Description: The sound. C is used for recording and playback. One particular note is: 1. Currently the sound card does not seem to open full duplex, so if fd = open("/dev/dsp", O_RDWR), it cannot be recorded and played back. Only RDONLY and WRONLY can be set respectively. It's half duplex. Otherwise, you can hear it when you're recording it, but you can't play it back. The analysis appears to be that the IIC bus only assigns a channel to the sound card, or only one channel is enabled, so there is no recording and playback synchronization. The solution is to open the audio recording and WRONLY mode in RDONLY mode separately.
Sound1.c is used to save the recording in the test.wav file and use cast test.wav > / dev/sound/DSP playback file. It is important to note that the recording frequency must be 44100 to be properly replayed. Otherwise, it will have a similar effect. The analysis should be cast in the way that the default playback frequency of DSP is 4,4100, so if the recording is lower than this frequency, it will be released quickly.
In addition, setting the sampling rate must be set to 16bit, otherwise the error will be prompted. The reason is not known, the estimate is related to the sound card.
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