I'm writing a program to open an ALSA device (USB S/PDIF) and capture the bitstream. Aside from having to tackle the bits about deciding whether the stream is PCM versus something else, I first have to figure out how to *properly* open the device for capture. Unfortunately, what programs I've seen that do seem to work in this capacities are littered with all kinds of other crap to serve as a real reference. Documentation is pitiful, at best, unless I've completely missed whatever page it's on the internet. So, assuming I can find the card and open it using snd_pcm_open I need to then configure the hardware parameters. My current attempt is to do the following ... snd_pcm_hw_params_set_access(..., ..., SND_PCM_ACCESS_RW_INTERLEAVED) snd_pcm_hw_params_set_format(..., ..., SND_PCM_FORMAT_S16) snd_pcm_hw_params_set_channels(..., ..., 2) snd_pcm_hw_params_set_rate_near(..., ..., 48000, 0) However, I'm not entirely clear what I'll get from this device. The S/PDIF standard talks about 32-bit words (which would be one frame read from the above configuration) that can be parsed to get the headers and payload. Will I be reading that, or the "payload" with the headers stripped off? Also, what if the device to which I am connected is a CD player outputting data at 44.1 KHz? I've set the sample rate (do I really need to?) so will that adversely affect how I'm reading data? Lots of questions but maybe because I'm the kind of person that deals with concise examples I haven't figured out the answers yet. Paul Braman ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
