8. A method for speaker identification, comprising: at a device having one or more processors and memory: receiving a spoken utterance; generating a first phoneme-independent representation based on the spoken utterance; decomposing the first phoneme-independent representation into at least one content-independent characteristic unit; comparing the at least one content-independent characteristic unit to at least one content-independent recognition distribution value associated with a registered user of the device, the at least one content-independent recognition distribution value previously generated by: generating a second phoneme-independent representation based on speech from the registered user; and decomposing the second phoneme-independent representation into a content-independent recognition unit, the at least one content-independent recognition distribution value based on the content-independent recognition unit; and determining that the spoken utterance is spoken by the registered user if the at least one content-independent characteristic unit is within a threshold limit of the at least one content-independent recognition distribution value.
8. A method for speaker identification, comprising: at a device having one or more processors and memory: receiving a spoken utterance; generating a first phoneme-independent representation based on the spoken utterance; decomposing the first phoneme-independent representation into at least one content-independent characteristic unit; comparing the at least one content-independent characteristic unit to at least one content-independent recognition distribution value associated with a registered user of the device, the at least one content-independent recognition distribution value previously generated by: generating a second phoneme-independent representation based on speech from the registered user; and decomposing the second phoneme-independent representation into a content-independent recognition unit, the at least one content-independent recognition distribution value based on the content-independent recognition unit; and determining that the spoken utterance is spoken by the registered user if the at least one content-independent characteristic unit is within a threshold limit of the at least one content-independent recognition distribution value. 13. The method of claim 8 , wherein the first phoneme-independent representation is further decomposed into at least one content input sequence, and wherein determining that the spoken utterance is spoken by the registered user further comprises determining that the spoken utterance is spoken by the registered user if the at least one content input sequence is similar to at least one content reference sequence previously trained by the registered speaker.