[alsa-devel] Via VT2020: issues with kernel 2.6.38.{2, 3} (alsa 1.0.23) - working with 2.6.33.2 (alsa 1.0.21)

[Raymond Yau]

2011/6/20 alex dot baldacchino dot alsasub at gmail dot com
>>
>> Can your hear the same signal from black and orange jack when you
>> playing stereo to hw:0,0,0 ?
>>
>> if you look at snd_hda_multi_out_analog_prepare() in hda_codec.c,
>>
>> if mout->no_share_stream=0 ,it seem that there is "upmix" feature when
>> mout->num_dacs is 4 for those 5 jacks/6 jacks motherboard
>>
>> i.e. the black and orange jacks can have the same signal as the green jack
>>
>>        /* front */
>>        snd_hda_codec_setup_stream(codec, nids[HDA_FRONT], stream_tag,
>>                                   0, format);
>>        if (!mout->no_share_stream &&
>>            mout->hp_nid && mout->hp_nid != nids[HDA_FRONT])
>>                /* headphone out will just decode front left/right (stereo) */
>>                snd_hda_codec_setup_stream(codec, mout->hp_nid, stream_tag,
>>                                           0, format);
>>        /* extra outputs copied from front */
>>        for (i = 0; i < ARRAY_SIZE(mout->extra_out_nid); i++)
>>                if (!mout->no_share_stream && mout->extra_out_nid[i])
>>                        snd_hda_codec_setup_stream(codec,
>>                                                   mout->extra_out_nid[i],
>>                                                   stream_tag, 0, format);
>>
>>        /* surrounds */
>>        for (i = 1; i < mout->num_dacs; i++) {
>>                if (chs >= (i + 1) * 2) /* independent out */
>>                        snd_hda_codec_setup_stream(codec, nids[i], stream_tag,
>>                                                   i * 2, format);
>>                else if (!mout->no_share_stream) /* copy front */
>>                        snd_hda_codec_setup_stream(codec, nids[i], stream_tag,
>>                                                   0, format);
>>        }
>>        return 0;
>> }
>>
>
>
> I fear I cannot test it the best way (I've got a 5.1 system, but have
> some 'logistic' problems using it). I've made an attempt by using two
> headphones, connected as follows:
>
> 1) one to (rear) green jack, one to orange,
> 2) one to green, one to black,
> 3) one to orange, one to black,
>
> and played a short two-channels file with aplay -Dhw:0,0,0 stereo.wav
> a few times, in each case I was able to here (same) sound from both
> headsets.
>
> However, it would seem to me that snd_hda_multi_out_analog_prepare()
> is not used by VIA Codecs, instead, some pcm operations are defined
> within patch_via.c and used by each codec, e.g.
>

Take a look at playback_multi_pcm_prep_0() in patch_via.c , it seem
this "copy front" mode is enabled by default in via codecs


	/* front */
	snd_hda_codec_setup_stream(codec, nids[HDA_FRONT], stream_tag,
				   0, format);

	if (mout->hp_nid && mout->hp_nid != nids[HDA_FRONT]
	    && !spec->hp_independent_mode)
		/* headphone out will just decode front left/right (stereo) */
		snd_hda_codec_setup_stream(codec, mout->hp_nid, stream_tag,
					   0, format);

	/* extra outputs copied from front */
	for (i = 0; i < ARRAY_SIZE(mout->extra_out_nid); i++)
		if (mout->extra_out_nid[i])
			snd_hda_codec_setup_stream(codec,
						   mout->extra_out_nid[i],
						   stream_tag, 0, format);

	/* surrounds */
	for (i = 1; i < mout->num_dacs; i++) {
		if (chs >= (i + 1) * 2) /* independent out */
			snd_hda_codec_setup_stream(codec, nids[i], stream_tag,
						   i * 2, format);
		else /* copy front */
			snd_hda_codec_setup_stream(codec, nids[i], stream_tag,
						   0, format);
	}