android dsd 播放器 Android中播放DSD音乐

Github上有个简单的Alsa DSD测试程序，可以播放DSD，地址位于：/zonque/alsa-dsd-player 细看其代码，发现有ALSA_FORMAT_SND_PCM_FORMAT_DSD_U8的定义，详情如下：

#if 1

/* 8-bit DSD */

#define ALSA_FORMAT SND_PCM_FORMAT_DSD_U8

#define SAMPLE_SIZE (sizeof(uint8_t) * 2)

#define SAMPLE_RATE_DIV 1

#else

/* 16-bit DSD */

#define ALSA_FORMAT SND_PCM_FORMAT_DSD_U16

#define SAMPLE_SIZE (sizeof(uint16_t) * 2)

#define SAMPLE_RATE_DIV 2

#endif

那么在Android中能运行这个测试程序吗？ALSA_FORMAT_SND_PCM_FORMAT_DSD_U8似乎是亮点，之前没有看到过。尝试在Android的源码中寻找它的定义，没找到。但是在标准的alsa-lib中找到了：

typedef enum _snd_pcm_format {

125 SND_PCM_FORMAT_UNKNOWN = -1,

127 SND_PCM_FORMAT_S8 = 0,

129 SND_PCM_FORMAT_U8,

131 SND_PCM_FORMAT_S16_LE,

133 SND_PCM_FORMAT_S16_BE,

135 SND_PCM_FORMAT_U16_LE,

137 SND_PCM_FORMAT_U16_BE,

139 SND_PCM_FORMAT_S24_LE,

141 SND_PCM_FORMAT_S24_BE,

143 SND_PCM_FORMAT_U24_LE,

145 SND_PCM_FORMAT_U24_BE,

147 SND_PCM_FORMAT_S32_LE,

149 SND_PCM_FORMAT_S32_BE,

151 SND_PCM_FORMAT_U32_LE,

153 SND_PCM_FORMAT_U32_BE,

155 SND_PCM_FORMAT_FLOAT_LE,

157 SND_PCM_FORMAT_FLOAT_BE,

159 SND_PCM_FORMAT_FLOAT64_LE,

161 SND_PCM_FORMAT_FLOAT64_BE,

163 SND_PCM_FORMAT_IEC958_SUBFRAME_LE,

165 SND_PCM_FORMAT_IEC958_SUBFRAME_BE,

167 SND_PCM_FORMAT_MU_LAW,

169 SND_PCM_FORMAT_A_LAW,

171 SND_PCM_FORMAT_IMA_ADPCM,

173 SND_PCM_FORMAT_MPEG,

175 SND_PCM_FORMAT_GSM,

177 SND_PCM_FORMAT_SPECIAL = 31,

179 SND_PCM_FORMAT_S24_3LE = 32,

181 SND_PCM_FORMAT_S24_3BE,

183 SND_PCM_FORMAT_U24_3LE,

185 SND_PCM_FORMAT_U24_3BE,

187 SND_PCM_FORMAT_S20_3LE,

189 SND_PCM_FORMAT_S20_3BE,

191 SND_PCM_FORMAT_U20_3LE,

193 SND_PCM_FORMAT_U20_3BE,

195 SND_PCM_FORMAT_S18_3LE,

197 SND_PCM_FORMAT_S18_3BE,

199 SND_PCM_FORMAT_U18_3LE,

201 SND_PCM_FORMAT_U18_3BE,

202 /* G.723 (ADPCM) 24 kbit/s, 8 samples in 3 bytes */

203 SND_PCM_FORMAT_G723_24,

204 /* G.723 (ADPCM) 24 kbit/s, 1 sample in 1 byte */

205 SND_PCM_FORMAT_G723_24_1B,

206 /* G.723 (ADPCM) 40 kbit/s, 8 samples in 3 bytes */

207 SND_PCM_FORMAT_G723_40,

208 /* G.723 (ADPCM) 40 kbit/s, 1 sample in 1 byte */

209 SND_PCM_FORMAT_G723_40_1B,

210 /* Direct Stream Digital (DSD) in 1-byte samples (x8) */

211 SND_PCM_FORMAT_DSD_U8,

212 /* Direct Stream Digital (DSD) in 2-byte samples (x16) */

213 SND_PCM_FORMAT_DSD_U16_LE,

214 SND_PCM_FORMAT_LAST = SND_PCM_FORMAT_DSD_U16_LE,

215

216 #if __BYTE_ORDER == __LITTLE_ENDIAN

217

218 SND_PCM_FORMAT_S16 = SND_PCM_FORMAT_S16_LE,

220 SND_PCM_FORMAT_U16 = SND_PCM_FORMAT_U16_LE,

222 SND_PCM_FORMAT_S24 = SND_PCM_FORMAT_S24_LE,

224 SND_PCM_FORMAT_U24 = SND_PCM_FORMAT_U24_LE,

226 SND_PCM_FORMAT_S32 = SND_PCM_FORMAT_S32_LE,

228 SND_PCM_FORMAT_U32 = SND_PCM_FORMAT_U32_LE,

230 SND_PCM_FORMAT_FLOAT = SND_PCM_FORMAT_FLOAT_LE,

232 SND_PCM_FORMAT_FLOAT64 = SND_PCM_FORMAT_FLOAT64_LE,

234 SND_PCM_FORMAT_IEC958_SUBFRAME = SND_PCM_FORMAT_IEC958_SUBFRAME_LE

235 #elif __BYTE_ORDER == __BIG_ENDIAN

236

237 SND_PCM_FORMAT_S16 = SND_PCM_FORMAT_S16_BE,

239 SND_PCM_FORMAT_U16 = SND_PCM_FORMAT_U16_BE,

241 SND_PCM_FORMAT_S24 = SND_PCM_FORMAT_S24_BE,

243 SND_PCM_FORMAT_U24 = SND_PCM_FORMAT_U24_BE,

245 SND_PCM_FORMAT_S32 = SND_PCM_FORMAT_S32_BE,

247 SND_PCM_FORMAT_U32 = SND_PCM_FORMAT_U32_BE,

249 SND_PCM_FORMAT_FLOAT = SND_PCM_FORMAT_FLOAT_BE,

251 SND_PCM_FORMAT_FLOAT64 = SND_PCM_FORMAT_FLOAT64_BE,

253 SND_PCM_FORMAT_IEC958_SUBFRAME = SND_PCM_FORMAT_IEC958_SUBFRAME_BE

254 #else

255 #error "Unknown endian"

256 #endif

257 } snd_pcm_format_t;

暂时还不知具体是怎么工作的，是透传DSD数据到硬件？还是alsa-lib中先转换为标准的PCM？ 但在Android的alsa-lib中，确实是没有SND_PCM_FORMAT_DSD的定义，应该是被精简掉了。因此只能考虑采用DSD->PCM转换成24bit 176K后，再按照标准的PCM方式来播放。

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