我必须解码全速率 gsm 音频文件。全速率 GSM 音频文件使用libgsm. 我已将 MSVC++ 与ffmpeg和libav的 Windows 夜间版本一起使用，但无法正确解码文件。谁能告诉我原因？我尝试使用以下编解码器进行解码：
/* various PCM "codecs" */
AV_CODEC_ID_FIRST_AUDIO = 0x10000,
AV_CODEC_ID_PCM_S16LE = 0x10000,
AV_CODEC_ID_PCM_S16BE,
AV_CODEC_ID_PCM_U16LE,
AV_CODEC_ID_PCM_U16BE,
AV_CODEC_ID_PCM_S8,
AV_CODEC_ID_PCM_U8,
AV_CODEC_ID_PCM_MULAW,
AV_CODEC_ID_PCM_ALAW,
AV_CODEC_ID_PCM_S32LE,
AV_CODEC_ID_PCM_S32BE,
AV_CODEC_ID_PCM_U32LE,
AV_CODEC_ID_PCM_U32BE,
AV_CODEC_ID_PCM_S24LE,
AV_CODEC_ID_PCM_S24BE,
AV_CODEC_ID_PCM_U24LE,
AV_CODEC_ID_PCM_U24BE,
AV_CODEC_ID_PCM_S24DAUD,
AV_CODEC_ID_PCM_ZORK,
AV_CODEC_ID_PCM_S16LE_PLANAR,
AV_CODEC_ID_PCM_DVD,
AV_CODEC_ID_PCM_F32BE,
AV_CODEC_ID_PCM_F32LE,
AV_CODEC_ID_PCM_F64BE,
AV_CODEC_ID_PCM_F64LE,
AV_CODEC_ID_PCM_BLURAY,
AV_CODEC_ID_PCM_LXF,
AV_CODEC_ID_S302M,
AV_CODEC_ID_PCM_S8_PLANAR,
/* various ADPCM codecs */
AV_CODEC_ID_ADPCM_IMA_QT = 0x11000,
AV_CODEC_ID_ADPCM_IMA_WAV,
AV_CODEC_ID_ADPCM_IMA_DK3,
AV_CODEC_ID_ADPCM_IMA_DK4,
AV_CODEC_ID_ADPCM_IMA_WS,
AV_CODEC_ID_ADPCM_IMA_SMJPEG,
AV_CODEC_ID_ADPCM_MS,
AV_CODEC_ID_ADPCM_4XM,
AV_CODEC_ID_ADPCM_XA,
AV_CODEC_ID_ADPCM_ADX,
AV_CODEC_ID_ADPCM_EA,
AV_CODEC_ID_ADPCM_G726,
AV_CODEC_ID_ADPCM_CT,
AV_CODEC_ID_ADPCM_SWF,
AV_CODEC_ID_ADPCM_YAMAHA,
AV_CODEC_ID_ADPCM_SBPRO_4,
AV_CODEC_ID_ADPCM_SBPRO_3,
AV_CODEC_ID_ADPCM_SBPRO_2,
AV_CODEC_ID_ADPCM_THP,
AV_CODEC_ID_ADPCM_IMA_AMV,
AV_CODEC_ID_ADPCM_EA_R1,
AV_CODEC_ID_ADPCM_EA_R3,
AV_CODEC_ID_ADPCM_EA_R2,
AV_CODEC_ID_ADPCM_IMA_EA_SEAD,
AV_CODEC_ID_ADPCM_IMA_EA_EACS,
AV_CODEC_ID_ADPCM_EA_XAS,
AV_CODEC_ID_ADPCM_EA_MAXIS_XA,
AV_CODEC_ID_ADPCM_IMA_ISS,
AV_CODEC_ID_ADPCM_G722,
AV_CODEC_ID_ADPCM_IMA_APC,
AV_CODEC_ID_VIMA = MKBETAG('V','I','M','A'),
/* AMR */
AV_CODEC_ID_AMR_NB = 0x12000,
AV_CODEC_ID_AMR_WB,
/* RealAudio codecs*/
AV_CODEC_ID_RA_144 = 0x13000,
