On Tuesday 19 June 2007 18:59:01 Takashi Iwai wrote: > At Mon, 18 Jun 2007 17:37:46 +0800, > > ChernYue Kwok wrote: > > Hello, > > > > I am using an SBLive! 5.1 sound card (emu10k1 chipset) with 6 channel > > output. Due to the nature of my work, I need to be able to play sound > > through all 6 channels at the same output level to an amplifier. > > > > Using Linux and the emu10k1 ALSA driver, I measured output voltage levels > > on an oscilloscope while playing a sine wave on all 6 channels, and I got > > three different output voltage amplitudes for the front, rear and > > center/subwoofer channels. > > Repeating the same test with the same card on WIndows using the Creative > > SBLive drivers from their website, I am able to get the same output > > voltage amplitude on all 6 channels. > > For both tests, all output levels in the relevant mixers were set to > > their maximum levels. > > > > I would like to know if this output normalizing 'feature' of the SBLive > > Windows driver can be found in the emu10k1 ALSA driver, or in any other > > ALSA driver. Failing that, is there any other solution to set output > > levels in the driver, or am I doomed to twiddle in alsamixer to get the > > output levels that I want? > > Did you check the dB level appearing in mixer? The recent version of > ALSA shows dB level in alsamixer and amixer. Note that the "Master" > and "PCM" controls are applied only for front channels. So, set them > to 0dB and control the volume via Wave* digital mixers. > > > Takashi Hi Takashi, Thanks for your suggestions. Based on your advice on dB levels, I set the PCM and Master channels to 0dB gain, and maxed the levels on the Center, LFE, and Surround channels. The Wave* channels were set to 0 since I was playing surround and not stereo sound. Playing the same 6-channel sine wave again, I was able to obtain the following, more evenly matched, results: Front channels: 0.64V peak to peak Rear channels: 0.68V peak to peak Center and subwoofer: 0.48V peak to peak The front and rear channel output voltages were more evenly matched, but the center/subwoofer channel shows a large difference from the other channels. For comparison, the results I obtained in Windows using the Creative SB Live drivers are: Front channels: 0.72V peak to peak Rear channels: 0.68V peak to peak Center and subwoofer: 0.64V peak to peak Is there any way to increase output on the center and subwoofer channels in ALSA? I already have the Center and LFE channels set to maximum gain in alsamixer, so any suggestions to further boost the output are most certainly welcome. :) Thanks in advance. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
