[Openvortex-dev] Re: au88x0 modem

[Raymond]

Manuel Jander wrote:
> Hi,
>
>
> > The easy way is to create a PCM device "modem" on au8810
> >
> >
> > DMA -> FIFO -> SRC -> MIXIN --------> MIXOUT -> MC97(Modem Out)
> >                         |
> >                         +-----------> MIXOUT -> EQ -> AC97(Audio Left)
> >
> >                                 Modem Speaker  On or Off
> >
> >                                   +-> MIXOUT -> EQ -> AC97(Audio Right)
> >                                   |
> > DMA <- FIFO <- SRC <- MIXOUT <- MIXIN <-------- MC97(Modem IN)
> >
> >
> > or
> >
> >
> > DMA -> FIFO -> SRC -> MC97(modem) (Playback)
> >
> > DMA <- FIFO <- SRC <- MC97(modem) (Capture)
>
>
> Remove the samplerate converter, it does not make any sense on a modem.

AC-link requried 48kHz , is it controlled by the modem application ?

Do we need to implement snd_vortex_modem_hw_params() ?

> You will only loose signal precision with the samplerate converter
> anyway, and there are very few of them. 

When comparing au8810 and au8830, vortex_fifo_init() fail at 17th FIFO.

au8810 seem to has only 16 FIFO and 16 SRC.

http://lists.nongnu.org/archive/html/openvortex-dev/2004-03/msg00039.html


> A direct route from the fifo to the modem codec will do it and the modem
> signal device will run at the codec native samplerate without any
> precision loss.

What is the format of the PCM ? (16bits signed/unsigned)

DMA -> FIFO -> MC97(modem) (Playback)

DMA <- FIFO <- MC97(modem) (Capture)

> > What is the difference between modem application and audio application ?
>
>
> Nothing. The only modem extra functionality is the ability to switch the
> modem line off/on hook. It just sends and captures QAM modulated
> signals.

What feature do SI3036 support ? (Data/Fax/speaker phone/Voice Modem)

May be we can add a simple dialer in vortex control panel to make a 
voice call ?

http://alsa.opensrc.org/au88x0

> > Do the modem application open two PCM streams (one for playback and the 
> > other for capture )?
>
>
> Yes, it should be full duplex. This will require 2 DMA's.

Do we need different playback_ops for the wavetable ?


diff -Naur modem/alsa-driver/alsa-kernel/pci/au88x0_orig/au88x0_pcm.c 
modem/alsa-driver/alsa-kernel/pci/au88x0/au88x0_pcm.c
--- modem/alsa-driver/alsa-kernel/pci/au88x0_orig/au88x0_pcm.c 
2005-09-15 19:34:02.000000000 +0800
+++ modem/alsa-driver/alsa-kernel/pci/au88x0/au88x0_pcm.c	2005-09-16 
23:19:55.000000000 +0800
@@ -525,11 +580,19 @@
        VORTEX_PCM_TYPE(pcm) = idx;
        pcm->private_data = chip;
        /* set operators */
-       snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK,
-                       &snd_vortex_playback_ops);
-       if (idx == VORTEX_PCM_ADB)
-               snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE,
-                               &snd_vortex_playback_ops);
+       switch (idx) {
+#ifdef CHIP_AU8810
+       case VORTEX_PCM_MODEM:
+		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, 
&snd_vortex_modem_playback_ops);
+		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, 
&snd_vortex_modem_capture_ops);
+               break;
+#endif
+       case VORTEX_PCM_ADB:
+               snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, 
&snd_vortex_playback_ops);
+       default:
+		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, 
&snd_vortex_playback_ops);
+               break;
+       };
        
        /* pre-allocation of Scatter-Gather buffers */
        


> > Where is the class SND_PCM_CLASS_MODEM specificed in the driver ?
>
>
> At least i did not.

How do the modem application know which device of the sound card is a 
modem ?