AV_CODEC_ID_RA_288,
/* various DPCM codecs */
AV_CODEC_ID_ROQ_DPCM = 0x14000,
AV_CODEC_ID_INTERPLAY_DPCM,
AV_CODEC_ID_XAN_DPCM,
AV_CODEC_ID_SOL_DPCM,
/* audio codecs */
AV_CODEC_ID_MP2 = 0x15000,
AV_CODEC_ID_MP3, ///< preferred ID for decoding MPEG audio layer 1, 2 or 3
AV_CODEC_ID_AAC,
AV_CODEC_ID_AC3,
AV_CODEC_ID_DTS,
AV_CODEC_ID_VORBIS,
AV_CODEC_ID_DVAUDIO,
AV_CODEC_ID_WMAV1,
AV_CODEC_ID_WMAV2,
AV_CODEC_ID_MACE3,
AV_CODEC_ID_MACE6,
AV_CODEC_ID_VMDAUDIO,
AV_CODEC_ID_FLAC,
AV_CODEC_ID_MP3ADU,
AV_CODEC_ID_MP3ON4,
AV_CODEC_ID_SHORTEN,
AV_CODEC_ID_ALAC,
AV_CODEC_ID_WESTWOOD_SND1,
AV_CODEC_ID_GSM, ///< as in Berlin toast format
AV_CODEC_ID_QDM2,
AV_CODEC_ID_COOK,
AV_CODEC_ID_TRUESPEECH,
AV_CODEC_ID_TTA,
AV_CODEC_ID_SMACKAUDIO,
AV_CODEC_ID_QCELP,
AV_CODEC_ID_WAVPACK,
AV_CODEC_ID_DSICINAUDIO,
AV_CODEC_ID_IMC,
AV_CODEC_ID_MUSEPACK7,
AV_CODEC_ID_MLP,
AV_CODEC_ID_GSM_MS, /* as found in WAV */
AV_CODEC_ID_ATRAC3,
AV_CODEC_ID_VOXWARE,
AV_CODEC_ID_APE,
AV_CODEC_ID_NELLYMOSER,
AV_CODEC_ID_MUSEPACK8,
AV_CODEC_ID_SPEEX,
AV_CODEC_ID_WMAVOICE,
AV_CODEC_ID_WMAPRO,
AV_CODEC_ID_WMALOSSLESS,
AV_CODEC_ID_ATRAC3P,
AV_CODEC_ID_EAC3,
AV_CODEC_ID_SIPR,
AV_CODEC_ID_MP1,
AV_CODEC_ID_TWINVQ,
AV_CODEC_ID_TRUEHD,
AV_CODEC_ID_MP4ALS,
AV_CODEC_ID_ATRAC1,
AV_CODEC_ID_BINKAUDIO_RDFT,
AV_CODEC_ID_BINKAUDIO_DCT,
AV_CODEC_ID_AAC_LATM,
AV_CODEC_ID_QDMC,
AV_CODEC_ID_CELT,
AV_CODEC_ID_G723_1,
AV_CODEC_ID_G729,
AV_CODEC_ID_8SVX_EXP,
AV_CODEC_ID_8SVX_FIB,
AV_CODEC_ID_BMV_AUDIO,
AV_CODEC_ID_RALF,
AV_CODEC_ID_IAC,
AV_CODEC_ID_ILBC,
AV_CODEC_ID_FFWAVESYNTH = MKBETAG('F','F','W','S'),
AV_CODEC_ID_8SVX_RAW = MKBETAG('8','S','V','X'),
AV_CODEC_ID_SONIC = MKBETAG('S','O','N','C'),
AV_CODEC_ID_SONIC_LS = MKBETAG('S','O','N','L'),
AV_CODEC_ID_PAF_AUDIO = MKBETAG('P','A','F','A'),
AV_CODEC_ID_OPUS = MKBETAG('O','P','U','S')