 10 and representing a probability of the source audio stream being a type of audio stream; an audio stream classification module configured to classify the source audio stream into one of a plurality of audio content categories based on a comparison of the confidence score of the source audio stream with a confidence score threshold, the audio stream classification module coupled to the audio stream metadata extraction module; an adaptive audio encoder configured to determine one or more transcoding parameters based on the metadata and classification of the source audio stream, the adaptive audio encoder coupled to the audio stream metadata extraction module and the audio stream classification module; and an adaptive audio transcoder configured to transcode the source audio stream to an output audio stream using the transcoding parameters, and the adaptive audio transcoder coupled to the adaptive audio encoder.