比特率：也叫码率，每秒的数据流量，同样分辨率，比特率越大，画面越清晰，压缩比越小，音质越好。文件体积也越大。
channelCount：省道数目。单声道、双声道。
sampleRate： 采样率
常见音频编码格式：
public static final String MIMETYPE_AUDIO_AMR_NB = "audio/3gpp";public static final String MIMETYPE_AUDIO_AMR_WB = "audio/amr-wb";public static final String MIMETYPE_AUDIO_MPEG = "audio/mpeg";public static final String MIMETYPE_AUDIO_AAC = "audio/mp4a-latm";public static final String MIMETYPE_AUDIO_QCELP = "audio/qcelp";public static final String MIMETYPE_AUDIO_VORBIS = "audio/vorbis";public static final String MIMETYPE_AUDIO_OPUS = "audio/opus";public static final String MIMETYPE_AUDIO_G711_ALAW = "audio/g711-alaw";public static final String MIMETYPE_AUDIO_G711_MLAW = "audio/g711-mlaw";public static final String MIMETYPE_AUDIO_RAW = "audio/raw";public static final String MIMETYPE_AUDIO_FLAC = "audio/flac";public static final String MIMETYPE_AUDIO_MSGSM = "audio/gsm";public static final String MIMETYPE_AUDIO_AC3 = "audio/ac3";public static final String MIMETYPE_AUDIO_EAC3 = "audio/eac3";