[alsa-devel] Using loopback card to Connect GSM two way call to the real sound card UDA1345TS

[Srinivasan S]

Dear All,

Could you please provide any inputs w.r.t the loopback card using snd-aloop & alsaloop, how this loopback card can be used to connect the GSM two way call simultanoeusly to the UDA1345TS codec on MCASP0 of the am335x (UDA1345TS ie., real sound card)

The codec has two output channels VOUTL, VOUTR & two input channels VINL , VINR

As I am pretty new to linux audio particularly ALSA Framework as I was involved only in intial codec bringup using aplay & arecord utilities , as I was having some trouble getting a grasp on it all, (as I want this to be darecord one in ALSA only without entering into gstreamer or ffmpeg, could you please confirm on the same that whether can it be done in ALSA only)


If this probably isn't the place to ask this question, but I am not sure where is.  Feel free to point me somewhere else if there is a better place :)


So it seems what is happening is basically when i up the channels from VINL to VOUTL, & VINR to VOUTR ie., I am able capture from VINR & play back using VOUTR & similarly I am able to capture from VINR & route to VOUTR using the below asound.conf & the attached application

With this am able to achieve only one way call at a time by running only one application at a time ie., alsa_loopback_min_mono_VINL.c or alsa_loopback_min_mono_VINR.c

Could you please kindly let me know how two way call can be established simultaneously finally with only one application , as I tried merging both apps ie., (alsa_loopback_min_mono_VINL & alsa_loopback_min_mono_VINR) at that moment am getting device resource busy,
when I tried to open snd_pcm_open (&playback_handle_left, pldevice, SND_PCM_STREAM_PLAYBACK, 0) in the application alsa_loopback_min_mono.c




Kindly do the needful as early as possible,


Awaiting for your replies,


Many Many Thanks a lot for your replies & would appreciate the same w.r.t my earlier two queries



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